JP2002072008A - Optical branching filter and optical coupler - Google Patents

Optical branching filter and optical coupler

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Publication number
JP2002072008A
JP2002072008A JP2000252966A JP2000252966A JP2002072008A JP 2002072008 A JP2002072008 A JP 2002072008A JP 2000252966 A JP2000252966 A JP 2000252966A JP 2000252966 A JP2000252966 A JP 2000252966A JP 2002072008 A JP2002072008 A JP 2002072008A
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Japan
Prior art keywords
optical
input
wavelength
signal
output
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JP2000252966A
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Japanese (ja)
Inventor
Hironori Hayata
博則 早田
Original Assignee
Matsushita Electric Ind Co Ltd
松下電器産業株式会社
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Priority to JP2000252966A priority Critical patent/JP2002072008A/en
Publication of JP2002072008A publication Critical patent/JP2002072008A/en
Pending legal-status Critical Current

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Abstract

(57) [Problem] To provide a low-cost optical multiplexer / demultiplexer that efficiently demultiplexes / combines light having a plurality of wavelengths adjacent to each other. An optical demultiplexer according to the present invention includes an optical fiber (10).
, An optical circulator 20, and optical collimators 40a-4
0c and an optical filter 50. Also,
Optical fibers 10a to 10d are connected to the above components, and a fiber grating 30 is formed on the optical fiber 10a. Fiber grating 30
Is set to reflect an optical signal of wavelength λ2. The optical filter 50 is a long wavelength transmission filter having a wavelength λ2 as an intermediate band. When an optical multiplexed signal obtained by multiplexing optical signals of three adjacent wavelengths λ1 to λ3 is input from the optical fiber 10, the optical multiplexing and demultiplexing is performed by the optical multiplexing / demultiplexing device.
Each propagates through another optical fiber.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an apparatus for demultiplexing / multiplexing an optical multiplex signal, and more particularly to an optical multiplexer / demultiplexer used for optical fiber communication and an optical transmission / reception system using the same.

[0002]

2. Description of the Related Art Hitherto, optical multiplex transmission in which a plurality of optical signals are propagated in one optical transmission line not only obtains effects such as an increase in transmission capacity but also expands an application area of optical communication. It is considered an important method. In the optical multiplex transmission, there is a method called wavelength multiplex transmission using optical signals having different wavelengths. This wavelength multiplex transmission is a method of separating channels according to wavelength differences. The wavelength multiplex transmission is a transmission form in which a plurality of optical signals having different wavelengths are multiplexed and transmitted via one optical fiber, and is characterized in that the low loss of the optical fiber over a wide wavelength range can be effectively used. . In the basic configuration of the wavelength multiplex transmission, on the transmission side, optical signals from light sources having different wavelengths are multiplexed into a wavelength multiplexed optical signal by an optical multiplexer and coupled to one optical fiber. On the receiving side, the wavelength division multiplexed optical signal from the optical fiber is demultiplexed for each wavelength by an optical demultiplexer, and the optical signal is converted into an electric signal by a light receiving element. In this way, in the wavelength division multiplexing transmission, a plurality of transmission paths independent of each other are formed using one optical fiber, and one-way or two-way communication becomes possible.

The basic components of the optical demultiplexer used for the wavelength division multiplexing transmission include an angle dispersion element and a wavelength selective reflection / transmission film. First, an optical demultiplexer using a conventional angle dispersion element will be described. FIG. 19 shows a basic configuration of an optical demultiplexer using a conventional angle dispersion element. Hereinafter, the optical demultiplexer will be described with reference to FIG.

In FIG. 19, the optical demultiplexer includes an optical fiber 100, an angular dispersion element 200, and a collimator lens 3.
00, condenser lens 400, light receiving elements 500-1 to 500
-N. The wavelength multiplexed optical signal emitted from the end face of the optical fiber 100 is converted into parallel light by the collimator lens 300 and enters the angle dispersion element 200. The angle dispersion element 200 converts a wavelength multiplexed optical signal obtained by multiplexing optical signals of a plurality of wavelengths into an optical signal demultiplexed for each wavelength by spatially dispersing the wavelength and giving an angle change. Things. Next, the optical signal demultiplexed for each wavelength by the angle dispersion element 200 is
0 and the light receiving elements 500-1 to 500-5 for each wavelength.
00-n. Incidentally, as the angle dispersive element 200, a prism is initially used, and a diffraction grating is mainly used at present.

Next, an optical demultiplexer using a conventional wavelength-selective reflection / transmission film will be described. FIG. 20 shows a basic configuration of a conventional optical demultiplexer using a wavelength-selective reflection / transmission film. Hereinafter, the optical demultiplexer will be described with reference to FIG.

In FIG. 20, the optical demultiplexer includes an optical fiber 100, a collimator lens 300, and a condenser lens 40.
0, light receiving element 500, wavelength selective reflection filter 600,
The wavelength selective transmission filter 700 is provided. The wavelength multiplexed optical signal emitted from the end face of the optical fiber 100 is converted into parallel light by the collimator lens 300 and enters the wavelength selective reflection filter 600. The wavelength-selective reflection filter 600 utilizes the wavelength selectivity of an interference filter film formed by laminating high / low-refractive-index dielectric films. ing. Accordingly, the optical signal that has entered the wavelength-selective reflection filter 600 reflects only the optical signal of the wavelength λ1 and transmits the optical signals of other wavelengths.
It is incident on 00. This wavelength selective transmission filter 700
Is also provided so as to transmit only the optical signal of the wavelength λ2 here using the same characteristics as described above. Therefore, the light incident on the wavelength-selective transmission filter 700 has the wavelength λ2
Is transmitted, and optical signals of other wavelengths are reflected.
The transmitted optical signal of the wavelength λ2 enters the condenser lens 400, is condensed by the condenser lens 400, and enters the light receiving element 500.

An optical multiplexer for coupling a plurality of optical signals to one transmission line can be realized by reversing the input / output terminals of the optical demultiplexer in consideration of the reversibility of light.

[0008]

By the way, in recent high-density wavelength division multiplexing transmission, a system for multiplexing adjacent wavelength bands of several tens nm or less is desired. In such a case, in the optical demultiplexer using the conventional angle dispersion element 200, the optical signal separation angle of each wavelength becomes small. That is, in FIG. 19, the interval between the light receiving elements 500-1 to 500-n is reduced,
The focal length of the condenser lens 400 (that is, the condenser lens 40
0 and the light receiving elements 500-1 to 500-n). Therefore, it is necessary to increase the size of the device and to suppress the mechanical accuracy. Further, in the optical demultiplexer using the wavelength-selective reflection / transmission film described above, the sharpness of the cutoff region of the wavelength-selection reflection / transmission film is insufficient, so that an optical signal having a close wavelength interval is separated / demultiplexed. It is not possible to multiplex, and it is necessary to increase the number of filters in response to the increase in the number of channels of the optical signal, which causes an increase in insertion loss.

On the other hand, a circuit disclosed in Japanese Patent Application Laid-Open No. 09-23210 is known as a low-loss and stable optical demultiplexer. FIG. 21 shows an example of the optical demultiplexer disclosed in Japanese Patent Application Laid-Open No. 09-23210. Hereinafter, the optical demultiplexer will be described with reference to FIG.

In FIG. 21, the optical demultiplexer includes an optical fiber 100 into which a wavelength multiplexed optical signal obtained by multiplexing optical signals of a plurality of wavelengths λ1 to λn is input, and an optical circulator 800
-1 to 800-n and the fiber grating 900-
Optical fibers 110-1 to 110-1 formed with 1-900-n
10-n. The optical circulator 80
Optical circulator 800-1 is provided for 0-1 to 800-n.
Optical fiber 120- that emits an optical signal from
1 to 120-n are connected.

Optical circulators 800-1 to 800-n
Has first to third light input / output terminals. In the optical circulators 800-1 to 800-n, the optical signal input of the first optical input / output terminal becomes the optical signal output of the second optical input / output terminal, and the optical signal input of the second optical input / output terminal. Are non-reciprocal light transmission characteristics which become the optical signal output of the third optical input / output terminal.

Fiber gratings 900-1 to 90
0-n has a minute and periodic change in the refractive index in the core portion of the optical fibers 110-1 to 110-n along the light propagation direction. Each of the fiber gratings 900-1 to 900-n has a characteristic of selectively reflecting only a signal having a wavelength equal to the above-described period of an optical signal propagating inside. Here, the fiber gratings 900-1 to 900-n have different reflection wavelengths from each other, and
It is set so that optical signals of wavelengths λ1 to λn are reflected for 1 to 900-n.

In the optical demultiplexer, the optical fiber 100
A wavelength-division multiplexed optical signal obtained by multiplexing a plurality of optical signals of wavelengths λ1 to λn incident on the optical circulator 800-1
Incident on the optical input / output end of Here, since the optical circulator 800-1 has non-reciprocal light passing characteristics as described above, the wavelength multiplexed optical signal is
The light is emitted from the second light input / output terminal 00-1. Next, the wavelength multiplexed optical signal propagates through the optical fiber 110-1,
The light enters the fiber grating 900-1 formed in the optical fiber 110-1. Here, since the fiber grating 900-1 has a reflection wavelength only at the wavelength λ1, as described above, it reflects only the optical signal of the wavelength λ1 and the optical signals of the other wavelengths λ2 to λn Pass -1. The reflected optical signal of wavelength λ1 enters the second optical input / output terminal of the optical circulator 800-1, exits from the third optical input / output terminal of the optical circulator 800-1, and propagates through the optical fiber 120-1. I do.
The optical signals of wavelengths λ2 to λn that have passed through the fiber grating 900-1 are separated by an optical circulator 800-2.
At the first optical input / output end. After that, wavelengths λ2 to λ
n optical signals propagate in the same manner and the optical circulator 800
At −n, the optical signal of wavelength λn reflected by the fiber grating 900-n is split into the optical fiber 120-n. Thus, a plurality of wavelengths λ1 to λ
The wavelength division multiplexed optical signal obtained by multiplexing the n optical signals is demultiplexed by the optical demultiplexer.

However, in the above optical demultiplexer,
Since an optical circulator must be installed for each wavelength to be demultiplexed, the size of the optical demultiplexer has been increased. Further, this optical circulator is made of an expensive optical crystal, so that the cost is high. Furthermore, since the optical multiplexed signal passes through a large number of optical circulators, the insertion loss due to the optical circulator has been large.

Therefore, an object of the present invention is to provide a low-cost optical multiplexer / demultiplexer that efficiently demultiplexes / combines optical signals of a plurality of wavelengths close to each other.

[0016]

Means for Solving the Problems and Effects of the Invention In order to achieve the above object, the present invention has the following features. A first invention is an optical demultiplexer for demultiplexing an optical multiplexed signal obtained by multiplexing three different optical signals having first to third wavelengths for each wavelength, wherein at least the first to third optical input / outputs are provided. The optical signal input to the first optical input / output terminal is output from the second optical input / output terminal, and the optical signal input to the second optical input / output terminal is input to the third optical input / output terminal. An optical circulator output from the end, a first optical fiber connected to the first optical input / output end of the optical circulator, and supplying an optical multiplexed signal to the first optical input / output end of the optical circulator; Is connected to a second optical input / output end of the optical circulator, and a second optical fiber in which a fiber grating for reflecting an optical signal of a second wavelength is formed on the way, and a second optical fiber from the other end. An optical filter for demultiplexing the output first and third wavelength optical signals; Optical signal having a wavelength of 2, characterized in that the output from the third light input and output ends of the optical circulator.

According to the first aspect, an optical signal of one wavelength is demultiplexed by a fiber grating from an optical multiplexed signal obtained by multiplexing optical signals of three different wavelengths, and the optical signals of the remaining wavelengths are separated. Demultiplex using an optical filter. Therefore, by using one optical circulator, one fiber grating, and one optical filter, it is possible to demultiplex an optical multiplexed signal obtained by multiplexing optical signals of three different wavelengths.

According to a second aspect of the present invention, there is provided an invention according to the first aspect, wherein a wavelength-transmittance change characteristic of the optical filter includes a cut-off region for reflecting an optical signal in the wavelength region and a wavelength region. Having a transmission region through which the optical signal is transmitted, and an intermediate region in which the transmittance gradually changes from the cutoff region to the transmission region, and the first wavelength is disposed in the cutoff region of the optical filter, Third
Is arranged in the transmission region of the optical filter, and the second wavelength is arranged in the middle region of the optical filter.

According to the second aspect of the present invention, the optical signal of the wavelength arranged in the above-mentioned intermediate region, which cannot be split by the optical filter, is split by the fiber grating, so that the three adjacent signals are separated.
An optical multiplexed signal obtained by multiplexing optical signals of two different wavelengths can be demultiplexed. That is, an optical signal located at an intermediate wavelength is split by a fiber grating having a sharp cutoff band from optical multiplexed signals obtained by multiplexing three adjacent optical signals having different wavelengths, and the optical signals having the remaining wavelengths are separated. The optical signal of the remaining wavelength is demultiplexed using an optical filter having a dull cutoff region.
Therefore, by using one optical circulator, one fiber grating, and one optical filter, it is possible to demultiplex an optical multiplexed signal obtained by multiplexing three adjacent optical signals having different wavelengths. As a result, the conventional Japanese Patent Application Laid-Open No. 09-23
The two optical circulators required in the optical demultiplexer disclosed in Japanese Patent Publication No. 210-210 can have the same demultiplexing function by one in the second invention. As mentioned earlier, optical circulators are made of expensive optical crystals,
The cost can be reduced by reducing the number used, and the insertion loss due to the optical circulator can also be reduced.

A third invention is an optical multiplexer for multiplexing optical signals of three different first to third wavelengths, the optical multiplexer having at least first to third optical input / output terminals, The optical signal input to the optical input / output terminal is output from the second optical input / output terminal,
The optical signal input to the optical input / output terminal of the optical circulator is connected to the optical circulator for outputting from the third optical input / output terminal and the first optical input / output terminal of the optical circulator. A first optical fiber for supplying to a first optical input / output end of the circulator, and one end connected to a second optical input / output end of the optical circulator for reflecting an optical signal of a second wavelength on the way; Combining a second optical fiber on which a fiber grating is formed, and optical signals of first and third wavelengths,
An optical filter for inputting the multiplexed optical signal to the other end of the second optical fiber, and an optical multiplexed signal in which the optical signals of the first to third wavelengths are multiplexed forms a third optical circulator.
Is output from the optical input / output terminal of

According to the third aspect of the invention, it is possible to realize an optical multiplexer for multiplexing optical signals of three different wavelengths by changing the input / output direction of the optical signal with the same structure as the first aspect. it can.

A fourth invention is an invention according to the third invention, wherein the wavelength-transmittance change characteristic of the optical filter includes a cut-off region for reflecting an optical signal in the wavelength region and a wavelength region in the wavelength region. Having a transmission region through which the optical signal is transmitted, and an intermediate region in which the transmittance gradually changes from the cutoff region to the transmission region, and the first wavelength is disposed in the cutoff region of the optical filter, Third
Is arranged in the transmission region of the optical filter, and the second wavelength is arranged in the middle region of the optical filter.

According to the fourth aspect, the same structure as that of the second aspect is adopted, and by changing the input / output direction of the optical signal, the three adjacent
An optical multiplexer for multiplexing optical signals of two different wavelengths can be realized.

A fifth invention is provided on the optical transmission device side,
An optical multiplexer for multiplexing optical signals of three different first to third wavelengths, and an optical multiplexed signal provided on the optical receiving device side and multiplexing the optical signals of the first to third wavelengths for each wavelength. A wavelength division multiplexing transmission system for transmitting an optical multiplexed signal by connecting an optical demultiplexer for demultiplexing with a first optical fiber, wherein the optical multiplexer comprises:
An optical signal having at least first to third optical input / output terminals, an optical signal input to the first optical input / output terminal is output from the second optical input / output terminal, and input to the second optical input / output terminal. A first optical circulator for outputting the transmitted optical signal from the third optical input / output terminal, one end of which is connected to the second optical input / output terminal of the first optical circulator, and the second wavelength A second optical fiber on which a first fiber grating for reflecting the first optical signal is formed; and a first optical input / output terminal of the first optical circulator, and the second optical fiber transmits the second wavelength optical signal to the first optical circulator. A third optical fiber for supplying to a first optical input / output end of the optical circulator, an optical signal of the first and third wavelengths being multiplexed, and the multiplexed optical signal being the other of the second optical fiber A first optical filter for inputting to the end, and the optical demultiplexer includes at least fourth to sixth optical input / output An optical signal input to the fourth optical input / output terminal is output from the fifth optical input / output terminal, and an optical signal input to the fifth optical input / output terminal is output to the sixth optical input / output terminal. A second optical circulator output from the first optical circulator, and one end thereof is connected to a fifth optical input / output terminal of the second optical circulator,
A fourth optical fiber on which a second fiber grating for reflecting an optical signal of a second wavelength is formed, and first and third optical fibers output from the other ends of the fourth optical fiber.
A second optical filter for demultiplexing an optical signal having a wavelength of
The first optical fiber connects a third optical input / output terminal of the first optical circulator and a fourth optical input / output terminal of the second optical circulator, and an optical multiplex signal propagates through the first optical fiber. The optical signal of the second wavelength is output from a sixth optical input / output terminal of the second optical circulator.

According to the fifth aspect, the first and third aspects are combined and connected by a single optical fiber, whereby an optical multiplexed signal obtained by multiplexing optical signals of three different wavelengths is propagated. A one-way wavelength division multiplexing transmission system can be configured.

A sixth invention is an invention according to the fifth invention, wherein the first and second optical filters have a wavelength-to-transmittance change characteristic, which is a cut-off for reflecting an optical signal in the wavelength region. Region, a transmission region through which an optical signal in the wavelength region is transmitted, and an intermediate region in which the transmittance gradually increases from the cut-off region to the transmission region. The third wavelength is disposed in a cutoff band of the second optical filter, the third wavelength is disposed in a transmission band of the first and second optical filters, and the second wavelength is
It is characterized in that it is arranged in an intermediate region between the first and second optical filters.

According to the sixth aspect of the present invention, the second and fourth aspects of the present invention are combined and connected by one optical fiber, thereby multiplexing three adjacent optical signals having different wavelengths. A one-way wavelength multiplexing transmission system for propagating the signal can be configured.

According to a seventh aspect of the present invention, there is provided an optical demultiplexer for demultiplexing an optical multiplexed signal obtained by multiplexing four different optical signals having first to fourth wavelengths for each wavelength. An optical input / output terminal, an optical signal input to the first optical input / output terminal is output from the second optical input / output terminal, and an optical signal input to the second optical input / output terminal is input to the third optical input / output terminal. An optical circulator output from the optical input / output end, a first optical fiber connected to the first optical input / output end of the optical circulator, and supplying an optical multiplexed signal to the first optical input / output end of the optical circulator; One end thereof is connected to a second optical input / output terminal of the optical circulator, and a first fiber grating that reflects an optical signal of a second wavelength and a second fiber that reflects an optical signal of a fourth wavelength on the way. A second optical fiber on which a fiber grating is formed;
A third optical fiber having one end connected to a third optical input / output end of the optical circulator, and an optical signal having first and third wavelengths output from the other end of the second optical fiber are demultiplexed. And an optical filter for splitting optical signals of the second and fourth wavelengths output from the other end of the third optical fiber.

According to the seventh aspect, the optical signal of the two wavelengths is demultiplexed by the fiber grating from the optical multiplexed signal obtained by multiplexing the optical signals of the four different wavelengths, and the optical signals of the remaining wavelengths are separated. The two optical signals split by the optical filter and split by the fiber grating are also split by the optical filter. Therefore, by using one optical circulator, two fiber gratings, and one optical filter, an optical multiplexed signal obtained by multiplexing optical signals of four different wavelengths can be demultiplexed. Further, in the seventh aspect, since two systems of optical multiplexed signals are demultiplexed by one optical filter, an increase in insertion loss of the optical filter due to an increase in channels can be prevented, and the cost of parts can be reduced. Can be.

An eighth invention is an invention according to the seventh invention, wherein the wavelength change characteristic of the optical filter with respect to the wavelength is a cut-off region for reflecting an optical signal in the wavelength region, and a wavelength region. Has a transmission region through which the optical signal is transmitted, and an intermediate region in which the transmittance gradually increases from the cut-off region to the transmission region. The first and second wavelengths are transmitted to the cut-off region of the optical filter. And the third and fourth wavelengths are arranged in the transmission region of the optical filter.

According to the eighth aspect, the first and second optical multiplexed signals are obtained by multiplexing optical signals of four different wavelengths.
The optical signal having the wavelength of? Is disposed in the cutoff region of the optical filter, and the optical signals having the third and fourth wavelengths are disposed in the transmission region of the optical filter. Then, the optical signals of the second and fourth wavelengths are split by a fiber grating having a sharp cutoff band.
Thereby, the interval between the first wavelength and the second wavelength and the interval between the third wavelength and the fourth wavelength can be made closer, that is, light of two wavelengths that are close to each other. An optical multiplexed signal obtained by multiplexing two sets of signals can be demultiplexed. As a result, the conventional Japanese Patent Application Laid-Open No. 09-23210 is disclosed.
The optical circulator, which was necessary in the three optical demultiplexers disclosed in Japanese Patent Application Laid-Open Publication No. H10-209, can have the same demultiplexing function with one. As described above, since the optical circulator is made of an expensive optical crystal, the cost can be reduced by reducing the number of used optical circulators, and the insertion loss due to the optical circulator can also be reduced.

A ninth invention is an optical multiplexer for multiplexing optical signals of four different first to fourth wavelengths, comprising at least first to third optical input / output terminals, The optical signal input to the optical input / output terminal is output from the second optical input / output terminal,
The optical signal input to the optical input / output terminal of the optical circulator is connected to the optical circulator for outputting the optical signal from the third optical input / output terminal and the third optical input / output terminal of the optical circulator. A first optical fiber that outputs an optical multiplexed signal obtained by multiplexing the signals from a third optical input / output terminal of the optical circulator, and one end thereof is connected to a second optical input / output terminal of the optical circulator;
A second optical fiber in which a first fiber grating that reflects an optical signal of a second wavelength and a second fiber grating that reflects an optical signal of a fourth wavelength are formed, and one end thereof Combines a third optical fiber connected to a first optical input / output end of an optical circulator with an optical signal having first and third wavelengths, and combines the combined optical signal with a second optical fiber And an optical filter for inputting the optical signals of the second and fourth wavelengths to each other and inputting the combined optical signal to the other end of the third optical fiber.

According to the ninth aspect, an optical multiplexer for multiplexing optical signals of four different wavelengths by changing a connection port of the optical circulator of the seventh aspect and changing an input / output direction of an optical signal. Can be realized.

A tenth invention is the invention according to the ninth invention, wherein the optical filter has a wavelength-transmittance change characteristic.
It has a cut-off region that reflects an optical signal in the wavelength region, a transmission region that transmits the optical signal in the wavelength region, and an intermediate region in which the transmittance gradually changes from the cut-off region to the transmission region. The first and second wavelengths are arranged in a cutoff region of the optical filter, and the third and fourth wavelengths are arranged in a transmission region of the optical filter.

