JP2011048078A - All-order dispersion compensation circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an all-order dispersion compensation circuit simultaneously compensating group velocity dispersion and polarization dispersion of an optical fiber in a long distance transmission device of an optical communication network. <P>SOLUTION: An optical signal is separated into frequency components by a first array waveguide diffraction grating; a main axis of polarized light is rotated for every frequency component by a first variable phase element using a lithium niobate waveguide; a polarization plane is rotated by 45° by a half-waveplate; a phase difference between two polarized light is compensated by a second variable phase element using a lithium niobate waveguide; polarization plane is made coincident with a TM or TE mode by a second half-waveplate; a phase distortion between frequency components is compensated by a third variable phase element and the optical signal in multiplexed by a second array waveguide diffraction grating. Thus all-order dispersion compensation can be attained. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a long-distance transmission apparatus for an optical communication network, and more particularly to a circuit for simultaneously compensating for group velocity dispersion and polarization dispersion of an optical fiber.

  2. Description of the Related Art In recent years, information transmission systems using optical fibers have become widespread with increasing information capacity and the need for long-distance communication.

  Conventional optical communication systems are constructed using optical components having linear optical characteristics, and are simple but have limited characteristics and functions. Recently, a repeaterless system or an optical amplification repeater system extending to several hundred km to several thousand km is being realized. The transmission speed of these systems is as high as several Gb / s to several tens Gb / s. In addition, an analog optical communication system including an optical modulator with extremely good linearity is being put into practical use.

  However, due to the dispersion characteristics of the system, various spectral components of the information signal propagate through the system at various group velocities (group velocity dispersion). As a result, a phase relationship different from the phase relationship of the spectral components generated by the transmitter arrives at the receiver, and a plurality of spectral components interfere with each other at the receiver.

  Also, in ultrahigh-speed optical transmission and long-distance optical transmission, transmission quality degradation due to polarization mode dispersion (PMD) in which the group speed of optical signals in an optical transmission line differs depending on two orthogonal polarization main axes. It becomes a big problem. PMD characteristics depend on optical fiber manufacturing processes and installation conditions, and show changes with time due to changes in stress and environmental temperature applied to the optical fiber.

  For this reason, it is necessary to adaptively compensate for transmission quality degradation due to group velocity dispersion and PMD.

  The prior art has a configuration of a total dispersion compensation circuit using a spectral diffraction grating and a phase control spatial light modulator in a spatial optical system. Total dispersion means group velocity dispersion and polarization dispersion. For example, Patent Document 1 and Non-Patent Document 1 disclose using a phase modulation element array using liquid crystal as a spatial light modulator (hereinafter abbreviated as SLM).

  The prior art will be described with reference to the accompanying drawings. FIG. 1 is a schematic diagram for explaining a total dispersion compensation circuit according to the prior art. The total dispersion compensation circuit includes sensors 102a and 102b, spectral modules 103a and 103b, a controller 104, and an SLM 105. The optical system 101 having PMD is an optical system that requires dispersion compensation. The light emitted from the optical system 101 having PMD becomes incident light 111 for the total dispersion compensation circuit according to Patent Document 1. In the incident light 111, first, a component for each wavelength is developed and separated into a space by the spectroscopic module 103a. This light enters the SLM 105 at the next stage and is compensated so that the phase and polarization components become the desired phase and polarization for each wavelength. The light developed, separated, and compensated in the space is then output again as a single light beam, that is, emitted light 112, by the spectroscopic module 103b. Here, the sensor 102a detects a part of the incident light 111, and the sensor 102b detects a part of the intensity of the emitted light 112. Based on the detected signal, the controller 104 performs necessary voltage control on the SLM 105.

