JP2010271645A - Wavelength selection switch - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wavelength selection switch which does not use an MEMS mirror. <P>SOLUTION: The wavelength selection switch includes an array waveguide diffraction grating separating an optical signal made incident on an input port for each wavelength and emitting the separated optical signal at an emission angle corresponding to the wavelength, first and second liquid crystal switches changing the traveling direction of each of the separated optical signals, and array waveguide diffraction gratings (A and B) formed on a substrate (10'-1) and array waveguide diffraction gratings (C and D) formed on a substrate (10'-2) multiplexing each of the optical signals whose traveling directions are changed and emitting the multiplexed optical signals from any of M (=4) output ports. The first liquid crystal switch is constituted by combination of a liquid crystal element (500) and a birefringence crystal (900) changing the traveling direction of each of the optical signals in the stack direction (direction y) of the substrate and the second liquid crystal switch is constituted by combination of a liquid crystal element (500') and a birefringence crystal (900') changing the traveling direction of each of the optical signals in a substrate plane (plane xz). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a wavelength selective switch applicable to an optical communication system.

  While an increase in capacity of optical communication has progressed and transmission capacity has been increased by a wavelength division multiplexing (WDM) method, an increase in throughput of a node having a path switching function is strongly demanded. Conventionally, path switching has been mainly performed by an electrical switch after converting the transmitted optical signal to an electrical signal, but using an optical switch or the like by taking advantage of the characteristics of an optical signal that is high-speed and broadband. ROADM (Reconfigurable Optical Add / Drop Multiplexer) system, which performs add / drop and the like with an optical signal, is now being introduced. In the ROADM system, each node configuring the ring network performs add / drop of an optical signal and passes an optical signal that does not need to be added / dropped as it is. Therefore, there is an advantage that the node device is small in size and low in power consumption. A wavelength selective switch (WSS) module is required as a device necessary for future development of these ROADM systems.

  Conventionally, WSS using MEMS (Micro Electro Mechanical Systems) mirror array is known (for example, refer to patent documents 1). FIG. 1 is a diagram showing the configuration of a WSS using such a MEMS mirror array. FIG. 1A is a plan view of the WSS, and FIG. 1B is a side view. The WSS shown in FIG. 1 is a slab in which an optical signal wavelength-division multiplexed (WDM) is input as input light to an optical fiber on the input side, and a wavelength demultiplexer (for example, quartz glass is formed on a silicon substrate as a material). Each optical signal having a wavelength different from each other by an arrayed waveguide grating (AWG) manufactured using a planar lightwave circuit (PLC) technology including the waveguide 12 and the arrayed waveguide 14. Each of the optical signals that have been demultiplexed into two is separated by a lens (cylindrical lens 20, main lens 40) onto a MEMS mirror 60 that constitutes a MEMS mirror array. Hereinafter, each demultiplexed optical signal may be referred to as an optical signal of each wavelength channel. Here, the MEMS mirror array is arranged so that the optical signals of the respective wavelength channels are input to the respective MEMS mirrors 60. Therefore, by adjusting the angle of each MEMS mirror, the optical signal of each wavelength channel can be steered in an arbitrary direction. For example, in the WSS shown in FIG. 1, the optical signal of each wavelength channel can be input to other AWGs on the same substrate by swinging the mirror in the left and right direction (x direction) with respect to the optical axis (z direction). It is. In this specification, the direction in which the light wave travels, that is, the direction perpendicular to the optical axis and parallel to the substrate surface is x, the direction perpendicular to the light wave travel direction and perpendicular to the substrate surface is y, and the light wave travel direction, Let the optical axis be z.

  As shown in FIG. 1B, this WSS has a configuration in which an input AWG substrate 10 and a plurality of output AWG substrates 10 'are stacked (in the y direction). The input-side AWG board 10 includes one input AWG and four output AWGs. Each output-side AWG substrate 10 'includes five output AWGs. Therefore, by further adjusting the angle of each MEMS mirror in the y direction, an optical signal can be input to the stacked output side AWG substrate 10 ′.

  In the WSS shown in FIG. 1, the optical signals of the respective wavelength channels are combined by the respective output AWGs and output again as WDM signals from the respective output ports. In the example of FIG. 1, since there are 24 output AWGs for one input AWG, it functions as a WSS with 1 input and 24 outputs (1 × 24).

