JP5015820B2 - Variable dispersion compensator - Google Patents

Description

  The present invention relates to a dispersion compensator used in optical fiber communication.

  High-capacity optical communication network systems that have shown rapid development in recent years are shifting from point-to-point systems, which have been the mainstream, to ring-mesh systems. This is because the ring-mesh type system can flexibly cope with changes in communication demand between nodes by using a transparent wavelength selective switch or the like that processes an optical signal in an optical state. Specifically, there is an advantage that the amount of on-site work accompanying the opening and closing of a new path can be greatly reduced by the dynamic switching of wavelength paths. However, in a ring-mesh network, the path length also changes as the wavelength path is switched, so the chromatic dispersion value of the path also changes dynamically.

  A conventional dispersion compensator is of a type in which a dispersion compensation fiber or a dispersion compensation amount is fixed, and is different for each WDM wavelength when the wavelength path distance is different in the network of the ring mesh type configuration as described above. The variance value could not be set. For this reason, adaptability is also required for dispersion compensation of wavelength paths in optical communications.

  On the other hand, from the viewpoint of miniaturization and integration of signal processing devices, research and development of waveguide type optical circuits (PLCs) are in progress. In the PLC, for example, a core made of quartz glass is formed on a silicon substrate and various functions are integrated in one chip, and an optical functional device with low loss and high reliability is realized. Furthermore, a composite optical signal processing component (apparatus) that combines a plurality of PLC chips and other optical functional components has also appeared.

  For example, Patent Document 1 discloses an optical signal processing device in which a waveguide type optical circuit (PLC) including an arrayed waveguide grating (hereinafter referred to as AWG) and a spatial modulation element such as a liquid crystal element are combined. . More specifically, a wavelength blocker including a PLC and a collimating lens arranged symmetrically with respect to the liquid crystal element, a wavelength equalizer, a dispersion compensator, and the like are being studied. In these optical signal processing devices, optical signal processing is performed independently for each wavelength for a plurality of optical signals having different wavelengths.

  FIG. 1 is a configuration diagram showing an example of a tunable dispersion compensator combining a PLC and a spatial modulation element. More specifically, a variable dispersion compensator in which AWG and LCOS (Liquid crystal on silicon) are combined is shown. In this tunable dispersion compensator, an external optical signal is input / output via the AWG 1. A more specific operation will be described with reference to FIG. 1A viewed from a direction perpendicular to the substrate surface of the AWG.

  The AWG 1 demultiplexes a plurality of optical signals having different wavelengths at an emission angle θ corresponding to the wavelengths. The demultiplexed optical signal is emitted in the z-axis direction toward the condenser lens 3. The optical signal collected by the condenser lens 3 is collected at predetermined positions on the x-axis of the spatial phase modulator 4 having a phase modulation function corresponding to the emission angle θ. That is, it should be noted that the optical signal is collected at different positions on the x-axis of the spatial phase modulator 4 depending on the wavelength of the input optical signal. The spatial phase modulator 4 is, for example, a liquid crystal element composed of a plurality of element elements (pixels). By controlling the refractive index of each element, the optical signal of each wavelength is given a predetermined phase amount and subjected to phase modulation, and a predetermined dispersion value is given for each wavelength. The dispersion-compensated optical signal is reflected by the spatial phase modulator 4 to reverse the traveling direction, passes through the condenser lens 3 again, and is multiplexed in the AWG 1. The combined optical signal of each wavelength is output to the outside of the AWG 1 again as output light. As can be seen by referring to FIG. 1B, which is a cross-sectional view of the substrate of AWG 1, a cylindrical lens 2 having a lens action only in the y-axis direction is disposed in the vicinity of the emission end face of AWG 1.

  As is well known, the AWG 1 has a configuration in which an input waveguide 1, a slab waveguide 11, and a waveguide array 12 are sequentially connected. In the AWG configuration shown in FIG. 1A, the input waveguide 1 also serves as an output waveguide that outputs a dispersion-compensated optical signal, but is not limited to this configuration. The optical signal to be subjected to dispersion compensation is input to the input optical fiber 6 and is input to the AWG input waveguide 10 via the circulator 9 and the connecting optical fiber 8. The dispersion-compensated optical signal is further output from the output optical fiber 7 to the outside through the input waveguide 10 via the connection waveguide 8 and the circulator 9.