  The prior art is described in more detail in Non-Patent Document 1. FIG. 2 shows the experimental arrangement of the total dispersion compensation circuit according to the prior art. This arrangement includes a femtosecond fiber laser 201, an erbium doped fiber amplifier (hereinafter referred to as EDFA) 202, a polarization mode dispersion emulator 203, circulators 204a and 204b, and a polarization spectrum / pulse shaper 205. , A broadband polarimeter 206b, a phase dedicated pulse shaper 212, an ultrashort pulse measuring device 213, and a personal computer 214. Here, the polarization spectrum / pulse shaper 205 includes a broadband polarimeter 206a, a mirror 207a, a liquid crystal modulator array (hereinafter referred to as an LCM array) 208a, a lens 209a, and a diffraction grating 210a. The phase-only pulse shaper 212 includes a mirror 207b, an LCM array 208b, a lens 209b, and a diffraction grating 210b.

  A set of the femtosecond fiber laser 201, the EDFA 202, and the polarization mode dispersion emulator 203 is an optical system that simulates the optical system 101 having the PMD in FIG. The light from the polarization mode dispersion emulator 203 is sent by the circulator 204a to the polarization spectrum / pulse shaper 205, where polarization dispersion compensation is performed, and the light travels again through the circulator 204a to the next circulator 204b. The signal is sent to the phase-only pulse shaper 212 by the circulator 204b, where phase dispersion compensation is performed, and the light again enters the ultrashort pulse measuring device 213 via the circulator 204b. The personal computer 214 controls the entire system by applying appropriate voltages to the LCM arrays 208a and 208b in conjunction with the broadband polarimeters 206a and 206b and the ultrashort pulse measuring device 213.

  Next, the configuration and outline of the polarization spectrum / pulse shaper 205 will be described. Incident light has its components for each wavelength developed and separated into space by the action of the diffraction grating 210a and the lens 209a. This light enters the next-stage LCM array 208a and is compensated so that the phase and polarization components of each wavelength become the desired phase and polarization, respectively. Since light of any wavelength component in the polarization spectrum / pulse shaper 205 is reflected by the mirror 207a and is emitted again following the same path, the compensation by the LCM array 208a is set to an appropriate amount in a round trip. ing. The light enters the LCM array 208a from the right, receives a half amount of compensation, is reflected by the mirror 207a, then travels to the right, and receives the remaining half amount of compensation by the LCM array 208a. The light expanded / separated in space and compensated is multiplexed into one light beam by the diffraction grating 210a and emitted. The phase-dedicated pulse shaper 212 has the same configuration as that of the polarization spectrum / pulse shaper 205, and thus the description thereof is omitted. In the phase dedicated pulse shaper 212, only the phase is compensated.

US Patent Application Publication No. 2002/0060760

M. Akbulut, and A. M. Weiner, “Broadband All-Order Polarization Mode Dispersion Compensation Using Liquid-Crystal Modulator Arrays,” J. Lightwave Technol., Vol. 24, No. 1, pp. 251-261 (2006)

  Using the above prior art, total dispersion can be compensated. However, since the conventional total dispersion compensation circuit is configured on the optical surface plate in a spatial system, it is difficult to reduce the size. In addition, since the response of the liquid crystal is slow, it is difficult to perform dispersion compensation at high speed. The prior art mentions the use of an arrayed waveguide diffraction grating, but does not mention a practical construction method and integration with a waveguide type phase control element.

  In view of the above, an object of the present invention is to configure an all-dispersion compensation circuit integrated in an all-waveguide type.

  One embodiment of the present invention is a total dispersion compensation circuit formed on a substrate, and this total dispersion compensation circuit has a z-axis as the optical axis direction on the surface on which the circuit elements of the substrate are formed, and the circuit on the substrate. When the normal direction of the surface on which the element is formed is the y-axis and the direction perpendicular to the optical axis on the surface on which the circuit element is formed is the x-axis, spectral processing is performed on the incident optical signal. A first array waveguide diffraction grating that outputs an optical signal for each wavelength component to each waveguide, and a first array waveguide connected to the first array waveguide diffraction grating and provided with a phase modulation electrode. A plurality of optical signals output from the waveguide diffraction grating to each waveguide are connected to a first waveguide array for converting the optical signal into an elliptically polarized wave whose principal axis is parallel to the x-axis or y-axis, and the first waveguide array; A first half-wave plate that rotates the main axis of elliptically polarized light of an optical signal output from the first waveguide array by 45 degrees in the xy plane. , Elliptic polarizations of a plurality of optical signals output from the first half-wave plate connected to the first half-wave plate and provided with phase modulation electrodes, the principal axis is the x-axis, and A second waveguide array that converts to linearly polarized waves inclined by 45 degrees with respect to the y-axis, and a main axis of linearly polarized light of an optical signal connected to the second waveguide array and output from the second waveguide array Is output from the second half-wave plate, which is connected to the second half-wave plate and the second half-wave plate and is provided with the phase modulation electrode. A third waveguide array in which the phases of the plurality of optical signals are all in phase, and a second waveguide array connected to the third waveguide array and multiplexing the plurality of optical signals output from the third waveguide array An arrayed waveguide diffraction grating.