According to the tenth aspect, by changing the connection port of the optical circulator of the eighth aspect and changing the input / output direction of the optical signal, two optical signals of two wavelengths close to each other are combined. An optical multiplexer can be realized.

An eleventh invention is provided on the optical transmission device side, and is provided on the optical receiving device side with an optical multiplexer for multiplexing four different optical signals of first to fourth wavelengths. A wavelength division multiplexing transmission system for transmitting an optical multiplexed signal by connecting an optical demultiplexer for demultiplexing an optical multiplexed signal obtained by multiplexing an optical signal of a fourth wavelength for each wavelength by a first optical fiber, The optical multiplexer is
An optical signal having at least first to third optical input / output terminals, an optical signal input to the first optical input / output terminal is output from the second optical input / output terminal, and input to the second optical input / output terminal. A first optical circulator for outputting the transmitted optical signal from the third optical input / output terminal, one end of which is connected to the second optical input / output terminal of the first optical circulator, and the second wavelength A second optical fiber in which a first fiber grating for reflecting an optical signal of the first type and a second fiber grating for reflecting an optical signal of the fourth wavelength are formed; A third optical fiber connected to the first optical input / output end, and optical signals of the first and third wavelengths are multiplexed, and the multiplexed optical signal is transmitted to the other end of the second optical fiber. Input, multiplex the optical signals of the second and fourth wavelengths, and combine the multiplexed optical signal with the third optical signal. A first optical filter for inputting to the other end of the optical fiber, wherein the optical demultiplexer has at least fourth to sixth optical input / output terminals, and a light input to the fourth optical input / output terminal. A second optical circulator for outputting a signal from the fifth optical input / output terminal and outputting an optical signal input to the fifth optical input / output terminal from the sixth optical input / output terminal; Connected to the fifth optical input / output terminal of the second optical circulator,
A fourth optical fiber in which a third fiber grating for reflecting the optical signal of the second wavelength and a fourth fiber grating for reflecting the optical signal of the fourth wavelength are formed in the middle thereof, and one end thereof. Is the sixth of the second optical circulator
A fifth optical fiber connected to the optical input / output end of the first optical fiber, and an optical signal of the first and third wavelengths output from the other end of the fourth optical fiber. A second branching device for splitting the optical signals of the second and fourth wavelengths output from the end;
Wherein the first optical fiber connects the third optical input / output terminal of the first optical circulator and the fourth optical input / output terminal of the second optical circulator, and It is characterized in that an optical multiplex signal propagates.

According to the eleventh aspect, the seventh aspect and the ninth aspect
By connecting with one optical fiber, a one-way wavelength multiplexing transmission system for propagating an optical multiplexed signal obtained by multiplexing optical signals of four different wavelengths can be configured.

A twelfth invention is a subordinate invention of the eleventh invention, wherein the first and second optical filters have wavelength-
The transmittance change characteristics are a cut-off region that reflects an optical signal in that wavelength region, a transmission region that transmits an optical signal in that wavelength region, and an intermediate portion where the transmittance gradually changes from the cut-off region to the transmission region. And a first wavelength and a second wavelength.
And the second and third optical filters are arranged in a cutoff region, and the third and fourth wavelengths are arranged in the transmission regions of the first and second optical filters.

According to the twelfth invention, the eighth invention and the first invention
A one-way wavelength multiplexing transmission system for transmitting an optical multiplexed signal obtained by multiplexing two sets of optical signals of two wavelengths close to each other by connecting with one optical fiber by combining the invention with the invention of FIG. Can be.

The thirteenth invention has four different first to fourth aspects.
An optical demultiplexer for demultiplexing an optical multiplexed signal obtained by multiplexing optical signals of wavelengths for each wavelength, having first to fourth optical input / output terminals,
The optical signal input to the first optical input / output terminal is output from the second optical input / output terminal, the optical signal input to the second optical input / output terminal is output from the third optical input / output terminal, The optical signal input to the third optical input / output terminal is output from the fourth optical input / output terminal, and the optical signal input to the fourth optical input / output terminal is output from the first optical input / output terminal. An optical circulator, a first optical fiber connected to a first optical input / output end of the optical circulator, for supplying an optical multiplexed signal to a first optical input / output end of the optical circulator, and one end of the first optical fiber connected to a first optical input / output end of the optical circulator; A first fiber grating that is connected to the second optical input / output end and reflects an optical signal of the second wavelength and a second fiber grating that reflects an optical signal of the fourth wavelength are formed on the way. A second optical fiber is connected to the third optical input / output end of the optical circulator. A third optical fiber in which a third fiber grating for reflecting an optical signal of the second wavelength is formed, and a first and third wavelengths output from the other ends of the second optical fiber. An optical filter for demultiplexing the optical signal, wherein the optical signal of the second wavelength is output from the fourth optical input / output terminal of the optical circulator, and the optical signal of the fourth wavelength is output from the third optical fiber. It is output.

According to the thirteenth aspect, from the optical multiplexed signal obtained by multiplexing the optical signals of four different wavelengths, the optical signals of the two wavelengths are separated by the fiber grating, and the optical signals of the remaining wavelengths are separated. Demultiplex using an optical filter. Therefore, one optical circulator and three fiber gratings 3
By using one optical filter and one optical filter, an optical multiplexed signal obtained by multiplexing optical signals of four different wavelengths can be split.

A fourteenth invention is a invention according to the thirteenth invention, wherein the wavelength-transmittance change characteristic of the optical filter includes a cut-off region for reflecting an optical signal in the wavelength region, and a wavelength region. Having a transmission region through which the optical signal is transmitted, and an intermediate region in which the transmittance gradually changes from the cutoff region to the transmission region, and the first wavelength is disposed in the cutoff region of the optical filter,
The third and fourth wavelengths are arranged in a transmission region of the optical filter, and the second wavelength is arranged in an intermediate region of the optical filter.

According to the fourteenth aspect, the optical signal of the second wavelength arranged in the intermediate region, which cannot be split by the optical filter, and the optical signal of the fourth wavelength arranged in the transmission region,
By demultiplexing with a fiber grating, an optical multiplexed signal obtained by multiplexing four adjacent optical signals having different wavelengths can be demultiplexed. That is, an optical signal located at an intermediate wavelength is split by a fiber grating having a sharp cutoff band from optical multiplexed signals obtained by multiplexing four adjacent optical signals having different wavelengths, and the optical signals having the remaining wavelengths are separated. The optical signal having the remaining wavelength is demultiplexed using an optical filter having a dull cutoff region. Therefore, by using one optical circulator, three fiber gratings, and one optical filter, an optical multiplexed signal obtained by multiplexing four adjacent optical signals having different wavelengths can be demultiplexed. As a result, the conventional Japanese Patent Publication
In the fourteenth invention, one optical circulator, which is required for three optical demultiplexers disclosed in Japanese Patent No. 23210, can have a similar demultiplexing function. As described above, since the optical circulator is made of an expensive optical crystal, the cost can be reduced by reducing the number of used optical circulators, and the insertion loss due to the optical circulator can also be reduced.

The fifteenth invention has four different first to fourth aspects.
An optical multiplexer for multiplexing optical signals having wavelengths of ???, having first to fourth optical input / output terminals, and an optical signal input to the first optical input / output terminal is supplied to a second optical input / output terminal. The optical signal output from the terminal and input to the second optical input / output terminal is output from the third optical input / output terminal, and the optical signal input to the third optical input / output terminal is input to the fourth optical input / output terminal. An optical circulator that outputs an optical signal output from the terminal and input to the fourth optical input / output terminal from the first optical input / output terminal; and a first optical input / output terminal of the optical circulator, A first optical fiber for outputting an optical multiplexed signal obtained by combining optical signals of the fourth to fourth wavelengths from a first optical input / output terminal of the optical circulator, and one end of which is a fourth optical input / output of the optical circulator A first fiber grating which is connected to an end and reflects an optical signal of a second wavelength on the way;
A second optical fiber on which a second fiber grating for reflecting an optical signal of a wavelength is formed, and a second optical fiber connected to a third optical input / output end of the optical circulator. A third optical fiber on which a reflecting third fiber grating is formed, and optical signals of the first and third wavelengths are multiplexed, and the multiplexed optical signal is transmitted to the other end of the second optical fiber. And an optical filter for inputting.
The optical signal of the wavelength is supplied from the second optical input / output terminal of the optical circulator, and the optical signal of the fourth wavelength is supplied from the third optical fiber.

According to the fifteenth aspect, an optical multiplexer for multiplexing optical signals of four different wavelengths by changing a connection port of the optical circulator of the thirteenth aspect and changing an input / output direction of an optical signal. Can be realized.

A sixteenth invention is a invention according to the fifteenth invention, wherein the optical filter has a wavelength-to-transmittance change characteristic which includes a cut-off region for reflecting an optical signal in the wavelength region and a wavelength region. Having a transmission region through which the optical signal is transmitted, and an intermediate region in which the transmittance gradually changes from the cutoff region to the transmission region, and the first wavelength is disposed in the cutoff region of the optical filter,
The third and fourth wavelengths are arranged in a transmission region of the optical filter, and the second wavelength is arranged in an intermediate region of the optical filter.

According to the sixteenth aspect, by changing the connection port of the optical circulator of the optical demultiplexer according to the fourteenth aspect and changing the input / output direction of the optical signal, the four adjacent wavelengths of the optical signal having different wavelengths are changed. Can be realized.

A seventeenth invention is provided in an optical transmission device,
An optical multiplexer for multiplexing optical signals of four different first to fourth wavelengths, and an optical multiplexed signal provided in the optical receiver and multiplexing the optical signals of the first to fourth wavelengths for each wavelength. A wavelength division multiplexing transmission system for transmitting an optical multiplexed signal by connecting an optical demultiplexer that oscillates with a first optical fiber.
A fourth optical input / output terminal, an optical signal input to the first optical input / output terminal is output from the second optical input / output terminal, and an optical signal input to the second optical input / output terminal is The optical signal output from the third optical input / output terminal and input to the third optical input / output terminal is output from the fourth optical input / output terminal, and the optical signal input to the fourth optical input / output terminal is A first optical circulator output from the first optical input / output terminal, one end of which is connected to a fourth optical input / output terminal of the first optical circulator; A second optical fiber in which a first fiber grating that reflects light, a second fiber grating that reflects an optical signal of a fourth wavelength is formed, and a third optical input / output end of the first optical circulator. A third fiber grating is formed on the way to reflect an optical signal of the second wavelength. A third optical fiber, and a first optical filter that multiplexes the optical signals of the first and third wavelengths and inputs the multiplexed optical signal to the other end of the second optical fiber; The optical demultiplexer has fifth to eighth optical input / output terminals, and an optical signal input to the fifth optical input / output terminal is output from the sixth optical input / output terminal, and the sixth optical input / output terminal is provided. The optical signal input to the output terminal is output from the seventh optical input / output terminal, the optical signal input to the seventh optical input / output terminal is output from the eighth optical input / output terminal, and the eighth optical input / output terminal A second optical circulator for outputting the optical signal input to the output terminal from the fifth optical input / output terminal, one end of which is connected to the sixth optical input / output terminal of the second optical circulator; A fourth fiber grating that reflects an optical signal of a second wavelength, and a fifth fiber grating that reflects an optical signal of a fourth wavelength Is connected to the seventh optical input / output end of the second optical circulator, and a sixth fiber grating that reflects an optical signal of the second wavelength is formed in the middle thereof. A fifth optical fiber and a second optical fiber that demultiplexes the optical signals of the first and third wavelengths output from the other ends of the fourth optical fiber.
Wherein the first optical fiber connects the first optical input / output terminal of the first optical circulator and the fourth optical input / output terminal of the second optical circulator, The optical multiplexed signal propagates, the optical signal of the second wavelength is supplied from the second optical input / output terminal of the first optical circulator, and is output from the eighth optical input / output terminal of the second optical circulator, 4th
Is supplied from the third optical fiber and output from the fifth optical fiber.

According to the seventeenth aspect, the thirteenth aspect and the fifteenth aspect are combined and connected by one optical fiber, whereby an optical multiplexed signal obtained by multiplexing optical signals of four different wavelengths is propagated. A one-way wavelength division multiplexing transmission system can be configured.

An eighteenth invention is a invention according to the seventeenth invention, wherein the first and second optical filters have a wavelength-
The transmittance change characteristic is a middle range where the transmittance gradually changes from a cutoff region to a transmission region, a transmission region where an optical signal in that wavelength region is reflected, a transmission region where an optical signal in that wavelength region is transmitted. And a first wavelength for the first and second wavelengths.
, And the third and fourth wavelengths are disposed in the transmission range of the first and second optical filters, and the second wavelength is disposed between the first and second optical filters. It is characterized by being arranged in the area.

According to the eighteenth aspect, by combining the fourteenth aspect and the sixteenth aspect and connecting them with one optical fiber, an optical multiplexed signal obtained by multiplexing four adjacent optical signals having different wavelengths. A one-way wavelength multiplexing transmission system for propagating the signal can be configured.

The nineteenth invention is directed to five different first to fifth aspects.
An optical demultiplexer for demultiplexing an optical multiplexed signal obtained by multiplexing optical signals of wavelengths for each wavelength, having first to fourth optical input / output terminals,
An optical signal input to the first optical input / output terminal is output from the second optical input / output terminal, an optical signal input to the second optical input / output terminal is output from the third optical input / output terminal, The optical signal input to the third optical input / output terminal is output from the fourth optical input / output terminal, and the optical signal input to the fourth optical input / output terminal is output from the first optical input / output terminal. An optical circulator, a first optical fiber connected to the first optical input / output end of the optical circulator, for supplying an optical multiplexed signal to the first optical input / output end of the optical circulator, and one end of the first optical fiber connected to the first optical input / output end of the optical circulator; A first fiber grating which is connected to the second optical input / output terminal and reflects an optical signal of the first wavelength, a second fiber grating which reflects an optical signal of the third wavelength, and And a third fiber grating for reflecting an optical signal having a wavelength. And an optical fiber having one end connected to the third optical input / output end of the optical circulator and a fourth fiber grating formed in the middle thereof for reflecting an optical signal of a third wavelength. And demultiplexes the optical signals of the second and fourth wavelengths output from the other end of the second optical fiber, and outputs the light of the first and fifth wavelengths output from the other end of the third optical fiber. An optical filter for splitting the signal, wherein the optical signal of the third wavelength is output from a fourth optical input / output terminal of the optical circulator.

According to the nineteenth aspect, out of the optical multiplexed signal obtained by multiplexing the optical signals of five different wavelengths, the optical signals of the three wavelengths are demultiplexed by the fiber grating, and the optical signals of the remaining wavelengths are separated. Two optical signals are split by the optical filter out of the three optical signals split by the fiber grating using the optical filter. Therefore, by using one optical circulator, four fiber gratings, and one optical filter, an optical multiplexed signal obtained by multiplexing optical signals of five different wavelengths can be demultiplexed. Also,
In the nineteenth aspect, since two systems of optical multiplexed signals are demultiplexed by one optical filter, an increase in insertion loss of the optical filter due to an increase in channels can be prevented, and component costs can be reduced. .

A twentieth aspect is an invention according to the nineteenth aspect, wherein the wavelength-transmittance change characteristic of the optical filter includes a cut-off region for reflecting an optical signal in the wavelength region and a wavelength region. Has a transmission region through which the optical signal is transmitted, and an intermediate region in which the transmittance gradually changes from the cutoff region to the transmission region. And the fourth and fifth wavelengths are arranged in a transmission region of the optical filter, and the third wavelength is arranged in an intermediate region of the optical filter.

According to the twentieth aspect, the optical signal of the third wavelength arranged in the intermediate region, which cannot be split by the optical filter, the optical signal of the first wavelength arranged in the cutoff region, By demultiplexing the optical signal of the fifth wavelength arranged in the transmission region with the fiber grating, it is possible to demultiplex an optical multiplexed signal obtained by multiplexing five adjacent optical signals of different wavelengths. That is, an optical signal located at an intermediate wavelength is split by a fiber grating having a sharp cutoff band from optical multiplexed signals obtained by multiplexing five adjacent optical signals having different wavelengths, and the optical signals having the remaining wavelengths are separated. . After that, the optical signal of the remaining wavelength is demultiplexed by using an optical filter whose cut-off region is dull. Therefore, by using one optical circulator, four fiber gratings, and one optical filter, an optical multiplexed signal obtained by multiplexing five adjacent optical signals having different wavelengths can be demultiplexed. As a result, in the twentieth invention, the optical circulator that required four optical demultiplexers disclosed in Japanese Patent Application Laid-Open No. 09-23210 was replaced by one in the twentieth invention.
Can have the same demultiplexing function. As described above, since the optical circulator is made of an expensive optical crystal, the cost can be reduced by reducing the number of used optical circulators, and the insertion loss due to the optical circulator can also be reduced.

According to a twenty-first aspect, five different first to fifth aspects are provided.
An optical multiplexer for multiplexing optical signals having wavelengths of ???, having first to fourth optical input / output terminals, and an optical signal input to the first optical input / output terminal is supplied to a second optical input / output terminal. The optical signal output from the terminal and input to the second optical input / output terminal is output from the third optical input / output terminal, and the optical signal input to the third optical input / output terminal is input to the fourth optical input / output terminal. An optical circulator that outputs an optical signal output from the terminal and input to the fourth optical input / output terminal from the first optical input / output terminal; and a first optical input / output terminal of the optical circulator, A first optical fiber for outputting an optical multiplexed signal obtained by multiplexing the optical signals of the fifth to fifth wavelengths from a first optical input / output end of the optical circulator, and one end of which is a fourth optical input / output of the optical circulator A first fiber grating which is connected to an end and reflects an optical signal of a first wavelength on the way;
A third fiber grating that reflects an optical signal of a wavelength of the third wavelength, a second optical fiber in which a third fiber grating that reflects an optical signal of the fifth wavelength is formed, and a third optical input of the optical circulator. A third optical fiber, which is connected to the output end and on which a fourth fiber grating for reflecting an optical signal of the third wavelength is formed, multiplexes the optical signals of the second and fourth wavelengths, The multiplexed optical signal is input to the other end of the second optical fiber, and the first and fifth optical fibers are input.
And multiplexes the optical signal having the wavelength of
And an optical filter for inputting to the other end of the optical fiber, wherein an optical signal of the third wavelength is supplied from a second optical input / output terminal of the optical circulator.

According to the twenty-first aspect, by changing the connection port of the optical circulator of the optical demultiplexer according to the nineteenth aspect and changing the input / output direction of the optical signal, the optical signals of five different wavelengths are combined. An undulating optical multiplexer can be realized.

A twenty-second invention is an invention according to the twenty-first invention, wherein the wavelength-transmittance change characteristic of the optical filter includes a cut-off region for reflecting an optical signal in the wavelength region and a wavelength region. Has a transmission region through which the optical signal is transmitted, and an intermediate region in which the transmittance gradually changes from the blocking region to the transmission region, and the first and second wavelengths are transmitted to the blocking region of the optical filter. And the fourth and fifth wavelengths are arranged in a transmission region of the optical filter, and the third wavelength is arranged in an intermediate region of the optical filter.

According to the twenty-second aspect, by changing the connection port of the optical circulator of the optical demultiplexer of the twentieth aspect and changing the input / output direction of the optical signal, five adjacent optical signals having different wavelengths are changed. Can be realized.

A twenty-third invention is provided in an optical transmission device,
An optical multiplexer for multiplexing optical signals of five different first to fifth wavelengths, and an optical multiplexed signal provided in the optical receiver and multiplexing the optical signals of the first to fifth wavelengths, for each wavelength; A wavelength division multiplexing transmission system for transmitting an optical multiplexed signal by connecting an optical demultiplexer that oscillates with a first optical fiber.
A fourth optical input / output terminal, an optical signal input to the first optical input / output terminal is output from the second optical input / output terminal, and an optical signal input to the second optical input / output terminal is The optical signal output from the third optical input / output terminal and input to the third optical input / output terminal is output from the fourth optical input / output terminal, and the optical signal input to the fourth optical input / output terminal is A first optical circulator output from the first optical input / output terminal, one end of which is connected to a fourth optical input / output terminal of the first optical circulator, and an optical signal of a first wavelength is supplied along the way; Second light in which a first fiber grating that reflects, a third fiber grating that reflects an optical signal of a third wavelength, and a third fiber grating that reflects an optical signal of a fifth wavelength are formed. A fiber, connected to a third optical input / output end of the first optical circulator,
A third optical fiber in which a fourth fiber grating for reflecting an optical signal of the third wavelength is formed on the way, an optical signal of the second and fourth wavelengths are multiplexed, and the multiplexed light is obtained. A first signal for inputting the signal to the other end of the second optical fiber, multiplexing the optical signals of the first and fifth wavelengths, and inputting the multiplexed optical signal to the other end of the third optical fiber; Wherein the optical demultiplexer has fifth to eighth optical input / output terminals, and an optical signal input to the fifth optical input / output terminal is output from the sixth optical input / output terminal. The optical signal input to the sixth optical input / output terminal is output from the seventh optical input / output terminal, and the optical signal input to the seventh optical input / output terminal is output from the eighth optical input / output terminal. A second optical circulator for outputting an optical signal input to the eighth optical input / output terminal from the fifth optical input / output terminal; A fifth fiber grating connected to a sixth optical input / output end of the circulator and reflecting an optical signal of the first wavelength, and a sixth fiber grating reflecting an optical signal of the third wavelength on the way; A fourth optical fiber on which a seventh fiber grating for reflecting an optical signal of a fifth wavelength is formed, and one end of which is connected to the seventh optical input / output end of the second optical circulator, A fifth optical fiber in which an eighth fiber grating for reflecting an optical signal of the third wavelength is formed, and an optical signal of the second and fourth wavelengths output from the other ends of the fourth optical fiber. A second optical fiber that demultiplexes the optical signals of the first and fifth wavelengths output from the other end of the fifth optical fiber;
Wherein the first optical fiber connects the first optical input / output terminal of the first optical circulator and the fourth optical input / output terminal of the second optical circulator, The optical multiplexed signal propagates, and the optical signal of the third wavelength is supplied from the second optical input / output terminal of the first optical circulator and output from the eighth optical input / output terminal of the second optical circulator. It is characterized by the following.

According to the twenty-third aspect, the nineteenth aspect and the twenty-first aspect are combined and connected by one optical fiber, thereby transmitting an optical multiplexed signal obtained by multiplexing optical signals of five different wavelengths. A one-way wavelength division multiplexing transmission system can be configured.

A twenty-fourth invention is an invention according to the twenty-third invention, wherein the first and second optical filters have a wavelength-
The transmittance change characteristics are a cut-off region that reflects an optical signal in that wavelength region, a transmission region that transmits an optical signal in that wavelength region, and an intermediate portion where the transmittance gradually changes from the cut-off region to the transmission region. And a first wavelength and a second wavelength.
And a fourth optical filter disposed in a cutoff band, a fourth and a fifth wavelength disposed in a transmission band of the first and second optical filters, and a third wavelength disposed in the first and second light filters. It is characterized in that it is arranged in the middle area of the filter.