  The dispersion compensator shown in FIG. 1A is configured to perform both demultiplexing and multiplexing of an optical signal by one AWG by folding the optical signal using a mirror. being called. The optical signal processing of the dispersion compensator is not limited to this configuration. In the apparatus configuration shown in FIG. 1A, by combining the direction of reflection by the spatial phase modulator 4, the optical signal is combined by another lens and an output system composed of an AWG arranged at an arbitrary position. It is also possible to perform the configuration. Moreover, it can also be set as the structure which overlaps and arrange | positions the entrance system AWG and the output system AWG in the y direction of FIG.

  The tunable dispersion compensator shown in FIG. 1A has high dispersion compensation characteristics, and can set a phase with a high degree of freedom derived from a fine cell structure of LCOS. Furthermore, it has a feature that it is possible to compensate for multiple channels at once.

Japanese Patent Laid-Open No. 2002-250828 (pages 16, 19, 20, 20, 27, 29D, etc.)

  FIG. 2 is a conceptual diagram illustrating the configuration of a spatial phase modulator having an LCOS structure used in a conventional variable dispersion compensator. In FIG. 2, it should be noted that the traveling direction of the optical signal is different from the direction shown in FIG. 1, and is shown as having a condenser lens in the lower part of FIG. 2. The spatial phase modulator 4 having the LCOS structure has a structure in which a liquid crystal material 25 is filled in a space between the rear silicon substrate 21 and the front glass substrate 24. A common transparent electrode 23 is formed on the front glass substrate 24, and N electrode arrays 22 a, 22 n are formed on the rear silicon substrate 21. The electrode arrays 22a, 22n are electrodes having a reflection function in the communication wavelength band, and for example, gold, aluminum, chrome, or the like is used.

  In each region between the electrode arrays 22a,... 22n and the common transparent electrode 23 facing each other, phase imparting function portions 26a,. By independently applying an electric field between the electrode arrays 22a,... 22n and the common transparent electrode 23, the phase amount given to the phase imparting functional units 26a,. Although the phase amount is set discretely in each of the phase providing function units 26a... 26n, any desired phase profile can be set in the entire N phase providing function units. In a ring-mesh network, variable dispersion compensation is realized with wavelength path switching.

  There has been a problem that ripples are generated in the dispersion characteristics provided in the tunable dispersion compensator using the spatial phase modulator having the LCOS structure as described above. Hereinafter, a case where the phase amount profile given by the LCOS is a quadratic function will be described as an example.

  FIG. 3 is a diagram showing dispersion compensation characteristics of a tunable dispersion compensator using a conventional spatial phase modulator having an LCOS structure. The graph labeled (a) shows the optical frequency (THz) on the horizontal axis and the transmission characteristics (dB) and group delay (ps) of the tunable dispersion compensator on the vertical axis. In both the transmission characteristics and the group delay, a significant ripple occurs as the distance from the center frequency increases. In the graph displayed as (b), the vertical axis indicates the phase shift amount (radian) given by the dispersion compensator, and the horizontal axis indicates the optical frequency (THz) together with the horizontal axis of the graph of (a). Yes.

  The dispersion compensator is usually used in an optical frequency range (referred to as a 1 dB transmission bandwidth) whose optical transmittance is within 1 dB from the center optical frequency. If attention is paid to the transmission characteristics in the graph of FIG. 3A, at the frequency at which the first dip appears 14.8 GHz up and down from the center optical frequency of 188.90 THz (188.88252 THz and 188.9149 THz), the ripple is Compared with the case where it is assumed that there is not, the transmittance | permeability fall of 2.13 dB or more is seen. Therefore, the ripple has an effect of narrowing the 1 dB transmission bandwidth including the center optical frequency when used as a dispersion compensator. Note that the 1 dB transmission bandwidth in the transmission characteristics of FIG. 3 is approximately 15.4 GHz (± 7.7 GHz).

  Further, the dispersion compensator characteristic is required to have as small a ripple of the group delay characteristic as possible within the 1 dB transmission band. For example, in high-speed optical communication of 40 Gbps class, it is generally required to be within about ± 5 ps. In a dispersion compensator having a larger group delay ripple, there is a risk of inducing distortion of the transmission waveform.

  Further, the ripple described above is not limited to the normal dispersion compensator, and the above-described ripple is an undesirable characteristic limitation and function for an application in which the spatial phase modulator is used in an optical frequency range that further exceeds the 1 dB transmission bandwidth. Gives the above limit. For this reason, it has been required to remove these ripples.