  In one embodiment of the present invention, the first waveguide array, the second waveguide array, and the third waveguide array are lithium niobate waveguide arrays.

  In one embodiment of the present invention, the first waveguide array, the second waveguide array, and the third waveguide array are lithium tantalate waveguide arrays.

  Another embodiment of the present invention is a total dispersion compensation circuit formed on a substrate, wherein the optical axis direction on the surface on which the circuit elements of the substrate are formed is the z axis, and the surface on which the circuit elements of the substrate are formed Where the normal direction is the y-axis and the direction perpendicular to the optical axis on the surface on which the circuit elements of the substrate are formed is the x-axis, spectral processing is performed on the incident optical signal, and wavelength is applied to each waveguide. A first array waveguide diffraction grating that outputs an optical signal for each component, and an optical signal that is connected to the first array waveguide diffraction grating and is output from the first array waveguide diffraction grating to each waveguide. Is connected to the first polarization delay control circuit and the ellipse of the optical signal output from the first polarization delay control circuit. A first half-wave plate whose main axis of polarization is rotated by 45 degrees in the xy plane and a first half-wave plate connected to the first half-wave plate Connected to the second polarization delay control circuit and the second polarization delay control circuit for converting the elliptically polarized light of the optical signal output from the light into a linearly polarized light whose main axis is inclined by 45 degrees with respect to the x-axis and the y-axis Connected to a second half-wave plate and a second half-wave plate that rotate the main axis of linear polarization of the optical signal output from the second polarization delay control circuit by 45 degrees in the xy plane. A phase control circuit that makes all the phases of the optical signals output from the second half-wave plate in phase, and a second that is connected to the phase control circuit and multiplexes a plurality of optical signals output from the phase control circuit And a first polarization multiplexing / demultiplexing circuit for separating the optical signal into TE mode light and TM mode light, respectively. Circuit and a first polarization multiplexing / demultiplexing circuit, and the phase difference between the TE mode light and the TM mode light is 90 degrees. A second polarization coupling circuit that is connected to the first polarization multiplexing / demultiplexing circuit and the phase control circuit, and that couples the TE mode light and the TM mode light input from the first polarization multiplexing / demultiplexing circuit and the phase control circuit. And a polarization multiplexing / demultiplexing circuit.

  In one embodiment of the present invention, the first polarization multiplexing / demultiplexing circuit includes: a demultiplexing circuit; a wave plate connected to the demultiplexing circuit; and a 2 × 2 direction connected to the demultiplexing circuit and the wave plate. It consists of a sex coupler.

  In one embodiment of the present invention, the second polarization multiplexing / demultiplexing circuit includes a 2 × 2 directional coupler, a wave plate connected to the 2 × 2 directional coupler, and a 2 × 2 directional coupler. And a multiplexing circuit connected to the wave plate.

  Furthermore, in one embodiment of the present invention, the branching circuit is either a Y-branch circuit, a multimode interference waveguide, or a directional coupling circuit.

  Since the total dispersion compensation circuit according to the present invention has an all-waveguide structure and is integrated, it can be miniaturized and has high reliability.

  In an embodiment, phase control can be performed at high speed, so that dispersion compensation can also be performed at high speed.

  In a further embodiment, there is no heterogeneous substrate connection and it can be integrated on the same quartz substrate, resulting in low loss. Further, it can be configured more compactly, and the reliability can be improved.