According to the twenty-fourth aspect, by combining the twentieth aspect and the twenty-second aspect and connecting them with one optical fiber, an optical multiplexed signal obtained by multiplexing optical signals of five different wavelengths close to each other. A one-way wavelength multiplexing transmission system for propagating the signal can be configured.

In the twenty-fifth aspect, four different first to fourth aspects are provided.
An optical multiplexing / demultiplexing device for demultiplexing an optical multiplexed signal obtained by multiplexing optical signals having different wavelengths for each wavelength, and for multiplexing optical signals having two different fifth and sixth wavelengths. The optical signal input to the first optical input / output terminal is output from the second optical input / output terminal, and the optical signal input to the second optical input / output terminal is The optical signal output from the optical input / output terminal of the first optical input / output terminal and input to the third optical input / output terminal is output from the fourth optical input / output terminal, and the optical signal input to the fourth optical input / output terminal is output from the first optical input / output terminal. An optical circulator output from an optical input / output end of the optical circulator; a first optical fiber connected to the first optical input / output end of the optical circulator and supplying an optical multiplexed signal to the first optical input / output end of the optical circulator; One end is connected to a second optical input / output terminal of the optical circulator, and a first filter for reflecting an optical signal of a first wavelength is provided in the middle thereof. A second optical fiber in which a bag rating and a second fiber grating for reflecting an optical signal of a third wavelength are formed; and a second optical fiber having one end connected to a third optical input / output end of the optical circulator. 3 optical fiber, a fourth optical fiber having one end connected to a fourth optical input / output end of the optical circulator, and second and fourth wavelengths output from the other ends of the second optical fiber. , The optical signals of the first and third wavelengths output from the other end of the third optical fiber are demultiplexed, and the optical signals of the fifth and sixth wavelengths are multiplexed. An optical filter for inputting the multiplexed optical signal to the other end of the fourth optical fiber.

According to the twenty-fifth aspect, from the optical multiplexed signal obtained by multiplexing the optical signals of four different wavelengths, the optical signals of the two wavelengths are separated by the fiber grating, and the optical signals of the remaining wavelengths are separated. The two optical signals split by the optical filter and split by the fiber grating are also split by the optical filter. Therefore, an optical multiplexed signal obtained by multiplexing optical signals of four different wavelengths can be demultiplexed. Also,
In the twenty-fifth aspect, since one optical filter performs demultiplexing of two systems of optical multiplexed signals and one system of multiplexing, it is possible to prevent an increase in insertion loss of the optical filter due to an increase in the number of channels. Cost can also be reduced. It also has a function of multiplexing optical signals of two different wavelengths. That is, by using one optical circulator, two fiber gratings, and one optical filter, an optical multiplexer / demultiplexer having multiple functions can be configured.

A twenty-sixth invention is an invention according to the twenty-fifth invention, wherein the wavelength-transmittance change characteristic of the optical filter includes a cut-off region for reflecting an optical signal in the wavelength region and a wavelength region. And a middle region in which the transmittance gradually increases from a cut-off region to a transmission region. The first, second, and fifth wavelengths of the optical filter It is characterized in that it is arranged in a cut-off area, and the third, fourth and sixth wavelengths are arranged in a transmission area of the optical filter.

According to the twenty-sixth aspect, with respect to the demultiplexing function, the optical signals of the first and second wavelengths are converted from the optical multiplexed signal obtained by multiplexing the optical signals of four different wavelengths into the cutoff region of the optical filter. And the optical signals of the third and fourth wavelengths are arranged in the transmission region of the optical filter. Then, the optical signals of the second and fourth wavelengths are split by a fiber grating having a sharp cutoff band. Thereby, the interval between the first wavelength and the second wavelength and the interval between the third wavelength and the fourth wavelength can be reduced, that is,
An optical multiplexed signal obtained by multiplexing two sets of optical signals of two wavelengths close to each other can be demultiplexed. As a result, an optical circulator, which required three optical demultiplexers disclosed in the conventional Japanese Patent Application Laid-Open No. 09-23210, can have the same demultiplexing function with one. As described above, since the optical circulator is made of an expensive optical crystal, the cost can be reduced by reducing the number of optical circulators,
Further, the insertion loss due to the optical circulator can be reduced.

In the twenty-seventh aspect, four different first to fourth aspects are provided.
And multiplexes the optical signals having the wavelengths of
An optical multiplexing / demultiplexing device for demultiplexing an optical multiplexed signal obtained by multiplexing optical signals of wavelengths for each wavelength, comprising first to fourth optical input / output terminals, and input to the first optical input / output terminal. The output optical signal is output from the second optical input / output terminal, and the optical signal input to the second optical input / output terminal is output from the third optical input / output terminal and input to the third optical input / output terminal. An optical circulator for outputting the optical signal output from the fourth optical input / output terminal, and outputting the optical signal input to the fourth optical input / output terminal from the first optical input / output terminal; A first optical fiber connected to the optical input / output end of the optical circulator and outputting an optical multiplexed signal obtained by multiplexing the optical signals of the first to fourth wavelengths from the first optical input / output end of the optical circulator;
One end thereof is connected to a fourth optical input / output terminal of the optical circulator, and a first optical signal reflecting a first wavelength optical signal is provided in the middle thereof.
And a second optical fiber formed with a second fiber grating that reflects an optical signal of a third wavelength, and one end of which is connected to a third optical input / output end of the optical circulator. A third optical fiber, a fourth optical fiber having one end connected to the second optical input / output end of the optical circulator, and a multiplexed optical signal having second and fourth wavelengths, The input optical signal is input to the other end of the second optical fiber, the optical signals of the first and third wavelengths are multiplexed, and the multiplexed optical signal is input to the other end of the third optical fiber. An optical filter for splitting optical signals of fifth and sixth wavelengths output from the other end of the fourth optical fiber.

According to the twenty-seventh aspect, by changing the connection port of the optical circulator according to the twenty-fifth aspect and changing the input / output direction of the optical signal, optical signals of four different wavelengths are multiplexed, An optical multiplexer / demultiplexer for demultiplexing an optical multiplexed signal obtained by multiplexing optical signals of different wavelengths can be realized.

A twenty-eighth invention is an invention according to the twenty-seventh invention, wherein the wavelength-transmittance change characteristic of the optical filter includes a cut-off region for reflecting an optical signal in the wavelength region and a wavelength region. And a middle region in which the transmittance gradually increases from a cut-off region to a transmission region. The first, second, and fifth wavelengths of the optical filter It is characterized in that it is arranged in a cut-off area, and the third, fourth and sixth wavelengths are arranged in a transmission area of the optical filter.

According to the twenty-eighth aspect, by changing the connection port of the optical circulator of the twenty-sixth aspect and changing the input / output direction of the optical signal, two optical signals having two wavelengths close to each other are combined. An optical multiplexer / demultiplexer can be realized.

A twenty-ninth aspect of the present invention is provided in the first optical transmitting / receiving apparatus, wherein the optical signals of four different first to fourth wavelengths are multiplexed, and the optical signals of two different fifth and sixth wavelengths are combined. A first optical multiplexer / demultiplexer for demultiplexing a first optical multiplexed signal obtained by multiplexing the wavelengths for each wavelength, and a second optical transmitting / receiving device,
A second optical multiplexed signal obtained by multiplexing the optical signals having the wavelengths described above is demultiplexed for each wavelength and the optical signals having the fifth and sixth wavelengths are multiplexed.
Are connected by a first optical fiber,
A wavelength division multiplexing transmission system for transmitting an optical multiplexed signal and a second optical multiplexed signal, wherein the first optical multiplexer / demultiplexer comprises
A fourth optical input / output terminal, an optical signal input to the first optical input / output terminal is output from the second optical input / output terminal, and an optical signal input to the second optical input / output terminal is The optical signal output from the third optical input / output terminal and input to the third optical input / output terminal is output from the fourth optical input / output terminal, and the optical signal input to the fourth optical input / output terminal is A first optical circulator output from the first optical input / output terminal, one end of which is connected to a fourth optical input / output terminal of the first optical circulator, and an optical signal of a first wavelength is supplied along the way; A second optical fiber in which a first fiber grating that reflects light and a second fiber grating that reflects an optical signal of a third wavelength are formed, and one end of which is the third light of the first optical circulator; A third optical fiber connected to the input / output end, and one end of which is connected to the second optical fiber of the first optical circulator; A fourth optical fiber connected to the output end and optical signals of the second and fourth wavelengths are multiplexed, and the multiplexed optical signal is input to the other end of the second optical fiber; And an optical signal of the third wavelength is multiplexed, and the multiplexed optical signal is input to the other end of the third optical fiber.
A first optical filter for demultiplexing the optical signals of the fifth and sixth wavelengths output from the other end of the fourth optical fiber, wherein the second optical multiplexer / demultiplexer includes fifth to eighth optical filters. The optical signal input to the fifth optical input / output terminal is output from the sixth optical input / output terminal, and the optical signal input to the sixth optical input / output terminal is The optical signal output from the optical input / output terminal of the first optical input / output terminal and input to the seventh optical input / output terminal is output from the eighth optical input / output terminal, and the optical signal input to the eighth optical input / output terminal is output from the fifth optical input / output terminal. A second optical circulator output from the optical input / output end of the second optical circulator and one end thereof is connected to the sixth optical input / output end of the second optical circulator, and reflects an optical signal of the first wavelength on the way. A fifth optical fiber in which a third fiber grating and a fourth fiber grating reflecting an optical signal of a third wavelength are formed; A sixth optical fiber whose one end is connected to a seventh optical input / output terminal of the second optical circulator, and a sixth optical fiber whose one end is connected to an eighth optical input / output terminal of the second optical circulator. 7, the optical signals of the second and fourth wavelengths output from the other ends of the fifth optical fiber are demultiplexed, and the first and third optical fibers are output from the other ends of the sixth optical fiber. A second optical filter for demultiplexing an optical signal having a wavelength of?, Multiplexing optical signals having fifth and sixth wavelengths, and inputting the multiplexed optical signal to the other end of the seventh optical fiber; Wherein the first optical fiber connects the first optical input / output terminal of the first optical circulator and the fourth optical input / output terminal of the second optical circulator, and the first and second optical fibers pass through the first and second optical fibers. 2
Characterized in that the optical multiplexed signal propagates.

According to the twenty-ninth aspect, the twenty-fifth aspect is combined with the twenty-seventh aspect, and an optical multiplexed signal obtained by multiplexing optical signals of four different wavelengths by connecting a single optical fiber therebetween. And a bidirectional wavelength multiplex transmission system for transmitting an optical multiplex signal obtained by multiplexing optical signals of two different wavelengths.

A thirtieth invention is an invention according to the twenty-ninth invention, wherein the first and second optical filters have wavelengths −
The transmittance change characteristic is a middle range where the transmittance gradually changes from the cutoff region to the transmission region, a transmission region where the optical signal in the wavelength region is reflected, a transmission region where the optical signal in the wavelength region is transmitted. And the first and second and fifth wavelengths are arranged in a cut-off area of the first and second optical filters.
The third, fourth, and sixth wavelengths are arranged in transmission regions of the first and second optical filters.

According to the thirtieth aspect, by combining the twenty-sixth aspect with the twenty-eighth aspect, and connecting them with one optical fiber, two sets of optical signals having two different wavelengths close to each other are obtained. A bidirectional wavelength multiplex transmission system for propagating the multiplexed optical multiplexed signal and the optical multiplexed signal obtained by multiplexing the optical signals of two different wavelengths can be configured.

[0076]

(First Embodiment) FIG. 1 is a diagram showing an optical demultiplexer according to a first embodiment of the present invention. FIG. 1A is a circuit diagram showing a configuration of the optical demultiplexer, and FIG. 1B is a diagram showing wavelength characteristics of components constituting the optical demultiplexer and wavelength characteristics of an incident optical signal. FIG. 6 is a characteristic diagram showing the relationship of FIG. Hereinafter, the first embodiment will be described with reference to FIG.

In FIG. 1A, an optical demultiplexer according to the first embodiment has an optical fiber 10 on which an optical multiplexed signal is incident.
, An optical circulator 20, and optical collimators 40a-4
0c and an optical filter 50. Also,
Optical fibers 10a to 10d are connected to the above components, and a fiber grating 30 is formed on the optical fiber 10a.

Here, the optical circulator 20 has at least first to third optical input / output terminals. In this optical circulator 20, the optical signal input at the first optical input / output terminal becomes the optical signal output at the second optical input / output terminal, and the optical signal input at the second optical input / output terminal is the third optical input / output terminal. It has non-reciprocal light passing characteristics, which is an optical signal output at the output end. The optical circulator 20 includes an optical fiber 10 at a first optical input / output end, an optical fiber 10a at a second optical input / output end,
Optical fibers 10d are respectively connected to the third optical input / output terminals. The first to third light input / output terminals may be connected as described above using an optical circulator having four light input / output terminals.

The fiber grating 30 has a small and periodic change in the refractive index along the light propagation direction in the core portion of the optical fiber 10a. The fiber grating 30 has a characteristic of selectively reflecting only a signal having a wavelength equal to the above-described period of an optical signal propagating inside. Here, as shown in FIG. 1B, the fiber grating 30 is set to reflect an optical signal of the wavelength λ2.

Further, as shown in FIG. 1B, the wavelength-to-transmittance change characteristic of the optical filter 50 includes a cut-off region for reflecting an optical signal in the wavelength region and an optical signal in the wavelength region. It has a transmission region through which the light passes, and an intermediate region in which the transmittance gradually increases from the above-mentioned blocking region to the above-mentioned transmission region. Here, the optical filter 50 is a long-wavelength transmission filter having the wavelength λ2 as the intermediate range. In FIG. 1A, the optical filter 50 is configured such that parallel light is incident from an optical collimator 40a, parallel light passing through the optical filter 50 is incident on an optical collimator 40b, and parallel light reflected by the optical filter 50 is an optical collimator. 40c. Here, the optical collimator 40a converts the light emitted from the optical fiber 10a into parallel light, and
Has a function of converging the incident parallel light to the optical fibers 10b and 10c, respectively. When the light incident angle on the optical filter 50 is large, the wavelength characteristic changes between the P-polarized light and the S-polarized optical signal. Therefore, the incident angle on the optical filter 50 is set to 22.5 ° or less. Is desirable.

Next, the propagation of an optical signal in the first embodiment will be described. In FIG. 1A, an optical multiplex signal is incident on an optical fiber 10. Here, the optical multiplex signal has optical signals of three different wavelengths λ1 to λ3 that are close to each other, and each of the wavelengths λ1 to λ3 is
As shown in (b), λ1 <λ2 <λ3.
The optical multiplex signal is input to a first optical input / output terminal of the optical circulator 20 and is output from a second optical input / output terminal of the optical circulator 20. Next, the optical multiplex signal propagates through the optical fiber 10 a and enters the fiber grating 30. Since the fiber grating 30 has the characteristic of reflecting only the optical signal of the wavelength λ2 as described above, the optical signal of the wavelength λ2 is reflected and enters the second optical input / output end of the optical circulator 20. Then, the wavelength λ2
Is emitted from the third optical input / output end of the optical circulator 20, and propagates through the optical fiber 10d.

On the other hand, the optical multiplexed signal obtained by multiplexing the optical signals of the wavelengths λ1 and λ3 transmitted through the fiber grating 30 enters the optical collimator 40a and is converted into parallel light.
This parallel light enters the optical filter 50. As described above, the optical filter 50 is a long-wavelength transmission filter having the wavelength λ2 as the intermediate band, so that the optical signal of the wavelength λ1 is reflected and the optical signal of the wavelength λ3 is transmitted. As a result, the wavelength λ1
Is incident on the optical collimator 40c and the optical fiber 10c.
Propagate c. The optical signal having the wavelength λ3 enters the optical collimator 40b and propagates through the optical fiber 10b. That is, an optical multiplexed signal obtained by multiplexing optical signals of wavelengths λ1 to λ3 is
The light is demultiplexed for each wavelength and propagates through different optical fibers.

The optical collimators 40a to 40c used in the above embodiment need not be used. FIG.
FIG. 3 is an enlarged view showing an optical demultiplexing structure near an optical filter 51 when an optical collimator is not used. In FIG.
The end face of the optical fiber 10a is cut, and the optical fiber 10a is cut.
To form an inclined surface. Next, an optical filter 5 is provided on the inclined surface.
1 is brought close. Here, like the optical filter 50, the optical filter 51 is a long-wavelength transmission filter having the wavelength λ2 as the intermediate range. When the light incident angle on the optical filter 51 is large, the wavelength characteristic changes between the P-polarized light and the S-polarized optical signal, so that the incident angle on the optical filter 51 is 22.5.
It is desirable to set it to less than °. Thereafter, the other optical fibers 10b and 10c are connected to the optical filter 5 as shown in FIG.
The optical collimators 40a to 40a are arranged so that the optical signals that reflect the light 1 enter the optical fiber 10c and the optical signals that pass through the optical filter 51 enter the optical fiber 10b.
A similar function can be realized without 40c.

As described above, in the optical demultiplexer according to the first embodiment, of the optical multiplexed signals obtained by multiplexing three adjacent optical signals having different wavelengths, the optical signal located at the intermediate wavelength has a sharp cutoff band. The optical signal having the other wavelength is demultiplexed by the fiber grating 30, the optical signal having the other wavelength is separated by an interval, and the optical signal having the other wavelength is demultiplexed by using the optical filter 50 whose cutoff band is dull. Therefore, by using one optical circulator, one fiber grating, and one optical filter, it is possible to demultiplex an optical multiplexed signal obtained by multiplexing three adjacent optical signals having different wavelengths. As a result, the conventional Japanese Patent Laid-Open No. 09-2321 is disclosed.
In the first embodiment, two optical circulators, which were required in the optical demultiplexer disclosed in Japanese Patent Publication No. 0, can have the same demultiplexing function in the first embodiment. As mentioned earlier, optical circulators are made of expensive optical crystals,
The cost can be reduced by reducing the number used, and the insertion loss due to the optical circulator can also be reduced.

(Second Embodiment) Although the first embodiment has been described as a form used as an optical demultiplexer,
In the second embodiment, a mode used as an optical multiplexer with the same configuration as the first embodiment will be described. In addition,
FIG. 3A is a circuit diagram illustrating a configuration of an optical multiplexer according to a second embodiment, and FIG. 3B is a diagram illustrating the wavelength characteristics of components constituting the optical multiplexer and the wavelength of an emitted optical signal. FIG. 4 is a characteristic diagram showing a relationship with characteristics. Hereinafter, the second embodiment will be described with reference to FIG.

In FIG. 3, the second embodiment differs from the first embodiment only in the directions of input and output of each optical signal.
Since the component configuration and component characteristics are the same as those of the first embodiment, the same components are denoted by the same reference numerals, and detailed description thereof will be omitted.

Next, the propagation of an optical signal in the second embodiment will be described. In FIG. 3A, an optical signal having a wavelength λ2 is incident on the optical fiber 10. The optical signal having the wavelength λ2 enters the first optical input / output terminal of the optical circulator 20 and exits from the second optical input / output terminal of the optical circulator 20. Next, the optical signal of the wavelength λ2 propagates through the optical fiber 10a and enters the fiber grating 30. Since the fiber grating 30 has the characteristic of reflecting only the optical signal of the wavelength λ2 as described above, the optical signal of the wavelength λ2 is reflected and enters the second optical input / output end of the optical circulator 20. After that, the optical signal having the wavelength λ2 is emitted from the third optical input / output terminal of the optical circulator 20, and propagates through the optical fiber 10d.

On the other hand, optical signals of wavelengths λ1 and λ3 are incident from optical fibers 10c and 10b, respectively.
Next, the optical signals of the wavelengths λ1 and λ3 are converted into parallel lights by the optical collimators 40c and 40b, respectively, and are incident on the optical filter 50. Here, the optical filter 50 is
As described above, since the filter is a long wavelength transmission filter having the wavelength λ2 as the intermediate band, the optical signal having the wavelength λ1 is reflected and the wavelength λ1 is reflected.
The optical signal of No. 3 is transmitted. As a result, the optical signal of wavelength λ1 enters the optical collimator 40a, and the optical signal of wavelength λ3 also enters the optical collimator 40a. That is, the optical filter 50
Then, the optical signals of the wavelengths λ1 and λ3 are multiplexed. next,
The optical multiplexed signal obtained by multiplexing the multiplexed optical signals of the wavelengths λ1 and λ3 propagates through the optical fiber 10a and enters the fiber grating 30. Since the fiber grating 30 has the characteristic of reflecting only the optical signal of the wavelength λ2 as described above, the optical multiplexed signal obtained by multiplexing the optical signals of the wavelengths λ1 and λ3 is
And enters the second optical input / output end of the optical circulator 20. Thereafter, the optical multiplexed signal obtained by multiplexing the optical signals of the wavelengths λ1 and λ3 is emitted from the third optical input / output terminal of the optical circulator 20, and propagates through the optical fiber 10d. That is, from the optical fiber 10d, an optical multiplexed signal in which optical signals of three different wavelengths λ1 to λ3 close to each other are multiplexed is emitted.

In this embodiment, even if the optical collimators 40a to 40c are not used, if the optical demultiplexing structure near the optical filter 50 is changed to the structure shown in FIG. It goes without saying that the present invention can be similarly applied.

As described above, in the second embodiment, an optical multiplexer can be realized by changing the input / output direction of the optical signal with the same structure as the optical demultiplexer in the first embodiment.

Further, the optical demultiplexer according to the first embodiment and the optical multiplexer according to the second embodiment may be combined. By using the optical demultiplexer as the receiving side and the optical multiplexer as the transmitting side, a one-way WDM transmission system can be configured. Hereinafter, the one-way WDM transmission system will be described.

FIG. 4 is a circuit diagram showing the configuration of the one-way wavelength multiplex transmission system. In the one-way wavelength multiplex transmission system, the optical multiplexer 1 in the second embodiment is the optical transmitter side, the optical demultiplexer 2 in the first embodiment is the optical receiver side, and both are optical fibers. The system is connected by 90. Here, the internal configuration of the optical multiplexer 1 and the propagation of the optical signal are the same as those in the second embodiment, and the internal configuration of the optical demultiplexer 2 and the propagation of the optical signal are also the same. Since this is the same as the first embodiment, a detailed description thereof will be omitted.

In FIG. 4, an optical fiber 90 is provided as a transmission line for performing optical wavelength multiplex transmission from the optical multiplexer 1 to the optical demultiplexer 2. One end of the optical fiber 90 is connected to the optical circulator 20 included in the optical multiplexer 1.
a is connected to the third optical input / output terminal. The other end of the optical fiber 90 is connected to a first optical input / output terminal of the optical circulator 20b included in the optical demultiplexer 2.

