JPH10221550A - Optical wavelength filter and optical wavelength selecting router - Google Patents

Abstract

PROBLEM TO BE SOLVED: To miniaturize an optical wavelength filter and switch the wavelength channel at high speed by providing a plurality of optical gate elements which are connected to an optical distributor element and control the passing and shielding of distributed optical signals individually. SOLUTION: An optical wavelength filter is provided with a star coupler 14 as an optical distributor element, fiber optical gate element 16 which control passing and shielding of optical signals individually, and a wavelength selecting reflection element 18 which selectively reflects optical signals having different wavelengths according to an optical gate element 16 where the optical signals pass through. The switching of the selection wavelength according to the optical gate element 16 can enhance the speed of switching the wavelength channel compared with a case of switching the selection wavelength by exciting a surface elastic wave. The connection via the optical distributor element 14, the wavelength selecting reflection element 18, and the optical gate element can increase the quenching ratio of the optical signals by the optical gate element 16 so as to reduce the cross talk.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical wavelength filter capable of selecting an optical signal of a specific wavelength channel from wavelength multiplexed optical signals, and a specific optical filter among wavelength multiplexed optical signals. The present invention relates to an optical wavelength selection router that can exchange optical signals of wavelength channels.

[0002]

2. Description of the Related Art An example of a conventional optical wavelength filter capable of simultaneously selecting optical signals of a plurality of wavelength channels from wavelength-multiplexed optical signals is disclosed in Reference 1: "1996".
IEICE General Conference Proceedings C-254 ". According to the optical wavelength filter disclosed in Document 1, the surface acoustic wave (SAW) and the acoustic wave
Select a light wavelength corresponding to one to one. As a result, it is possible to simultaneously select optical signals of a plurality of wavelength channels by exciting surface acoustic waves of a plurality of frequencies.

[0003] Another example of an optical wavelength filter is disclosed in Document 2: "Journal of Lightwave Technology" Vol.
4, No. 6, p. 977 (1996) ". In particular, FIG. According to the optical wavelength filter disclosed in 1 (a), an optical gate element is provided on each optical path connecting a 1 × N demultiplexer and an N × 1 multiplexer for each wavelength channel. The optical gate element controls passage and cutoff of an optical signal for each wavelength channel to select a wavelength channel.

[0004] In particular, FIG. According to the optical wavelength filter disclosed in 1 (b), one optical multiplexer / demultiplexer is provided, and the output of the optical multiplexer / demultiplexer is provided with a loopback optical path for each wavelength channel for re-input to the optical multiplexer / demultiplexer. I have. An optical gate element provided on each loopback optical path controls passage and cutoff of an optical signal for each wavelength channel, and selects a wavelength channel.

Also, in optical communication using wavelength-multiplexed optical signals, when a specific wavelength channel is separated and extracted, a new optical signal is inserted into an empty wavelength channel to add a wavelength channel. It is desired to make effective use of. An example of an optical wavelength selection router that selectively replaces an optical signal of a specific wavelength channel among such wavelength-multiplexed optical signals is disclosed in Reference 3: “Journal of Lightwave Technology”.
ogy) Vol. 14, pp. 1320-1340 (19
96)). In particular, FIG.
According to the optical wavelength selection router disclosed in No. 17, a demultiplexing element for demultiplexing a wavelength-multiplexed optical signal for each wavelength channel and a multiplexing element are connected for each wavelength channel. Then, 2 × 2 optical switches are provided on the optical fibers of the respective wavelength channels. By switching each 2 × 2 optical switch, an optical signal can be inserted or separated for each wavelength channel.

[0006]

However, in the optical wavelength filter disclosed in the above document 1, the switching speed is limited by the speed of the surface acoustic wave because the selected wavelength is switched by exciting the surface acoustic wave. For this reason, there is a problem that it takes about a microsecond (10 ^-6 seconds) to switch the selected wavelength. On the other hand, in order to perform packet switching, it is required to switch wavelength channels at high speed in a time of about nanoseconds (10 ⁻⁹ seconds).

Further, FIG. 1 of (a)
However, the optical wavelength filter disclosed in JP-A-2003-157404 requires an optical demultiplexing element and an optical multiplexing element, and thus has a problem that it is difficult to reduce the size of the optical wavelength filter. In addition, FIG. In the optical wavelength filter disclosed in 1 (b), the functions of the optical demultiplexer and the optical multiplexer can be performed by one optical multiplexer / demultiplexer, but the loopback optical path needs to be routed. For this reason, it is difficult to reduce the size of the optical wavelength filter, and it is considered that the waveguide loss in the long loopback optical path increases.

For this reason, in an optical wavelength filter capable of extracting optical signals of a plurality of wavelength channels from wavelength-multiplexed optical signals, the size of the optical wavelength filter can be reduced and the wavelength channel can be switched at a higher speed than in the past. It has been desired to realize an optical wavelength switch capable of performing the above.

[0009] In the optical wavelength selection router described in Document 3, a 2 × 2 optical switch is used. 2x
With a two-optical switch, a switch with a sufficiently high switching speed has not been obtained. In addition, the 2 × 2 optical switch generally requires a large drive voltage, and it is difficult to sufficiently reduce crosstalk and increase the accuracy of the selected wavelength.
It has polarization dependence. For this reason, in the optical wavelength selection router, the switching speed of the wavelength channel and the accuracy of the selected wavelength are restricted by the 2 × 2 optical switch.

For this reason, it has been desired to realize a novel optical wavelength selective router that does not require the use of a 2 × 2 optical switch.

[0011]

According to the optical wavelength filter of the present invention, an optical distribution element and a plurality of optical signals connected to the optical distribution element and individually controlling passage and blocking of the distributed optical signal are provided. A gate element and a wavelength selective reflection element that is connected to the light distribution element via the optical gate element and selectively reflects optical signals of different wavelengths by the optical gate element through which the optical signal has passed. Features.

As described above, according to the optical wavelength filter of the present invention, each of the wave selective reflection elements is connected to the light distribution element via the optical gate element. For this reason, when the optical gate element is in a state of passing an optical signal (hereinafter also referred to as “ON state”), the wavelength-multiplexed optical signal input to the input port is connected to the optical gate element in the ON state. Input to the wavelength selective reflection element. The wavelength selective reflection element selectively reflects only the optical signal of the wavelength channel that matches the reflection wavelength of the element. The selectively reflected optical signal is output to an output port via an optical gate element and an optical distribution element.

Therefore, the optical gate element connected to the wavelength selective reflection element having the reflection wavelength coincident with the specific wavelength channel is turned on, and the other optical gate elements are cut off the optical signal (hereinafter, referred to as "the optical gate element"). Also referred to as "OFF state".)
Thus, an optical signal of the specific wavelength channel can be selected from the wavelength-multiplexed optical signals input from the input port and extracted from the output port. Also,
By simultaneously turning on a plurality of optical gate elements, optical signals of a plurality of wavelength channels can be selected and extracted.

Therefore, according to the optical wavelength filter of the present invention, since the selected wavelength is switched by the optical gate element, the wavelength channel is switched at a higher speed than in the case where the surface acoustic wave is excited to switch the selected wavelength. be able to.

Further, according to the optical wavelength filter of the present invention, since the light distribution element, the wavelength selective reflection element, and the optical gate element are connected via the optical gate element, the optical signal passing through the optical gate element can be used as an optical signal. And passes through the optical gate element again. As a result, the optical signal of the wavelength channel that is not selected is blocked again by the optical gate element on the return path even if there is light leakage that is not completely blocked by the optical gate element on the outward path. Therefore, the extinction ratio of the optical signal by the optical gate element can be increased. For this reason, crosstalk can be reduced.

Further, according to the optical wavelength filter of the present invention, an optical demultiplexing element and an optical multiplexing element are not required.
Since a loopback optical path is not required and the configuration is simple, the wavelength optical filter can be reduced in size.

In the optical wavelength filter according to the present invention, preferably, the light distribution element has an input connection point connected to the input port and an output connection point connected to the output port.

As described above, by providing the input connection point and the output connection point in the optical distribution element, the optical signal input from this input terminal is distributed to each of the optical gate elements and output, and
The optical signal that has passed through the optical gate and reflected by the wavelength selective reflection element can be output from the output connection point to the output port. Further, if an optical signal of the selected wavelength is output from the output connection point of the optical distribution element to the output port, there is no need to provide a new configuration for extracting the optical signal of the selected wavelength. The structure of the wavelength filter can be made simpler.

In the optical wavelength filter according to the present invention, preferably, an optical isolator is provided on an optical path between the input port and the optical distribution element.

Thus, if an optical isolator is provided,
It is possible to suppress a part of the optical signal reflected by the wavelength selective reflection element from being output from the optical distribution element to the input port as return light.