U.S. Pat. No. 7,088,882

By Hector, Hector Optics II, September 2004, p88

  However, the wavelength selective switch of FIG. 1 has the following problems. In the wavelength selective switch of FIG. 1, since the WDM optical signal is divided into optical signals having different wavelengths by the AWG and processed by being applied to the MEMS mirror array, it is necessary to make the gap between the MEMS mirrors as narrow as possible. That is, the MEMS mirror has a structure in which the same number of mirrors as the number of wavelength channels are arranged without gaps as shown in FIG. 2, and a hinge (a spring supporting the mirror) is typically provided only above and below the MEMS mirror. ing. This is because the optical signal divided for each wavelength by the AWG is incident on the AA ′ of the MEMS mirror surface, and the wavelength region incident on the gap between the mirrors cannot be practically used. . That is, in order to incline up / down / left / right, it is advantageous to provide hinges at the top / bottom / right / left.

  Nevertheless, in the conventional example, it is necessary to tilt the MEMS mirror in the upper, lower, right and left directions to reflect the optical signal in a two-dimensional direction. This is because the end faces of the output AWG are two-dimensionally arranged. Thus, in principle, it is necessary to rotate in the biaxial direction regardless of the hinge structure suitable for the rotation in the uniaxial direction, and there is a problem in reliability and the like because excessive stress is applied to the hinge.

  The present invention has been made in view of such problems, and an object thereof is to provide a wavelength selective switch that does not use a MEMS mirror.

  The wavelength selective switch according to the present invention includes a spectroscopic unit that splits an optical signal incident on an input port into a plurality of optical signals having different wavelengths and emits the optical signal at an emission angle corresponding to the wavelength, and an optical signal that is spectrally separated for each wavelength. Spatial deflecting means for changing the direction or position of the optical axis with respect to each of the optical signals, and combining means for combining each of the optical signals whose direction or position of the optical axis has changed and emitting them from one of the output ports. . At least two spectral planes of the multiplexing means are in the same plane, and the spatial deflecting means can change the direction or position of each optical axis of the optical signal dispersed for each wavelength within the same plane. It is configured to be able to.

  In one embodiment of the present invention, the spectroscopic means and the multiplexing means can be configured using an arrayed waveguide grating.

  According to the present invention, an optical signal is input from a single input port, and is separated into a plurality of optical signals having different wavelengths, and the direction or position of the optical axis is changed with respect to the optical signals having different wavelengths. 1 × 1 having one input port and two output ports that correspond to two desired output ports, combine optical signals of each wavelength corresponding to each output port, and output from each output port It can be implemented as a two-wavelength selective switch.

  The 1 × 2 wavelength selective switch according to an embodiment of the present invention includes a light collecting unit that collects an optical signal that is input from an input port and spectrally separated for each wavelength by the spectral unit, and is collected by the light collecting unit. And combining means for combining each of the optical signals whose direction or position of the optical axis has been changed by the spatial deflecting means and emitting them from one of the two output ports.

  In the example of the 1 × 2 wavelength selective switch, the multiplexing means is connected to two different output ports of the two output ports, and two arrayed waveguide diffractions in which each spectral plane is in the same plane. It can be configured using a grid. The spatial deflecting means includes a liquid crystal element that changes the polarization state of the signal light arranged in order from the condensing means, and each optical axis of the optical signal in the same plane of the multiplexing means corresponding to the polarization state of the signal light. It can be configured by polarization separation means for changing the direction or position.

  Further, according to the present invention, by inputting an optical signal from one input port and separating it into a plurality of optical signals of different wavelengths, the optical axis is changed for the optical signals of each wavelength. One input port and M units that correspond to M desired output ports (M is an integer of 3 or more), combine optical signals of respective wavelengths corresponding to each output port, and output from each output port It can be implemented as a 1 × M wavelength selective switch having a number of output ports.

  The 1 × M wavelength selective switch according to an embodiment of the present invention includes a light collecting unit that collects an optical signal that is input from an input port and spectrally separated for each wavelength by the spectral unit, and is collected by the light collecting unit. And a multiplexing unit that combines each of the optical signals whose direction or position of the optical axis has been changed by the spatial deflection unit and emits the optical signal from any one of the M output ports. The multiplexing means can be configured using M arrayed waveguide gratings each connected to a different output port of the M output ports.