Next, propagation of an optical signal in the one-way wavelength multiplex transmission system will be described. In the optical multiplexer 1, as in the second embodiment, optical signals of three different wavelengths λ1 to λ3 close to each other are multiplexed to form an optical multiplexed signal. The optical multiplex signal is supplied to the optical circulator 20a.
Out of the third optical input / output end and propagates through the optical fiber 90. Next, the optical multiplexed signal propagated through the optical fiber 90 is supplied to the optical circulator 20 b of the optical demultiplexer 2.
At the first optical input / output end. The optical multiplexed signal incident on the optical demultiplexer 2 is demultiplexed for each wavelength, and propagates through different optical fibers, similarly to the first embodiment.

As described above, by combining the optical demultiplexer according to the first embodiment and the optical multiplexer according to the second embodiment, optical signals of three different wavelengths close to each other are multiplexed. A one-way wavelength multiplex transmission system for propagating an optical multiplex signal can be configured.

(Third Embodiment) FIG. 5 shows a third embodiment of the present invention.
It is a figure which shows the optical demultiplexer which concerns on embodiment. FIG.
FIG. 5A is a circuit diagram showing a configuration of the optical demultiplexer, and FIG.
(B) is a characteristic diagram showing the relationship between the wavelength characteristics of components constituting the optical demultiplexer and the wavelength characteristics of an incident optical signal.
Hereinafter, the third embodiment will be described with reference to FIG.

In FIG. 5A, an optical demultiplexer according to the third embodiment has an optical fiber 10 on which an optical multiplexed signal is incident.
, An optical circulator 20, and optical collimators 40a-4
0f and an optical filter 50. Also,
Optical fibers 10a to 10f are connected to the above components, and fiber gratings 30a and 30b are formed on the optical fiber 10a.

Here, the optical circulator 20 has at least first to third optical input / output terminals. In this optical circulator 20, the optical signal input at the first optical input / output terminal becomes the optical signal output at the second optical input / output terminal, and the optical signal input at the second optical input / output terminal is the third optical input / output terminal. It has non-reciprocal light passing characteristics, which is an optical signal output at the output end. The optical circulator 20 includes an optical fiber 10 at a first optical input / output end, an optical fiber 10a at a second optical input / output end,
Optical fibers 10b are connected to the third optical input / output terminals, respectively. The first to third light input / output terminals may be connected as described above using an optical circulator having four light input / output terminals.

The fiber gratings 30a and 30b have a small and periodic change in the refractive index along the light propagation direction in the core of the optical fiber 10a. The fiber gratings 30a and 30a
0b has a characteristic of selectively reflecting only those optical signals whose wavelengths are equal to the above-mentioned period. Here, as shown in FIG. 5B, the fiber grating 30a is set to reflect the optical signal of the wavelength λ2, and the fiber grating 30b is set to reflect the optical signal of the wavelength λ4.

As shown in FIG. 5 (b), the wavelength-transmittance change characteristic of the optical filter 50 includes a cut-off region for reflecting an optical signal in the wavelength region and an optical signal in the wavelength region. It has a transmission region through which the light passes, and an intermediate region in which the transmittance gradually increases from the above-mentioned blocking region to the above-mentioned transmission region. Here, the optical filter 50 is a long-wavelength transmission filter having the wavelength between the wavelengths λ2 and λ3 as the intermediate range. In FIG. 5A, the optical filter 50 receives parallel light from the optical collimators 40a and 40b, and transmits the parallel light passing through the optical filter 50 to the optical collimator 40c.
And 40d, and are arranged such that the parallel light reflected by the optical filter 50 is incident on the optical collimators 40e and 40f, respectively. Here, the optical collimators 40a and 40b convert the light emitted from the optical fibers 10a and 10b into parallel light, respectively.
Are the optical fibers 10c to 10c
It has a function of converging to f. When the light incident angle on the optical filter 50 is large, the wavelength characteristic changes between the P-polarized light and the S-polarized optical signal.
It is desirable to set the incident angle to 0 to 22.5 ° or less.

Next, propagation of an optical signal in the third embodiment will be described. In FIG. 5A, an optical multiplex signal is incident on an optical fiber 10. Here, the optical multiplex signal has two different wavelengths λ1 and λ2 close to each other.
And optical signals of two different wavelengths λ3 and λ4 which are close to each other, and each wavelength is shown in FIG.
As shown in FIG. 7, λ1 <λ2≪λ3 <λ4.
The optical multiplex signal is input to a first optical input / output terminal of the optical circulator 20 and is output from a second optical input / output terminal of the optical circulator 20. Next, the optical multiplex signal propagates through the optical fiber 10a and enters the fiber grating 30a. Since the fiber grating 30a has the characteristic of reflecting only the optical signal of the wavelength λ2 as described above, the optical signal of the wavelength λ2 is reflected and enters the second optical input / output terminal of the optical circulator 20. Then, the wavelengths λ1, λ3, λ that have passed through the fiber grating 30a
The optical multiplexed signal obtained by multiplexing the four optical signals enters the fiber grating 30b. Since the fiber grating 30b has the characteristic of reflecting only the optical signal of the wavelength λ4 as described above, the optical signal of the wavelength λ4 is reflected and passes through the fiber grating 30a. Incident on the optical input / output end of.

The optical signals of wavelengths λ2 and λ4 incident on the second optical input / output terminal of the optical circulator 20 are emitted from the third optical input / output terminal of the optical circulator 20, and propagate through the optical fiber 10b. Thereafter, the optical signals of the wavelengths λ2 and λ4 are incident on the optical collimator 40b and are converted into parallel light. This parallel light enters the optical filter 50. As described above, the optical filter 50 is a long-wavelength transmission filter having the wavelength between the wavelengths λ2 and λ3 as the intermediate band, so that the optical signal of the wavelength λ2 is reflected and the optical signal of the wavelength λ4 is transmitted. . As a result, the optical signal of the wavelength λ2 enters the optical collimator 40f and propagates through the optical fiber 10f, and the optical signal of the wavelength λ4 enters the optical collimator 40d and propagates through the optical fiber 10d.

On the other hand, the optical multiplexed signal obtained by multiplexing the optical signals of the wavelengths λ1 and λ3 transmitted through the fiber gratings 30a and 30b enters the optical collimator 40a and is converted into parallel light. This parallel light enters the optical filter 50. The optical filter 50 has the wavelength λ2 and the wavelength λ
Since the filter is a long-wavelength transmission filter having a wavelength between the wavelengths 3 and 3 as the intermediate band, the optical signal of the wavelength λ1 is reflected and the optical signal of the wavelength λ3 is transmitted. As a result, the optical signal of the wavelength λ1 is incident on the optical collimator 40e and propagates through the optical fiber 10e.
The optical signal having the wavelength λ3 is incident on the optical collimator 40c and propagates through the optical fiber 10c. That is, the wavelength λ1
An optical multiplexed signal obtained by multiplexing the optical signals of .lambda..about..lambda.4 is demultiplexed for each wavelength and propagates through different optical fibers.

Note that the optical collimators 40a to 40f used in the above embodiment need not be used. FIG.
FIG. 3 is an enlarged view showing an optical demultiplexing structure near an optical filter 51 when an optical collimator is not used. In FIG.
The optical demultiplexing structure is a structure in which the above-described optical demultiplexing structures of FIG. 2 are arranged in parallel. The end faces of the optical fibers 10a and 10b are cut, and the optical fibers 10a and 10b are respectively cut.
b. An inclined surface is formed. Next, the optical filters 51 are brought close to the respective inclined surfaces. Here, the optical filter 51
Is a long-wavelength transmission filter having a wavelength between the wavelengths λ2 and λ3 as the above-mentioned intermediate band, similarly to the optical filter 50. When the light incident angle on the optical filter 51 is large,
Since the wavelength characteristics change between the P-polarized light signal and the S-polarized light signal, it is desirable to set the angle of incidence on the optical filter 51 to 22.5 ° or less. Then, the other optical fibers 10c-1
0f, the optical signal reflected by the optical filter 51 is incident on the optical fibers 10e and 10f, respectively, as shown in FIG.
If the optical signals passing through the optical filter 51 are brought close to each other so as to enter the optical fibers 10c and 10d, the same function can be realized without the optical collimators 40a to 40f.

As described above, in the optical demultiplexer according to the third embodiment, an optical multiplexed signal obtained by multiplexing optical signals of adjacent wavelengths is demultiplexed by the fiber grating having a sharp cutoff band, and the wavelength interval of the optical signal is reduced. The optical signal is demultiplexed using an optical filter that is open and has a dull cut-off area. Therefore, by using one optical circulator, two fiber gratings, and one optical filter, an optical multiplexed signal obtained by multiplexing two sets of optical signals of two wavelengths close to each other can be demultiplexed. As a result, an optical circulator that required three optical demultiplexers disclosed in the conventional Japanese Patent Application Laid-Open No. 09-23210 was
In the third embodiment, one can have a similar demultiplexing function. As described above, since the optical circulator is made of an expensive optical crystal, the cost can be reduced by reducing the number of used optical circulators, and the insertion loss due to the optical circulator can also be reduced. Furthermore, since two systems of optical multiplexed signals are demultiplexed by one optical filter, insertion loss due to an increase in channels can be prevented, and the cost of parts can be reduced.

(Fourth Embodiment) In the third embodiment described above, the mode used as an optical demultiplexer has been described. An embodiment used as a container will be described. FIG. 7A is a circuit diagram showing a configuration of an optical multiplexer according to a fourth embodiment, and FIG. 7B is a diagram showing wavelength characteristics of components constituting the optical multiplexer and an optical signal to be emitted. FIG. 4 is a characteristic diagram showing a relationship with a wavelength characteristic. Hereinafter, with reference to FIG.
An embodiment will be described.

In FIG. 7A, in the fourth embodiment, the direction of the light passage characteristic of the optical circulator 20 is described in reverse, as compared with FIG. 5A used in the description of the third embodiment. ing. This is for the purpose of simplifying the comparison with the third embodiment, and means that the optical input / output end of the optical circulator 20 to which the optical fibers 10a and 10b are connected has changed. In the third embodiment, the optical circulator 20 includes an optical fiber 10 at a first optical input / output end.
However, the optical fiber 10a was connected to the second optical input / output terminal, and the optical fiber 10b was connected to the third optical input / output terminal. However, in the fourth embodiment, the optical fiber 10b is provided at the first optical input / output end, and the optical fiber 1 is provided at the second optical input / output end.
The optical fiber 0a is connected to the third optical input / output terminal. That is, in the fourth embodiment, the third
In this embodiment, the optical input / output terminals of the optical circulator 20 to which the optical fibers 10 and 10b are connected are replaced. Otherwise, the component configuration and component characteristics are the same as those of the third embodiment.

Next, propagation of an optical signal in the fourth embodiment will be described. In FIG. 7A, optical signals of wavelengths λ1 and λ3 are incident from optical fibers 10e and 10c, respectively. Next, the optical signals of the wavelengths λ1 and λ3 are converted into parallel lights by the optical collimators 40e and 40c, respectively, and enter the optical filter 50. Here, the optical filter 50 has the wavelength λ2 and the wavelength λ as described above.
Since the filter is a long-wavelength transmission filter having a wavelength between the wavelengths 3 and 3 as the intermediate band, the optical signal of the wavelength λ1 is reflected and the optical signal of the wavelength λ3 is transmitted. As a result, the optical signal of wavelength λ1 enters the optical collimator 40a, and the optical signal of wavelength λ3 also enters the optical collimator 40a. That is, the optical filter 50
Then, the optical signals of the wavelengths λ1 and λ3 are multiplexed. next,
An optical multiplexed signal obtained by multiplexing the multiplexed optical signals of wavelengths λ1 and λ3 propagates through the optical fiber 10a and enters the fiber grating 30b. Since the fiber grating 30b has a characteristic of reflecting only the optical signal of the wavelength λ4 as described above, the optical multiplexed signal obtained by multiplexing the optical signals of the wavelengths λ1 and λ3 passes through the fiber grating 30b. Thereafter, the optical multiplexed signal obtained by multiplexing the optical signals of the wavelengths λ1 and λ3 propagates through the optical fiber 10a and enters the fiber grating 30a. The fiber grating 30a has the wavelength λ as described above.
Since the optical multiplexed signal has the characteristic of reflecting only the optical signal of the optical circulator 20, the optical multiplexed signal obtained by multiplexing the optical signals of the wavelengths λ1 and λ3 also passes through the fiber grating 30a, and Incident. After that, the wavelength λ1
The optical multiplexed signal obtained by multiplexing the optical signals having the wavelengths of λ and λ 3 is emitted from the third optical input / output terminal of the optical circulator 20 and propagates through the optical fiber 10.

On the other hand, optical signals of wavelengths λ2 and λ4 are incident from optical fibers 10f and 10d, respectively.
Next, the optical signals of the wavelengths λ2 and λ4 are converted into parallel lights by the optical collimators 40f and 40d, respectively, and enter the optical filter 50. Here, the optical filter 50 is
As described above, since the long wavelength transmission filter has the wavelength between the wavelengths λ2 and λ3 as the intermediate band, the optical signal of the wavelength λ2 is reflected and the optical signal of the wavelength λ4 is transmitted. As a result, the optical signal of the wavelength λ2 enters the optical collimator 40b,
Further, an optical signal having a wavelength λ4 also enters the optical collimator 40b. That is, in the optical filter 50, the wavelengths λ2 and λ4
Are multiplexed. Next, an optical multiplexed signal obtained by multiplexing the multiplexed optical signals of wavelengths λ2 and λ4 is
0b, and is incident on the first optical input / output terminal of the optical circulator 20. Thereafter, an optical multiplexed signal obtained by multiplexing the optical signals of the wavelengths λ2 and λ4 is emitted from the second optical input / output terminal of the optical circulator 20. Next, wavelengths λ2 and λ4
The optical multiplexed signal obtained by multiplexing the optical signals is propagated through the optical fiber 10a and enters the fiber grating 30a. Since the fiber grating 30a has a characteristic of reflecting only the optical signal of the wavelength λ2 as described above,
The optical signal having the wavelength λ2 is reflected and made incident on the second optical input / output terminal of the optical circulator 20.

On the other hand, the optical signal of wavelength λ4 that has passed through the fiber grating 30a is
0b. This fiber grating 30b
Has the characteristic of reflecting only the optical signal of wavelength λ4 as described above, so that the optical signal of wavelength λ4 is reflected and passes through the fiber grating 30a, and then the second optical input / output terminal of the optical circulator 20. Is incident on. That is, the optical signals of the wavelengths λ2 and λ4 are both
0 is input to the second light input / output terminal. Then, the wavelength λ2
The optical multiplexed signal obtained by multiplexing the optical signals of λ and λ 4 is emitted from the third optical input / output terminal of the optical circulator 20 and propagates through the optical fiber 10. As a result, an optical multiplexed signal obtained by multiplexing optical signals of wavelengths λ1 to λ4 is emitted from the optical fiber 10.

In this embodiment, even if the optical collimators 40a to 40f are not used, if the optical demultiplexing structure near the optical filter 50 is changed to the structure shown in FIG. It goes without saying that the present invention can be similarly applied.

As described above, in the fourth embodiment, an optical multiplexer is realized by changing the connection port of the optical circulator 20 of the optical demultiplexer in the third embodiment and changing the input / output direction of the optical signal. can do.

Further, the optical demultiplexer according to the third embodiment and the optical multiplexer according to the fourth embodiment may be combined. By using the optical demultiplexer as the receiving side and the optical multiplexer as the transmitting side, a one-way WDM transmission system can be configured. Hereinafter, the one-way WDM transmission system will be described.

FIG. 8 is a circuit diagram showing a configuration of the one-way wavelength multiplex transmission system. In the one-way wavelength division multiplexing transmission system, the optical multiplexer 1 in the fourth embodiment is the optical transmitter side, the optical demultiplexer 2 in the third embodiment is the optical receiver side, and both are optical fiber. The system is connected by 90. Here, the configuration of the components inside the optical multiplexer 1 and the propagation of the optical signal are the same as in the fourth embodiment, and the configuration of the components inside the optical demultiplexer 2 and the propagation of the optical signal are also the same. Since this is the same as the third embodiment, a detailed description thereof will be omitted.

In FIG. 8, an optical fiber 90 is provided as a transmission line for performing optical wavelength multiplex transmission from the optical multiplexer 1 to the optical demultiplexer 2. One end of the optical fiber 90 is connected to the optical circulator 20 included in the optical multiplexer 1.
a is connected to the third optical input / output terminal. The other end of the optical fiber 90 is connected to a first optical input / output terminal of the optical circulator 20b included in the optical demultiplexer 2.

Next, propagation of an optical signal in the one-way WDM transmission system will be described. In FIG.
In the optical multiplexer 1, as in the fourth embodiment, optical signals of two different wavelengths λ1 and λ2 close to each other and two different wavelengths λ3 and λ4 close to each other are multiplexed, and an optical multiplexed signal is obtained. Becomes The optical multiplexed signal is emitted from the third optical input / output terminal of the optical circulator 20 a and propagates through the optical fiber 90. Next, the optical multiplexed signal propagated through the optical fiber 90 is incident on the first optical input / output terminal of the optical circulator 20b included in the optical demultiplexer 2. The optical multiplexed signal incident on the optical demultiplexer 2 is demultiplexed for each wavelength, as in the third embodiment, and propagates through different optical fibers.

As described above, by combining the optical demultiplexer according to the third embodiment and the optical multiplexer according to the fourth embodiment, two sets of optical signals of two wavelengths close to each other are obtained. A one-way wavelength multiplex transmission system for propagating the multiplexed optical multiplex signal can be configured.

(Fifth Embodiment) FIG. 9 shows a fifth embodiment of the present invention.
It is a figure which shows the optical demultiplexer which concerns on embodiment. Note that FIG.
FIG. 9A is a circuit diagram showing a configuration of the optical demultiplexer, and FIG.
(B) is a characteristic diagram showing the relationship between the wavelength characteristics of components constituting the optical demultiplexer and the wavelength characteristics of an incident optical signal.
Hereinafter, the fifth embodiment will be described with reference to FIG.

In FIG. 9A, an optical demultiplexer according to the fifth embodiment has an optical fiber 10 on which an optical multiplexed signal is incident.
, An optical circulator 20, and optical collimators 40a-4
0c and an optical filter 50. Also,
Optical fibers 10a to 10e are connected to the above components, and fiber gratings 30a and 30b are formed on the optical fiber 10a. A fiber grating 30c is formed on the optical fiber 10d.

Here, the optical circulator 20 comprises
It has a fourth light input / output terminal. In this optical circulator 20, the optical signal input of the first optical input / output terminal becomes the optical signal output of the second optical input / output terminal, and the optical signal input of the second optical input / output terminal is the third optical input / output terminal. The optical signal output of the third optical input / output terminal becomes the optical signal output of the fourth optical input / output terminal, and the optical signal input of the fourth optical input / output terminal becomes the first optical input / output terminal. It has non-reciprocal light passing characteristics, which is an optical signal output at the output end. The optical circulator 20 has an optical fiber 10 at a first optical input / output end, an optical fiber 10a at a second optical input / output end, an optical fiber 10d at a third optical input / output end, and a fourth optical input / output end. Optical fibers 10e are connected to the input and output terminals, respectively.

The fiber gratings 30a to 30a-3
0c has a minute and periodic change in the refractive index along the light propagation direction in the core portions of the optical fibers 10a and 10d. This fiber grating 30
Reference numerals a to 30c each have a characteristic of selectively reflecting only a signal whose wavelength is equal to the above-described period of an optical signal propagating inside. Here, as shown in FIG. 9B, the fiber gratings 30a and 30c are both set so as to reflect the optical signal of the wavelength λ2.
The fiber grating 30b is set so as to reflect an optical signal of wavelength λ4.

Further, as shown in FIG. 9B, the wavelength-to-transmittance change characteristic of the optical filter 50 includes a cut-off region for reflecting an optical signal in the wavelength region and an optical signal in the wavelength region. It has a transmission region through which the light passes, and an intermediate region in which the transmittance gradually increases from the above-mentioned blocking region to the above-mentioned transmission region. Here, the optical filter 50 is a long-wavelength transmission filter having the wavelength λ2 as the intermediate range. In FIG. 9A, the optical filter 50 is configured such that parallel light is incident from an optical collimator 40a, parallel light passing through the optical filter 50 is incident on an optical collimator 40b, and parallel light reflected from the optical filter 50 is an optical collimator. 40c. Here, the optical collimator 40a converts the light emitted from the optical fiber 10a into parallel light, and
Converts the incident parallel light into the optical fiber 10 respectively.
b and 10c.
When the light incident angle on the optical filter 50 is large, the wavelength characteristic changes between the P-polarized light and the S-polarized optical signal.
The angle of incidence on the optical filter 50 is desirably set to 22.5 ° or less.

Next, the propagation of an optical signal in the fifth embodiment will be described. In FIG. 9A, an optical multiplex signal is incident on an optical fiber 10. Here, the optical multiplex signal has optical signals of four different wavelengths λ1 to λ4 close to each other, and the respective wavelengths are λ1 <λ2 <λ3 <λ4, as shown in FIG. 9B. It has become. The optical multiplex signal is input to a first optical input / output terminal of the optical circulator 20 and is output from a second optical input / output terminal of the optical circulator 20. Next, the optical multiplex signal propagates through the optical fiber 10a and enters the fiber grating 30a. Since the fiber grating 30a has a characteristic of reflecting only the optical signal of the wavelength λ2 as described above, the optical signal of the wavelength λ2 is reflected and the optical circulator 2a is reflected.
0 enters the second optical input / output terminal. Thereafter, the optical multiplexed signal obtained by multiplexing the optical signals of the wavelengths λ1, λ3, λ4 that has passed through the fiber grating 30a enters the fiber grating 30b. This fiber grating 30
b has the characteristic of reflecting only the optical signal of the wavelength λ4 as described above, so that the optical signal of the wavelength λ4 is reflected and passes through the fiber grating 30a. Light enters the output end.

The optical signals of wavelengths λ2 and λ4 incident on the second optical input / output terminal of the optical circulator 20 are emitted from the third optical input / output terminal of the optical circulator 20, propagate through the optical fiber 10d, and The light enters the grating 30c. Since the fiber grating 30c has the characteristic of reflecting only the optical signal of the wavelength λ2 as described above, the optical signal of the wavelength λ2 is reflected and enters the third optical input / output terminal of the optical circulator 20. Thereafter, the optical signal of wavelength λ4 transmitted through the fiber grating 30c propagates through the optical fiber 10d. The optical signal of wavelength λ2 that has entered the third optical input / output terminal of the optical circulator 20 is emitted from the fourth optical input / output terminal of the optical circulator 20 and propagates through the optical fiber 10e.

On the other hand, the optical multiplexed signal obtained by multiplexing the optical signals of the wavelengths λ1 and λ3 transmitted through the fiber gratings 30a and 30b enters the optical collimator 40a and is converted into parallel light. This parallel light enters the optical filter 50. As described above, the optical filter 50 is a long-wavelength transmission filter having the wavelength λ2 as the intermediate band, so that the optical signal of the wavelength λ1 is reflected and the optical signal of the wavelength λ3 is transmitted. As a result, the optical signal of the wavelength λ1 enters the optical collimator 40c and propagates through the optical fiber 10c, and the optical signal of the wavelength λ3 enters the optical collimator 40b and propagates through the optical fiber 10b. That is, an optical multiplexed signal obtained by multiplexing optical signals of wavelengths λ1 to λ4 is demultiplexed for each wavelength and propagates through different optical fibers.