In the optical wavelength filter according to the present invention, preferably, an optical circulator is provided on an optical path between the input port and the optical distribution element, and the optical circulator includes a first terminal, the first terminal And a third terminal for outputting an optical signal input from the second terminal. The first terminal is connected to the input port, and the second terminal is connected to the input port. , And an input connection terminal of the light distribution element.

As described above, if an optical isolator is provided,
It is possible to suppress a part of the optical signal reflected by the wavelength selective reflection element from being output from the optical distribution element to the input port as return light.

In the optical wavelength filter according to the present invention, it is preferable that an optical amplifier is provided on an optical path connecting the input port and the optical distribution element.

As described above, by providing the optical amplifier, the intensity of the optical signal output from the optical amplifier can be amplified with respect to the intensity of the optical signal input to the optical amplifier. As a result, it is possible to compensate for the loss of the optical signal strength due to the distribution of the optical signal in the optical distribution element. The spontaneous emission light noise generated by the optical amplifier over a wide wavelength range is cut by the wavelength selective reflection element except for the wavelength of the selected wavelength channel. Therefore, spontaneous emission noise other than the wavelength of the wavelength channel is not output to the output port.

In the optical wavelength filter according to the present invention, it is preferable that the optical gate element includes an electroabsorption optical modulator.

The electroabsorption optical modulator utilizes a phenomenon in which when a reverse bias is applied to a waveguide having a pin structure i-layer as a waveguide layer, the band gap of the waveguide is shifted by an electric field generated by the reverse bias. Things. When the band gap shifts, the transmittance of the optical signal of the waveguide changes. Therefore, by controlling the reverse bias, it is possible to operate as an optical gate element.

Therefore, if an electroabsorption optical modulator is provided as an optical gate element, the wavelength channel to be selected can be switched at high speed by controlling the reverse bias.

Further, in the electro-absorption type optical modulator,
Current due to reverse bias hardly flows. For this reason,
If an electro-absorption type optical modulator is provided as an optical gate element, an operation as an optical gate can be performed with low driving power.

Further, in the optical wavelength filter of the present invention, preferably, an optical amplifier is provided as the optical gate element.

The optical amplifier can substantially cut off the optical signal by reducing the amplification factor of the intensity of the optical signal output from the optical amplifier with respect to the intensity of the optical signal input to the optical amplifier. Therefore, the optical amplifier can operate as an optical gate element. Further, when the amplification factor of the optical amplifier is increased when the optical gate element is in the ON state, not only can the optical signal be passed, but also the loss of the optical signal intensity due to the distribution of the optical signal in the optical distribution element. Can be compensated for. The spontaneous emission light noise generated by the optical amplifier over a wide wavelength range is cut by the wavelength selective reflection element except for the wavelength of the selected wavelength channel. Therefore, spontaneous emission noise other than the wavelength of the wavelength channel is not output to the output port.

In the optical wavelength filter according to the present invention, preferably, a grating is provided as the wavelength selective reflection element.

The grating has a narrow half width of the reflection wavelength. Therefore, if a grating is provided as a wavelength selective reflection element, crosstalk can be reduced.
As a result, the accuracy of wavelength selection of the optical wavelength filter can be improved.

In the optical wavelength filter according to the present invention, it is preferable that a multilayer film is provided as the wavelength selective reflection element.

If a multilayer film is provided as the wavelength selective reflection element, the structure of the optical wavelength filter can be made simpler, and the production of the optical wavelength filter becomes easy.

Further, in the optical wavelength filter of the present invention, it is preferable that a reflection type waveguide array grating is provided as the wavelength selective reflection element.

If a reflection type waveguide array grating is provided as the wavelength selective reflection element, an optical wavelength filter can be easily manufactured without forming a grating.

In the optical wavelength filter according to the present invention, preferably, the wavelength selective reflection element is constituted by a reflection element set for selectively reflecting optical signals having mutually different wavelengths. Each is constituted by a pair of a first reflection element and a second reflection element for selectively reflecting an optical signal having the same wavelength, and for each of the reflection element sets, the first reflection element is Connected to the light distribution element via an optical gate element by a first optical path, and for each of the reflective element sets, the second reflection element is connected to the light distribution element via the optical gate element by a second optical path to the first light distribution element. A first optical signal input from the first optical path to the light distribution element for each of the reflective element sets;
The phase of the first optical signal and the phase of the second optical signal are such that interference light due to the second optical signal input from the optical path to the optical distribution element reinforces at the output connection point and weakens at the input connection point. And a phase control element for giving a phase difference between the first and second optical paths.

As described above, the phase control element is provided for each wavelength selective reflection element, and the phase of the first optical signal and the phase of the second optical signal respectively reflected by the first and second reflection elements are determined. By providing a phase difference between the first and second optical signals so that the interference light generated by the first optical signal and the second optical signal reinforce each other at the output connection point and weaken each other at the input connection point, wavelength selective reflection on the light distribution element can be achieved. The optical signal input from the element can be selectively guided to the output port. As a result, light returning to the input port can be suppressed.

Further, according to the optical wavelength selective router of the present invention, the input port is connected to an input port to which an input optical signal in which optical signals of a plurality of wavelength channels are wavelength-multiplexed is input via an optical amplifier and an optical isolator. A first optical coupler for distributing an input optical signal and outputting it from the first and second output terminals; and a first optical coupler connected to the first output terminal, the input optical signal being output from the first output terminal. A first optical wavelength filter for selecting an optical signal of a specific wavelength channel and outputting the selected optical signal as a separated optical signal to a separation port; and a second output terminal connected to the first optical wavelength filter, the input signal output from the second output terminal A second optical wavelength filter for selecting an optical signal of a wavelength channel other than the wavelength channel of the separated signal and outputting as a residual optical signal, a first input terminal connected to the second optical wavelength filter, and a wavelength channel of the separated signal. Having a second input terminal connected to an insertion port to which an insertion optical signal of a wavelength channel included in the optical signal is input, and a residual optical signal input from the first input terminal and an insertion light input from the second input terminal. A second optical coupler for wavelength-multiplexing the signal and outputting the output optical signal to an output port.

As described above, according to the optical wavelength selective router of the present invention, of the input optical signals input to the input port,
Outputting an optical signal of a specific wavelength channel to a separation port as a separation optical signal, and combining an insertion optical signal and a residual optical signal input from the insertion port, and outputting the resultant signal as an output optical signal from the output port. Can be. Therefore, the optical signal of a specific wavelength channel among the wavelength-multiplexed optical signals can be replaced without the need for a 2 × 2 coupler.

Further, in the optical wavelength selective router of the present invention, it is preferable that the optical wavelength filter of the present invention is provided as the first and second optical wavelength filters.

As described above, if the optical wavelength filter of the present invention is provided as the first and second optical wavelength filters, the wavelength channel to be selected can be switched at high speed as described above, Talk can be reduced.

In the optical wavelength selective router according to the present invention, when the optical wavelength filter according to the present invention is provided, preferably, the wavelength selective reflection element and the second optical wavelength filter that constitute the first optical wavelength filter are constituted. The wavelength selective reflection element is configured with a common grating, configures a first optical wavelength filter, configures an optical gate element connected to one end of the grating, and configures a second optical wavelength filter;
As for the optical gate element connected to the other end of the grating, one of the optical gate elements preferably allows an optical signal to pass and the other optical gate element blocks the optical signal for each grating.

As described above, if the wavelength selective reflection elements of the first optical wavelength filter and the second optical wavelength filter are formed as a common grating, the configuration of the elements can be simplified.

[0045]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of an optical wavelength filter and an optical wavelength selection router according to the present invention will be described below with reference to the drawings. It should be noted that the drawings referred to merely schematically show the size, shape and arrangement of each component to the extent that these inventions are understood. Therefore, these inventions are not limited to the illustrated examples.

1. First Embodiment In a first embodiment, an example of an optical wavelength filter according to the present invention will be described. FIG. 1 is a configuration diagram for explaining an optical wavelength filter according to the first embodiment.

The optical wavelength filter 10 according to the first embodiment
A p-type InP substrate 12 includes a star coupler 14 as an optical distribution element, five optical gate elements 16 for individually controlling passage and cutoff of an optical signal, and a star through these optical gate elements 16. A wavelength selective reflector 18 is connected to the coupler 14 and selectively reflects optical signals of different wavelengths by the optical gate element 16 through which the optical signal has passed.

Here, the wavelength selective reflection element 18 is formed by first to fifth gratings 18a to 18a utilizing Bragg reflection.
18e. The first to fifth gratings 18a to 18e selectively reflect optical signals having different wavelengths, respectively. That is, the first to fifth gratings 18a to 18e respectively have wavelengths λ ₁ , λ ₂ , λ
₃ , λ ₄ and λ ₅ are selectively reflected. Since the grating has a narrow half-value width of the reflection wavelength, if a grating is provided as the wavelength selection reflection element 18, crosstalk can be reduced. As a result, the accuracy of wavelength selection of the optical wavelength filter can be improved.