  In the example of the 1 × M wavelength selective switch, the multiplexing means includes at least two spectral planes of the M arrayed waveguide gratings in the same plane (first plane) and M array waveguides. It is configured such that at least one spectral plane of the waveguide grating is in a plane different from the first plane. The spatial deflecting unit is arranged in order from the light collecting unit side, and includes at least one first liquid crystal element and a first liquid crystal element that change the direction or position of each optical axis of the optical signal in a direction not included in the same plane. A combination of polarization separation means and a combination of a pair of second liquid crystal elements and second polarization separation means for changing the direction or position of each optical axis of the optical signal within the same plane. be able to.

  In one embodiment of the present invention, the polarization separation means may be configured using a wedge-type birefringent crystal or polarization separation crystal.

  As described above, according to the present invention, it is possible to provide a wavelength selective switch having a plurality of output ports without using a MEMS mirror. Since the MEMS mirror is not used, there are no movable parts, and a wavelength selective switch having high reliability can be provided.

It is a figure for demonstrating schematic structure of the conventional wavelength selective switch, (a) is a top view, (b) is a side view. It is a figure for demonstrating schematic structure of the MEMS mirror used for the conventional wavelength selective switch. It is a figure for demonstrating schematic structure of the wavelength selective switch which concerns on embodiment of this invention, (a) is a top view, (b) is a side view. It is a figure for demonstrating the basic operation principle of the liquid crystal switch used for the wavelength selection switch which concerns on embodiment of this invention. It is a figure for demonstrating the function of the wedge type birefringent crystal used for the wavelength selective switch which concerns on one Example of this invention. It is a figure for demonstrating the function of the wedge type birefringent crystal used for the wavelength selective switch which concerns on one Example of this invention.

  As described above, the wavelength selective switch according to the present invention includes the AWG and the liquid crystal switch, and the liquid crystal switch steers the optical signal of the desired wavelength channel separated by the input AWG in the x direction so that the output side It functions as a switch for selecting the AWG. The wavelength selective switch of the present invention can be implemented as a transmission type. In addition, by placing stacked AWGs on the output side, and using a liquid crystal switch that steers the wavelength separated optical signal of the desired wavelength channel in the stack direction (y direction) of the AWG, more output ports can be used. It is possible to configure a wavelength selective switch having the same. Hereinafter, embodiments of the present invention will be described with reference to the drawings. In this specification, the same or similar elements are referred to by the same or similar reference numerals.

  FIG. 3 is a configuration diagram of a WSS according to an embodiment of the present invention. 3A is a plan view and FIG. 3B is a side view. The WSS shown in FIG. 3 is a transmissive WSS, which includes an input-side AWG substrate 10 including one AWG, and output-side AWG substrates 10′-1 and 10 ′ each including two AWGs and stacked in the y direction. -2, and a first liquid crystal switch that steers and switches the optical signal of each wavelength channel in the y direction, and a second liquid crystal switch that steers and switches the optical signal of each wavelength channel in the x direction.

  The input-side AWG substrate 10 has a quartz glass core and clad formed on a silicon substrate, and constitutes an AWG comprising an optical waveguide 11, a slab waveguide 12, and an arrayed waveguide 14. The output side AWGs 10'-1 and 10'-2 have the same structure, and two are stacked in the y-axis direction. The output side AWG substrate 10′-1 constitutes AWG A composed of the optical waveguide 11′A, the slab waveguide 12′A, and the arrayed waveguide 14′A, and further, the optical waveguide 11′B and the slab waveguide 12 ′. AWG B composed of B and the arrayed waveguide 14′B is formed. Similarly, the output-side AWG substrate 10′-2 constitutes AWG C including the optical waveguide 11′C, the slab waveguide 12′C, and the arrayed waveguide 14′C, and further, the optical waveguide 11′D and the slab waveguide. AWG D composed of 12′D and arrayed waveguide 14′D is formed.

  The AWG of the input side AWG substrate 10 and the AWGs A to D of the output side AWG substrates 10'-1 and 10'-2 are configured to have equal angular dispersion values as spectroscopic elements. The free transmission range (FSR) of the AWG of the input side AWG substrate 10 and the AWGs A to D of the output side AWG substrates 10'-1 and 10'-2 is a wavelength multiplexed optical signal input from the optical waveguide 11A. The wavelength bandwidth of the (WDM optical signal) is set.

  The first liquid crystal switch includes a liquid crystal element 550 and a wedge-type birefringent crystal 900 on which light transmitted through the liquid crystal element 550 is incident, and emits light emitted from the input side AWG in the vertical direction (stack on the output side AWG substrate). Direction: y direction).

