JP2001111488A - Device for branching wdm signal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the cost even in a multi-wavelength optical communication system by branching the WDM signal of high density. SOLUTION: A WDM signal branching device is provided with a first branching means 10 for sampling an input WDM signal by an optical filter which has a periodical transmission wavelength characteristic and has a narrow transmission half-value width, a means 20 for dividing the power of the sampled WDM signal and the second branching means 30 for individually sampling a desired signal channel by an optical band pass filter which has a transmission band only in the neighborhood of a single wavelength and has a wide transmission half-value width concerning each divided WDM signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the technical field of optical communication, and in particular, to wavelength division multiplexing (WDM).
Multiplexing) device.

[0002]

2. Description of the Related Art Conventionally, a wavelength division multiplexed signal (hereinafter referred to as WDM) has been used.
As a device for splitting a signal, a fiber grating, an arrayed waveguide diffraction grating (AWG), and the like are widely used. In these demultiplexers having n-channel input / output ports, it is possible to demultiplex an n-channel signal at a time with respect to one-channel WDM signal input at an output.

[0003]

By the way, in the above-described demultiplexer, a device having wavelength transmission characteristics at intervals of 25 GHz has been realized, but it is possible to demultiplex a higher density WDM signal. It is difficult to design a device having a narrow transmission half width, and the cost per unit channel is high, so that there is a problem that the cost is increased in the multi-wavelength optical communication system.

[0004] The present invention has been made under such a background, and is capable of demultiplexing a high-density WDM signal to reduce the cost even in a multi-wavelength optical communication system.
An object of the present invention is to provide a DM signal demultiplexer.

[0005]

A WDM signal demultiplexer according to the present invention is an optical filter (periodic optical filter) having a periodic transmission wavelength characteristic and a narrow transmission half-width for an input WDM signal. A first demultiplexing means for extracting a signal at a transmission wavelength position at a time, a means for dividing the extracted WDM signal power, and a single transmission bandwidth having a wide transmission half width for each of the divided WDM signals. An optical band-pass filter having a transmission band only in the vicinity of a wavelength, comprising a second demultiplexing unit for individually extracting a desired signal channel.

FIG. 1 shows the operation principle of the WDM signal demultiplexing device according to the present invention. In the figure, a mark “x” is a desired channel. The WDM signal input as shown in FIG.
As shown in FIG. 1B, the light is transmitted through an optical filter (first demultiplexing means) whose transmission wavelength changes periodically, and a signal at the transmission wavelength position is extracted at a time as shown in FIG. 1C. . The extracted WDM signal power is divided, and each divided WDM signal is supplied to an optical bandpass filter (second demultiplexing means) having a transmission band only around a single wavelength as shown in FIG. Transmit individually. This allows
As shown in FIG. 1E, a desired signal channel can be extracted.

As described above, an optical filter (periodic optical filter) having a periodic transmission wavelength characteristic and a narrow transmission half width is provided.
The combination of an optical bandpass filter with a narrow transmission half-width but a transmission band only around a single wavelength enables high-density WD
Even for the M signal input, one desired signal channel can be demultiplexed for one optical path from the signal input to the optical bandpass filter.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to FIGS. FIG. 2 shows a configuration example of the WDM signal demultiplexer according to the first embodiment of the present invention. Here, among the N channel WDM signals arranged at equal wavelength intervals, i channel signals (λ _{1 to} λ _j−1 , λ _j , λ _{j + 1} to λ _i )
Is demultiplexed.

As shown in FIG. 2, the WDM signal demultiplexing apparatus of this embodiment includes a periodic optical filter 10 (first demultiplexing means), an optical splitter 20, and an i-channel optical bandpass filter. 30 (second demultiplexing means). The periodic optical filter 10, which is the first demultiplexing unit, is, for example,
A Fabry-Perot filter having a free spectral range (FSR) equal to the wavelength interval of the signal channel to be demultiplexed.
The signal of the channel is extracted at a time, and is incident on the optical splitter 20. The optical splitter 20 divides the input WDM signal power into i powers, and inputs each of them into an optical bandpass filter 30 as a second demultiplexing unit. Optical bandpass filter 3
Reference numeral 0 denotes a filter having a wide transmission half width but having a transmission band only in the vicinity of a single wavelength, and extracts a desired signal channel from each of the input signal lights.