The first to fifth gratings 18a to 18a
18e are the optical gate elements 16, that is, the first
To the light distribution element 14 through the fifth to fifth optical gate elements 16a to 16e.

Therefore, when the wavelength-multiplexed optical signal passes through the first optical gate element 16a, the wavelength λ ₁
Is selectively reflected by the first grating of the wavelength selective reflection element 18. Similarly, the optical signal passing through the second optical gate element 16a has a wavelength λ
Only ₂ of the optical signal is selectively reflected by the second grating. Similarly, in the optical signal that has passed through the third optical gate element 16c, only the optical signal having the wavelength λ ₂ is selectively reflected by the third grating. Similarly, the fourth
Optical signal passed through the optical gate element 16d, only the optical signal having the wavelength lambda ₄ of which is selectively reflected by the fourth grating. Similarly, the fifth optical gate element 16e
Only the optical signal of wavelength λ ₅ is selectively reflected by the fifth grating.

Therefore, the first to fifth optical gate elements 16a to 16a
By individually controlling the passage and cutoff of each optical signal of 16e, the wavelength of the optical signal reflected by the wavelength selective reflection element 18 can be selected.

As the optical gate element 16, for example, an electroabsorption type optical modulator may be used. The electro-absorption optical modulator applies, for example, a reverse bias to a pin-structured waveguide in which a p-type InP substrate, an i-layer (low impurity concentration layer) as a waveguide layer, and an n-type clad layer are sequentially stacked. This utilizes the phenomenon that the band gap of a waveguide shifts due to an electric field generated by a reverse bias. When the band gap shifts, the transmittance of the optical signal of the waveguide changes. Therefore, by controlling the reverse bias, it is possible to operate as an optical gate element. Therefore,
If an electro-absorption optical modulator is provided as the optical gate element 16, the wavelength channel to be selected can be switched at high speed by controlling the reverse bias.

Further, in the electro-absorption type optical modulator,
Current due to reverse bias hardly flows. For this reason,
If an electro-absorption type optical modulator is provided as an optical gate element, an operation as an optical gate can be performed with low driving power.

As another example of the optical gate element 16, for example, an optical amplifier may be used. The optical amplifier can substantially cut off the optical signal and turn it off by reducing the amplification factor of the intensity of the optical signal. Therefore, the optical amplifier can operate as an optical gate element. If the amplification factor of the optical amplifier is increased when the optical gate element 16 is in the ON state, not only can the optical signal pass, but also the optical signal intensity can be reduced by the distribution of the optical signal by the optical distribution element. Loss can be compensated. In addition, spontaneous emission noise over a wide wavelength range emitted by the optical amplifier is cut by the wavelength selective reflection element 18 except for wavelengths that are selectively reflected. Therefore, spontaneous emission light noise other than the reflection wavelength is not output to the output port.

When an electroabsorption modulator is provided as the optical gate element 16, it is necessary to use a compound semiconductor substrate having a pin structure. In the case of this optical amplifier, however, it is not necessary to use a compound semiconductor substrate. Instead, for example, a glass substrate may be used.

When the intensity of an optical signal is amplified using an optical amplifier, the grating 18 and the input port 20
In order to prevent an optical signal from resonating by using a resonator between the input port 20a and the output port 20b, an antireflection film (not shown in FIG. 1) may be provided on the input port 20a and the output port 20b.

In this embodiment, the light distribution element 14 for distributing light to these optical gate elements 16 is:
It has an input connection point 24a connected to the input port 20a and an output connection point 24b connected to the output port 20b.
As such a light distribution element 14, here,
A star coupler 14 is provided. This star coupler 14
Is composed of a planar waveguide having a symmetry axis X, and two input / output surfaces 14 each intersecting with the symmetry axis X.
a and 14b. One input / output surface 14a
Forms an arc with a radius r about the point O ₁ on the symmetry axis X. The other of the input and output surface 14b is an arc of radius r centered at the intersection of O ₂ axis of symmetry X and one of the input and output surfaces 14a.

The input / output surface 14a of the star coupler 14 has an input connection point 24a and an output connection point 24b at positions symmetrical with respect to the symmetry axis X. The input connection point 24a is connected to the input port 2 via the input waveguide 22a.
0a. The output connection point 24b is connected to the output port 20b via the output waveguide 22b.

The other input / output surface 14b of the star coupler 14 has first to fifth input / output connection points 26a to 26e, respectively. The third input / output connection point 26c is
It is provided at the position of the center point O ₁ on the symmetry axis X. The first to fifth input / output connection points 26a to 26e are respectively connected to the first
They are connected to the first to fifth optical gate elements 16a to 16e via the fifth to fifth input / output waveguides 28a to 28e, respectively.

By the way, when the optical signal is distributed by the star coupler 14, the input connection point 24a of the one input / output surface 14a
The optical signal input from the optical disk spreads in a fan shape toward the other input / output surface 14b. However, the other input / output surface 14b
The intensity of the optical signal arriving at each portion becomes smaller as the portion moves away from the position in front of the input connection point 24a. Here, the input connection point 24a is provided near the symmetry axis X. For this reason, the intensity of the optical signal reaching the input / output connection point 26 becomes substantially smaller as the position of the input / output connection point 26 is further away from the symmetry axis X.

The reflected light signal input from any of the input / output terminals 26 to the star coupler 14 also spreads in a fan shape toward one of the input / output surfaces 14a. Therefore, the intensity of the reflected light signal when it reaches each part of the one input / output surface 14a also decreases as the part moves away from the position in front of the input / output connection point 26. Here, the output connection point 24
b is provided near the symmetry axis X. For this reason, the intensity of the optical signal reaching the output connection point 24b from the input / output connection point 26 becomes substantially smaller as the position of the input / output connection point 26 is further away from the axis of symmetry X.

For example, the intensity of the optical signal reaching the first and fifth input / output connection points 26a and 26e from the input connection point 14a is the intensity of the optical signal reaching the third input / output connection point 26a on the axis of symmetry X. Consider a case that is smaller by 1 dB. In this case, the first and fifth input / output connection points 26a and 2
6e, the intensity of the optical signal reaching the output connection point 24b is also
The intensity of the optical signal reaching the output connection point 24b from the third input / output connection point 26c is further reduced by 1 dB. Therefore, the intensity of the optical signal that has traveled to and from the first and fifth input / output connection points 26a and 26e is smaller by 2 dB than the intensity of the optical signal that has traveled to and from the third input / output connection point 26c.

Therefore, it is preferable that the angle from the input connection point 24a to the first input / output connection point 26a and the fifth input / output connection point 26e, which are input / output connection points at both ends, is small.

Then, the star coupler 14 distributes the optical signal input from the input connection point 24a and outputs it from the first to fifth input / output connection points 26a to 26e. Optical signals output from the first to fifth input / output connection points 26a to 26e are input to the first to fifth optical gate elements 16a to 16e, respectively. The optical signal is transmitted to the optical gate element 1
When 6 is in the ON state, it is input to the wavelength selective reflection filter 18 corresponding to the optical gate element 16.

As described above, the optical wavelength filter 10 controls the passage and cutoff of each of the optical signals of the first to fifth optical gate elements 16a to 16e, respectively, so that the wavelength selective reflection element The wavelength of the optical signal reflected at 18 can be selected. Then, the optical signal reflected by the wavelength selective reflection element 18 (hereinafter, “reflected optical signal”
Also called. ) Is input to the optical demultiplexing element 14 again through the optical gate element 16 that has passed on the outward path. Then, the reflected light signal is output from the output connection point 24b of the light distribution element 14 to the output port 20b via the output waveguide 22b.

Incidentally, the wavelength λ of the Bragg reflection of the above-mentioned grating depends on the effective refractive index n of the waveguide on which the grating is formed and the period Λ of the grating in the case of the waveguide type. Given.

Λ = 2Λn (1) The effective refractive index n of the waveguide depends on the composition of the waveguide. The composition of the waveguide can be controlled by, for example, a selective growth method. As a control method by the selective growth method, for example, first, a SiO ₂ mask having an opening is formed on an InP substrate. Next, a waveguide is grown in the opening by MOCVD (metal organic chemical vapor deposition). By controlling the width of the opening, the composition of the waveguide can be controlled as is well known in the art.

Therefore, even if the grating period Λ is the same, gratings having different reflection wavelengths can be easily obtained over the entire wavelength range (for example, about 50 nm) of the wavelength-multiplexed optical channel only by changing the composition of the waveguide. be able to.

When the selective growth method is used, the band gap of the waveguide can be controlled by changing the composition of the waveguide. In an optical amplifier or an electro-absorption optical modulator, by reducing the difference between the band gap and the energy of the optical signal, the amplification efficiency of the optical amplifier and the modulation efficiency when a reverse bias is applied to the electro-absorption optical modulator. Can be improved.