In this embodiment, even if the optical collimators 40a to 40c are not used, if the optical demultiplexing structure near the optical filter 50 is changed to the structure shown in FIG. It goes without saying that the present invention can be similarly applied.

As described above, in the optical demultiplexer according to the fifth embodiment, the wavelengths to be demultiplexed are four different wavelengths, all of which are close to the wavelength of the optical multiplexed signal according to the third embodiment. It is. Therefore, an optical signal of one of the wavelengths located in the middle is demultiplexed by a fiber grating, and then demultiplexed by an optical filter having that wavelength as an intermediate band. Further, since the optical signal of the above wavelength cannot enter the optical filter, it is independently emitted from the third or fourth optical input / output terminal of the optical circulator. In this way, an optical multiplexed signal obtained by multiplexing four adjacent optical signals having different wavelengths is demultiplexed by a fiber grating having a sharp cut-off band, and the optical signal is separated by a wavelength filter and an optical filter having a dull cut-off band is used. The optical signals of other wavelengths are demultiplexed. Therefore, by using one optical circulator, three fiber gratings, and one optical filter, an optical multiplexed signal in which four different wavelengths adjacent to each other are multiplexed can be demultiplexed. As a result, in the fifth embodiment, one optical circulator required in the conventional optical demultiplexer disclosed in Japanese Patent Application Laid-Open No. 09-23210 can be provided with the same demultiplexing function by one in the fifth embodiment. It is. As described above, since the optical circulator is made of an expensive optical crystal, the cost can be reduced by reducing the number of used optical circulators, and the insertion loss due to the optical circulator can also be reduced.

(Sixth Embodiment) In the fifth embodiment, the mode used as an optical demultiplexer has been described. An embodiment used as a container will be described. FIG. 10A is a circuit diagram showing a configuration of an optical multiplexer according to the sixth embodiment, and FIG. 10B is a diagram showing wavelength characteristics of components constituting the optical multiplexer and an output optical signal. FIG. 4 is a characteristic diagram showing a relationship with a wavelength characteristic. Hereinafter, the sixth embodiment will be described with reference to FIG.

In FIG. 10A, in the sixth embodiment, the direction of the light passing characteristic of the optical circulator 20 is described in reverse, as compared with FIG. 9A used in the description of the fifth embodiment. ing. This is for the purpose of simplifying the comparison with the fifth embodiment, and means that the optical input / output end of the optical circulator 20 to which the optical fibers 10a and 10e are connected has changed. In the fifth embodiment, the optical circulator 20 includes an optical fiber 10 at a first optical input / output end.
However, the optical fiber 10a was connected to the second optical input / output terminal, the optical fiber 10d was connected to the third optical input / output terminal, and the optical fiber 10e was connected to the fourth optical input / output terminal. However, in the sixth embodiment, the optical fiber 10 is connected to the first optical input / output end.
However, an optical fiber 10e is connected to the second optical input / output terminal, an optical fiber 10d is connected to the third optical input / output terminal, and an optical fiber 10a is connected to the fourth optical input / output terminal. That is,
In the sixth embodiment, the optical fiber 10 according to the fifth embodiment is used.
Optical circulator 20 to which a and 10e were connected
Means that the optical input / output terminals of the above have been replaced. Otherwise, the component configuration and component characteristics are the same as those of the fifth embodiment, and thus the same components are denoted by the same reference characters and detailed description thereof will not be repeated.

Next, the propagation of an optical signal in the sixth embodiment will be described. In FIG. 10A, the wavelength λ1
And λ3 are input from the optical fibers 10c and 10b, respectively. Next, the optical signals of the wavelengths λ1 and λ3 are converted into parallel lights by the optical collimators 40c and 40b, respectively, and are incident on the optical filter 50. Here, since the optical filter 50 is a long-wavelength transmission filter having the wavelength λ2 as the intermediate region as described above, the wavelength λ1
Is reflected, and the optical signal of wavelength λ3 is transmitted. As a result, the optical signal of wavelength λ1 enters the optical collimator 40a, and the optical signal of wavelength λ3 also enters the optical collimator 40a. That is, the optical signals of the wavelengths λ1 and λ3 are multiplexed by the optical filter 50. Next, the multiplexed wavelength λ1
An optical multiplexed signal obtained by multiplexing the optical signals of λ3 and λ3 propagates through the optical fiber 10a and enters the fiber grating 30b. Since the fiber grating 30b has a characteristic of reflecting only the optical signal of the wavelength λ4 as described above, the optical multiplexed signal obtained by multiplexing the optical signals of the wavelengths λ1 and λ3 passes through the fiber grating 30b.
Thereafter, the optical multiplexed signal obtained by multiplexing the optical signals of the wavelengths λ1 and λ3 propagates through the optical fiber 10a and enters the fiber grating 30a. Since the fiber grating 30a has a characteristic of reflecting only the optical signal of the wavelength λ2 as described above, the optical multiplexed signal obtained by multiplexing the optical signals of the wavelengths λ1 and λ3 is
Oa also passes through and enters the fourth optical input / output terminal of the optical circulator 20. Thereafter, the optical multiplexed signal obtained by multiplexing the optical signals of the wavelengths λ1 and λ3 is emitted from the first optical input / output terminal of the optical circulator 20 and propagates through the optical fiber 10.

On the other hand, the optical signal of wavelength λ4 is
0d is incident. Next, the optical signal of the wavelength λ4 propagates through the optical fiber 10d, and the fiber grating 30c
Incident on. Since the fiber grating 30c has the characteristic of reflecting only the optical signal of the wavelength λ2 as described above, the optical signal of the wavelength λ4 is transmitted. afterwards,
The optical signal having the wavelength λ4 propagates through the optical fiber 10d, enters the third optical input / output terminal of the optical circulator 20, and exits from the fourth optical input / output terminal. Next, the optical signal of wavelength λ4 is
Propagating through the optical fiber 10a, the fiber grating 3
0a. This fiber grating 30a
Has the characteristic of reflecting only the optical signal of the wavelength λ2 as described above, so that the optical signal of the wavelength λ4 is transmitted. The optical signal of wavelength λ4 that has passed through the fiber grating 30a enters the fiber grating 30b. Since the fiber grating 30b has a characteristic of reflecting only the optical signal of the wavelength λ4 as described above, the optical signal of the wavelength λ4 is reflected,
After passing through Oa, the light enters the fourth light input / output terminal of the optical circulator 20. After that, the optical signal of the wavelength λ4 is emitted from the first optical input / output terminal of the optical circulator 20, and propagates through the optical fiber 10.

On the other hand, the optical signal of wavelength λ2 is
0e. Next, the optical signal of the wavelength λ2 propagates through the optical fiber 10e and enters the second optical input / output terminal of the optical circulator 20. Then, the optical signal of wavelength λ2 is
The light is emitted from the third light input / output end of the optical circulator 20. Next, the optical signal having the wavelength λ2 propagates through the optical fiber 10d and enters the fiber grating 30c. Since the fiber grating 30c has the characteristic of reflecting only the optical signal of the wavelength λ2 as described above, the optical signal of the wavelength λ2 is reflected and made incident on the third optical input / output terminal of the optical circulator 20. You.

Thereafter, the optical signal having the wavelength λ2 that has entered the third optical input / output terminal of the optical circulator 20 is emitted from the fourth optical input / output terminal of the optical circulator 20. next,
The optical signal having the wavelength λ2 propagates through the optical fiber 10a and enters the fiber grating 30a. Since the fiber grating 30a has the characteristic of reflecting only the optical signal of the wavelength λ2 as described above, the optical signal of the wavelength λ2 is reflected and is incident on the fourth optical input / output terminal of the optical circulator 20. You. After that, the optical signal of the wavelength λ2 is emitted from the first optical input / output terminal of the optical circulator 20 and propagates through the optical fiber 10. As a result, an optical multiplexed signal obtained by multiplexing optical signals of wavelengths λ1 to λ4 is emitted from the optical fiber 10.

In this embodiment, even if the optical collimators 40a to 40c are not used, if the optical demultiplexing structure near the optical filter 50 is changed to the structure shown in FIG. It goes without saying that the present invention can be similarly applied.

As described above, in the sixth embodiment, an optical multiplexer is realized by changing the connection port of the optical circulator 20 of the optical demultiplexer in the fifth embodiment and changing the input / output direction of the optical signal. can do.

Further, the optical demultiplexer according to the fifth embodiment may be combined with the optical multiplexer according to the sixth embodiment. By using the optical demultiplexer as the receiving side and the optical multiplexer as the transmitting side, a one-way WDM transmission system can be configured. Hereinafter, the one-way WDM transmission system will be described.

FIG. 11 is a circuit diagram showing the configuration of the one-way wavelength multiplex transmission system. In the one-way wavelength division multiplexing transmission system, the optical multiplexer 1 in the sixth embodiment is on the optical transmitter side, the optical demultiplexer 2 in the fifth embodiment is on the optical receiver side, and both are optical fibers. The system is connected by 90. Here, the configuration of the components inside the optical multiplexer 1 and the propagation of the optical signal are the same as those in the sixth embodiment, and the configuration of the components inside the optical demultiplexer 2 and the propagation of the optical signal are also the same. Since this is the same as the fifth embodiment, a detailed description thereof will be omitted.

In FIG. 11, an optical fiber 90 is provided as a transmission line for performing optical wavelength multiplex transmission from the optical multiplexer 1 to the optical demultiplexer 2. One end of the optical fiber 90 is connected to the optical circulator 2 included in the optical multiplexer 1.
0a is connected to the first optical input / output terminal. The other end of the optical fiber 90 is connected to a first optical input / output terminal of the optical circulator 20b included in the optical demultiplexer 2.

Next, propagation of an optical signal in the one-way wavelength multiplex transmission system will be described. 11, in the optical multiplexer 1, as in the sixth embodiment, optical signals of four different wavelengths λ1 to λ4 close to each other are multiplexed to form an optical multiplexed signal. The optical multiplexed signal is emitted from the first optical input / output terminal of the optical circulator 20 a and propagates through the optical fiber 90. Next, the optical multiplexed signal propagated through the optical fiber 90 is incident on the first optical input / output terminal of the optical circulator 20b included in the optical demultiplexer 2. The optical multiplexed signal incident on the optical demultiplexer 2 is demultiplexed for each wavelength, and propagates through different optical fibers, similarly to the fifth embodiment.

As described above, by combining the optical demultiplexer according to the fifth embodiment with the optical multiplexer according to the sixth embodiment, four adjacent optical signals having different wavelengths are multiplexed. A one-way wavelength multiplex transmission system for propagating an optical multiplex signal can be configured.

(Seventh Embodiment) FIG. 12 is a view showing an optical demultiplexer according to a seventh embodiment of the present invention. FIG. 12A is a circuit diagram showing a configuration of the optical demultiplexer.
FIG. 12B is a characteristic diagram showing the relationship between the wavelength characteristics of components constituting the optical demultiplexer and the wavelength characteristics of an incident optical signal. Hereinafter, the seventh embodiment will be described with reference to FIG.

In FIG. 11A, an optical demultiplexer according to the seventh embodiment has an optical fiber 10 on which an optical multiplexed signal is incident.
, An optical circulator 20, and optical collimators 40a-4
0f and an optical filter 50. Also,
Optical fibers 10a to 10g are connected to the above components, and fiber gratings 30a to 30c are formed on the optical fiber 10a. Optical fiber 1
A fiber grating 30d is formed on 0b.

Here, the optical circulator 20 includes
It has a fourth light input / output terminal. In this optical circulator 20, the optical signal input of the first optical input / output terminal becomes the optical signal output of the second optical input / output terminal, and the optical signal input of the second optical input / output terminal is the third optical input / output terminal. The optical signal output of the third optical input / output terminal becomes the optical signal output of the fourth optical input / output terminal, and the optical signal input of the fourth optical input / output terminal becomes the first optical input / output terminal. It has non-reciprocal light passing characteristics, which is an optical signal output at the output end. The optical circulator 20 includes an optical fiber 10 at a first optical input / output end, an optical fiber 10a at a second optical input / output end, an optical fiber 10b at a third optical input / output end, and a fourth optical input / output end. Optical fibers 10g are connected to the input and output terminals, respectively.

The fiber gratings 30a to 30
0d has a minute and periodic change in the refractive index along the light propagation direction in the core portions of the optical fibers 10a and 10b. This fiber grating 30
Reference numerals a to 30d each have a characteristic of selectively reflecting only a signal whose wavelength is equal to the above-described period of an optical signal propagating inside. Here, as shown in FIG. 12B, the fiber grating 30a is set to reflect the optical signal of the wavelength λ1, and both the fiber gratings 30b and 30d are set to reflect the optical signal of the wavelength λ3. The fiber grating 3
0c is set so as to reflect the optical signal of the wavelength λ5.

As shown in FIG. 12B, the wavelength-transmittance change characteristic of the optical filter 50 has a cut-off region for reflecting an optical signal in the wavelength region and an optical signal in the wavelength region. It has a transmission region through which the light passes, and an intermediate region in which the transmittance gradually increases from the above-mentioned blocking region to the above-mentioned transmission region. Here, the optical filter 50 is a long-wavelength transmission filter having the wavelength λ3 as the intermediate band. In FIG. 12A,
The optical filter 50 includes optical collimators 40a and 40a.
b, parallel light passing through the optical filter 50 is incident on the optical collimators 40c and 40d, respectively, and parallel light reflecting on the optical filter 50 is incident on the optical collimators 40e and 40f, respectively. . Here, the optical collimators 40a and 40b convert outgoing light from the optical fibers 10a and 10b into parallel light, respectively, and the optical collimators 40c to 40f have a function of converging the incident parallel light to the optical fibers 10c to 10f, respectively. Things. When the light incident angle on the optical filter 50 is large, the wavelength characteristic changes between the P-polarized light and the S-polarized optical signal.
It is desirable to set it to 2.5 ° or less.

Next, the propagation of an optical signal in the fifth embodiment will be described. In FIG. 9A, an optical multiplex signal is incident on an optical fiber 10. Here, the optical multiplex signal has optical signals of five different wavelengths λ1 to λ5 which are close to each other, and the respective wavelengths are λ1 <λ2 <λ3 <λ4 as shown in FIG. <Λ5. The optical multiplex signal is input to a first optical input / output terminal of the optical circulator 20 and is output from a second optical input / output terminal of the optical circulator 20. Next, the optical multiplex signal is
The fiber grating 30 propagates through the optical fiber 10a.
a. This fiber grating 30a
As described above, since the optical signal has the characteristic of reflecting only the optical signal of the wavelength λ1, the optical signal of the wavelength λ1 is reflected and enters the second optical input / output terminal of the optical circulator 20. Thereafter, the wavelengths λ2 to λ4 that have passed through the fiber grating 30a
An optical multiplexed signal obtained by multiplexing the above optical signals enters the fiber grating 30b. This fiber grating 3
0b has the characteristic of reflecting only the optical signal of the wavelength λ3 as described above, so that the optical signal of the wavelength λ3 is reflected,
After passing through the fiber grating 30a, the light enters the second optical input / output end of the optical circulator 20. afterwards,
Wavelengths λ2 and λ passing through fiber grating 30b
The optical multiplexed signal obtained by multiplexing the optical signals of 4, λ5 enters the fiber grating 30c. Since the fiber grating 30c has the characteristic of reflecting only the optical signal of the wavelength λ5 as described above, the optical signal of the wavelength λ5 is reflected and passes through the fiber gratings 30b and 30a. The light enters the second light input / output terminal.

The wavelength λ 1 incident on the second optical input / output end,
The optical multiplexed signal obtained by multiplexing the optical signals of λ3 and λ5 is emitted from the third optical input / output terminal of the optical circulator 20, propagates through the optical fiber 10b, and enters the fiber grating 30d. Since the fiber grating 30d has the characteristic of reflecting only the optical signal of the wavelength λ3 as described above, the optical signal of the wavelength λ3 is reflected and enters the third optical input / output end of the optical circulator 20. Then, the wavelength λ
The optical signal No. 3 is emitted from the fourth optical input / output terminal of the optical circulator 20, and propagates through the optical fiber 10g.

On the other hand, the optical multiplexed signal obtained by multiplexing the optical signals of the wavelengths λ1 and λ5 transmitted through the fiber grating 30d enters the optical collimator 40b and is converted into parallel light.
This parallel light enters the optical filter 50. As described above, the optical filter 50 is a long-wavelength transmission filter having the wavelength λ3 as the intermediate band, so that the optical signal of the wavelength λ1 is reflected and the optical signal of the wavelength λ5 is transmitted. As a result, the wavelength λ1
Is incident on the optical collimator 40f and propagates through the optical fiber 10f, and the optical signal having the wavelength λ5 is incident on the optical collimator 40d and propagates through the optical fiber 10d.

On the other hand, the fiber gratings 30a to 30a-3
The optical multiplexed signal obtained by multiplexing the optical signals of wavelengths λ2 and λ4 transmitted through Oc enters the optical collimator 40a and is converted into parallel light. This parallel light enters the optical filter 50.
As described above, the optical filter 50 is a long-wavelength transmission filter having the wavelength λ3 as the intermediate band, so that the optical signal of the wavelength λ2 is reflected and the optical signal of the wavelength λ4 is transmitted. as a result,
The optical signal of the wavelength λ2 is incident on the optical collimator 40e and propagates through the optical fiber 10e.
The light enters the optical collimator 40c and propagates through the optical fiber 10c. That is, an optical multiplexed signal obtained by multiplexing optical signals of wavelengths λ1 to λ5 is demultiplexed for each wavelength and propagates through different optical fibers.

In this embodiment, even if the optical collimators 40a to 40f are not used, if the optical demultiplexing structure near the optical filter 50 is changed to the structure shown in FIG. It goes without saying that the present invention can be similarly applied.

As described above, in the optical demultiplexer according to the seventh embodiment, the wavelength to be demultiplexed is different from the wavelength of the optical multiplexed signal in the third embodiment by five different wavelengths which are all close to each other. It is. Therefore, an optical signal having a wavelength located in the middle is demultiplexed by a fiber grating, and then demultiplexed by an optical filter having the wavelength in the intermediate range. In addition, since the optical signal having the wavelength cannot enter the optical filter, it is independently emitted from the fourth optical input / output terminal of the optical circulator. In this way, an optical multiplexed signal obtained by multiplexing five adjacent optical signals having different wavelengths is demultiplexed by a fiber grating having a sharp cutoff band, and the optical signal is separated by a wavelength filter and an optical filter having a dull cutoff band is used. The optical signals of other wavelengths are demultiplexed. Therefore, by using one optical circulator, four fiber gratings, and one optical filter, an optical multiplexed signal in which five different wavelengths adjacent to each other are multiplexed can be demultiplexed. As a result, in the seventh embodiment, the optical circulator that required four optical demultiplexers disclosed in Japanese Patent Application Laid-Open No. 09-23210 is replaced by one in the seventh embodiment.
Can have the same demultiplexing function. As described above, since the optical circulator is made of an expensive optical crystal, the cost can be reduced by reducing the number of used optical circulators, and the insertion loss due to the optical circulator can also be reduced. Furthermore, since two systems of optical multiplexed signals are demultiplexed by one optical filter, insertion loss due to an increase in channels can be prevented, and the cost of parts can be reduced.

(Eighth Embodiment) In the seventh embodiment, the mode used as an optical demultiplexer has been described. However, in the eighth embodiment, an optical multiplexing device having the same configuration as that of the seventh embodiment is used. The form used as a container will be described. FIG. 13A is a circuit diagram showing a configuration of an optical multiplexer according to the eighth embodiment, and FIG. 13B is a diagram showing wavelength characteristics of components constituting the optical multiplexer and an optical signal to be emitted. FIG. 4 is a characteristic diagram showing a relationship with a wavelength characteristic. Hereinafter, the eighth embodiment will be described with reference to FIG.

In FIG. 13A, in the eighth embodiment, the direction of the light passage characteristic of the optical circulator 20 is described in reverse, as compared with FIG. 12A used in the description of the seventh embodiment. ing. This is to simplify the comparison with the eighth embodiment, and the optical fibers 10a and 10g
Indicates that the optical input / output terminal of the optical circulator 20 to which the optical circulator 20 is connected has changed. In the seventh embodiment, the optical circulator 20 includes an optical fiber 1 at the first optical input / output end.
0, the optical fiber 10a was connected to the second optical input / output terminal, the optical fiber 10b was connected to the third optical input / output terminal, and the optical fiber 10g was connected to the fourth optical input / output terminal. But,
In the eighth embodiment, an optical fiber 1 is connected to a first optical input / output end.
0, an optical fiber 10g is connected to the second optical input / output terminal, an optical fiber 10b is connected to the third optical input / output terminal, and an optical fiber 10a is connected to the fourth optical input / output terminal. That is, the eighth embodiment means that the optical input / output terminals of the optical circulator 20 to which the optical fibers 10a and 10g are connected in the seventh embodiment are replaced. Otherwise, the component configuration and component characteristics are the same as those of the seventh embodiment, and thus the same components are denoted by the same reference characters and detailed description thereof will not be repeated.

Next, the propagation of an optical signal in the eighth embodiment will be described. In FIG. 13A, the wavelength λ2
And λ4 are input from the optical fibers 10e and 10c, respectively. Next, the optical signals of the wavelengths λ2 and λ4 are converted into parallel lights by the optical collimators 40e and 40c, respectively, and are incident on the optical filter 50. Here, since the optical filter 50 is a long-wavelength transmission filter having the wavelength λ3 as an intermediate band as described above, the wavelength λ2
Is reflected, and the optical signal of wavelength λ4 is transmitted. As a result, the optical signal of the wavelength λ2 enters the optical collimator 40a, and the optical signal of the wavelength λ4 also enters the optical collimator 40a. That is, the optical filters 50 combine the optical signals of the wavelengths λ2 and λ4. Next, the multiplexed wavelength λ2
The optical multiplexed signal obtained by multiplexing the optical signals of λ4 and λ4 propagates through the optical fiber 10a and enters the fiber grating 30c. Since the fiber grating 30c has the characteristic of reflecting only the optical signal of the wavelength λ5 as described above, the optical multiplexed signal obtained by multiplexing the optical signals of the wavelengths λ2 and λ4 passes through the fiber grating 30c. Thereafter, the optical multiplexed signal obtained by multiplexing the optical signals of the wavelengths λ2 and λ4 enters the fiber grating 30b. Since the fiber grating 30b has the characteristic of reflecting only the optical signal of the wavelength λ3 as described above, the optical multiplexed signal obtained by multiplexing the optical signals of the wavelengths λ2 and λ4 passes through the fiber grating 30b. Next, the wavelength λ
The optical multiplexed signal obtained by multiplexing the optical signals of 2 and λ4 propagates through the optical fiber 10a and enters the fiber grating 30a. Since the fiber grating 30a has the characteristic of reflecting only the optical signal of the wavelength λ1 as described above, the optical multiplexed signal obtained by multiplexing the optical signals of the wavelengths λ2 and λ43 also passes through the fiber grating 30a, and The light enters the fourth light input / output terminal of the circulator 20. Thereafter, the optical multiplexed signal obtained by multiplexing the optical signals of the wavelengths λ2 and λ4 is emitted from the first optical input / output terminal of the optical circulator 20, and propagates through the optical fiber 10.