FIG. 3 shows a WD according to a second embodiment of the present invention.
2 shows a configuration example of an M signal demultiplexer. Here, of the N-channel WDM signals arranged at equal wavelength intervals,
I-channel signals (λ _{1,1 to} λ _{1 , j−1} , λ _{1, j} , λ _{1, j + 1 to} λ _{1, i} ) at every other channel indicated by “x” and
The i-channel signals (λ _{2,1 to} λ _{2, j-1} , λ _{2, j} , λ _{2, j + 1 to} λ _{2, i} ) indicated by “O” adjacent to the signals of “X” are It shall be split.

As shown in FIG. 3, a WDM signal demultiplexing apparatus according to this embodiment comprises an optical splitter 1, two periodic optical filters 1
0,12 (first demultiplexing means), two optical demultiplexers 20,2
2 and two sets of optical band-pass filters 30 and 32 (second demultiplexing means) for i channels.

The optical splitter 1 splits the input WDM signal power into two, and inputs the split signal lights to the periodic optical filters 10 and 20, respectively. Thereafter, a periodic optical filter (first dividing unit) 10 -optical divider 20 -optical band-pass filter (second dividing unit) 30 and periodic optical filter (first dividing unit) 12- The operation of each system of the optical splitter 22 and the optical bandpass filter (second splitting means) 32 is the same as the operation of the first embodiment in FIG.

Next, an embodiment of the periodic optical filter of the first dividing means and the optical bandpass filter of the second dividing means used in the WDM signal demultiplexing device of the present invention will be described.

FIG. 4 shows a first embodiment including a Fabry-Perot filter used for a periodic optical filter of the first dividing means. This is an example of a disk-type optical filter as indicated by 400 in FIG. As shown in FIGS. 4B and 4C, the optical filter 400 has a plurality of transmission center wavelengths at an arbitrary circumference at a position θ1 and exhibits a periodic transmission wavelength characteristic. A plurality of signals at the transmission center wavelength position can be separated at a time, and the transmission center wavelength can be changed by rotating the optical filter or moving the incident light to the optical filter.

FIG. 5 shows a second embodiment comprising a Fabry-Perot filter and the like used for the periodic optical filter of the first dividing means. This is an example of a plate-shaped optical filter as indicated by 500 in FIG. The optical filter 500 has a plurality of transmission center wavelengths at an arbitrary linear position x1, as shown in FIGS.
And, since it shows a periodic transmission wavelength characteristic, a plurality of signals at the transmission center wavelength position can be demultiplexed at a time.
The center wavelength of transmission can be changed by moving the optical filter in the linear direction or by moving the incident position of the incident light to the optical filter.

Here, the detailed configuration of the optical filter 400 of the disk type shown in FIG. 4 will be described as an example. As shown in FIG. 6, this optical filter has a basic configuration of a Fabry-Perot etalon including a wedge layer 412 and two high-reflectivity layers 411 and 413 on a substrate 410 which changes according to an estimated angle θ on a disk. .

The transmittance T corresponding to a vertically incident light beam
Is

(Equation 1) Becomes Here, R is the reflectance of the high reflectance layer, and n and h are the refractive index and thickness of the wedge layer. Also, the transmission center wavelength λ
_c is an integer m,

(Equation 2) It is represented by

In the optical filter having such a wedge-type Fabry-Perot structure, the transmission wavelength characteristic as shown in FIGS. 4B and 4C is obtained by changing the thickness h of the wedge layer according to the expected angle θ. Can have. Note that a plate-shaped optical filter having transmission wavelength characteristics as shown in FIGS. 5B and 5C can be similarly realized.

FIG. 7 shows a first embodiment of the optical bandpass filter as the second dividing means. This is shown in FIG.
2 is an example of a disk-type optical filter as indicated by reference numeral 700. As shown in FIG. 7B, the optical filter 700 has a characteristic that the transmission center wavelength monotonously changes in the circumferential direction (the θ direction in the figure), and the optical filter 700 rotates the optical filter or transmits the incident light to the optical filter. , The transmission center wavelength can be changed.

FIG. 8 shows a second embodiment of the optical bandpass filter which is also the second dividing means. This is Figure 8
(A) is an example of a plate-shaped optical filter as shown by 800. As shown in FIG. 8B, the optical filter 800 has a characteristic that the transmission center wavelength monotonically changes in a linear direction (x direction in the figure), and moves the optical filter in the x direction or adjusts the light of the incident light. By moving the incident position on the filter, the transmission center wavelength can be changed.