The optical signal of the wavelength channel selectively reflected by the grating 18 passes through the optical gate element 16 again and is input to the input / output connection point 26 of the other surface 14 b of the star coupler 14. . As described above, the optical signal that has passed through the optical gate element 15 is reflected by the wavelength selective reflection element, and passes through the optical gate element again. As a result, the optical signal of the wavelength channel that is not selected is blocked again by the optical gate element on the return path even if there is light leakage that is not completely blocked by the optical gate element on the outward path. Therefore, the extinction ratio of the optical signal by the optical gate element can be increased. For this reason, crosstalk can be reduced.

In this embodiment, the optical signal of the selected wavelength channel input to the input / output connection point 26 is
Input connection point 24a and output connection point 2 on one surface 14a
4b. Then, an optical signal of the selected wavelength channel is output from the output connection point 24.

In this embodiment, the input connection point 2
An optical signal is also output to 4a. Therefore, here, in order to prevent the return light to the input port 20a, the isolator 30 is provided on the input waveguide 22a between the input port 20a and the input connection point 24a.

Next, λ ₁ , λ ₂ , λ ₃ , λ ₄ and λ ₅
From among the optical signals wavelengths are wavelength-multiplexed, the operation of the optical wavelength filter when taking out by selecting the lambda ₂ and lambda ₄ optical signals of wavelengths will be described.

First, the λ input from the input port 20a
₁ to [lambda] ₅ of the optical signals of wavelength channels (hereinafter, "lambda ₁ to [lambda] ₅
Optical signal ". ) Is input to the star coupler 14 from the input connection point 24a of one input / output surface 14a via the input waveguide 22a. The optical signals of λ ₁ to λ ₅ input to the star coupler 14 are distributed to the first to fifth input / output connection points 26 a to 26 e on the other surface 14 b and input. Optical signals of lambda ₁ to [lambda] _5, which are respectively input to the first to fifth output connection point 26a~26e propagates through the first to fifth input and output waveguides 28a to 28e, first to each of the first 5 Input to the optical gate elements 16a to 16e.

Here, in order to select λ ₂ and λ ₃ , the second optical gate element 16 b and λ 2 connected to the second grating 18 b that selectively reflects light of wavelength λ ₂ are used.
_Third grating 1 that selectively reflects light of ₃ wavelengths
Only the third optical gate element 16c connected to 8c is turned on. And the first, fourth and fifth optical gate elements 1
6a, 16d and 16e are turned off. As a result, only the optical signals of λ ₁ to λ ₅ input to the second and third optical gates 28b and 28c are input to the second and third gratings 18b and 18c, respectively.
Then, the second and gratings 18b are λ _{1 to} λ
Only the optical signal of λ ₂ among the _five optical signals is selectively reflected. Further, the third and gratings 18c are λ ₁ to
Only selectively reflects lambda ₃ of the optical signal of the lambda ₅ of the optical signal. Therefore, the star coupler 14 has λ ₂ and λ ₃
Is input again from the second and third input / output connection points 26b and 26c. The optical signals of λ ₂ and λ ₃ input again from the second and third input / output connection points 26b and 26c are connected to the input connection point 24a and the output connection point 2
4b. Then, the optical signals of λ ₂ and λ ₃ input to the output connection point 24b are output from the output port 20b via the output waveguide 22b.

Note that the λ ₂ input to the input connection point 24a is
Since the optical signals of λ ₃ and λ ₃ are cut off by the optical isolator 30, they are not output from the input port 20a.

[0077] 2. Second Embodiment In a second embodiment, an example of the optical wavelength filter according to the present invention will be described. FIG. 2 is a configuration diagram for explaining an optical wavelength filter 10a according to the second embodiment.

The configuration of the optical wavelength filter according to the second embodiment is such that an optical circulator 32 is provided instead of an isolator, and a multi-mode waveguide 34 is used as an optical wavelength distribution element instead of a star coupler. Except for the configuration, the configuration is the same as that of the optical wavelength filter of the first embodiment described above. For this reason, in the second embodiment,
The same constituent components as those of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and the details will not be described.

Optical wavelength filter 10a of the second embodiment
In, an optical circulator 32 is provided on an input waveguide 22a between an input port 20a and a multimode waveguide 34 as an optical distribution element. The optical circulator 32 includes a first terminal 32a, a second terminal 32b that outputs an optical signal input from the first terminal 32b, and a second terminal 32b.
Third terminal 3 for outputting an optical signal input from terminal 32b
2c. The first terminal 32a is connected to the input port 20a. The second terminal 32b is
It is connected to the input connection point 24a of the light distribution element 34. As a result, the return light input to the second terminal 32b is output to the third terminal 32c. Therefore, the wavelength selective reflection element 18
Can be prevented from returning from the light distribution element 34 to the input port 20a as return light.

In the second embodiment, if the input connection point 24a and the output connection point 24b are shared, an optical signal of the selected wavelength can be output from the third terminal 32c of the optical circulator 32. it can.

In the optical wavelength filter 10a according to the second embodiment, the multimode waveguide 34 composed of a planar waveguide having a rectangular planar pattern is used as the light distribution element 34.
It has. This multimode waveguide 34 has two input / output surfaces 34a and 34b facing each other. An input connection point 36a and an output connection point 36b are provided on one input / output surface 34a. The input connection point 36a and the output connection point 36b are connected to the input waveguide 22a and the output waveguide 22b, respectively.

The first input / output surface 34b has the first
And fifth connection points 38a to 38e. The first to fifth input / output connection points 38a to 38e are connected to the first input / output waveguides 28a to 28e, respectively.

The multimode waveguide 34 has the following (2)
By satisfying the expressions (3) and (3), the device functions in the same manner as the star coupler 14 described above.

D = W / N (2) where d is the distance between the input connection point 36a and the output connection point 36b and the distance between the input / output connection points 38a to 38e (for example, d
= 7 μm). W represents the width of the multi-mode waveguide 34 (for example, W = 35 μm), that is, the length of the two input / output surfaces 34a and 34b along the substrate surface. N represents the number of input / output connection points (in this case, N = 5).

L = 3L _C / N (3) where L is the length of the multimode waveguide 34 (for example, L = 2
200 μm), that is, the distance between one input / output surface 34a and the other input / output surface 34b. L _C satisfies the following equation (4).

L _C ≒ 4nW ² / 3λ (4) where n is the refractive index of the multimode waveguide (for example, n = 3.
5). Λ represents the center wavelength (for example, λ = 1.55 μm) of the wavelength-multiplexed optical signal.

[0087] 3. Third Embodiment In a third embodiment, an example of the optical wavelength filter of the present invention will be described. FIG. 3 is a configuration diagram for explaining an optical wavelength filter 10b according to the third embodiment.

The configuration of the optical wavelength filter according to the third embodiment is such that the optical amplifier 37 is provided on the input waveguide 22a connecting the input port 20a and the light distribution element 14, and the input port 20a and the output The configuration is the same as the configuration of the optical wavelength filter according to the above-described first embodiment except that an antireflection film 39 is provided on the port 20b. For this reason,
In the third embodiment, the same components as those in the first embodiment are denoted by the same reference numerals as those in the first embodiment, and the detailed description thereof is omitted. In FIG. 3, the illustration of the isolator is omitted.

By the way, in the star coupler 14 and the multi-mode waveguide 34 as the light distribution elements, the loss of the intensity of the optical signal occurs due to the distribution. For example, when an optical signal input from an input connection point is distributed to N input / output connection points and output, the optical signal output from one input / output connection point has the intensity of the input optical signal. Of about 1 / N. Further, in the return path, as in the forward path, a loss of the intensity of the optical signal occurs, so that the intensity of the optical signal reciprocating at one input / output point is about 1 / N ² of the intensity of the input optical signal.

On the other hand, in the third embodiment, since the optical amplifier 37 is provided, the intensity of the optical signal can be amplified. As a result, it is possible to compensate for the loss of the optical signal strength due to the distribution of the optical signal in the optical distribution element.

The optical amplifier 37 generates spontaneous emission noise over a wide wavelength range, but is cut by the wavelength selective reflection element except for the wavelength of the selected wavelength channel. Therefore, spontaneous emission noise other than the wavelength of the wavelength channel is not output to the output port.

When the intensity of the optical signal is amplified using the optical amplifier 37, the resonator between the grating 18 and the input port 20a and the output port 20b is used as a resonator.
Optical signals may resonate. Therefore, in this embodiment, an antireflection film 39 is provided on the input port 20a and the output port 20b in order to prevent resonance. Further, instead of providing the antireflection film 39, the input waveguide 22
end face at the input port 20a and the output waveguide 2
The resonance of the optical signal may be prevented by forming the end faces of the output port 20b of the 2b obliquely with respect to the propagation direction of the optical signal.

Although the optical star coupler 14 is used as the light distribution element in this embodiment, the same effect can be obtained by using the multimode waveguide 34 as the light distribution element.

[0094] 4. Fourth Embodiment In a fourth embodiment, an example of the optical wavelength filter according to the present invention will be described. FIG. 4 is a configuration diagram for explaining an optical wavelength filter 10c according to the fourth embodiment.