On the other hand, optical signals of wavelengths λ1 and λ5 are incident from optical fibers 10f and 10d, respectively.
Next, the optical signals of the wavelengths λ1 and λ5 are converted into parallel lights by the optical collimators 40f and 40d, respectively, and are incident on the optical filter 50. Here, the optical filter 50 is
As described above, since the filter is a long wavelength transmission filter having the wavelength λ3 as the intermediate band, the optical signal of the wavelength λ1 is reflected and the wavelength λ3 is reflected.
The optical signal of No. 5 is transmitted. As a result, the optical signal of the wavelength λ1 enters the optical collimator 40b, and the optical signal of the wavelength λ5 also enters the optical collimator 40b. That is, the optical signals of the wavelengths λ1 and λ5 are multiplexed by the optical filter 50.
Next, the optical multiplexed signal obtained by multiplexing the multiplexed optical signals of the wavelengths λ1 and λ5 propagates through the optical fiber 10b and enters the fiber grating 30d. Since the fiber grating 30d has the characteristic of reflecting only the optical signal of the wavelength λ3 as described above, the wavelengths λ1 and λ5
The optical multiplexed signal obtained by multiplexing the optical signals of (1) and (2) passes through the fiber grating 30d. Thereafter, the optical multiplexed signal obtained by multiplexing the optical signals of the wavelengths λ1 and λ5 propagates through the optical fiber 10b, enters the third optical input / output terminal of the optical circulator 20, and exits from the fourth optical input / output terminal. Then, the wavelength λ
The optical multiplexed signal obtained by multiplexing the optical signals of 1 and λ5 enters the fiber grating 30a. Since the fiber grating 30a has the characteristic of reflecting only the optical signal of the wavelength λ1 as described above, it reflects only the optical signal of the wavelength λ1 and enters the fourth optical input / output end of the optical circulator 20. I do. Thereafter, the optical signal having the wavelength λ1 is emitted from the first optical input / output terminal and propagates through the optical fiber 10.

On the other hand, the optical signal of wavelength λ5 transmitted through the fiber grating 30a propagates through the optical fiber 10a and enters the fiber grating 30b. The fiber grating 30b has the wavelength λ as described above.
3 has the characteristic of reflecting only the optical signal of No. 3, the optical signal of wavelength λ5 also passes through the fiber grating 30b and enters the fiber grating 30c. The fiber grating 30c has the wavelength λ as described above.
5, the optical signal of wavelength λ5 is reflected, and the fiber grating 30b
And 30a, and enters the fourth optical input / output end of the optical circulator 20. Then, the optical signal of wavelength λ5 is
The light is emitted from the first optical input / output end and propagates through the optical fiber 10.

On the other hand, the optical signal of wavelength λ3 is
0 g is incident. Next, the optical signal having the wavelength λ3 enters the second optical input / output terminal of the optical circulator 20 and is emitted from the third optical input / output terminal of the optical circulator 20. Next, the optical signal of the wavelength λ3 propagates through the optical fiber 10b,
The light enters the fiber grating 30d. Since the fiber grating 30d has the characteristic of reflecting only the optical signal of the wavelength λ3 as described above,
Is reflected and is incident on the third optical input / output terminal of the optical circulator 20.

After that, the optical signal of wavelength λ3 which has entered the third optical input / output terminal of the optical circulator 20 is emitted from the fourth optical input / output terminal of the optical circulator 20. next,
The optical signal having the wavelength λ3 propagates through the optical fiber 10a and enters the fiber grating 30a. Since the fiber grating 30a has the characteristic of reflecting only the optical signal of the wavelength λ1 as described above, the optical signal of the wavelength λ3 is transmitted and enters the fiber grating 30b. Since the fiber grating 30b has a characteristic of reflecting only the optical signal of the wavelength λ3 as described above, the optical signal of the wavelength λ3 is reflected, passes through the fiber grating 30a, and is reflected by the fourth light of the optical circulator 20. It is incident on the input / output end. Then, the optical signal of wavelength λ3 is
The light is emitted from the first optical input / output end of the optical circulator 20 and propagates through the optical fiber 10. As a result, an optical multiplexed signal obtained by multiplexing the optical signals of the wavelengths λ1 to λ5 is emitted from the optical fiber 10.

In this embodiment, even if the optical collimators 40a to 40f are not used, if the optical demultiplexing structure in the vicinity of the optical filter 50 is changed to the structure shown in FIG. It goes without saying that the present invention can be similarly applied.

As described above, in the eighth embodiment, an optical multiplexer is realized by changing the connection port of the optical circulator 20 of the optical demultiplexer in the seventh embodiment and changing the input / output direction of the optical signal. can do.

Further, the optical demultiplexer according to the seventh embodiment and the optical multiplexer according to the eighth embodiment may be combined. By using the optical demultiplexer as the receiving side and the optical multiplexer as the transmitting side, a one-way WDM transmission system can be configured. Hereinafter, the one-way WDM transmission system will be described.

FIG. 14 is a circuit diagram showing a configuration of the one-way wavelength multiplex transmission system. In the one-way wavelength division multiplexing transmission system, the optical multiplexer 1 in the eighth embodiment is the optical transmitter side, the optical demultiplexer 2 in the seventh embodiment is the optical receiver side, and both are optical fiber. The system is connected by 90. Here, the internal configuration of the optical multiplexer 1 and the propagation of the optical signal are the same as in the eighth embodiment, and the internal configuration of the optical demultiplexer 2 and the propagation of the optical signal are also the same. Since this is the same as the seventh embodiment, a detailed description thereof will be omitted.

In FIG. 14, an optical fiber 90 is provided as a transmission line for performing optical wavelength multiplex transmission from the optical multiplexer 1 to the optical demultiplexer 2. One end of the optical fiber 90 is connected to the optical circulator 2 included in the optical multiplexer 1.
0a is connected to the first optical input / output terminal. The other end of the optical fiber 90 is connected to a first optical input / output terminal of the optical circulator 20b included in the optical demultiplexer 2.

Next, propagation of an optical signal in the one-way WDM transmission system will be described. In FIG. 14, in the optical multiplexer 1, as in the eighth embodiment, optical signals of five different wavelengths λ1 to λ5 close to each other are multiplexed to form an optical multiplexed signal. The optical multiplexed signal is emitted from the first optical input / output terminal of the optical circulator 20 a and propagates through the optical fiber 90. Next, the optical multiplexed signal propagated through the optical fiber 90 is incident on the first optical input / output terminal of the optical circulator 20b included in the optical demultiplexer 2. The optical multiplexed signal that has entered the optical demultiplexer 2 is demultiplexed for each wavelength and propagates through different optical fibers as in the seventh embodiment.

As described above, by combining the optical demultiplexer according to the seventh embodiment and the optical multiplexer according to the eighth embodiment, optical signals of five different wavelengths close to each other are multiplexed. A one-way wavelength multiplex transmission system for propagating an optical multiplex signal can be configured.

(Ninth Embodiment) FIG. 15 is a diagram showing an optical multiplexer / demultiplexer according to a ninth embodiment of the present invention. FIG. 15A is a circuit diagram showing the configuration of the optical demultiplexer, and FIG. 15B shows the wavelength characteristics of the components constituting the optical demultiplexer and the wavelength characteristics of the incident optical signal. FIG. 6 is a characteristic diagram showing the relationship of FIG. Hereinafter, the ninth embodiment will be described with reference to FIG.

In FIG. 15 (a), an optical demultiplexer according to the ninth embodiment includes an optical fiber 1 for inputting and outputting an optical multiplexed signal.
0, the optical circulator 20, and the optical collimators 40a to 40a.
40i and an optical filter 50. Optical fibers 10a to 10i are connected to the above components, and fiber gratings 30a and 30b are formed on the optical fiber 10a.

Here, the optical circulator 20 comprises
It has a fourth light input / output terminal. In this optical circulator 20, the optical signal input of the first optical input / output terminal becomes the optical signal output of the second optical input / output terminal, and the optical signal input of the second optical input / output terminal is the third optical input / output terminal. The optical signal output of the third optical input / output terminal becomes the optical signal output of the fourth optical input / output terminal, and the optical signal input of the fourth optical input / output terminal becomes the first optical input / output terminal. It has non-reciprocal light passing characteristics, which is an optical signal output at the output end. The optical circulator 20 includes an optical fiber 10 at a first optical input / output end, an optical fiber 10a at a second optical input / output end, an optical fiber 10b at a third optical input / output end, and a fourth optical input / output end. Optical fibers 10c are connected to the input and output terminals, respectively.

The fiber gratings 30a and 30b have minute and periodic changes in the refractive index along the light propagation direction in the core of the optical fiber 10a. The fiber gratings 30a and 30a
0b has a characteristic of selectively reflecting only those optical signals whose wavelengths are equal to the above-mentioned period. Here, as shown in FIG. 15B, the fiber grating 30a is set to reflect an optical signal of wavelength λ1, and the fiber grating 30b is set to reflect an optical signal of λ3.

Further, as shown in FIG. 15B, the wavelength-to-wavelength change characteristic of the optical filter 50 includes a cut-off region for reflecting an optical signal in the wavelength region and an optical signal in the wavelength region. It has a transmission region through which the light passes, and an intermediate region in which the transmittance gradually increases from the above-mentioned blocking region to the above-mentioned transmission region. Here, the optical filter 50 is a long-wavelength transmission filter having the wavelength between the wavelengths λ2 and λ3 as the intermediate range.
In FIG. 15A, the optical filter 50 receives parallel light from the optical collimators 40a to 40c, and converts the parallel light passing through the optical filter 50 into the optical collimator 40d.
To 40f, and are arranged such that the parallel light reflected by the optical filter 50 respectively enters the optical collimators 40g to 40i. Here, the optical collimators 40a to 40i
It has a function of converting the emitted light from the optical fibers 10a to 10i into parallel light, or converging the incident parallel light to the optical fibers 10a to 10i, respectively. When the light incident angle on the optical filter 50 is large, the wavelength characteristic changes between the P-polarized light and the S-polarized optical signal. Therefore, the incident angle on the optical filter 50 is set to 22.5 ° or less. Is desirable.

Next, propagation of an optical signal in the ninth embodiment will be described. The optical multiplexing / demultiplexing device according to the ninth embodiment has both an optical demultiplexing function and an optical multiplexing function.
Here, propagation of an optical signal in the optical demultiplexing function will be described first.

In FIG. 15A, an optical multiplex signal is incident on the optical fiber 10. Here, the optical multiplex signal is
It has two different wavelengths λ1 and λ2 which are close to each other and two different wavelengths λ3 and λ4 which are close to each other, and each wavelength is λ1 <λ2 < as shown in FIG. λ3 <λ4. The optical multiplex signal is input to a first optical input / output terminal of the optical circulator 20 and is output from a second optical input / output terminal of the optical circulator 20. Next, the optical multiplex signal propagates through the optical fiber 10a and enters the fiber grating 30a. Since the fiber grating 30a has the characteristic of reflecting only the optical signal of the wavelength λ1 as described above, the optical signal of the wavelength λ1 is reflected and the optical circulator 20a is reflected.
At the second optical input / output end. Thereafter, the optical multiplexed signal obtained by multiplexing the optical signals of wavelengths λ2 to λ4 that have passed through the fiber grating 30a is
Incident on. Since the fiber grating 30b has the characteristic of reflecting only the optical signal of the wavelength λ3 as described above, the optical signal of the wavelength λ3 is reflected and passes through the fiber grating 30a.
0 enters the second optical input / output terminal.

The optical multiplexed signal obtained by multiplexing the optical signals of the wavelengths λ1 and λ3 incident on the second optical input / output terminal of the optical circulator 20 is output from the third optical input / output terminal of the optical circulator 20, and Propagate 10b. afterwards,
An optical multiplexed signal obtained by multiplexing optical signals of wavelengths λ1 and λ3 is
The light enters the optical collimator 40b and is converted into parallel light. This parallel light enters the optical filter 50. Optical filter 50
Is a long wavelength transmission filter having the wavelength between the wavelengths λ2 and λ3 as the intermediate band as described above.
The optical signal of 1 is reflected, and the optical signal of wavelength λ3 is transmitted. As a result, the optical signal of the wavelength λ1 enters the optical collimator 40h and propagates through the optical fiber 10h, and the optical signal of the wavelength λ3 enters the optical collimator 40f and propagates through the optical fiber 10f.

On the other hand, the optical multiplexed signal obtained by multiplexing the optical signals of the wavelengths λ2 and λ4 transmitted through the fiber gratings 30a and 30b enters the optical collimator 40a and is converted into parallel light. This parallel light enters the optical filter 50. The optical filter 50 has the wavelength λ2 and the wavelength λ as described above.
Since the filter is a long-wavelength transmission filter having the wavelength between the wavelengths 3 and 3 as the intermediate band, the optical signal of the wavelength λ2 is reflected and the optical signal of the wavelength λ4 is transmitted. As a result, the optical signal of the wavelength λ2 enters the optical collimator 40i and propagates through the optical fiber 10i, and the optical signal of the wavelength λ4 enters the optical collimator 40d and propagates through the optical fiber 10d. That is, the wavelengths λ1 to λ
The optical multiplexed signal obtained by multiplexing the four optical signals is demultiplexed for each wavelength and propagates through different optical fibers.

Next, propagation of an optical signal in the multiplexing function of the optical multiplexer / demultiplexer will be described. In the optical multiplexer / demultiplexer, optical signals of wavelengths λ1 ′ and λ2 ′ are multiplexed. Here, in FIG. 15B, the wavelength λ1 ′ is λ1 ′ <
Although described in relation to λ1, this is for the sake of simplicity, and the wavelength λ1 ′ may be any wavelength as long as it is within the cutoff band of the optical filter 50. Although the wavelength λ2 ′ is also described in the relationship of λ2 ′> λ4, this is also for the sake of simplicity of description. It doesn't matter.

In FIG. 15 (a), optical signals of wavelengths λ1 ′ and λ2 ′ are
0f is incident. Next, the optical signals of the wavelengths λ1 ′ and λ2 ′ are converted into parallel lights by the optical collimators 40g and 40f, respectively, and enter the optical filter 50. Here, as described above, since the wavelength λ1 ′ is in the cutoff band of the optical filter 50 and the wavelength λ2 ′ is in the transmission band of the optical filter 50, the optical signal of the wavelength λ1 ′ is reflected and the light of the wavelength λ2 ′ is reflected. The signal is transmitted. As a result, the optical signal of the wavelength λ1 ′ enters the optical collimator 40c, and the optical signal of the wavelength λ2 ′ also enters the optical collimator 40c. That is, the optical filters 50 combine the optical signals of the wavelengths λ1 ′ and λ2 ′. Next, the optical multiplexed signal obtained by multiplexing the multiplexed optical signals of the wavelengths λ1 ′ and λ2 ′ propagates through the optical fiber 10c,
The light enters the fourth optical input / output terminal of the optical circulator 20.
Thereafter, an optical multiplexed signal obtained by multiplexing the optical signals of the wavelengths λ1 ′ and λ2 ′ is output from the first optical input / output terminal of the optical circulator 20 and propagates through the optical fiber 10.

Note that the optical collimators 40a to 40i used in the above embodiments need not be used. FIG.
Is an optical filter 5 when no optical collimator is used.
FIG. 2 is an enlarged view showing an optical demultiplexing structure near 1; In FIG. 16, the optical demultiplexing structure is a structure in which the above-described optical demultiplexing structures of FIG. 2 are arranged in parallel. Optical fibers 10a to 10c
Of the optical fibers 10a to 10c, respectively.
To form an inclined surface. Next, the optical filters 51 are brought close to the respective inclined surfaces. Here, the optical filter 51
Is a long-wavelength transmission filter having a wavelength between the wavelengths λ2 and λ3 as the above-mentioned intermediate band, similarly to the optical filter 50. When the light incident angle on the optical filter 51 is large,
Since the wavelength characteristics change between the P-polarized light signal and the S-polarized light signal, it is desirable to set the incident angle on the optical filter 51 to 22.5 ° or less. Then, the other optical fibers 10d-1
16, the optical signals reflected by the optical filter 51 enter the optical fibers 10g to 10i, respectively, and the optical signals transmitted through the optical filter 51 are assigned to the optical fiber 1 as shown in FIG.
If they are close to each other so as to be incident on 0d to 10f, similar functions can be realized without the optical collimators 40a to 40i.

As described above, in the optical multiplexer / demultiplexer according to the ninth embodiment, the optical multiplexed signal obtained by multiplexing the optical signals having the wavelengths λ1 to λ4 is demultiplexed for each wavelength, and at the same time, the wavelengths λ1 ′ and λ2 ′ are used. Has the function of multiplexing the optical signals. this is,
This is a mode in which an optical multiplexing function is added to the optical demultiplexer in the third embodiment, and an optical multiplexing system is configured by increasing the number of optical input / output terminals of an optical circulator. As described above, in the optical demultiplexer according to the ninth embodiment, an optical multiplexer / demultiplexer having multiple functions can be configured by using one optical circulator, two fiber gratings, and one optical filter.

In the multiplexing function in the ninth embodiment, an optical multiplexed signal obtained by multiplexing optical signals of adjacent wavelengths is separated by a fiber grating having a sharp cutoff band, and the wavelengths of the optical signals are separated. An optical filter having a dull cut-off band is used to split optical signals of other wavelengths. Therefore, in the ninth embodiment, one optical circulator, which was required in the conventional optical demultiplexer disclosed in Japanese Patent Application Laid-Open No. 09-23210, can have the same demultiplexing function. is there.
As described above, since the optical circulator is made of an expensive optical crystal, the cost can be reduced by reducing the number of used optical circulators, and the insertion loss due to the optical circulator can also be reduced. Furthermore, since one optical filter performs demultiplexing / multiplexing of three systems of optical multiplexed signals, insertion loss due to an increase in channels can be prevented, and component costs can be reduced.

(Tenth Embodiment) FIG. 17 is a diagram showing an optical multiplexer / demultiplexer according to a tenth embodiment of the present invention.
FIG. 17A is a circuit diagram showing a configuration of the optical multiplexer / demultiplexer, and FIG. 17B is a diagram showing the wavelength characteristics of components constituting the optical multiplexer / demultiplexer and the wavelength of an incident optical signal. FIG. 4 is a characteristic diagram showing a relationship with characteristics. Hereinafter, with reference to FIG.
Embodiment 0 will be described.

In FIG. 17A, in the tenth embodiment, the direction of the light passage characteristic of the optical circulator 20 is described in reverse, as compared with FIG. 15A used in the description of the ninth embodiment. ing. This is to simplify comparison with the ninth embodiment, and the optical fibers 10a and 10
This means that the optical input / output terminal of the optical circulator 20 to which c is connected has changed. In the ninth embodiment, the optical circulator 20 includes an optical fiber 10 at a first optical input / output end, an optical fiber 10a at a second optical input / output end, and a third
The optical fiber 10b is connected to the optical input / output end of the optical fiber and the optical fiber 10c is connected to the fourth optical input / output end. However, in the tenth embodiment, the optical fiber 10 is provided at the first optical input / output end, and the optical fiber 10c is provided at the second optical input / output end.
The optical fiber 10b is connected to the third optical input / output terminal, and the optical fiber 10a is connected to the fourth optical input / output terminal. That is, the tenth embodiment means that the optical input / output terminals of the optical circulator 20 to which the optical fibers 10a and 10c are connected in the ninth embodiment are replaced. Otherwise, the component configuration and component characteristics are the same as those of the ninth embodiment, and thus the same components are denoted by the same reference characters and detailed description thereof will not be repeated.

Next, propagation of an optical signal in the tenth embodiment will be described. The optical multiplexer / demultiplexer according to the tenth embodiment has both an optical demultiplexing function and an optical multiplexing function. Here, first, propagation of an optical signal in the optical multiplexing function will be described.

In FIG. 17A, the wavelengths λ2 and λ
4 are optical fibers 10i and 10d, respectively.
Incident from. Next, the optical signals of the wavelengths λ2 and λ4 are converted into parallel lights by the optical collimators 40i and 40d, respectively, and are incident on the optical filter 50. here,
As described above, the optical filter 50 is a long-wavelength transmission filter having the wavelength between the wavelengths λ2 and λ3 as the intermediate band, so that the optical signal of the wavelength λ2 is reflected and the optical signal of the wavelength λ4 is transmitted. . As a result, the optical signal of the wavelength λ2 enters the optical collimator 40a, and the optical signal of the wavelength λ4 also enters the optical collimator 40a. That is, in the optical filter 50,
Optical signals of wavelengths λ2 and λ4 are multiplexed. Next, the optical multiplexed signal obtained by multiplexing the multiplexed optical signals of the wavelengths λ2 and λ4 propagates through the optical fiber 10a and enters the fiber grating 30b. This fiber grating 3
0b has the characteristic of reflecting only the optical signal of the wavelength λ3 as described above, so that the optical multiplexed signal obtained by multiplexing the optical signals of the wavelengths λ2 and λ4
b. Thereafter, the optical multiplexed signal obtained by multiplexing the optical signals of the wavelengths λ2 and λ4 propagates through the optical fiber 10a and enters the fiber grating 30a. Since the fiber grating 30a has the characteristic of reflecting only the optical signal of the wavelength λ1 as described above, the optical multiplexed signal obtained by multiplexing the optical signals of the wavelengths λ2 and λ4 also passes through the fiber grating 30a, and The light enters the fourth light input / output terminal of the circulator 20. Thereafter, the optical multiplexed signal obtained by multiplexing the optical signals of the wavelengths λ2 and λ4 is emitted from the first optical input / output terminal of the optical circulator 20, and
Propagate 0.

On the other hand, optical signals of wavelengths λ1 and λ3 are incident from optical fibers 10h and 10e, respectively.
Next, the optical signals of the wavelengths λ1 and λ3 are converted into parallel lights by the optical collimators 40h and 40e, respectively, and are incident on the optical filter 50. Here, the optical filter 50 is
As described above, since the long wavelength transmission filter has the wavelength between the wavelengths λ2 and λ3 as the intermediate band, the optical signal of the wavelength λ1 is reflected and the optical signal of the wavelength λ3 is transmitted. As a result, the optical signal of the wavelength λ1 enters the optical collimator 40b,
Further, the optical signal of the wavelength λ3 also enters the optical collimator 40b. That is, in the optical filter 50, the wavelengths λ1 and λ3
Are multiplexed. Next, an optical multiplexed signal obtained by multiplexing the multiplexed optical signals of wavelengths λ1 and λ3 is
0b, and enters the third optical input / output terminal of the optical circulator 20. Thereafter, an optical multiplexed signal obtained by multiplexing the optical signals of the wavelengths λ1 and λ3 is emitted from the fourth optical input / output terminal of the optical circulator 20. Next, the wavelengths λ1 and λ3
The optical multiplexed signal obtained by multiplexing the optical signals is propagated through the optical fiber 10a and enters the fiber grating 30a. Since the fiber grating 30a has a characteristic of reflecting only the optical signal of the wavelength λ1 as described above,
The optical signal having the wavelength λ1 is reflected and made incident on the fourth optical input / output terminal of the optical circulator 20.