It is the schematic explaining the total dispersion compensation circuit which concerns on a prior art. It is the schematic explaining the total dispersion compensation circuit which concerns on a prior art. It is a figure which shows the structure of the 1st Example of the total dispersion compensation circuit which concerns on this invention. It is a figure which shows the polarization state in the location of A thru | or E shown by FIG. 3 of 1st Example of the total dispersion compensation circuit which concerns on this invention. It is a figure which shows the structure of the 3rd Example of the total dispersion compensation circuit which concerns on this invention. It is a figure which shows the structure of the polarization delay control circuit used in the 3rd Example of the total dispersion compensation circuit which concerns on this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 3A is a diagram showing the configuration of the first embodiment of the total dispersion compensating circuit according to the present invention, and is a top view of the substrate 310 on which circuit elements are formed. Here, for the following explanation, the optical axis direction on the surface of the substrate 310 where the circuit elements are formed is the z axis, the normal direction of the surface where the circuit elements of the substrate 310 are formed is the y axis, and the circuit of the substrate 310 The direction perpendicular to the optical axis on the surface on which the element is formed is defined as the x-axis.

  This total dispersion compensation circuit performs spectral processing on the incident optical signal and outputs an optical signal for each wavelength component to each waveguide of the first waveguide array 302. And a plurality of optical signals output from the first arrayed waveguide diffraction grating 301 connected to the first arrayed waveguide diffraction grating 301 and provided with phase modulation electrodes to the respective waveguides are principally x-axis Alternatively, the first waveguide array 302 that converts to elliptically polarized waves parallel to the y-axis and the elliptically polarized wave of the optical signal connected to the first waveguide array 302 and output from the first waveguide array 302 A first half-wave plate 303 whose main axis is rotated by 45 degrees in the xy plane, and a first half-wave plate connected to the first half-wave plate 303 and provided with a phase modulation electrode The elliptical polarization of a plurality of optical signals output from 303 is inclined 45 degrees with respect to the x-axis and the y-axis. A second waveguide array 304 that converts the linearly polarized wave into a linearly polarized wave, and a main axis of linearly polarized light of an optical signal output from the second waveguide array 304 that is connected to the second waveguide array 304 in the xy plane. A second half-wave plate 305 rotated by 45 degrees and a second half-wave plate 305 connected to the second half-wave plate 305 and provided with a phase modulation electrode. A third waveguide array 306 that makes all the phases of the plurality of optical signals in phase, and a third waveguide array 306 that is connected to the third waveguide array 306 and that multiplexes the plurality of optical signals output from the third waveguide array 306. 2 arrayed waveguide diffraction gratings 307.

  The arrayed waveguide diffraction gratings 301 and 307 have the same characteristics such as the center frequency and the channel spacing. Each of the waveguide arrays 302, 304, and 306 is provided with a phase modulation electrode. When an electric field is applied to the electrode, the waveguide propagation constant changes and the phase of the propagating light is controlled. As the waveguide arrays 302, 304, and 306, lithium niobate waveguide arrays can be used. Since the lithium niobate waveguide has anisotropy, different phase changes are given to propagating light in the TE mode and TM mode. The first half-wave plate 303 and the second half-wave plate 305 are provided in each waveguide, and the optical axis thereof is 22.5 degrees with respect to the surface on which the circuit element of the substrate 310 is formed. Tilt 67.5 degrees.

  An optical signal propagated through a transmission line having group velocity dispersion and polarization dispersion is incident on the total dispersion compensation circuit according to this embodiment. The incident optical signal is decomposed into frequency components by the first arrayed waveguide diffraction grating 301 and distributed to a plurality of output waveguides. For example, as a typical value, the center frequency of the arrayed waveguide grating is 193.1 THz, the channel spacing is 5 GHz, the number of channels is 20, and the frequency band of 100 GHz allocated by wavelength division multiplexing is covered.

  FIG. 4 shows the polarization state at points A to E shown in FIG. Although it is decomposed into frequency components by the arrayed waveguide diffraction grating, the polarization state of each channel differs depending on the polarization dispersion of the transmission path. Further, the phase of each frequency component has a difference due to group velocity dispersion of the transmission path.