The configuration of the optical wavelength filter of the fourth embodiment is the same as that of the first embodiment except that a multilayer film 40 is provided instead of the grating 18 as a wavelength selective reflection element. This is the same as the configuration of the optical wavelength filter. For this reason, in the fourth embodiment, the same components as those of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and the details will not be described. .

Generally, a multilayer film is formed by alternately laminating two types of layers having different refractive indices from each other, and the difference in the optical distance between the reflected lights reflected at the interface between the layers constituting the multilayer film is the light. Can be selectively reflected only light that is an odd multiple of half the wavelength of. This difference in optical path length depends on the refractive index and thickness of each layer constituting the multilayer film. Therefore, by determining the refractive index and the thickness of each layer constituting the multilayer film for each wavelength selective reflection element, it is possible to selectively reflect optical signals having mutually different wavelengths.

In this embodiment, a multilayer film 40 manufactured by Applied Photoelectric Co., Ltd. is provided so as to cover the cross sections of the first to fifth input / output waveguides 28a to 28e exposed on the end face of the substrate 12, respectively. . The optical signal propagating through the input / output waveguide 28 is incident on the multilayer film surface almost perpendicularly to the film surface. The multilayer film 40 is formed by alternately laminating thin films of titanium dioxide (TiO ₂ ) and thin films of silicon dioxide (SiO ₂ ). In the multilayer film 40, the wavelength of the reflected light is changed by changing the thickness of the laminated thin film depending on the surface portion of the multilayer film 40.

As described above, if the multilayer film 40 is provided as the wavelength selective reflection element, the structure of the optical wavelength filter can be made simpler, and the production of the optical wavelength filter becomes easy.

Further, in this embodiment, the optical star coupler 14 is used as the light distribution element, but the same effect can be obtained by using the multimode waveguide 34 as the light distribution element.

[0100] 5. Fifth Embodiment In a fifth embodiment, an example of the optical wavelength filter according to the present invention will be described. FIG. 5 is a configuration diagram for explaining an optical wavelength filter 10d according to the fifth embodiment.

The configuration of the optical wavelength filter of the fifth embodiment is the same as that of the above-described optical wavelength filter except that a reflection type waveguide array grating 42 is provided instead of the grating 18 as a wavelength selective reflection element. The configuration is the same as that of the optical wavelength filter according to the first embodiment. For this reason, in the fifth embodiment, the same components as those of the first embodiment are denoted by the same reference numerals as those of the first embodiment,
The details are omitted.

The reflection type waveguide array grating 42 used in this embodiment includes a star coupler 44 composed of a planar waveguide, a plurality of phase control waveguides 46, and a mirror 48.

The star coupler 44 has two input / output surfaces 44a and 44b facing each other. The one input / output surface 44a is connected to the first to fifth connection points 50a.
５０50e. First to fifth connection points 50a to 50e
Are the first to fifth input / output waveguides 28a to 28e, respectively.
Connected to each other.

The other input / output surface 44b has first to fifth phase connection points 52a to 52e sequentially arranged. The first to fifth phase connection points 52a to 52e are connected to one end of each of the phase control waveguides 46 whose optical path lengths are different from each other by a fixed distance from the side of the first phase connection point 52 in ascending order of the optical path length. It is. In each of the phase control waveguides 46, the other input / output surface 44b is also connected in the order of shorter optical path length. At the other end of each of the phase control waveguides 46, a mirror 48 is provided. Optical signals input from the star coupler 44 to the phase control waveguide 46 are reflected by the mirrors 48 and input to the star coupler 44 again. Therefore, adjacent phase connection points 5
2, a phase difference corresponding to twice the optical path length difference between the adjacent phase control waveguides 46 is generated between the optical signals input to the star couplers 44. This phase difference differs depending on the wavelength of the optical signal.

The optical signals input from each phase connection point 52 interfere with each other, and are output from the connection point 50 provided at a position where the intensity of the optical signal is increased as a result of the interference. The position where the intensity of the optical signal becomes strong depends on the wavelength of the optical signal. In this embodiment, each of the connection points 5 is located at a position where the intensity of the optical signal of the wavelength channel is increased.
0 is provided. Accordingly, optical signals having different wavelengths are output from the respective connection points 50. In this embodiment, the star coupler 44 connects to the same connection point 50 where the wavelength-multiplexed optical signal is input.
An optical signal of a specific wavelength is selected from the optical signals and output.

Each connection point 50 is connected to the optical gate element 16 via the input / output waveguide 28. Therefore, by controlling the passage and cutoff of each optical signal of the optical gate element 16, the wavelength reflected by the reflection type waveguide array grating 42 as the wavelength selective reflection element can be selected.

When a reflection type waveguide array grating is provided as a wavelength selective reflection element, an optical wavelength filter can be manufactured more easily than when a grating is formed.

In this embodiment, the optical star coupler 14 is used as the light distribution element as the light distribution element. However, similar effects can be obtained by using the multimode waveguide 34 as the light distribution element. .

6. Sixth Embodiment In a sixth embodiment, an example of the optical wavelength filter according to the present invention will be described. FIG. 6 is a configuration diagram for explaining an optical wavelength filter 10e according to the sixth embodiment.

In the configuration of the optical wavelength filter according to the sixth embodiment, a plurality of reflection element sets are provided as wavelength selective reflection elements instead of the first to fifth gratings 18, and a phase control unit is further provided. Except for this point, the configuration is the same as that of the optical wavelength filter of the first embodiment described above. For this reason, in the sixth embodiment, the same components as those of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and the details of the configuration and operation are described. Detailed description is omitted.

In the optical wavelength filter according to the sixth embodiment of the present invention, the wavelength-selective reflecting elements are five reflecting element sets 56 for selectively reflecting optical signals having different wavelengths from each other. Element sets 56a to 56e are provided.

Each of the reflection element sets 56 includes a pair of first reflection elements 58a and second reflection elements 58b that selectively reflect optical signals having the same wavelength. Here, the first and second reflection elements 5
8 comprises a first and a second grating, respectively.

In each of the reflection element sets 56, the first reflection element 58a is connected to the light distribution element 14 via the optical gate element 16 by the first optical path 60a and to the first connection point 62a.
Connected.

In each of the reflecting element sets 56, the second reflecting element 58b is provided at a position different from the first optical path 60 in the light distribution element 14 via the optical gate element 16 by the second optical path 60b. They are connected at two connection points 62b. Further, for each of the reflective element sets 56, the second connection point 62b is located near the first connection point 62a. Here, for each of the reflection element sets 56, the first connection point 62a
The distance between the second connection point 62b and S is defined as S.

Further, with respect to each of the reflection element sets 56, the light distribution element 1 from the first optical path 60a through the first connection point 62a.
4 and a second optical signal from the second optical path 60b.
Interference light due to the second optical signal input to the optical distribution element 14 via the connection point 62b reinforces at the output connection point 24b,
Further, a phase control element 64 for giving a phase difference between the phase of the first optical signal and the phase of the second optical signal so as to weaken each other at the input connection point 24a is connected to the first and second optical paths 60a and 60b. It is provided on at least one side. Here, the first
A phase control element 64 is provided on the optical path 60a.

In the sixth embodiment, the first optical path 6
The waveguide 0a has a pin structure, similarly to the structure of the optical amplifier described in the first embodiment. Therefore, here, in order to configure the phase control element 64, an electrode (not shown) is provided on a part of the first optical path 60a. The first optical path 60a is formed by the electrode.
When a reverse bias current is injected into a portion, the phase of the first optical signal passing through the first optical path 60a can be controlled by changing the refractive index of the portion.

When the optical wavelength filter is formed on a glass substrate, at least one of the first and second optical paths can be heated by a heater to change the refractive index of that part. In addition, the first and second
Even when the optical path is constituted by an optical fiber, the refractive index of the portion of the phase control element can be changed by heating the portion with the heater.

Next, referring to FIG. 7, paying attention to one reflection element set 56, the interference light due to the first and second optical signals reinforces each other at the output connection point 24b and at the input connection point 24b. 2
An example of an interference condition for weakening in 4a will be described.
FIG. 7 is an enlarged view of the star coupler 14. In FIG.
In the star coupler 14, the optical path is schematically shown by a straight line for the purpose of explaining the interference condition.

Here, the phase control element 64 determines whether the first optical signal input to the star coupler 14 from the first connection point 62a is equal to the optical signal input to the star coupler 14 from the second connection point 62b, A case where a phase difference is given will be described.

First, in FIG. 7, an intermediate point 62c between the first connection point 62a and the second connection point 62b and an input connection point 24
A straight line connecting a with the output connection point 24b is defined as a straight line La and a straight line Lb, respectively. Also, the first connection point 62a
An angle between a straight line P ₀ connecting the second connection point 62 and the straight line La is defined as θa. Further, the angle formed by the straight line P ₀ and the line Lb and .theta.b. The wavelengths of the first and second optical signals are λ.