On the other hand, the optical signal of wavelength λ3 that has passed through the fiber grating 30a is
0b. This fiber grating 30b
Has the characteristic of reflecting only the optical signal of the wavelength λ3 as described above, so that the optical signal of the wavelength λ3 is reflected and passes through the fiber grating 30a, and then the fourth optical input / output terminal of the optical circulator 20. Is incident on. That is, the optical signals of the wavelengths λ1 and λ3 are both
0 is input to the fourth light input / output terminal. After that, the wavelength λ1
An optical multiplexed signal obtained by multiplexing the optical signals of the optical circulator 20 and the optical signal λ 3 is emitted from the first optical input / output terminal of the optical circulator 20 and propagates through the optical fiber 10. As a result, an optical multiplexed signal obtained by multiplexing optical signals of wavelengths λ1 to λ4 is emitted from the optical fiber 10.

Next, propagation of an optical signal in the demultiplexing function of the optical multiplexer / demultiplexer will be described. In the optical multiplexer / demultiplexer, optical signals of wavelengths λ1 ′ and λ2 ′ are demultiplexed. Here, in FIG. 17B, the wavelength λ1 ′ is λ1 ′ <
Although described in relation to λ1, this is for the sake of simplicity, and the wavelength λ1 ′ may be any wavelength as long as it is within the cutoff band of the optical filter 50. Further, the wavelength λ2 ′ is described in the relationship of λ2 ′> λ4, but this is also for the sake of simplicity of description. It doesn't matter.

In FIG. 17A, an optical multiplex signal is incident on the optical fiber 10. Here, the optical multiplex signal is
It has optical signals of two different wavelengths λ1 ′ and λ2 ′. The optical multiplex signal is input to a first optical input / output terminal of the optical circulator 20 and is output from a second optical input / output terminal of the optical circulator 20. Next, the optical multiplex signal is
After propagating through the optical fiber 10c, it enters the optical collimator 40c and is converted into parallel light. This parallel light enters the optical filter 50. Here, as described above, the wavelength λ1 ′
Is in the cutoff band of the optical filter 50, and the wavelength λ2 ′ is in the transmission band of the optical filter 50, so that the optical signal of the wavelength λ1 ′ is reflected and the optical signal of the wavelength λ2 ′ is transmitted. As a result, the optical signal of the wavelength λ1 ′ is incident on the optical collimator 40g and propagates through the optical fiber 10g, and the optical signal of the wavelength λ2 ′ is incident on the optical collimator 40f and propagates through the optical fiber 10f.

In this embodiment, even if the optical collimators 40a to 40i are not used, if the optical demultiplexing structure near the optical filter 50 is changed to the structure shown in FIG.
Needless to say, the present invention can be applied similarly to the ninth embodiment.

As described above, the optical multiplexer / demultiplexer according to the tenth embodiment multiplexes optical signals of wavelengths λ1 to λ4 and simultaneously multiplexes optical signals of wavelengths λ1 ′ and λ2 ′. It has a function of demultiplexing for each wavelength. This is a form in which an optical demultiplexing function is added to the optical multiplexer according to the fourth embodiment, and an optical demultiplexing system is configured by increasing the number of optical input / output terminals of an optical circulator. As described above, in the optical multiplexer / demultiplexer according to the tenth embodiment, an optical multiplexer / demultiplexer having multiple functions can be configured by using one optical circulator, two fiber gratings, and one optical filter. In addition, since one optical filter performs demultiplexing / multiplexing of three systems of optical multiplexed signals, insertion loss due to an increase in channels can be prevented, and component costs can be reduced.

Further, the optical multiplexer / demultiplexer according to the ninth embodiment may be combined with the optical multiplexer / demultiplexer according to the tenth embodiment. By transmitting and receiving by both optical multiplexer / demultiplexers, a bidirectional wavelength multiplex transmission system can be configured. Hereinafter, the bidirectional wavelength multiplex transmission system will be described.

FIG. 18 is a circuit diagram showing a configuration of the bidirectional wavelength division multiplexing transmission system. In the bidirectional wavelength division multiplexing transmission system, the first optical multiplexer / demultiplexer 3 in the tenth embodiment is set to the first optical transmitting / receiving device side, and the second optical multiplexer / demultiplexer in the ninth embodiment is used. 4 is a second optical transmitting / receiving apparatus side, and both are connected by an optical fiber 90. Here, the internal component configuration of the first optical multiplexer / demultiplexer 3 and the propagation of the optical signal are the same as those in the tenth embodiment, and the internal components of the second optical multiplexer / demultiplexer 4. The component configuration and the propagation of the optical signal are the same as those in the ninth embodiment, and a detailed description thereof will be omitted.

In FIG. 18, the optical fiber 90 is the first
Between the optical multiplexer / demultiplexer 3 and the second optical multiplexer / demultiplexer 4 as a transmission path for performing optical wavelength multiplex transmission.
One end of the optical fiber 90 is connected to the first optical multiplexer / demultiplexer 3.
Is connected to the first optical input / output terminal of the optical circulator 20a. The other end of the optical fiber 90 is connected to the first optical input / output terminal of the optical circulator 20b included in the second optical multiplexer / demultiplexer 4.

First, propagation of an optical signal from the first optical multiplexer / demultiplexer 3 to the second optical multiplexer / demultiplexer 4 in the bidirectional wavelength division multiplexing transmission system will be described. In FIG. 18, in the first optical multiplexer / demultiplexer 3, as in the tenth embodiment, two different wavelengths λ1 and λ2 close to each other and two different wavelengths λ3 and λ
4 are multiplexed to form a first optical multiplexed signal. This first optical multiplexed signal is transmitted to the first optical circulator 20a.
And propagates through the optical fiber 90. Next, the first optical multiplexed signal propagated through the optical fiber 90 enters the first optical input / output terminal of the optical circulator 20b included in the second optical multiplexer / demultiplexer 4. The first optical multiplexed signal that has entered the second optical multiplexer / demultiplexer 4 is demultiplexed for each wavelength, as in the ninth embodiment, and propagates through different optical fibers.

Next, propagation of an optical signal from the second optical multiplexer / demultiplexer 4 to the first optical multiplexer / demultiplexer 3 in the bidirectional wavelength division multiplexing transmission system will be described. In FIG. 18, in the second optical multiplexer / demultiplexer 4, as in the ninth embodiment, optical signals of two different wavelengths λ1 ′ and λ2 ′ are multiplexed, and a second optical multiplexed signal is Become. The second optical multiplexed signal is emitted from the first optical input / output terminal of the optical circulator 20b and propagates through the optical fiber 90. Next, the second optical multiplexed signal that has propagated through the optical fiber 90 enters the first optical input / output terminal of the optical circulator 20a included in the first optical multiplexer / demultiplexer 3. The second optical multiplexed signal incident on the first optical multiplexer / demultiplexer 3 is demultiplexed for each wavelength and propagates through different optical fibers, similarly to the tenth embodiment.

As described above, by combining the optical multiplexer / demultiplexer according to the ninth embodiment with the optical multiplexer / demultiplexer according to the tenth embodiment, optical signals of two wavelengths close to each other are obtained. Can be configured to propagate a first optical multiplexed signal obtained by multiplexing two sets of optical signals and a second optical multiplexed signal obtained by multiplexing optical signals of two different wavelengths.

[Brief description of the drawings]

FIG. 1 is a circuit diagram and a wavelength characteristic diagram of an optical demultiplexer according to a first embodiment of the present invention.

FIG. 2 is a detailed view of an optical demultiplexing structure of the optical demultiplexer according to the first embodiment of the present invention.

FIG. 3 is a circuit diagram and a wavelength characteristic diagram of an optical multiplexer according to a second embodiment of the present invention.

FIG. 4 is a circuit diagram of a one-way wavelength division multiplexing transmission system in which the optical demultiplexer according to the first embodiment of the present invention and the optical multiplexer according to the second embodiment are combined.

FIG. 5 is a circuit diagram and a wavelength characteristic diagram of an optical demultiplexer according to a third embodiment of the present invention.

FIG. 6 is a detailed view of an optical demultiplexing structure of an optical demultiplexer according to a third embodiment of the present invention.

FIG. 7 is a circuit diagram and a wavelength characteristic diagram of an optical multiplexer according to a fourth embodiment of the present invention.

FIG. 8 is a circuit diagram of a one-way wavelength division multiplexing transmission system in which an optical splitter according to a third embodiment of the present invention and an optical multiplexer according to a fourth embodiment are combined.

FIG. 9 is a circuit diagram and a wavelength characteristic diagram of an optical multiplexer according to a fifth embodiment of the present invention.

FIG. 10 is a circuit diagram and a wavelength characteristic diagram of an optical multiplexer according to a sixth embodiment of the present invention.

FIG. 11 shows an optical demultiplexer according to a fifth embodiment of the present invention;
FIG. 14 is a circuit diagram of a one-way wavelength multiplex transmission system combining an optical multiplexer according to a sixth embodiment.

FIG. 12 is a circuit diagram and a wavelength characteristic diagram of an optical multiplexer according to a seventh embodiment of the present invention.

FIG. 13 is a circuit diagram and a wavelength characteristic diagram of an optical multiplexer according to an eighth embodiment of the present invention.

FIG. 14 is an optical demultiplexer according to a seventh embodiment of the present invention;
FIG. 21 is a circuit diagram of a one-way wavelength multiplex transmission system in which an optical multiplexer according to an eighth embodiment is combined.

FIG. 15 is a circuit diagram and a wavelength characteristic diagram of an optical multiplexer / demultiplexer according to a ninth embodiment of the present invention.

FIG. 16 is a detailed view of an optical demultiplexing structure of an optical demultiplexer according to a ninth embodiment of the present invention.

FIG. 17 is a circuit diagram and a wavelength characteristic diagram of an optical multiplexer / demultiplexer according to a tenth embodiment of the present invention.

FIG. 18 is a circuit diagram of a bidirectional wavelength division multiplexing transmission system in which an optical multiplexer / demultiplexer according to a ninth embodiment of the present invention and an optical multiplexer / demultiplexer according to the tenth embodiment are combined.

FIG. 19 is a diagram showing a basic structure of an optical demultiplexer using a conventional angle dispersion element.

FIG. 20 is a diagram showing a basic structure of a conventional optical demultiplexer using a wavelength-selective reflection / transmission film.

FIG. 21 is a circuit diagram showing a conventional optical splitter disclosed in Japanese Patent Application Laid-Open No. 09-23210.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Optical multiplexer 2 ... Optical multiplexer / demultiplexer 3 ... 1st optical multiplexer / demultiplexer 4 ... 2nd optical multiplexer / demultiplexer 10, 90 ... Optical fiber 20 ... Optical circulator 30 ... Fiber grating 40 ... Optical collimator 50 , 51 ... Optical filter

Claims (30)