  The present invention has been made in view of such a problem, and an object of the present invention is to solve the problem of ripples in dispersion characteristics generated in a conventional variable dispersion compensator using a spatial phase modulator having an LCOS structure. There is to do. The present invention provides a dispersion compensator with a wider usable bandwidth, and further expands the applicability other than the dispersion compensator by the ripple removal of the dispersion characteristic.

According to a first aspect of the present invention, there is provided a spectroscopic unit that splits an optical signal at an emission angle corresponding to a wavelength of an input optical signal, a condensing lens that condenses the optical signal output from the spectroscopic unit, and a spectroscopic method using the spectroscopic unit. A spatial phase having a plurality of phase providing cells arranged in a direction intersecting with the surface, and applying a predetermined phase amount to the collected optical signal by the plurality of phase providing cells and reflecting the light to the spectroscopic means A phase modulator, the spatial phase modulator is a liquid crystal element composed of liquid crystal filled in a space defined by a front transparent substrate and a rear transparent substrate on the condenser lens side, and the phase providing The cell is formed over the entire area of the plurality of phase-imparting cells on the inner surface of the spatial phase modulator of the front transparent substrate, and faces the common transparent electrode having a common potential, the common transparent electrode, wherein the rear transparent substrate Formed between the phase modulator inner surface, a plurality of transparent electrode array defining each of the plurality of phases imparted cells, said plurality of transparent electrodes array Each electrode set phase amount of the phase imparted cells A transparent electrode array to which a control voltage to be determined is applied; and a mirror array comprising a plurality of mirrors that are formed on the modulator outer surface of the rear transparent substrate and reflect an optical signal transmitted through the plurality of transparent electrode arrays; The dispersion compensator is characterized by including:

According to a second aspect of the present invention, there is provided a spectroscopic unit that splits an optical signal at an emission angle corresponding to a wavelength of an input optical signal, a condensing lens that condenses the optical signal output from the spectroscopic unit, and a spectroscopic method using the spectroscopic unit. A spatial phase having a plurality of phase providing cells arranged in a direction intersecting with the surface, and applying a predetermined phase amount to the collected optical signal by the plurality of phase providing cells and reflecting the light to the spectroscopic means A phase modulator, the spatial phase modulator is a liquid crystal element composed of liquid crystal filled in a space defined by a front transparent substrate and a rear transparent substrate on the condenser lens side, and the phase providing The cell is formed over the entire area of the plurality of phase-applying cells on the inner surface of the spatial phase modulator of the front transparent substrate, facing the common transparent electrode having a common potential, wherein the rear transparent substrate Formed between the phase modulator inner surface, a mirror array comprising a plurality of mirrors for partitioning each of the plurality of phases imparted cells, each of the mirrors of the mirror array configuration phase amount of the phase imparted cells a mirror array which acts a control voltage determining as capable of applying electrodes, a dispersion compensator, which comprises a.

A third aspect of the invention is the variable dispersion compensator according to the first or second aspect , wherein the spectroscopic means is an AWG.

  As described above, according to the present invention, the ripple generated in the dispersion characteristics of the conventional variable dispersion compensator using the spatial phase modulator of the LCOS structure is greatly reduced, and the operable bandwidth is wider. A dispersion compensator is provided. Furthermore, the ripple removal of the dispersion characteristic widens the application possibilities other than the dispersion compensator.

  The tunable dispersion compensator of the present invention is characterized in that it has a configuration that prevents reflection of an optical signal in a gap portion that is generated to form and partition a phase difference providing function portion. By reducing the reflected light in the gap part, interference between the signal light of the phase difference providing function part and the reflected light from the gap part is suppressed, and the ripple generated in the compensation dispersion characteristic is greatly reduced.

  The inventors focused on the fact that there is a certain relationship between the ripple generated in the transmission characteristics and the group delay characteristics in FIG. 3 and the phase shift amount set in the spatial phase modulator. Referring to FIG. 3 again, it can be seen that ripples are generated in the transmission characteristics and the like when the phase shift amount given by the spatial phase modulator is π. Therefore, further study will be made on the phase assignment in the spatial phase modulator of the LCOS structure.