Then, when the first optical signal from the first connection point 62a and the second optical signal from the second connection point 62b reach the input connection point 24a, the phase difference ψa is given by the following equation (5). Given by

Ψa = (2π / λ) S sin θa + 2Φ (5) Next, at the input connection point 24a, the first optical signal and the second optical signal interfere with each other in order to eliminate return light from the input port 20a. The condition of the phase difference Φ for canceling out is given by the following equation (6).

Φ = (2m ₁ +1) π / 2− (π / λ) Ssin θa (6) where m ₁ is an integer.

On the other hand, the first optical signal from the first connection point 62a and the second optical signal from the second connection point 62b are
4b is given by the following equation (7).

Ψa = (2π / λ) S sin θbΦ (7) Next, at the output connection point 24a, the first optical signal and the second optical signal interfere and reinforce to output to the output port 20b. Is given by the following equation (8).

Φ = m ₂ π− (π / λ) Sin θb (8) where m ₂ is an integer.

The condition for the above-mentioned expressions (6) and (8) to be satisfied simultaneously for the common Φ is given by the following expression (9).

Π / 2 = (π / λ) S (sin θa−sin θb) (9) Then, when θa and θb << 1, sin θa ≒ θ
a, sin θb ≒ θb. In this case, since sin θa−sin θb ≒ θa−θb = θ, the above equation (9) can be expressed by the following equation (10).

Π / 2 ≒ (π / λ) Sθ (10) where θ corresponds to the angle between the straight line La and the straight line Lb.

Therefore, it can be seen from the above equation (10) that the input connection point 24a and the output connection point 24b should be provided at positions satisfying the following equation (11).

Θ ≒ λ / (2S) (11) As described above, in the sixth embodiment, for each of the reflecting element sets 56, the interference light by the first optical signal and the second optical signal Are strengthened at the output connection point 24a and weakened at the input connection point 24a, so that the optical signal input from the wavelength selective reflection element 18e can be selectively guided to the output port to the optical distribution element. it can. As a result, light returning to the input port can be suppressed.

In this embodiment, individual optical gate elements may be provided on the first optical path 60a and the second optical path 60b for each of the reflecting element sets 56. However, since the respective optical gate elements on the first and second optical paths 60a and 60b perform the same operation as each other, that is, simultaneously switch the ON state and the OFF state, it is necessary to individually control the passage and cutoff of the optical signal. There is no. Therefore, even if individual optical gate elements are provided on the first and second optical paths 60a and 60b, respectively, the two optical gate elements correspond to one optical gate element 14.

[0133] 7. Seventh Embodiment In a seventh embodiment, an example of the optical wavelength selective router according to the present invention will be described. FIG. 8 is a configuration diagram for explaining an optical wavelength selection filter 70 according to the seventh embodiment.

Optical wavelength selection router 70 of the seventh embodiment
According to the first optical coupler 72 and the first optical wavelength filter 7,
4, a second optical wavelength filter 76 and a second optical coupler 78 are provided.

The first optical coupler 72 is a 1 × 2 coupler and has an input terminal 72a and first and second output terminals 72b and 72c. Then, the first optical coupler 7
The second input terminal 72a is connected to an input port 80 via an optical amplifier 82 and an optical isolator 84. The input port 80 receives an input optical signal obtained by wavelength multiplexing optical signals of a plurality of wavelength channels. And the first
The optical coupler 72 distributes the input optical signal input from the input terminal 72a and outputs the input optical signal from the first and second fishing terminals 72b and 72c, respectively.

The optical amplifier 82 is provided for compensating for a loss caused by the splitting of the optical signal by the first optical coupler. The optical isolator 84 is connected to the input port 80.
This is provided to prevent return light to the light source. The optical amplifier 82 and the optical isolator 84 may be arranged in the reverse order.

The first optical wavelength filter 74 has an input terminal 74a and an output terminal 74b. And
The input terminal 74a is connected to the first output terminal 72b of the first optical coupler 72. Then, the first optical wavelength filter 74 selects an optical signal of a specific wavelength channel from the input optical signals output from the first output terminal 72b of the first optical coupler 72 and input to the input terminal 74a. And
The first optical wavelength filter 74 outputs the selected optical signal as a separated optical signal from the output terminal 74b to the separation port 86.

The second optical wavelength filter 76 has an input terminal 76a and an output terminal 76b. And
This input terminal 76a is connected to the second output terminal 72c of the first optical coupler 72. Then, the second optical wavelength filter 76 outputs the optical signal of the wavelength channel other than the wavelength channel of the separation signal among the input signals output from the second output terminal 72c of the first optical coupler 72 and input to the input terminal 76a. Select Then, the optical signal of the selected wavelength channel is output from the output terminal 76b as a residual optical signal.

The configuration of the first and second optical wavelength filters 74 and 76 used in the seventh embodiment is the same as the configuration of the optical wavelength filter of the first embodiment described above. For this reason, in the eighth embodiment, the first and second
Detailed description of the optical wavelength filter is omitted. In addition, the input port 2 of the optical wavelength filter 10 in the first embodiment
0a is the first and second optical wavelength filters 74 and 76
Respectively correspond to the input terminals 74a and 76a. The output port 20b of the optical wavelength filter 10 in the first embodiment is connected to the first and second optical wavelength filters 74.
And 76 correspond to output terminals 74b and 76ba, respectively.

The second optical coupler 78 is a 2 × 1 coupler, and has first and second input terminals 78a and 78b.
And an output terminal 78c. The input terminal 72 a of the first optical coupler 72 is connected to the second optical wavelength filter 7.
6 is connected to the output terminal 76b. Further, the second input terminal 78b is connected to the insertion port 88. To this insertion port 88, an insertion optical signal of a wavelength channel included in the wavelength channel of the separation signal is input. Then, the second optical coupler 78 wavelength-multiplexes the residual optical signal input from the first input terminal 78a and the insertion optical signal input from the second input terminal 78b as an output optical signal to obtain an output optical signal 78c.
To the output port 90.

Next, in the optical wavelength selective router 70 according to the seventh embodiment, wavelength multiplexed input signals of wavelengths λ ₁ , λ ₂ , λ ₃ , λ ₄ and λ ₅ are input from the input port 80. of, removed from the isolated port 86 by selecting the optical signal of the wavelength lambda ₂ and lambda _3, and the wavelength lambda ₂ and lambda
₃ new optical signal is inserted from the insertion port 88 and the wavelength λ
For example in the case of output from the output port 90 as an output signal of ₁ to [lambda] ₅ will be described.

First, the input optical signal input from the input port 80 passes through the optical amplifier 82 and the optical isolator 84 sequentially and is input to the first optical coupler 72. In the first optical coupler, the divided input signals are respectively transmitted to the first optical coupler.
And input to the second optical wavelength filters 74 and 76.

The first optical wavelength filter 74 selects only the optical signals of the wavelengths λ ₂ and λ _{3 from} the input optical signals, and outputs the selected optical signals to the separation port 86 as a separated optical signal.

[0144] The second optical wavelength filter 76, out of the input optical signal, other than the wavelength lambda ₂ and lambda _3, the wavelength lambda _1, lambda
The optical signals of ₄ and λ ₅ are selected as remaining optical signals and output to the second optical coupler 78.

Further, new optical signals of wavelengths λ ₂ and λ ₃ are input from the insertion port 88 to the second optical coupler 78 as an insertion optical signal. Then, the second optical coupler 78 wavelength-multiplexes the remaining optical signals of wavelengths λ ₁ , λ ₄ and λ ₅ and the insertion optical signals of wavelengths λ ₂ and λ ₃ and outputs the output optical signals of wavelengths λ _{1 to} λ _5. Is output to the output port 90.

The wavelength of the insertion optical signal input from the insertion port 88 is, for example, only the wavelength λ ₁ or the wavelength λ ₂
Only, and if necessary, the insertion optical signal may not be input.

As described above, according to the optical wavelength selective router 70 according to the seventh embodiment of the present invention, among the input optical signals input to the input port 80, the optical signal of the specific wavelength channel is used as the separated optical signal. The output optical signal can be output to the separation port 86, and the add optical signal and the residual optical signal input from the add port 88 can be multiplexed and output from the output port 90 as an output optical signal. Therefore, the optical signal of a specific wavelength channel among the wavelength-multiplexed optical signals can be replaced without the need for a 2 × 2 coupler.

[0148] 8. Eighth Embodiment In an eighth embodiment, another example of the optical wavelength selective router of the present invention will be described. FIG. 9 is a configuration diagram for explaining an optical wavelength selection filter 70a according to the eighth embodiment. The configuration of the optical wavelength filter according to the eighth embodiment is similar to that of the first embodiment.
Except that the wavelength selective reflection element forming the optical wavelength filter and the wavelength selection reflection element forming the second optical wavelength filter are configured with a common grating, the seventh embodiment described above is different from the seventh embodiment. The configuration is the same as that of the optical wavelength filter. For this reason, in the eighth embodiment, the same components as those of the seventh embodiment are denoted by the same reference numerals as those of the seventh embodiment, and detailed description thereof will be omitted. .