  As shown in FIG. 4A, in general, the incident optical signal is elliptically polarized light whose principal axis (one of the fast axis and the slow axis) is inclined, and both the TE mode and the TM mode are excited.

  Since the arrayed waveguide diffraction grating 301 is generally composed of a quartz waveguide, when the waveguide array is a lithium niobate waveguide array, the first waveguide array 302 composed of lithium niobate is used. Connection of dissimilar substrates is necessary. This connection technique is a known technique.

  The role of the first waveguide array 302 is to change the propagation constant of each mode by applying a voltage, rotate the main axis of the elliptically polarized light by setting the phase difference between the modes to 90 degrees, and to the x axis or the y axis. To match. This is shown in FIG. In the lithium niobate waveguide, it is possible to decide mainly whether to change the phase of the TE mode light or the TM mode light by selecting the electrode arrangement and the crystal axis. In addition, since the electro-optic effect is used, the time required for control is very short.

  Next, the elliptical polarization main axis is rotated 45 degrees in the xy plane by the first half-wave plate 303 connected to the quartz waveguide and disposed in the quartz waveguide. This is shown in FIG.

  Each waveguide is then connected to a second waveguide array 304. The second waveguide array 304 changes the propagation constant of each mode by applying a voltage and makes the phase difference between them 0 degrees to make elliptically polarized light a straight line whose principal axis is inclined 45 degrees with respect to the x axis and the y axis. Convert to polarized light. This is shown in FIG. Here, the linearly polarized light means that the TE mode and the TM mode have the same phase, and the electric field amplitude is equal.

  Next, each waveguide is connected to the quartz waveguide, and the principal axis of the linearly polarized light is made to coincide with the x-axis or the y-axis by the second half-wave plate 305 disposed in the quartz waveguide. This is indicated by E or E 'in FIG. At this time, each frequency component is only TE mode light or TM mode light.

  Next, each waveguide is connected to the third waveguide array 306, and the phase between each frequency component is in phase, so that the group velocity dispersion is compensated when the optical signal is multiplexed by the arrayed waveguide grating 307. When the waveguide array is a lithium niobate waveguide array, the lithium niobate waveguide has birefringence even when the phase is not controlled. Therefore, when propagating through the waveguide arrays 302 and 304, TE mode light and TM There may be a phase difference of an integral multiple of the wavelength in the mode light. In order to compensate for this, a half-wave plate 311 is inserted after the waveguide arrays 302 and 304, and the polarization plane is rotated by 90 degrees to propagate through another lithium niobate waveguide 312 (FIG. 3B). )), Or a method of inserting an n-wave plate 313 (having a retardation of n times the wavelength) (see FIG. 3C) or the like.

  Since the total dispersion compensation circuit according to this embodiment can perform phase control at high speed, dispersion compensation can also be performed at high speed. The phase control time is about 1/1000 to 1/100000 compared with the liquid crystal.

  As mentioned above, it was shown that the total dispersion can be compensated by this configuration. The present invention does not include a technique for measuring the phase distortion due to the polarization state / group velocity dispersion of a signal for determining the phase control amount in the waveguide arrays 302, 304, and 306. Can be used.

  In the total dispersion compensation circuit of the first embodiment, a lithium tantalate waveguide can be used instead of the lithium niobate waveguide. Other components are the same as those in the first embodiment. When the lithium tantalate waveguide has a larger electro-optic constant than the lithium niobate waveguide, signal amplification at a low voltage is possible, reducing the drive voltage and downsizing the power supply. It becomes effective for conversion.

  Since the total dispersion compensation circuit according to this embodiment can perform phase control at high speed, dispersion compensation can also be performed at high speed. The phase control time is about 1/1000 to 1/100000 as compared with the liquid crystal.

  FIG. 5 is a diagram showing a configuration of a third embodiment of the total dispersion compensating circuit according to the present invention, and is a top view of a substrate 510 on which circuit elements are formed. Here, for the following explanation, the optical axis direction on the surface of the substrate 510 where the circuit elements are formed is the z axis, the normal direction of the surface where the circuit elements of the substrate 510 are formed is the y axis, and the circuit of the substrate 510 The direction perpendicular to the optical axis on the surface on which the element is formed is defined as the x-axis.