  FIG. 4 is a conceptual diagram for explaining the phase providing operation in the spatial phase modulator having the LCOS structure. FIG. 4 conceptually shows the phase difference providing function units 26a and 26b in the spatial phase modulator. Compare the actual configuration of LCOS shown in FIG. 2 with reference to the conceptual diagram of FIG. In the spatial phase modulator having the LCOS structure, the optical signals incident on the phase applying units 26a and 26b are reflected by the electrode arrays 22a and 22n. In the phase difference providing function units 26a and 26b, a desired phase shift amount is given to the optical signal by a control voltage applied between electrodes sandwiching the phase difference providing function unit. Here, since the phase difference providing function units 26a and 26b are partitioned by the electrode arrays 22a and 22n formed separately, gap portions 40a, 40b, 40c, 40d exists. As can be seen from FIG. 2, since the optical signal is also incident on the gap portion, the optical signal reaching the gap portion is reflected on the surface of the silicon substrate 21.

Here, an optical signal that is given a predetermined phase shift amount in the phase difference providing function unit and an optical signal that is reflected in the gap unit are considered. If a phase difference φ of 2π is given in the phase difference providing function unit 26a, an optical signal reflected by the phase difference providing function unit 26a and a phase shift φ _G of 0 in the adjacent two gap portions 40a and 40b. Interference with the reflected light from the gap that is reflected by the light so as to strengthen each other. On the other hand, if the phase difference providing function unit 26b is given a phase difference φ of π, the optical signal reflected by the phase difference providing function unit 26b and the phase of 0 in the two adjacent gap portions 40c and 40d are displayed. The gap reflected light reflected by the shift φ _G interferes with each other so as to weaken each other. Therefore, the intensity of the dispersion-compensated optical signal emitted from the phase difference providing function unit 26b decreases.

  As described above, the inventors have come to the conclusion that the reflected light in the gap part affects the ripple of the dispersion compensation characteristic. Therefore, in the spatial phase modulator of the present invention, ripples are reduced by reducing the reflection of the optical signal in the gap portion adjacent to each phase difference providing function unit.

  FIG. 5 is a diagram showing the configuration of the spatial phase modulator in the tunable dispersion compensator according to the first embodiment of the present invention. FIG. 5A is a diagram of the spatial phase modulator 4 as viewed from the traveling direction of the optical signal, and N phase providing cells 35a, 35b,... 35n arranged in the x-axis direction with a repetition period P. Is formed. The overall configuration of the dispersion compensator is the same as that shown in FIG. 1, and the respective axes in FIG. 1 should be referred to by comparing (A) and (B) in FIG. The gap distance between adjacent phase providing cells is G. A discrete phase amount is set for each incident optical signal by each phase providing cell, output after dispersion compensation.

  FIG. 5B is a diagram illustrating a cross-sectional configuration of the spatial phase modulator 4. In FIG. 5B, it is shown that there is a condenser lens below. The spatial phase modulator 4 of this embodiment has a structure in which a liquid crystal material 25 is filled in a space between the rear glass substrate 31 and the front glass substrate 24. A common transparent electrode 23 is formed on the front glass substrate 24, and N transparent electrode arrays 32 a... 32 n are formed on the rear glass substrate 31 so as to face the common transparent electrode 23. For example, indium tin oxide is used as the material of the transparent electrode arrays 32a, 32n. On the surface of the rear glass substrate 31 opposite to the N transparent electrode arrays 32a, 32n, N mirror arrays 30a, 30n are provided at positions corresponding to the transparent electrode arrays 32a, 32n. Yes. For the mirror arrays 30a, 30n, for example, gold or chrome is used.

  In each region between the transparent electrode arrays 32a,... 32n and the common transparent electrode 23 facing each other, phase imparting function portions 26a,. By applying an electric field independently between the transparent electrode arrays 32a,... 32n and the common transparent electrode 23, the phase amount given to the phase applying function units 26a,. Although the phase amount is set discretely in each of the phase providing function units 26a... 26n, any desired phase profile can be set in the entire N phase providing function units.

  Unlike the LCOS structure, the spatial phase modulator of this configuration is characterized in that a transparent glass substrate 31 that transmits an optical signal is used for the rear substrate. A gap section that partitions the phase providing function section is formed between the adjacent phase providing function sections. However, an optical signal that enters the gap section from the condenser lens is not reflected and passes through the glass substrate 31 as it is. To do. On the other hand, the optical signals are transmitted through the transparent electrode arrays 32a... 32n and further reflected by the mirror arrays 30a. A predetermined phase amount is given only to the optical signal incident on the phase imparting function part, and the optical signal incident on the gap part disappears without being reflected. Therefore, the optical signal incident on the phase providing function unit and subsequently reflected does not interfere with the optical signal incident on the gap adjacent to each phase difference providing function unit. The reflected light in the gap does not cause a ripple in the dispersion compensation characteristic. Other configurations that can reduce the reflected light in the gap portion can also be adopted.