Optical wavelength router 70a according to the eighth embodiment
Comprises first and second optical wavelength filters 94 and 96. The first optical wavelength filter 94 includes an input terminal 94a.
And an output terminal 94b. This input terminal 94a
Are connected to the first output terminal 72b of the first optical coupler 72. The output terminal 94b is connected to the separation port 86.

The second optical wavelength filter 96 has an input terminal 96a and an output terminal 96b. This input terminal 96a is connected to the second output terminal 72c of the first optical coupler 72. The output terminal 96b is connected to the first input port 78a of the second optical coupler 78.

In the optical wavelength selective router 70a according to the eighth embodiment, the wavelength selective reflective element forming the first optical wavelength filter 94 and the wavelength selective reflective element forming the second optical wavelength filter 96 are shared. Gratings 98, that is, first to third gratings 98a to 98a
c. First to third grating 9
8a to 98c have different wavelengths λ _{1 to} λ ₃ , respectively.
Are selectively reflected.

Therefore, the first optical wavelength filter is composed of the first light distribution element 100 corresponding to the light distribution element 14 in the first embodiment and the separation side corresponding to the optical gate element 16 in the first embodiment. It comprises an optical gate element 102 and a grating 98 corresponding to the grating 18 in the first embodiment. The separation-side optical gate element 102 includes first to third distribution-side optical gate elements 102a to 102c.

The second optical wavelength filter includes a second light distribution element 104 corresponding to the light distribution element 14 in the first embodiment and an optical gate element 1 in the first embodiment.
6 and an grating 98 corresponding to the grating 18 in the first embodiment. The insertion-side optical gate element 106 includes first to third insertion-side optical gate elements 106a to 106c.

Here, the configurations and operations of the first and second optical distribution elements 100 and 104 and the first and second optical gate elements 102 and 106 are the same as those of the above-described first embodiment. A detailed description of this point will be omitted.

The three separation-side optical gate elements 102 constituting the first optical wavelength filter 94 are connected to one end 98a of the grating 98, respectively. Also, the second
The three insertion-side optical gate elements 106 constituting the optical wavelength filter 96 are respectively connected to the other end 98b of the grating 98.
Connected to

The separation-side optical gate element 102 and the insertion-side optical gate element 106 are arranged such that, for each grating 98, one of the optical gate elements allows an optical signal to pass therethrough.
Further, the other optical gate element blocks the optical signal. For example, when one of the first separation-side optical gate element 102a and the first insertion-side optical gate element 106a is on, the other is off.

Next, in the optical wavelength selective router 70a of the eighth embodiment, of the wavelength multiplexed input signals of wavelengths λ ₁ , λ ₂ and λ ₃ inputted from the input port 80, the wavelength λ ₂ Is selected from the separation port 86 and taken out from the separation port 86, a new optical signal of wavelength λ ₂ is input from the insertion port 88, and output from the output port 90 as output signals of wavelengths λ _{1 to} λ _3. explain.

First, the input optical signal input from the input port 80 passes through the optical amplifier 82 and the optical isolator 84 sequentially and is input to the first optical coupler 72. In the first optical coupler, the divided input signals are respectively transmitted to the first optical coupler.
And input to the second optical wavelength filters 94 and 96.

The first optical wavelength filter 94 selects only the optical signal of the wavelength λ _{2 from} the input optical signals and outputs the selected optical signal to the separation port 86 as a separated optical signal. Therefore, the second separation-side optical gate element 10 of the separation-side optical gate element 102
Only 2b is turned on. As a result, in the first optical wavelength filter 94, an input optical signal is input only to the second grating 98b. And the second grating 98b
Selectively reflects an optical signal of wavelength λ ₂ . Then, the reflected optical signal of the wavelength λ ₂ is converted into the first optical signal as a separated optical signal.
From the output terminal 94b of the wavelength filter 94 to the separation port 86
Output to

On the other hand, the second optical wavelength filter 96 selects only the optical signals of the wavelengths λ ₁ and λ _{3 from} the input optical signals and outputs them to the second optical coupler 78 as the remaining optical signals. Therefore, the first of the insertion-side optical gate elements 106
And third separation-side optical gate elements 106a and 106c
Is turned on. As a result, the second optical wavelength filter 96
Then, the first and third gratings 98a and 98
An input optical signal is input only to c. Then, the first and third gratings 98a and 98c are reflected wavelength lambda ₂ and lambda ₃ of the optical signals, respectively selectively. Then, the reflected optical signals of the wavelengths λ ₁ and λ ₃ are output from the output terminal 96 b of the second wavelength filter 96 as residual optical signals.

A new optical signal of wavelength λ ₂ is input from the insertion port 88 to the second optical coupler 78 as an insertion optical signal. Then, the second optical coupler 78 wavelength-multiplexes the residual optical signals of the wavelengths λ ₁ and λ ₃ and the insertion optical signal of the wavelength λ ₂ to output the optical signals of the wavelengths λ _{1 to} λ _{3 to} the output port 90. Output.

As described above, if the wavelength selective reflection elements of the first optical wavelength filter and the second optical wavelength filter are formed as a common grating, the configuration of the element can be simplified.

In each of the embodiments described above, only examples in which these inventions are configured using specific materials and under specific conditions have been described. However, these inventions can be subjected to many changes and modifications. For example, in the above-described embodiment, an example of the waveguide type optical wavelength filter has been described. However, the optical filter of the present invention is not limited to the waveguide type, and for example, an optical fiber is used instead of the waveguide. May be.

Further, in the above-described embodiment, the example of the optical wavelength filter provided on the InP substrate made of a compound semiconductor has been described.
For example, it may be formed on a glass substrate.

Further, in the above-described embodiment, all the optical signals of the selected wavelength are extracted through the optical distribution element. However, in the optical wavelength filter of the present invention, the optical signal of the selected wavelength is extracted. Alternatively, it may be taken out without passing through the light distribution element. For example, a half mirror may be provided between the light distribution element and the optical gate, and light incident on the half mirror may be extracted from the optical gate element side.

[0166]

According to the optical wavelength filter of the present invention, since the selected wavelength is switched by the optical gate element, compared with the case where the selected wavelength is switched by exciting the surface acoustic wave.
Switching of wavelength channels can be performed at high speed.

According to the optical wavelength filter of the present invention, since the light distribution element, the wavelength selective reflection element and the optical gate element are connected to each other, the optical signal of the wavelength channel which is not selected passes through the optical gate element in the forward path. Even if there is light leakage that is not completely blocked by the light gate element, it is blocked again by the optical gate element on the return path. For this reason, the extinction ratio of the optical signal by the optical gate element can be increased to reduce crosstalk.

Further, according to the optical wavelength filter of the present invention, since the configuration is simple, the size of the wavelength optical filter can be reduced.

In the optical wavelength filter according to the present invention, if an input connection terminal and an output connection terminal are provided in the wavelength distribution element, an optical signal of the selected wavelength is output from the output connection point of the optical distribution element to the output port. be able to. As a result, there is no need to provide a new configuration for extracting an optical signal of the selected wavelength, so that the structure of the optical wavelength filter can be simplified.

Further, in the optical wavelength filter of the present invention, if an optical isolator is provided on the optical path between the input port and the optical distribution element, a part of the optical signal reflected by the wavelength selective reflection element will be returned light. Output from the light distribution element to the input port can be suppressed.

In the optical wavelength filter according to the present invention, if an optical circulator is provided on the optical path between the input port and the optical distribution element, a part of the optical signal reflected by the wavelength selective reflection element is returned as return light. Output from the light distribution element to the input port can be suppressed.

In the optical wavelength filter of the present invention, if an optical amplifier is provided on the optical path connecting the input port and the optical distribution element, the intensity of the optical signal can be amplified. As a result, it is possible to compensate for the loss of the optical signal strength due to the distribution of the optical signal in the optical distribution element.

In the optical wavelength filter of the present invention, if an electro-absorption type optical modulator is provided as an optical gate element, the wavelength channel to be selected can be switched at high speed by controlling reverse bias. The operation as an optical gate can be performed with low driving power.

Further, in the optical wavelength filter of the present invention, if an optical amplifier is provided as an optical gate element, it is possible to compensate for a loss in optical signal intensity due to the distribution of optical signals in the optical distribution element.

In the optical wavelength filter of the present invention, if a grating is provided as the wavelength selective reflection element, crosstalk can be reduced. As a result, the accuracy of wavelength selection of the optical wavelength filter can be improved.

In the optical wavelength filter of the present invention, if a multilayer film is provided as the wavelength selective reflection element, the structure of the optical wavelength filter can be made simpler, and the production of the optical wavelength filter becomes easy.