  The total dispersion compensation circuit performs spectral processing on an incident optical signal and outputs an optical signal for each wavelength component to each waveguide, and a first array waveguide. A first polarization delay control circuit 502 connected to the diffraction grating 501 for converting an optical signal output from the first arrayed waveguide diffraction grating 501 into an elliptically polarized wave whose principal axis is parallel to the x-axis or y-axis; A first half-wave plate 503 that is connected to one polarization delay control circuit 502 and rotates the principal axis of elliptically polarized light of an optical signal output from the first polarization delay control circuit 502 by 45 degrees in the xy plane; The elliptically polarized wave of the optical signal connected to the first half-wave plate 503 and output from the first half-wave plate 503 is linearly polarized with the main axis inclined 45 degrees with respect to the x-axis and the y-axis. Connected to a second polarization delay control circuit 504 for converting to a wave and a second polarization delay control circuit 504 The second half-wave plate 505 and the second half-wave plate 505 rotate the main axis of linear polarization of the optical signal output from the second polarization delay control circuit 504 by 45 degrees in the xy plane. A phase control circuit 506 that is connected to make all the phases of the optical signals output from the second half-wave plate 505 in phase, and a plurality of lights that are connected to the phase control circuit 506 and output from the phase control circuit 506 And a second arrayed waveguide grating 507 for multiplexing signals. Here, the first polarization delay control circuit 502 and the second polarization delay control circuit 504 respectively include a first polarization multiplexing / demultiplexing circuit that separates an optical signal into TE mode light and TM mode light, and a first polarization Connected to the multiplexing / demultiplexing circuit, connected to the phase control circuit for setting the phase difference between the TE mode light and the TM mode light to 90 degrees, the first polarization multiplexing / demultiplexing circuit, and the phase control circuit; And a second polarization multiplexing / demultiplexing circuit that couples the TE mode light and TM mode light input from the polarization multiplexing / demultiplexing circuit and the phase control circuit.

  In this total dispersion compensation circuit, all waveguides are made of quartz. For this reason, since there are no dissimilar substrate joints, a low-loss total dispersion compensation circuit can be configured. The polarization state at each of A to E is the same as in Example 1 (see FIG. 4).

  Here, the first polarization delay control circuit 502 that does not exist in the total dispersion compensation circuit according to the first embodiment will be described with reference to FIG. The polarization delay control circuit 502 includes a demultiplexing circuit 601 that demultiplexes an incident signal, a first wave plate 602 that is connected to the demultiplexing circuit 601, and a first wave plate that is connected to the demultiplexing circuit 601 and the first wave plate 602. 1 2 × 2 directional coupler 603, phase control circuit 604 connected to first 2 × 2 directional coupler 603, connected to first 2 × 2 directional coupler 603 and phase control circuit 604 Second 2 × 2 directional coupler 605, second wave plate 606 connected to second 2 × 2 directional coupler 605, second 2 × 2 directional coupler 605 and second And a multiplexing circuit 607 connected to the second wavelength plate 606. The second polarization delay control circuit 504 has the same configuration as that of the first polarization delay control circuit 502. In the first polarization delay control circuit 502, first, the incident signal is branched by the branching circuit 601. As the branching circuit 601, a Y branch circuit, a multimode interference waveguide, a directional coupling circuit, or the like can be used. A first wave plate 602 is inserted into one of the branched optical waveguides, and its axis is parallel to the x-axis or y-axis. Here, if the phase difference between the TM mode light propagating through both waveguides and the TE mode light is made appropriate, the TM mode light and the TE are output on the output side of the first 2 × 2 directional coupler 603. Mode light can be separated. Note that a circuit including the demultiplexing circuit 601, the first wave plate 602, and the first 2 × 2 directional coupler 603 is a waveguide-type polarization multiplexing / demultiplexing circuit, and is a known technique. Next, the phase control circuit 604 controls the phase of either the separated TE mode or TM mode. The phase control circuit 604 uses the refractive index change due to the thermo-optic effect by heating the waveguide with a heater in order to perform phase control. The phase control circuit 604 can set the phase difference between the two mode lights to 90 degrees. Next, the TE mode light and the TM mode light are synthesized by the waveguide-type polarization multiplexing / demultiplexing circuit including the second 2 × 2 directional coupler 605, the second wave plate 606, and the multiplexing circuit 607. The At this time, since the phase difference between the two mode lights is 90 degrees, the principal axis of the elliptically polarized light can coincide with the x-axis or the y-axis.