    [Claims]
  1. An optical demultiplexer for demultiplexing an optical multiplexed signal obtained by multiplexing optical signals of three different first to third wavelengths for each wavelength, wherein at least the first to third optical input / output terminals Wherein the optical signal input to the first optical input / output terminal is output from the second optical input / output terminal, and the optical signal input to the second optical input / output terminal is An optical circulator output from an optical input / output terminal; and an optical circulator connected to the first optical input / output terminal of the optical circulator and transmitting the optical multiplexed signal to the first optical circulator.
    A first optical fiber that supplies an optical input / output end of the optical circulator, one end of which is connected to the second optical input / output end of the optical circulator and reflects an optical signal of the second wavelength in the middle thereof A second optical fiber on which a grating is formed; and the first optical fiber output from the other end of the second optical fiber.
    And an optical filter for demultiplexing an optical signal of a third wavelength, wherein the optical signal of the second wavelength is output from the third optical input / output terminal of the optical circulator.
    Optical splitter.
  2. 2. The wavelength-to-transmittance change characteristic of the optical filter includes a cut-off region for reflecting an optical signal in the wavelength region;
    The optical filter has a transmission region through which an optical signal in the wavelength region is transmitted, and an intermediate region in which the transmittance gradually increases from the cutoff region to the transmission region. Wherein the third wavelength is arranged in the transmission area of the optical filter, and the second wavelength is arranged in the intermediate area of the optical filter. Item 2. The optical demultiplexer according to Item 1.
  3. 3. An optical multiplexer for multiplexing optical signals of three different first to third wavelengths, the optical multiplexer having at least first to third optical input / output terminals, An optical circulator in which an optical signal input to an output terminal is output from the second optical input / output terminal, and an optical signal input to the second optical input / output terminal is output from the third optical input / output terminal Connected to a first optical input / output end of the optical circulator,
    The optical signal of the second wavelength is transmitted to a first optical circulator.
    A first optical fiber for supplying an optical input / output end of the optical circulator, one end of which is connected to the second optical input / output end of the optical circulator, and which reflects an optical signal of the second wavelength on the way. A second optical fiber on which a grating is formed, and an optical filter for multiplexing the optical signals of the first and third wavelengths and inputting the multiplexed optical signal to the other end of the second optical fiber Wherein the optical multiplexed signal obtained by multiplexing the optical signals of the first to third wavelengths is output from the third optical input / output terminal of the optical circulator. .
  4. 4. The wavelength-transmittance change characteristic of the optical filter includes a cut-off region for reflecting an optical signal in the wavelength region;
    The optical filter has a transmission region through which an optical signal in the wavelength region is transmitted, and an intermediate region in which the transmittance gradually changes from the cutoff region to the transmission region. Wherein the third wavelength is arranged in the transmission area of the optical filter, and the second wavelength is arranged in the intermediate area of the optical filter. Item 4. An optical multiplexer according to item 3.
  5. 5. An optical multiplexer provided on an optical transmitting device side for multiplexing optical signals of three different first to third wavelengths, and an optical multiplexer provided on an optical receiving device side, wherein the first to third optical multiplexers are provided. An optical demultiplexer that demultiplexes an optical multiplexed signal obtained by multiplexing optical signals of wavelengths for each wavelength,
    A wavelength division multiplexing transmission system connected by a first optical fiber and transmitting the optical multiplexed signal, wherein the optical multiplexer has at least first to third optical input / output terminals, and the first optical An optical signal input to the input / output terminal is output from the second optical input / output terminal, and an optical signal input to the second optical input / output terminal is output from the third optical input / output terminal. One optical circulator, and one end thereof is connected to the second optical input / output end of the first optical circulator, and a first fiber grating that reflects the optical signal of the second wavelength is formed in the middle thereof. A first optical input / output terminal of the first optical circulator, the second optical fiber being connected to a first optical input / output terminal of the first optical circulator, and connected to a first optical input / output terminal of the first optical circulator. A third optical fiber supplying the first and third wavelengths A first optical filter for multiplexing an optical signal and inputting the multiplexed optical signal to the other end of the second optical fiber, wherein the optical demultiplexer includes at least a fourth to a sixth optical filter. An optical input / output terminal, an optical signal input to the fourth optical input / output terminal is output from the fifth optical input / output terminal, and an optical signal input to the fifth optical input / output terminal is A second optical circulator output from the sixth optical input / output terminal, one end of which is connected to the fifth optical input / output terminal of the second optical circulator; A fourth optical fiber on which a second fiber grating for reflecting an optical signal is formed; and the first optical fiber output from the other end of the fourth optical fiber.
    And a second optical filter for demultiplexing an optical signal of a third wavelength, wherein the first optical fiber comprises: a third optical input / output end of the first optical circulator; and a second optical filter. The optical circulator is connected to the fourth optical input / output terminal, and the optical multiplexed signal propagates through the optical circulator, and the optical signal of the second wavelength is transmitted to the sixth optical input of the second optical circulator. A wavelength division multiplexing transmission system output from an output end.
  6. 6. The wavelength-transmittance change characteristics of the first and second optical filters include a cut-off region for reflecting an optical signal in the wavelength region and a transmission region for transmitting an optical signal in the wavelength region. And an intermediate region in which the transmittance gradually changes from the cutoff region to the transmission region, wherein the first wavelength is disposed in the cutoff region of the first and second optical filters. And disposing the third wavelength in the transmission region of the first and second optical filters, and disposing the second wavelength in the intermediate region of the first and second optical filters. The wavelength division multiplexing transmission system according to claim 5, characterized in that:
  7. 7. An optical demultiplexer for demultiplexing an optical multiplexed signal obtained by multiplexing optical signals of four different first to fourth wavelengths for each wavelength, wherein at least the first to third optical input / output terminals Wherein the optical signal input to the first optical input / output terminal is output from the second optical input / output terminal, and the optical signal input to the second optical input / output terminal is An optical circulator output from an optical input / output terminal; and an optical circulator connected to the first optical input / output terminal of the optical circulator and transmitting the optical multiplexed signal to the first optical circulator.
    A first optical fiber for supplying an optical input / output end of the optical circulator, one end of which is connected to the second optical input / output end of the optical circulator and which reflects an optical signal of the second wavelength on the way; A second optical fiber on which a first fiber grating and a second fiber grating for reflecting the optical signal of the fourth wavelength are formed; and one end of which is the third optical input / output end of the optical circulator. A third optical fiber connected to the second optical fiber, and the first optical fiber output from the other end of the second optical fiber.
    And an optical filter that demultiplexes the optical signal of the third wavelength and demultiplexes the optical signal of the second and fourth wavelengths output from the other end of the third optical fiber. vessel.
  8. 8. A wavelength-transmittance change characteristic of the optical filter includes a cut-off region for reflecting an optical signal in the wavelength region;
    A transmission region that transmits an optical signal in the wavelength region, and an intermediate region in which the transmittance gradually changes from the cutoff region to the transmission region, wherein the first and second wavelengths are The optical demultiplexer according to claim 7, wherein the optical filter is disposed in the cutoff region of the optical filter, and the third and fourth wavelengths are disposed in the transmission region of the optical filter.
  9. 9. An optical multiplexer for multiplexing optical signals of four different first to fourth wavelengths, the optical multiplexer having at least first to third optical input / output terminals, An optical circulator in which an optical signal input to an output terminal is output from the second optical input / output terminal, and an optical signal input to the second optical input / output terminal is output from the third optical input / output terminal An optical multiplexed signal connected to the third optical input / output terminal of the optical circulator and multiplexed with the optical signals of the first to fourth wavelengths; And a first fiber grating having one end connected to the second optical input / output end of the optical circulator and reflecting an optical signal of the second wavelength in the middle thereof. , A second fiber grating for reflecting the optical signal of the fourth wavelength A second optical fiber having one end connected to the first optical input / output end of the optical circulator; and an optical signal having the first and third wavelengths. And the multiplexed optical signal is input to the other end of the second optical fiber, the optical signals of the second and fourth wavelengths are multiplexed, and the multiplexed optical signal is An optical multiplexer comprising: an optical filter that is input to the other end of the third optical fiber.
  10. 10. The wavelength-transmittance change characteristic of the optical filter includes a cut-off region for reflecting an optical signal in the wavelength region, a transmission region for transmitting an optical signal in the wavelength region, and the cut-off region. An intermediate region in which transmittance gradually increases toward the transmission region, wherein the first and second wavelengths are arranged in the cutoff region of the optical filter, The optical multiplexer according to claim 9, wherein a wavelength is arranged in the transmission region of the optical filter.
  11. 11. An optical multiplexer provided on an optical transmitting device side for multiplexing optical signals of four different first to fourth wavelengths, and an optical multiplexer provided on an optical receiving device side, wherein the first to fourth optical multiplexers are provided. A wavelength division multiplexing transmission system for transmitting the optical multiplexed signal by connecting a first optical fiber to an optical demultiplexer for demultiplexing an optical multiplexed signal obtained by multiplexing optical signals of wavelengths for each wavelength, The optical device has at least first to third optical input / output terminals, and an optical signal input to the first optical input / output terminal is output from the second optical input / output terminal; A first optical circulator in which an optical signal input to an optical input / output terminal is output from the third optical input / output terminal; one end of which is connected to the second optical input / output terminal of the first optical circulator; A first fiber grating that is connected and reflects an optical signal of the second wavelength on the way; A second optical fiber in which a second fiber grating for reflecting an optical signal having a wavelength of? Is formed; and a third optical fiber having one end connected to the first optical input / output end of the first optical circulator. And an optical signal having the first and third wavelengths is multiplexed, and the multiplexed optical signal is input to the other end of the second optical fiber, and the second and fourth wavelengths are input. A first optical filter for multiplexing the optical signals of the first and second optical fibers and inputting the multiplexed optical signal to the other end of the third optical fiber. The optical demultiplexer includes at least a fourth to a sixth optical filter. The optical signal input to the fourth optical input / output terminal is output from the fifth optical input / output terminal, and the optical signal input to the fifth optical input / output terminal A second optical circulator output from the sixth optical input / output terminal, and one end of the second optical circulator A third fiber grating which is connected to the fifth optical input / output terminal of the optical circulator and reflects an optical signal of the second wavelength on the way, and a fourth fiber grating which reflects an optical signal of the fourth wavelength. A fourth optical fiber on which a fiber grating is formed; a fifth optical fiber having one end connected to the sixth optical input / output end of the second optical circulator; and the fourth optical fiber The first output from the other end of
    And a second optical filter that splits the optical signal of the third wavelength and splits the optical signal of the second and fourth wavelengths output from the other end of the fifth optical fiber, The first optical fiber connects the third optical input / output terminal of the first optical circulator to the fourth optical input / output terminal of the second optical circulator, and the first optical fiber connects the fourth optical input / output terminal to the fourth optical input / output terminal of the second optical circulator. A wavelength division multiplexing transmission system characterized in that a multiplex signal propagates.
  12. 12. The wavelength-transmittance change characteristics of the first and second optical filters include a cut-off region for reflecting an optical signal in the wavelength region and a transmission region for transmitting an optical signal in the wavelength region. And an intermediate region in which the transmittance gradually increases from the cutoff region to the transmission region, wherein the first and second wavelengths are cut off by the first and second optical filters. The wavelength division multiplexing transmission system according to claim 11, wherein the third and fourth wavelengths are arranged in the transmission area of the first and second optical filters.
  13. 13. An optical demultiplexer for demultiplexing an optical multiplexed signal obtained by multiplexing optical signals of four different first to fourth wavelengths for each wavelength, wherein the first to fourth optical input / output terminals are connected to each other. The optical signal input to the first optical input / output terminal is output from the second optical input / output terminal, and the optical signal input to the second optical input / output terminal is the third optical input / output terminal. The optical signal output from the input / output terminal and input to the third optical input / output terminal is output from the fourth optical input / output terminal, and the optical signal input to the fourth optical input / output terminal is An optical circulator output from a first optical input / output terminal, connected to the first optical input / output terminal of the optical circulator, and transmitting the optical multiplex signal to the first optical input / output terminal of the optical circulator;
    A first optical fiber for supplying an optical input / output end of the optical circulator, one end of which is connected to the second optical input / output end of the optical circulator and which reflects an optical signal of the second wavelength on the way; A second optical fiber on which a first fiber grating and a second fiber grating for reflecting the optical signal of the fourth wavelength are formed; and a second optical fiber connected to the third optical input / output end of the optical circulator; On the way, a third signal reflecting the optical signal of the second wavelength
    A third optical fiber on which a fiber grating is formed, and the first optical fiber output from the other end of the second optical fiber.
    And an optical filter that demultiplexes an optical signal of a third wavelength. The optical signal of the second wavelength is output from the fourth optical input / output end of the optical circulator, and The optical demultiplexer outputs an optical signal from the third optical fiber.
  14. 14. The wavelength-transmittance change characteristic of the optical filter includes a cut-off region for reflecting an optical signal in the wavelength region, a transmission region for transmitting an optical signal in the wavelength region, and the cut-off region. An intermediate region in which the transmittance gradually changes to the transmission region, wherein the first wavelength is arranged in the cutoff region of the optical filter, and the third and fourth wavelengths are The optical demultiplexer according to claim 13, wherein the second wavelength is disposed in the transmission band of the optical filter, and the second wavelength is disposed in the intermediate region of the optical filter.
  15. 15. An optical multiplexer for multiplexing optical signals of four different first to fourth wavelengths, the optical multiplexer having first to fourth optical input / output terminals, wherein the first optical input / output is provided. The optical signal input to the terminal is output from the second optical input / output terminal, the optical signal input to the second optical input / output terminal is output from the third optical input / output terminal, and the third The optical signal input to the optical input / output terminal is output from the fourth optical input / output terminal, and the optical signal input to the fourth optical input / output terminal is output from the first optical input / output terminal. An optical circulator, which is connected to the first optical input / output terminal of the optical circulator, and multiplexes the optical signals of the first to fourth wavelengths with the first optical signal of the optical circulator. A first optical fiber output from an input / output end, and one end connected to the fourth optical input / output end of the optical circulator A second optical fiber in which a first fiber grating that reflects the optical signal of the second wavelength and a second fiber grating that reflects the optical signal of the fourth wavelength are formed. A third optical input / output terminal of the optical circulator, which reflects an optical signal of the second wavelength in the middle thereof;
    A third optical fiber on which a fiber grating is formed, and the optical signals of the first and third wavelengths are multiplexed, and the multiplexed optical signal is input to the other end of the second optical fiber. An optical filter, wherein the optical signal of the second wavelength is supplied from the second optical input / output end of the optical circulator, and the optical signal of the fourth wavelength is supplied from the third optical fiber. An optical multiplexer.
  16. 16. The wavelength-transmittance change characteristic of the optical filter includes a cut-off region for reflecting an optical signal in the wavelength region, a transmission region for transmitting an optical signal in the wavelength region, and the cut-off region. An intermediate region in which the transmittance gradually changes to the transmission region, wherein the first wavelength is arranged in the cutoff region of the optical filter, and the third and fourth wavelengths are 16. The optical multiplexer according to claim 15, wherein the second wavelength is disposed in the transmission band of the optical filter, and the second wavelength is disposed in the intermediate region of the optical filter.
  17. 17. An optical multiplexer that is provided in an optical transmitter and multiplexes optical signals of four different first to fourth wavelengths, and an optical multiplexer that is provided in an optical receiver and has the first to fourth wavelengths. A wavelength division multiplexing transmission system for transmitting an optical multiplexed signal by connecting an optical demultiplexer for demultiplexing an optical multiplexed signal obtained by multiplexing an optical signal for each wavelength by a first optical fiber, Comprises a first optical input / output terminal, an optical signal input to the first optical input / output terminal is output from the second optical input / output terminal, and the second optical input / output terminal The optical signal input to the terminal is output from the third optical input / output terminal, and the optical signal input to the third optical input / output terminal is output from the fourth optical input / output terminal. A first optical circulator for outputting an optical signal input to the optical input / output terminal of the first optical input / output terminal from the first optical input / output terminal; A first fiber grating which is connected to the fourth optical input / output end of the optical circulator and reflects an optical signal of the second wavelength in the middle thereof, and a second fiber grating which reflects an optical signal of the fourth wavelength. And a third optical fiber connected to the third optical input / output end of the first optical circulator and reflecting an optical signal of the second wavelength in the middle thereof. A third optical fiber on which a fiber grating is formed, and the optical signals of the first and third wavelengths are multiplexed, and the multiplexed optical signal is input to the other end of the second optical fiber. A first optical filter, wherein the optical demultiplexer has fifth to eighth optical input / output terminals, and an optical signal input to the fifth optical input / output terminal is the sixth optical input / output terminal. Output from the input / output terminal and input to the sixth optical input / output terminal An optical signal is output from the seventh optical input / output terminal, and an optical signal input to the seventh optical input / output terminal is output from the eighth optical input / output terminal, and the eighth optical input / output terminal A second optical circulator for outputting an optical signal input to the fifth optical input / output terminal, one end of which is connected to the sixth optical input / output terminal of the second optical circulator, A fourth optical fiber in which a fourth fiber grating that reflects the optical signal of the second wavelength and a fifth fiber grating that reflects the optical signal of the fourth wavelength are formed on the way; A fifth optical fiber which is connected to the seventh optical input / output end of the second optical circulator and in which a sixth fiber grating for reflecting the optical signal of the second wavelength is formed; Output from the other end of the optical fiber 1
    And a second optical filter for demultiplexing an optical signal of a third wavelength, wherein the first optical fiber is provided with the first optical input / output end of the first optical circulator, and the second optical filter. The optical circulator is connected to the fourth optical input / output terminal, and the optical multiplexed signal propagates through the optical circulator. The optical signal of the fourth wavelength is supplied from the output end, is output from the eighth optical input / output end of the second optical circulator, and is supplied from the third optical fiber, and the fifth light A wavelength division multiplexing transmission system output from a fiber.
  18. 18. The wavelength-transmittance change characteristics of the first and second optical filters include a cut-off region for reflecting an optical signal in the wavelength region and a transmission region for transmitting an optical signal in the wavelength region. And an intermediate region in which the transmittance gradually changes from the cutoff region to the transmission region, wherein the first wavelength is disposed in the cutoff region of the first and second optical filters. And disposing the third and fourth wavelengths in the transmission range of the first and second optical filters, and setting the second wavelength in the intermediate range of the first and second optical filters. The wavelength division multiplex transmission system according to claim 17, wherein the wavelength division multiplex transmission system is arranged.
  19. 19. An optical demultiplexer for demultiplexing an optical multiplexed signal obtained by multiplexing optical signals of five different first to fifth wavelengths for each wavelength, wherein the first to fourth optical input / output terminals are connected to each other. The optical signal input to the first optical input / output terminal is output from the second optical input / output terminal, and the optical signal input to the second optical input / output terminal is the third optical input / output terminal. The optical signal output from the input / output terminal and input to the third optical input / output terminal is output from the fourth optical input / output terminal, and the optical signal input to the fourth optical input / output terminal is An optical circulator output from a first optical input / output terminal, connected to the first optical input / output terminal of the optical circulator, and transmitting the optical multiplex signal to the first optical input / output terminal of the optical circulator;
    A first optical fiber for supplying an optical input / output end of the optical circulator, one end of which is connected to the second optical input / output end of the optical circulator, and which reflects an optical signal of the first wavelength on the way A second optical fiber in which a first fiber grating, a second fiber grating that reflects the third wavelength optical signal, and a third fiber grating that reflects the fifth wavelength optical signal are formed. A third optical fiber having one end connected to the third optical input / output end of the optical circulator and a fourth fiber grating formed on the way to reflect an optical signal of the third wavelength. And the second output from the other end of the second optical fiber
    And an optical filter that demultiplexes the optical signal of the fourth wavelength and demultiplexes the optical signal of the first and fifth wavelengths output from the other end of the third optical fiber. An optical signal having a wavelength of is output from the fourth optical input / output terminal of the optical circulator,
    Optical splitter.
  20. 20. The wavelength-transmittance change characteristic of the optical filter includes a cut-off region for reflecting an optical signal in the wavelength region, a transmission region for transmitting an optical signal in the wavelength region, and the cut-off region. An intermediate region in which the transmittance gradually changes to the transmission region, wherein the first and second wavelengths are arranged in the cut-off region of the optical filter; 20. The optical demultiplexer according to claim 19, wherein a wavelength is arranged in the transmission region of the optical filter, and the third wavelength is arranged in the intermediate region of the optical filter.
  21. 21. An optical multiplexer for multiplexing optical signals of five different first to fifth wavelengths, the optical multiplexer having first to fourth optical input / output terminals, wherein the first optical input / output is provided. The optical signal input to the terminal is output from the second optical input / output terminal, and the optical signal input to the second optical input / output terminal is output from the third optical input / output terminal. The optical signal input to the optical input / output terminal is output from the fourth optical input / output terminal, and the optical signal input to the fourth optical input / output terminal is output from the first optical input / output terminal. An optical circulator, which is connected to the first optical input / output terminal of the optical circulator, and multiplexes the optical signals of the first to fifth wavelengths with the first optical signal of the optical circulator. A first optical fiber output from the input / output end, and one end connected to the fourth optical input / output end of the optical circulator A first fiber grating that reflects the optical signal of the first wavelength, a third fiber grating that reflects the optical signal of the third wavelength, and an optical signal of the fifth wavelength A second optical fiber on which a reflecting third fiber grating is formed; and a second optical fiber connected to the third optical input / output end of the optical circulator and reflecting an optical signal of the third wavelength on the way. 4
    A third optical fiber on which a fiber grating is formed, and the optical signals of the second and fourth wavelengths are multiplexed, and the multiplexed optical signal is input to the other end of the second optical fiber. An optical filter for multiplexing the optical signals of the first and fifth wavelengths and inputting the multiplexed optical signal to the other end of the third optical fiber; The signal is supplied from the second optical input / output terminal of the optical circulator,
    Optical multiplexer.
  22. 22. The wavelength-transmittance change characteristic of the optical filter includes a cut-off region for reflecting an optical signal in the wavelength region, a transmission region for transmitting an optical signal in the wavelength region, and the cut-off region. An intermediate region in which the transmittance gradually changes to the transmission region, wherein the first and second wavelengths are arranged in the cut-off region of the optical filter; 22. The optical multiplexer according to claim 21, wherein a wavelength is arranged in the transmission region of the optical filter, and the third wavelength is arranged in the intermediate region of the optical filter.
  23. 23. An optical multiplexer that is provided in an optical transmitter and multiplexes optical signals of five different first to fifth wavelengths, and an optical multiplexer that is provided in an optical receiver and has the first to fifth wavelengths. A wavelength division multiplexing transmission system for transmitting an optical multiplexed signal by connecting an optical demultiplexer for demultiplexing an optical multiplexed signal obtained by multiplexing an optical signal for each wavelength by a first optical fiber, Comprises a first optical input / output terminal, an optical signal input to the first optical input / output terminal is output from the second optical input / output terminal, and the second optical input / output terminal The optical signal input to the terminal is output from the third optical input / output terminal, and the optical signal input to the third optical input / output terminal is output from the fourth optical input / output terminal. A first optical circulator for outputting an optical signal input to an optical input / output terminal of the first optical input / output terminal from the first optical input / output terminal; A first fiber grating which is connected to the fourth optical input / output end of the optical circulator and reflects an optical signal of the first wavelength, and a third fiber grating which reflects an optical signal of the third wavelength on the way. And a second optical fiber on which a third fiber grating for reflecting the optical signal of the fifth wavelength is formed, and connected to the third optical input / output end of the first optical circulator. A third optical fiber in which a fourth fiber grating for reflecting the optical signal of the third wavelength is formed, and the optical signals of the second and fourth wavelengths are multiplexed. The multiplexed optical signal is input to the other end of the second optical fiber, the optical signals of the first and fifth wavelengths are multiplexed, and the multiplexed optical signal is transmitted to the third optical fiber. The first optical fiber to be input to the other end Wherein the optical demultiplexer has fifth to eighth optical input / output terminals, and an optical signal input to the fifth optical input / output terminal is transmitted from the sixth optical input / output terminal. The optical signal output and input to the sixth optical input / output terminal is output from the seventh optical input / output terminal, and the optical signal input to the seventh optical input / output terminal is output from the eighth optical input / output terminal. A second optical circulator for outputting an optical signal output from the input / output terminal and input to the eighth optical input / output terminal from the fifth optical input / output terminal; A fifth fiber grating connected to the sixth optical input / output end of the circulator and reflecting an optical signal of the first wavelength in the middle thereof, and a sixth fiber reflecting the optical signal of the third wavelength A grating and a seventh fiber grating that reflects the optical signal of the fifth wavelength. An eighth fiber grating, one end of which is connected to the seventh optical input / output end of the second optical circulator and which reflects an optical signal of the third wavelength in the middle thereof And a second optical fiber output from the other end of the fourth optical fiber.
    And a second optical filter that demultiplexes the optical signal of the fourth wavelength and demultiplexes the optical signal of the first and fifth wavelengths output from the other end of the fifth optical fiber, The first optical fiber connects the first optical input / output terminal of the first optical circulator to the fourth optical input / output terminal of the second optical circulator, and the optical fiber passes through the first optical fiber. The multiplex signal propagates, and the optical signal of the third wavelength is supplied from the second optical input / output terminal of the first optical circulator, and the eighth optical input / output terminal of the second optical circulator A wavelength division multiplexing transmission system characterized by being output from a transmission line.
  24. 24. The wavelength-transmittance change characteristics of the first and second optical filters include a cut-off region for reflecting an optical signal in the wavelength region and a transmission region for transmitting an optical signal in the wavelength region. And an intermediate region in which the transmittance gradually increases from the cutoff region to the transmission region, wherein the first and second wavelengths are blocked by the first and second optical filters. And the fourth and fifth wavelengths are arranged in the transmission area of the first and second optical filters, and the third wavelength is arranged in the first and second optical filters. 24. The wavelength division multiplexing transmission system according to claim 23, wherein the wavelength division multiplexing transmission system is arranged in an intermediate band.
  25. 25. An optical multiplexer that multiplexes four different optical signals of first to fourth wavelengths, demultiplexes an optical multiplexed signal for each wavelength, and multiplexes two different optical signals of fifth and sixth wavelengths. A wave splitter having first to fourth optical input / output terminals, wherein an optical signal input to the first optical input / output terminal is output from the second optical input / output terminal; An optical signal input to a second optical input / output terminal is output from the third optical input / output terminal, and an optical signal input to the third optical input / output terminal is output from the fourth optical input / output terminal. An optical circulator that outputs an optical signal input to the fourth optical input / output terminal and outputs the optical signal from the first optical input / output terminal; and is connected to the first optical input / output terminal of the optical circulator, The optical multiplexed signal is transmitted to the first
    A first optical fiber for supplying an optical input / output end of the optical circulator, one end of which is connected to the second optical input / output end of the optical circulator, and which reflects an optical signal of the first wavelength on the way. A second optical fiber in which a first fiber grating and a second fiber grating for reflecting the optical signal of the third wavelength are formed; and one end of which is the third optical input / output end of the optical circulator. A fourth optical fiber, one end of which is connected to the fourth optical input / output end of the optical circulator; and a third optical fiber which is output from the other end of the second optical fiber. The second
    And the optical signals of the fourth and fourth wavelengths are demultiplexed, and the optical signals of the first and third wavelengths output from the other ends of the third optical fibers are demultiplexed to obtain the fifth and sixth wavelengths. An optical multiplexer / demultiplexer, comprising: an optical filter that multiplexes the optical signals of the fourth optical fiber and the optical signal that is input to the other end of the fourth optical fiber.
  26. 26. The wavelength-transmittance change characteristic of the optical filter includes a cut-off region for reflecting an optical signal in the wavelength region, a transmission region for transmitting an optical signal in the wavelength region, and the cut-off region. An intermediate region in which the transmittance gradually changes to the transmission region, wherein the first, second, and fifth wavelengths are arranged in the cutoff region of the optical filter; 3. The apparatus according to claim 2, wherein fourth and sixth wavelengths are arranged in the transmission region of the optical filter.
    6. The optical multiplexer / demultiplexer according to 5.
  27. 27. An optical multiplexer for multiplexing optical signals of four different first to fourth wavelengths and demultiplexing an optical multiplexed signal obtained by multiplexing two different optical signals of fifth and sixth wavelengths for each wavelength. A wave splitter having first to fourth optical input / output terminals, wherein an optical signal input to the first optical input / output terminal is output from the second optical input / output terminal, An optical signal input to a second optical input / output terminal is output from the third optical input / output terminal, and an optical signal input to the third optical input / output terminal is output from the fourth optical input / output terminal. An optical circulator that outputs an optical signal input to the fourth optical input / output terminal and outputs the optical signal from the first optical input / output terminal; and is connected to the first optical input / output terminal of the optical circulator, An optical multiplexed signal obtained by multiplexing the optical signals of the first to fourth wavelengths is output from the first optical input / output terminal of the optical circulator. A first optical fiber, one end of which is connected to the fourth optical input / output end of the optical circulator, and a first fiber grating that reflects an optical signal of the first wavelength in the middle thereof; A second optical fiber on which a second fiber grating for reflecting an optical signal of wavelength 3 is formed; and a third light having one end connected to the third optical input / output end of the optical circulator. A fourth optical fiber, one end of which is connected to the second optical input / output end of the optical circulator; and a multiplexed optical signal having the second and fourth wavelengths. The optical signal is input to the other end of the second optical fiber, the optical signals of the first and third wavelengths are multiplexed, and the multiplexed optical signal is transmitted to the other end of the third optical fiber. And the other end of the fourth optical fiber And a said fifth and sixth optical filter for demultiplexing the optical signal of the wavelength of the al output, optical multiplexer demultiplexer.
  28. 28. The wavelength-transmittance change characteristic of the optical filter includes a cut-off region for reflecting an optical signal in the wavelength region, a transmission region for transmitting the optical signal in the wavelength region, and the cut-off region. An intermediate region in which the transmittance gradually changes to the transmission region, wherein the first, second, and fifth wavelengths are arranged in the cutoff region of the optical filter; 3. The apparatus according to claim 2, wherein fourth and sixth wavelengths are arranged in the transmission region of the optical filter.
    8. The optical multiplexer / demultiplexer according to 7.
  29. 29. A first optical transmission / reception device, comprising four different first to fourth wavelength optical signals multiplexed and two different fifth and sixth wavelength optical signals multiplexed. A first optical multiplexer / demultiplexer for demultiplexing one optical multiplexed signal for each wavelength, and a second light provided in the second optical transmitting / receiving device and multiplexing the optical signals of the first to fourth wavelengths Demultiplex the multiplex signal for each wavelength,
    A second optical multiplexer / demultiplexer for multiplexing the optical signals of the fifth and sixth wavelengths with a first optical fiber;
    A wavelength division multiplexing transmission system for transmitting the optical multiplexed signal and the second optical multiplexed signal, wherein the first optical multiplexer / demultiplexer has first to fourth optical input / output terminals, An optical signal input to a first optical input / output terminal is output from the second optical input / output terminal, and an optical signal input to the second optical input / output terminal is output from the third optical input / output terminal. An optical signal output and input to the third optical input / output terminal is output from the fourth optical input / output terminal, and an optical signal input to the fourth optical input / output terminal is output from the first optical input / output terminal. A first optical circulator output from the input / output terminal, one end of which is connected to the fourth optical input / output terminal of the first optical circulator, and reflects an optical signal of the first wavelength in the middle thereof And a second fiber grating that reflects the optical signal of the third wavelength. A second optical fiber, one end of which is connected to the third optical input / output end of the first optical circulator, and one end of which is the first optical circulator. A fourth optical fiber connected to the second optical input / output end of the second optical fiber, and multiplexing the optical signals of the second and fourth wavelengths, and combining the multiplexed optical signal with the second optical fiber To the other end of the third optical fiber, the optical signals of the first and third wavelengths are multiplexed, and the multiplexed optical signal is input to the other end of the third optical fiber. A first optical filter for demultiplexing the optical signals of the fifth and sixth wavelengths output from the other end of the first optical filter, wherein the second optical multiplexer / demultiplexer comprises: An output terminal, wherein an optical signal input to the fifth optical input / output terminal is output from the sixth optical input / output terminal; The optical signal input to the sixth optical input / output terminal is output from the seventh optical input / output terminal, and the optical signal input to the seventh optical input / output terminal is output from the eighth optical input / output terminal. A second optical circulator that outputs an optical signal from the fifth optical input / output terminal and is input from the fifth optical input / output terminal to the eighth optical input / output terminal; A third fiber grating which is connected to a sixth optical input / output terminal and reflects the optical signal of the first wavelength and a fourth fiber grating which reflects the optical signal of the third wavelength in the middle thereof. A fifth optical fiber to be formed; a sixth optical fiber having one end connected to the seventh optical input / output end of the second optical circulator; and a fifth optical fiber having one end connected to the second optical circulator. A seventh optical fiber connected to the eighth optical input / output end of When the second output from the other end of the fifth optical fiber
    And the optical signal of the fourth wavelength is demultiplexed, and the optical signals of the first and third wavelengths output from the other end of the sixth optical fiber are demultiplexed. A second optical filter that multiplexes the optical signals of the first and second optical signals, and inputs the multiplexed optical signal to the other end of the seventh optical fiber. The first optical input / output terminal of the circulator is connected to the fourth optical input / output terminal of the second optical circulator, and the first and second optical multiplexed signals propagate therethrough. Characteristic, wavelength multiplex transmission system.
  30. 30. The wavelength-transmittance change characteristics of the first and second optical filters include a cut-off region for reflecting an optical signal in the wavelength region and a transmission region for transmitting an optical signal in the wavelength region. And an intermediate region in which the transmittance gradually increases from the cutoff region to the transmission region, wherein the first, second, and fifth wavelengths are changed to the first and second optical filters. 30. The wavelength according to claim 29, wherein the third, fourth, and sixth wavelengths are arranged in the transmission area of the first and second optical filters. Multiplex transmission system.
JP2000252966A 2000-08-23 2000-08-23 Optical branching filter and optical coupler Pending JP2002072008A (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2017138091A1 (en) * 2016-02-09 2017-08-17 三菱電機株式会社 Optical multiplexer
WO2018098858A1 (en) * 2016-11-30 2018-06-07 武汉光迅科技股份有限公司 Optical multiplexer/demultiplexer optical interface device for high-speed optical module

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2017138091A1 (en) * 2016-02-09 2017-08-17 三菱電機株式会社 Optical multiplexer
WO2018098858A1 (en) * 2016-11-30 2018-06-07 武汉光迅科技股份有限公司 Optical multiplexer/demultiplexer optical interface device for high-speed optical module

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