In the optical wavelength filter of the present invention, if a reflection type waveguide array grating is provided as the wavelength selective reflection element, the optical wavelength filter can be easily manufactured without forming a grating.

Also, in the optical wavelength filter of the present invention, a phase control element is provided for each wavelength selective reflection element, and the phase of the first optical signal reflected by the first and second reflection elements and the second By giving a phase difference between the phase of the optical signal and the interference light by the first optical signal and the second optical signal,
If the light distribution element is strengthened at the output connection point and is strengthened at the input connection point, the optical signal input from the wavelength selective reflection element to the light distribution element can be selectively guided to the output port. As a result, light returning to the input port can be suppressed.

Further, according to the optical wavelength selection router of the present invention, the optical signal of a specific wavelength channel among the wavelength-multiplexed optical signals can be replaced without requiring a 2 × 2 coupler.

In the optical wavelength selective router according to the present invention, if the optical wavelength filter according to the present invention is provided as the first and second optical wavelength filters, the wavelength channel to be selected is switched at high speed as described above. In addition, crosstalk can be reduced.

Further, in the optical wavelength selective router of the present invention, if the wavelength selective reflection element of the first optical wavelength filter and the second optical wavelength filter is a common grating, the configuration of the element can be simplified.

[Brief description of the drawings]

FIG. 1 is a configuration diagram for describing an optical wavelength filter according to a first embodiment.

FIG. 2 is a configuration diagram for explaining an optical wavelength filter according to a second embodiment;

FIG. 3 is a configuration diagram for describing an optical wavelength filter according to a third embodiment.

FIG. 4 is a configuration diagram for explaining an optical wavelength filter according to a fourth embodiment;

FIG. 5 is a configuration diagram for explaining an optical wavelength filter according to a fifth embodiment;

FIG. 6 is a configuration diagram for explaining an optical wavelength filter according to a sixth embodiment;

FIG. 7 is an enlarged view of a star coupler.

FIG. 8 is a configuration diagram for describing an optical wavelength selection router according to a seventh embodiment;

FIG. 9 is a configuration diagram illustrating an optical wavelength selective router according to an eighth embodiment;

[Explanation of symbols]

10, 10a, 10b, 10c, 10d, 10e: optical wavelength filter 12: InP substrate 14: optical distribution element (star coupler) 14a: one input / output surface 14b: other input / output surface 16: optical gate element 16a: 1 optical gate element 16b: second optical gate element 16c: third optical gate element 16d: fourth optical gate element 16e: fifth optical gate element 18: wavelength selective reflection element (grating) 18a: first grating 18b: second Grating 18c: Third grating 18d: Fourth grating 18e: Fifth grating 20a: Input port 20b: Output port 22a: Input waveguide 22b: Output waveguide 24a: Input connection point 24b: Output connection point 26a: First input / output Connection point 26b: Second input / output connection point 26c: Third input / output connection point 26d: 4 input / output connection points 26e: fifth input / output connection point 32: optical circulator 32a: first terminal 32b: second terminal 32c: third terminal 34: multi-mode waveguide 34a: one input / output surface 34b: other input Output surface 36a: Input connection point 36b: Output connection point 38a: First input / output connection point 38b: Second input / output connection point 38c: Third input / output connection point 38d: Fourth input / output connection point 38e: Fifth input / output Connection point 40: Multilayer film 42: Waveguide array grating 44: Star coupler 46: Phase control waveguide 48: Mirror 50a: First connection point 50b: Second connection point 50c: Third connection point 50d: Fourth connection point 50e : 5th connection point 52a: 1st phase connection point 52b: 2nd phase connection point 52c: 3rd phase connection point 52d: 4th phase connection point 52e: 5th phase connection point 56: reflective element set 56a First reflective element set 56b: Second reflective element set 56c: Third reflective element set 56d: Fourth reflective element set 56e: Fifth reflective element set 58a: First reflective element (first grating) 58b: Second reflective element (Second grating) 60a: first optical path 60b: second optical path 62a: first connection point 62b: second connection point 64: phase control element 70, 70a: optical wavelength selection router 72: first optical coupler 74: first Optical wavelength filter 76: Second optical wavelength filter 78: Second optical coupler 80: Input port 82: Optical amplifier 84: Optical isolator 86: Separation port 88: Insertion port 90: Output port 94: First optical wavelength filter 94a: Input Terminal 94b: Output terminal 96: Second optical wavelength filter 96a: Input terminal 96b: Output terminal 98: Grating 98a: First grating 9 b: second grating 98c: third grating 100: first light distribution element 102: separation side light gate element 102a: first separation side light gate element 102b: second separation side light gate element 102c: third separation side light gate Element 104: second light distribution element 106: insertion-side optical gate element 106a: first insertion-side optical gate element 106b: second insertion-side optical gate element 106c: third insertion-side optical gate element

Claims (14)

[Claims] 1. An optical distribution element, a plurality of optical gate elements connected to the optical distribution element and individually controlling passage and blocking of a distributed optical signal, and the optical distribution element via the optical gate element An optical wavelength filter, comprising: a wavelength selective reflection element connected to an element and selectively reflecting optical signals of different wavelengths by the optical gate element through which the optical signal has passed. 2. The optical wavelength filter according to claim 1, wherein the light distribution element is provided with an input connection point connected to an input port and an output connection point connected to an output port. filter. 3. The optical wavelength filter according to claim 2, wherein an optical isolator is provided on an optical path between said input port and said optical distribution element. 4. The optical wavelength filter according to claim 2, wherein an optical circulator is provided on an optical path between the input port and the optical distribution element, wherein the optical circulator is provided with a first terminal and the second terminal. At least a second terminal for outputting an optical signal input from one terminal and a third terminal for outputting an optical signal input from the second terminal, wherein the first terminal is connected to the input port; The optical wavelength filter according to claim 1, wherein the second terminal is connected to the input connection terminal of the light distribution element. 5. The optical wavelength filter according to claim 2, wherein an optical amplifier is provided on an optical path connecting the input port and the optical distribution element. 6. The optical wavelength filter according to claim 1, wherein the optical gate element includes an electro-absorption optical modulator. 7. The optical wavelength filter according to claim 1, wherein an optical amplifier is provided as the optical gate element. 8. The optical wavelength filter according to claim 1, wherein a grating is provided as the wavelength selective reflection element. 9. The optical wavelength filter according to claim 1, wherein the wavelength selective reflection element includes a multilayer film. 10. The optical wavelength filter according to claim 1, wherein the wavelength selective reflection element includes a reflection type waveguide array grating. 11. The optical wavelength filter according to claim 2, wherein the wavelength-selective reflecting element includes a plurality of different reflecting element sets, and each of the reflecting element sets is different from each other. It comprises a pair of first and second reflective elements for selectively reflecting optical signals of the same wavelength, and for each of the reflective element sets, the first reflective element is:
Connected to the light distribution element via the optical gate element by a first optical path, and for each of the reflection element sets, the second reflection element
A second light path connected to the light distribution element via the light gate element at a different position from the first light path; and for each of the reflection element sets, the reflection element set is input from the first light path to the light distribution element. The first optical signal and the interference light due to the second optical signal input from the second optical path to the optical distribution element reinforce each other at the output connection point, and weaken each other at the input connection point. The phase of the first optical signal and the second
An optical wavelength filter comprising a phase control element for providing a phase difference between the phase of an optical signal and at least the first optical path. 12. An optical amplifier and an optical isolator are connected to an input port to which an input optical signal in which optical signals of a plurality of wavelength channels are wavelength-multiplexed is input. A first optical coupler that outputs from a first and a second output terminal, and an optical signal of a specific wavelength channel among the input optical signals that are connected to the first output terminal and output from the first output terminal. A first optical wavelength filter for selecting and outputting to the separation port as a separation optical signal; a wavelength of the separation signal of the input signals connected to the second output terminal, among the input signals output from the second output terminal A second optical wavelength filter for selecting an optical signal of a wavelength channel other than the channel and outputting the selected optical signal as a residual optical signal; a first input terminal connected to the second optical wavelength filter and a wavelength channel of the separated signal; A second input terminal connected to an insertion port to which an insertion optical signal of a wavelength channel is input, the remaining optical signal input from the first input terminal, and the insertion light input from the second input terminal. An optical wavelength selective router, comprising: a second optical coupler for wavelength multiplexing a signal and outputting the multiplexed signal to an output port as an output optical signal. 13. An optical wavelength selective router according to claim 12, comprising the optical wavelength filter according to claim 1 as said first and second optical wavelength filters. . 14. The optical wavelength selective router according to claim 13, wherein said wavelength selective reflection element forming said first optical wavelength filter and said wavelength selective reflection element forming said second optical wavelength filter are common. The first optical wavelength filter, the optical gate element connected to one end of the grating, and the second optical wavelength filter, connected to the other end of the grating. The optical gate element, for each of the gratings, one of the optical gate elements to pass an optical signal,
An optical wavelength selective router, wherein the other optical gate element blocks an optical signal.