  As described above, after the elliptical polarization main axis is aligned with the x-axis or y-axis, the elliptical polarization main axis is rotated 45 degrees by the first half-wave plate 503 disposed in the quartz waveguide.

  Next, similarly to the polarization delay control circuit 502, the second polarization delay control circuit 504 separates the light into TE mode light and TM mode light, controls only the phase of one mode, and the phase difference between both modes. The TE mode light and the TM mode light are coupled again to obtain linearly polarized light whose main axis is inclined by 45 degrees.

  Next, the principal axis of linearly polarized light is made to coincide with the x axis or the y axis by the second half-wave plate 505 disposed in the quartz waveguide. At this time, each frequency component is only TE mode light or TM mode light.

  Next, the phase control circuit 506 makes the phase between the frequency components in phase, and the second array waveguide diffraction grating 507 compensates the group velocity dispersion when the optical signal is multiplexed. Similarly to the phase control circuit 604, the phase control circuit 506 uses the thermo-optic effect. Since the quartz waveguide generally has little polarization dependency, the same effect can be obtained even if the second half-wave plate 505 is omitted.

101 Optical System with PMD 102 Sensor 103 Spectroscopic Module 104 Controller 105 SLM
111 incident light 112 outgoing light 201 femtosecond fiber laser 202 erbium-doped fiber amplifier (EDFA)
203 Polarization Mode Dispersion Emulator 204 Circulator 205 Polarization Spectrum / Pulse Shaper 206 Broadband Polarimeter 207 Mirror 208 LCM Array 209 Lens 210 Diffraction Grating 212 Phase Dedicated Pulse Shaper 213 Ultrashort Pulse Measuring Instrument 214 Personal Computer 301 First Array Conductor Waveguide diffraction grating 302 First waveguide array 303 First half-wave plate 304 Second waveguide array 305 Second half-wave plate 306 Third waveguide array 307 Second array waveguide diffraction Grating 308 Quartz waveguide 310 Substrate 311 1/2 wave plate 312 Lithium niobate waveguide 313 n Wave plate 501 First array waveguide diffraction grating 502 First polarization delay control circuit 503 First half wave plate 504 Second polarization delay control circuit 505 Second half-wave plate 506 Phase control circuit 50 Second arrayed waveguide grating 510 Substrate 601 Demultiplexing circuit 602 First wave plate 603 First two-to-two directional coupler 604 Phase control circuit 605 Second two-to-two directional coupler 606 Second Wave plate 607 multiplexing circuit

Claims (7)