  FIG. 6 is a diagram showing the configuration of the spatial phase modulator in the tunable dispersion compensator according to the second embodiment of the present invention. FIG. 6A is a diagram of the spatial phase modulator 4 as seen from the traveling direction of the optical signal, and N phase providing cells 35a, 35b,... 35n arranged at a repetition distance P in the x-axis direction. Is formed. The overall configuration of the dispersion compensator is the same as that shown in FIG. 1 as in the first embodiment. Refer to FIG. 1 by comparing each axis with FIG. 6 (A) and (B). . The gap distance between adjacent phase providing cells is G. A discrete phase amount is set for each incident optical signal by each phase providing cell, output after dispersion compensation.

  FIG. 6B is a diagram illustrating a cross-sectional configuration of the spatial phase modulator 4. In FIG. 6B, it is indicated that there is a condenser lens. The spatial phase modulator 4 of this embodiment has a structure in which a liquid crystal material 25 is filled in a space between the rear glass substrate 31 and the front glass substrate 24. A common transparent electrode 23 is formed on the front glass substrate 24, and N mirror arrays 33 a, 33 n with electrode functions are formed on the rear glass substrate 31. As a material of the mirror arrays 33a, 33n, for example, gold, chrome, or the like is used.

  In each region between the mirror arrays 33a,... 33n and the common transparent electrode 23 facing each other, phase giving function portions 26a,. By applying an electric field independently between the mirror arrays 33a,... 33n and the common transparent electrode 23, the phase amount given to the phase applying functional units 26a,. Although the phase amount is set discretely in each of the phase providing function units 26a... 26n, any desired phase profile can be set in the entire N phase providing function units.

  Unlike the LCOS structure, the spatial phase modulator of this configuration is characterized in that a transparent glass substrate 31 that transmits an optical signal is used as a rear substrate. This is different from the first embodiment in that the mirror array 33a... 33n for partitioning adjacent phase providing function sections in the region filled with the liquid crystal also has an electrode function. A gap section that partitions the phase providing function section is formed between the adjacent phase providing function sections. However, an optical signal that enters the gap section from the condenser lens passes through the glass substrate 31 as it is without being reflected. . On the other hand, the optical signal incident on the phase providing function part is reflected by the mirror arrays 33a, 33n. A predetermined phase is imparted only to the optical signal incident on the phase imparting function section, and the optical signal incident on the gap section disappears without being reflected. Therefore, the optical signal incident on the phase providing function unit and subsequently reflected does not interfere with the optical signal incident on the gap portion adjacent to each phase difference providing function unit. The reflected light in the gap does not cause a ripple in the dispersion compensation characteristic.

  In both the first and second embodiments, for example, glass is used for the rear substrate.

  FIG. 7 is a diagram showing dispersion compensation characteristics of a tunable dispersion compensator using the spatial phase modulator of the present invention. The specific configuration of the phase-giving cells was such that the total number N of cells was 256, the cell repetition distance P was 10 μm, and the gap distance G between cells was 1.0 μm. The distance between the common transparent electrode and the opposing electrode was 5 μm. The horizontal axis represents the optical frequency (THz), and the vertical axis represents the transmission characteristics (dB) and group delay (ps) of the tunable dispersion compensator. In FIG. 7, the characteristics of the spatial phase modulator of the prior art LCOS configuration having the same phase difference cell are also shown by dotted lines.

  As is apparent from FIG. 7, the ripple is almost eliminated in both the light transmittance and the group delay. In the spatial phase modulator of the present invention, a part of the signal light is lost, and thus a loss of about 0.9 dB occurs. However, the function as a tunable dispersion compensator is at a level with no problem. The 1 dB transmission bandwidth where the light transmittance is 1 dB lower than the light transmittance at the center frequency is approximately 18.8 GHz, which is 22% lower than the 15.4 GHz of the spatial phase modulator with the conventional LCOS structure. I was able to expand. The group delay ripple within the 1 dB transmission bandwidth was 1 ps or less, and the ripple could be reduced to about 1/10.