FIG. 9 shows an arrangement in which an optical circulator 910 and a reflector 930 are arranged before and after an optical band-pass filter (represented by 920 in FIG. 9) as a second dividing means, and the signal light transmitted through the optical band-pass filter 920. Is reflected by the reflection plate 930 and transmitted again through the optical bandpass filter 920, whereby the transmission wavelength characteristic of the optical bandpass filter as the second demultiplexing unit is made steeper and the wavelength selectivity is improved. It is an example. In general, it is possible to connect an optical band-pass filter, which is a second demultiplexing means, in multiple stages in n stages (n ≧ 1), and to dispose an optical circulator on the input side and a reflector on the output side. FIG. 9 shows a case where the number of stages of the optical bandpass filter is n = 1.

FIG. 10 shows a configuration in which a bidirectional optical amplifier 1010 which can be used in both directions is further disposed between the optical bandpass filter 920 and the reflector 930 in the configuration of FIG.
By transmitting the signal light twice through the bidirectional optical amplifier 1010, the transmission wavelength characteristic of the optical band-pass filter as the second demultiplexing unit is made steep, and the transmission loss is efficiently compensated. is there. FIG. 10 shows a case where the number of stages of the optical bandpass filter is n = 1, as in FIG.

Next, an embodiment of the control system of the periodic optical filter as the first demultiplexing means and the band-pass filter as the second demultiplexing means in the WDM signal demultiplexing device of the present invention will be described.

FIG. 11 shows a first embodiment of a control system for a periodic optical filter (second demultiplexing means) and a band-pass filter (second demultiplexing means) in the WDM signal demultiplexing apparatus of the present invention. Show. FIG. 11 shows a case where one wavelength is demultiplexed by one optical path for convenience. In FIG. 11, a control unit 1110 includes an arithmetic unit 1111 and controllers 1112 and 1113.

When there is a change in the wavelength of a desired signal channel to be demultiplexed on the optical path due to a system change or the like, wavelength change information from the WDM light source 1100 is sent to the control unit 1110. In the control unit 1110, the arithmetic unit 1111 receives the wavelength change information from the WDM light source unit 1100, and calculates the intersection of the incident light and the optical filter necessary for the wavelength change based on the information stored in advance. Based on the operation result,
The controller 1112 controls the periodic optical filter 10 as the first demultiplexing unit, and the controller 1113 controls the optical bandpass filter 30 as the second demultiplexing unit. That is, the positions of the intersections between the incident light and the optical filter are controlled by the controllers 1112 and 1113 in accordance with the change in the wavelength of the signal light.

FIG. 12 shows a second embodiment of the control system of the periodic optical filter (first demultiplexing means) and the band-pass filter (second demultiplexing means) in the WDM signal demultiplexing apparatus of the present invention. Show. In the present embodiment, as shown in FIG. 12, an optical splitter 1200 is inserted at any position in the optical path (in the figure, inserted before a periodic optical filter in a receiving optical circuit), and the split WDM signal is measured for wavelength. 11 and the first and second demultiplexing means in consideration of the wavelength information measured by the wavelength measuring device 1210 in addition to the wavelength change information from the WDM light source unit 1100 in the embodiment of FIG. By controlling the optical filters 10 and 30, it is possible to cope with a temporal change in the signal wavelength.

The control unit 1110 shown in FIGS.
In the case where the change in the wavelength is small, only the periodic optical filter 10 of the first demultiplexing means may be controlled.

[0028]

As described above, according to the present invention,
An optical filter (first demultiplexing means) having a periodic transmission wavelength characteristic and a narrow transmission half-value width, and an optical band-pass filter having a wide transmission half-value width but having a transmission band only near a single wavelength (a second division filter). High-density WD by combining
In a multi-wavelength system in which the M signal can be demultiplexed, and a large number of signal channels can be extracted at one time by an optical filter having a periodic transmission wavelength characteristic, which is the first demultiplexing means, Cost can be reduced.

In particular, the optical filter as the first and second demultiplexing means may be a disk-type filter whose transmission center wavelength changes monotonously with respect to the expected angle of intersection with the incident light, or an intersection with the incident light. If the center wavelength changes monotonically with respect to the linear movement of the filter, the change in the system such as the signal wavelength and the number of wavelengths to be demultiplexed, and the change in the signal wavelength over time, the incident light and the optical filter It is possible to respond by controlling the position of the intersection.

[Brief description of the drawings]

FIG. 1 is a diagram showing the operation principle of a WDM signal demultiplexing device according to the present invention.

FIG. 2 is a diagram showing a first embodiment of the WDM signal demultiplexing device of the present invention.

FIG. 3 is a diagram showing a second embodiment of the WDM signal demultiplexer of the present invention.

FIG. 4 is a diagram showing a disk-type optical filter used for a periodic optical filter of the device of the present invention.