  Similar to the first liquid crystal switch, the second liquid crystal switch includes a liquid crystal element 550 ′ and a wedge-type birefringent crystal 900 ′ on which light transmitted through the liquid crystal element 550 ′ is incident. It has a function of steering the light transmitted through the left and right direction (x direction).

  FIG. 4 shows the structure of the first liquid crystal switch. However, the case where the polarization separation crystal 840 is used instead of the wedge-type birefringent crystal 900 is shown. An ITO electrode 506, which is a transparent conductive film, is formed by patterning on one surface of the glass substrate 504, and electrode pixels are arranged in the x direction. Each pixel has a long shape in the y direction, like the MEMS mirror shown in FIG. The optical signals of the respective wavelength channels demultiplexed by the AWG of the input side AWG substrate 10 are incident on the respective pixels.

  By applying a desired voltage to the ITO electrode 506, the polarization plane of the optical signal of each wavelength channel can be rotated from 0 to 90 degrees on a plane perpendicular to the optical axis. That is, by controlling the voltage applied to the ITO electrode 506, the liquid crystal element 550 can control the rotation angle of the polarization plane at 0 and 90 degrees. Therefore, when the liquid crystal element 550 and the polarization separation crystal 840 are used, a 1 × 2 switch for separating light as shown in FIG. 4 can be configured. Although FIG. 4 shows the structure of the first liquid crystal switch, the structure of the second liquid crystal switch is the same. However, the first liquid crystal switch causes a shift in the y direction in the polarization splitting crystal 840, but the second liquid crystal switch differs in that it causes a shift in the x direction. The operation of the polarization separation crystal is described in Non-Patent Document 1. Finally, a WSS can be configured by installing an AWG on the output side of each optical path. In the WSS shown in FIG. 3, the wedge-type birefringent crystal 900 is used for the separation (shift) of the optical axis in the vertical direction (y direction) and the horizontal direction (x direction) in the liquid crystal switch instead of the polarization separation crystal 840. Yes. Next, the operation will be described.

FIG. 5 is a diagram for explaining the operation of the wedge-type birefringent crystal 900 (900 ′) constituting a part of the liquid crystal switch of FIG. Here, a birefringent crystal YVO ₄ is used as the birefringent crystal. Here, the refractive index in the horizontal direction of the birefringent crystal YVO ₄ is n (//) = 1.9447, and the refractive index in the vertical direction is n = 2.1486. Here, it is assumed that light is vertically incident on the incident surface of the birefringent crystal YVO ₄ . As shown in the figure, when the exit surface is tilted with respect to the entrance surface, the exit angle changes depending on the direction of the input polarized light according to Snell's law. Therefore, by adjusting the offset angle of the exit surface of the birefringent crystal YVO ₄ , the refraction angle of each polarization can be changed to a desired value, and the refraction angle difference between the vertical light and the horizontal light is also increased. It can be increased uniformly. Therefore, by controlling the polarization direction of light to 0 or 90 degrees in the liquid crystal element 550 (550 ′) arranged in the front stage of the birefringent crystal, the emission angle of the first liquid crystal switch and the second liquid crystal switch is changed. It can function as a 1 × 2 optical switch to be changed. FIG. 6 shows a second liquid crystal switch. The liquid crystal element 550 ′ and the wedge-type birefringent crystal 900 ′ are arranged in this order with respect to the traveling direction of the light. The liquid crystal element 550 ′ has a rotation angle of the polarization plane of the light of 0 when the light is transmitted once. Alternatively, it is configured to be controlled at 90 degrees.

  Further, a cylindrical lens 20 and a polarization separation unit 30 are arranged on the AWG array waveguide 14 side of the input side AWG substrate 10. A condenser lens 41 is disposed between the polarization separation unit 30 and the first liquid crystal switch.

  The condenser lens 41 is followed by a liquid crystal element 550 and a wedge-type birefringent crystal 900 constituting the first liquid crystal switch, a liquid crystal element 550 ′ constituting the second liquid crystal switch, and a wedge-type birefringent crystal 900 ′. The condenser lenses 41 ′ are arranged in order. A polarization coupling unit 30'-1, a cylindrical lens 20'-1, and an output-side AWG substrate 10'-1 are arranged at the subsequent stage of the condenser lens 41 '. Similarly, a polarization coupling unit 30'-2, a cylindrical lens 20'-2, and an output side AWG substrate 10'-2 are also arranged at the subsequent stage of the condenser lens 41 '.