A total dispersion compensation circuit created on a substrate, wherein the optical axis direction on the surface of the substrate on which the circuit elements are formed is the z axis, and the normal direction of the surface on which the circuit elements of the substrate are formed is the y axis When the x-axis is the direction perpendicular to the optical axis on the surface of the substrate on which the circuit elements are formed,
A first arrayed waveguide grating that performs spectral processing on the incident optical signal and outputs an optical signal for each wavelength component to each waveguide;
A plurality of optical signals output from the first arrayed waveguide diffraction grating connected to the first arrayed waveguide diffraction grating and provided with a phase modulation electrode to the respective waveguides are principal axes x-axis or a first waveguide array that converts to elliptically polarized waves parallel to the y-axis;
A first half-wave plate connected to the first waveguide array and rotating the main axis of elliptically polarized light of an optical signal output from the first waveguide array by 45 degrees in the xy plane;
Elliptical polarization of a plurality of optical signals output from the first half-wave plate connected to the first half-wave plate and provided with a phase modulation electrode, the principal axis is the x-axis, And a second waveguide array for converting to linearly polarized waves inclined 45 degrees with respect to the y-axis,
A second half-wave plate connected to the second waveguide array and rotating the principal axis of linear polarization of an optical signal output from the second waveguide array by 45 degrees in the xy plane;
A third waveguide that is connected to the second half-wave plate and is provided with a phase modulation electrode and that makes the phases of a plurality of optical signals output from the second half-wave plate all in phase. A waveguide array;
A total dispersion compensation circuit, comprising: a second arrayed waveguide diffraction grating connected to the third waveguide array and multiplexing a plurality of optical signals output from the third waveguide array.   2. The total dispersion compensation circuit according to claim 1, wherein the first waveguide array, the second waveguide array, and the third waveguide array are lithium niobate waveguide arrays. Total dispersion compensation circuit.   2. The total dispersion compensation circuit according to claim 1, wherein the first waveguide array, the second waveguide array, and the third waveguide array are lithium tantalate waveguide arrays. Total dispersion compensation circuit. A total dispersion compensation circuit created on a substrate, wherein the optical axis direction on the surface of the substrate on which the circuit elements are formed is the z axis, and the normal direction of the surface on which the circuit elements of the substrate are formed is the y axis When the x-axis is the direction perpendicular to the optical axis on the surface of the substrate on which the circuit elements are formed,
A first arrayed waveguide grating that performs spectral processing on the incident optical signal and outputs an optical signal for each wavelength component to each waveguide;
An optical signal connected to the first arrayed waveguide diffraction grating and output from the first arrayed waveguide diffraction grating to each of the waveguides is converted into an elliptically polarized wave whose principal axis is parallel to the x axis or the y axis. A first polarization delay control circuit;
A first half-wave plate connected to the first polarization delay control circuit and rotating the principal axis of elliptically polarized light of an optical signal output from the first polarization delay control circuit by 45 degrees in the xy plane;
An elliptically polarized wave of an optical signal connected to the first half-wave plate and output from the first half-wave plate is linearly polarized with the main axis inclined 45 degrees with respect to the x-axis and the y-axis. A second polarization delay control circuit for converting to a wave;
A second half-wave plate connected to the second polarization delay control circuit and rotating the principal axis of linear polarization of the optical signal output from the second polarization delay control circuit by 45 degrees in the xy plane;
A phase control circuit connected to the second half-wave plate and configured to make all phases of optical signals output from the second half-wave plate in phase;
A total dispersion compensation circuit connected to the phase control circuit and comprising a second arrayed waveguide grating that multiplexes a plurality of optical signals output from the phase control circuit, wherein the first and second polarizations Each delay control circuit
A first polarization multiplexing / demultiplexing circuit for separating an optical signal into TE mode light and TM mode light;
A phase control circuit connected to the first polarization multiplexing / demultiplexing circuit, wherein the phase difference between the TE mode light and the TM mode light is 90 degrees;
The TE mode light and the TM mode light input from the first polarization multiplexing / demultiplexing circuit and the phase control circuit are connected to the first polarization multiplexing / demultiplexing circuit and the phase control circuit. A total dispersion compensation circuit comprising: a second polarization multiplexing / demultiplexing circuit.   5. The total dispersion compensation circuit according to claim 4, wherein the first polarization multiplexing / demultiplexing circuit is connected to the demultiplexing circuit, the wave plate connected to the demultiplexing circuit, and the demultiplexing circuit and the wave plate. A total dispersion compensation circuit comprising: a 2 × 2 directional coupler.   5. The total dispersion compensation circuit according to claim 4, wherein the second polarization multiplexing / demultiplexing circuit includes a 2 × 2 directional coupler, a wave plate connected to the 2 × 2 directional coupler, and the 2 × A total dispersion compensation circuit comprising: a bidirectional circuit and a multiplexing circuit connected to the wave plate.   6. The total dispersion compensation circuit according to claim 5, wherein the branching circuit is any one of a Y branch circuit, a multimode interference waveguide, and a directional coupling circuit.

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