  As described above in detail, according to the present invention, the ripple of the dispersion compensation characteristic generated in the variable dispersion compensator of the prior art using the spatial phase modulator of the LCOS structure is greatly reduced, and the operable bandwidth is further reduced. Provide a wide dispersion compensator. Furthermore, the possibility of application other than the dispersion compensator is broadened by almost eliminating the ripple of the dispersion characteristic.

  The present invention can be applied to optical communication. In particular, it is suitable for use in a network of a ring mesh type configuration using a wavelength selective switch.

It is a block diagram of the variable dispersion compensator which combined PLC and the spatial modulation element. It is a block diagram of the spatial phase modulator with the LCOS structure used for the conventional variable dispersion compensator. It is the figure which showed the dispersion compensation characteristic of the variable dispersion compensator using the spatial phase modulator of the LCOS structure of a prior art. It is a conceptual diagram explaining the operation | movement of phase provision in the spatial phase modulator of LCOS structure. It is a figure which shows the structure of the spatial phase modulator of 1st Example of this invention. It is a figure which shows the structure of the spatial phase modulator of the 2nd Example of this invention. It is a figure which shows the dispersion compensation characteristic of the variable dispersion compensator using the spatial phase modulator of this invention.

Explanation of symbols

1 AWG
2 Cylindrical lens 3 Condensing lens 4 Spatial phase modulator 21 Silicon substrate 22a, 22b, 22n Electrode array
23 Transparent common electrode 24 Glass substrate 25 Liquid crystal 26a, 26b, 26n Phase imparting function part 30a, 30b, 30n Mirror array 31 Transparent glass substrate 32a, 32b, 32n Transparent electrode array 33a, 33b, 33n Mirror array with electrode function 35a, 35b , 35n Phase imparting cell 40a, 40b, 40c, 40d Gap part

Claims (3)

A spectroscopic means for dispersing the optical signal at an emission angle corresponding to the wavelength of the input optical signal;
A condensing lens for condensing the optical signal emitted from the spectroscopic means;
A plurality of phase applying cells arranged in a direction intersecting with a spectral plane by the spectroscopic means, and applying the predetermined phase amount to the optical signal collected by the plurality of phase applying cells; A spatial phase modulator that reflects to
The spatial phase modulator is a liquid crystal element composed of liquid crystal filled in a space defined by a front transparent substrate and a rear transparent substrate on the condenser lens side,
The phase imparting cell is
A common transparent electrode having a common potential formed on the inner surface of the spatial phase modulator of the front transparent substrate over the entire region of the plurality of phase applying cells;
A plurality of transparent electrode arrays facing the common transparent electrode, formed on the inner surface of the spatial phase modulator of the rear transparent substrate, and partitioning each of the plurality of phase imparting cells, wherein the plurality of transparent electrodes A transparent electrode array to which each electrode of the array is applied with a control voltage that determines a set phase amount of the phase-giving cell;
A dispersion compensator, comprising: a mirror array formed on the outer surface of the modulator on the rear transparent substrate, the mirror array including a plurality of mirrors that reflect optical signals transmitted through the plurality of transparent electrode arrays. A spectroscopic means for dispersing the optical signal at an emission angle corresponding to the wavelength of the input optical signal;
A condensing lens for condensing the optical signal emitted from the spectroscopic means;
A plurality of phase applying cells arranged in a direction intersecting with a spectral plane by the spectroscopic means, and applying the predetermined phase amount to the optical signal collected by the plurality of phase applying cells; A spatial phase modulator that reflects to
The spatial phase modulator is a liquid crystal element composed of liquid crystal filled in a space defined by a front transparent substrate and a rear transparent substrate on the condenser lens side,
The phase imparting cell is
A common transparent electrode having a common potential formed on the inner surface of the spatial phase modulator of the front transparent substrate over the entire region of the plurality of phase applying cells;
A mirror array comprising a plurality of mirrors formed on the inner surface of the spatial phase modulator of the rear transparent substrate so as to face the common transparent electrode and partitioning each of the plurality of phase applying cells, Each of the mirrors in the array includes a mirror array that acts as an electrode to which a control voltage that determines a set phase amount of the phase applying cell can be applied. The spectroscopic means, the dispersion compensator according to claim 1 or 2, characterized in that the AWG.

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