FIG. 5 is a diagram showing a plate-shaped optical filter used as a periodic optical filter of the device of the present invention.

FIG. 6 is a diagram illustrating a detailed configuration example of the disk-type optical filter of FIG. 4;

FIG. 7 is a diagram showing a disk-type optical filter used for an optical band-pass filter of the device of the present invention.

FIG. 8 is a diagram showing a plate-shaped optical filter used for an optical band-pass filter of the device of the present invention.

FIG. 9 is a diagram showing a configuration example in which an optical circulator is arranged on the input side and a reflector is arranged on the output side of the optical bandpass filter of the device of the present invention.

FIG. 10 is a diagram showing a configuration example in which a bidirectional optical amplifier is further arranged in FIG. 9;

FIG. 11 is a diagram showing a first embodiment of a control system of a periodic optical filter and an optical bandpass filter of the device of the present invention.

FIG. 12 is a diagram showing a second embodiment of the control system of the periodic optical filter and the optical bandpass filter of the device of the present invention.

[Explanation of symbols]

 Reference Signs List 1 light splitter 10, 12 periodic optical filter (first splitting means) 20, 22 light splitter 30, 32 optical bandpass filter (second splitting means) 400 disk-type periodic optical filter 500 plate-shaped Periodic filter 700 Disc-type optical bandpass filter 800 Plate-shaped optical bandpass filter 910 Optical circulator 930 Reflector 1010 Bidirectional optical amplifier 1110 Control unit

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Noboru Kochio 2-3-1 Otemachi, Chiyoda-ku, Tokyo F-term in Nippon Telegraph and Telephone Corporation (reference) 5K002 BA05 BA21 CA05 CA13 DA02

Claims (11)

[Claims] An apparatus for demultiplexing a wavelength-division multiplexed signal (hereinafter, referred to as a WDM signal), comprising an input WDM signal having an optical filter having a periodic transmission wavelength characteristic and a narrow transmission half-width (hereinafter, a periodic optical filter). ), Means for dividing the extracted WDM signal power, and for each of the divided WDM signals, the transmission band is wide only around a single wavelength, although the transmission half width is wide. A WDM signal demultiplexing device, comprising: a second demultiplexing means for individually extracting a desired signal channel by using an optical bandpass filter. 2. The WDM signal demultiplexing apparatus according to claim 1, wherein a means for dividing the WDM signal power is arranged on the input side of the periodic optical filter as the first demultiplexing means. 3. The WDM signal demultiplexing device according to claim 1, wherein the periodic optical filter serving as the first demultiplexing means is a Fabry-Perot filter. 4. A periodic optical filter, which is a first demultiplexing means, has a disk shape, has a plurality of transmission center wavelengths at arbitrary positions on a circumference, and is expected to intersect with incident light. 4. The WDM signal demultiplexer according to claim 1, wherein the WDM signal demultiplexer is an optical filter whose transmission center wavelength changes with respect to an angle. 5. A periodic optical filter, which is a first demultiplexing means, has a plate-like shape, has a plurality of transmission center wavelengths at arbitrary linear positions, and has a linear shape at an intersection with incident light. 4. The WDM signal demultiplexer according to claim 1, wherein the WDM signal demultiplexer is an optical filter whose transmission center wavelength changes with movement. 6. An optical band-pass filter, which is a second demultiplexing means, has a disk shape and has a center wavelength that changes monotonically with respect to an expected angle of intersection with incident light. The WDM signal demultiplexer according to claim 1, wherein: 7. An optical filter having a plate-like shape, wherein the center wavelength changes monotonously with linear movement of an intersection with incident light. The WDM signal demultiplexer according to claim 1, wherein: 8. A device according to claim 4, further comprising means for controlling a position of an intersection between the incident light and a periodic optical filter as the first demultiplexing means in accordance with a change in the wavelength of the signal light. 6. The WDM signal demultiplexer according to 5. 9. A device according to claim 6, further comprising means for controlling a position of an intersection between the incident light and a band-pass optical filter as a second demultiplexing means in accordance with a change in the wavelength of the signal light. 8. The WDM signal demultiplexer according to 7. 10. An optical band-pass filter, which is a second demultiplexing means, is connected in multiple stages of n stages (≧ 1), and an optical circulator is arranged on the input side and a reflection plate is arranged on the output side. The WDM signal demultiplexer according to claim 1. 11. A bidirectional optical amplifier is disposed at least at one position between an optical bandpass filter, an optical circulator, and a reflector, which are second branching means connected in multiple stages of n stages (≧ 1). The WDM according to claim 10,
Signal splitter.