Here, the structure and function of the WSS of this embodiment will be described in the order of propagation of optical signals.
Output light from the input-side AWG substrate 10 is emitted at different angles within the substrate surface (xz surface) depending on the wavelength. That is, wavelength separation is performed. A surface including the wavelength-separated optical axis is called a spectral surface.

  The light beam emitted from the end face of the input-side AWG substrate 10 passes through the cylindrical lens 20 in order to prevent spreading in the vertical direction (y direction).

  Next, since the liquid crystal elements 550 and 550 ′ constituting the first liquid crystal switch and the second liquid crystal switch have polarization dependency, the light in an arbitrary polarization state transmitted through the cylindrical lens 20 at the polarization separation unit 30 Are separated into two light beams having the same direction with linearly polarized light. The two light beams are made to be parallel light having a gap in the y-axis direction. The polarization separation unit 30 includes, for example, a polarization separation crystal that functions as a polarization displacer, and a half-wave plate disposed at a position where only one polarization beam separated by the polarization separation crystal is transmitted. Since the behavior of the two adjacent light beams can be handled equivalently to one beam that is thick in the y-axis direction, it will be omitted in the following description and drawings.

  The optical signal of each wavelength channel output from the polarization separation unit 30 passes through the condenser lens 41.

  The optical signals of the respective wavelength channels transmitted through the condenser lens 41 enter different pixels (patterned ITO electrodes) of the liquid crystal element 550, the rotation angle of the polarization plane is controlled, and the wedge-type birefringent crystal 900 is input. Incident. That is, the optical signal is incident on the birefringent crystal wedge 900 after the rotation angle of the polarization plane is controlled to 0 or 90 degrees in the liquid crystal element 550.

  The light incident on the wedge-type birefringent crystal 900 is emitted at a refraction angle corresponding to the rotation angle of the polarization plane. In this way, the light is steered in the AWG stacking direction (y direction) of the output AWG substrate 10 '.

  In the liquid crystal element 550, when the polarization plane is not rotated (when the control amount of the liquid crystal element 550 is 0 degree), the light travels in the direction of AWG A or B of the output-side AWG substrate 10'-1. Further, in the liquid crystal element 550, when the polarization plane is rotated by 90 degrees, the light travels in the direction of AWG C or D of the output side AWG substrate 10'-2.

  Next, light from the wedge-type birefringent crystal 900 enters a different pixel (patterned ITO electrode) of the liquid crystal element 550 ′, and the rotation angle of the polarization plane is controlled in the same manner as the liquid crystal element 550, so that the wedge-type Of the birefringent crystal 900 ′. The light incident on the wedge-type birefringent crystal 900 ′ is emitted at a refraction angle corresponding to the rotation angle of the polarization plane. In this way, the light is steered in the x direction.

  In the liquid crystal element 550 ′, when the plane of polarization is not rotated (when the control amount of the liquid crystal element 550 ′ is 0 degree), the light passes through the condenser lens 41 ′ and is input to the polarization coupling unit 30 ′. A process reverse to that of the wave separation unit 30 is performed. That is, two light beams with linear polarization and aligned in direction are combined into light having a certain polarization state. Then, after passing through the cylindrical 20 ′, it is combined with AWG A of the output side AWG substrate 10 ′-1 or AWG C of the output side AWG substrate 10 ′-2 and outputted. In the liquid crystal element 550 ′, when the polarization plane is rotated by 90 degrees, the light passes through the condenser lens 41 ′, and then the AWG B of the output AWG substrate 10′-1 or the output AWG substrate 10′-2. The output is combined with AWG D.

  In this way, 1 × 4 WSS can be realized. Here, in order to output an optical signal of a specific wavelength to an intended output port, light whose deflection direction is controlled by a specific pixel of the first liquid crystal switch is transmitted in the same wavelength channel in the second liquid crystal switch. It is necessary to enter the pixel corresponding to. That is, the x coordinate of each pixel of the first liquid crystal switch needs to match the x coordinate of each pixel of the second liquid crystal switch. If they do not coincide completely, a part of the optical signal deflected by the first liquid crystal switch is incident on an adjacent pixel in the second liquid crystal switch and is deflected in an unintended direction. Accuracy is reduced.

  In the embodiment of FIG. 3, the incident position of the optical signal to the liquid crystal element 550 'of the second liquid crystal switch changes in the y-axis direction depending on the deflection operation state of the first liquid crystal switch. Here, if each pixel of the liquid crystal element 550 'of the second liquid crystal switch is sufficiently long in the y-axis direction, there is no problem even if the incident position of the optical signal is changed in the y-direction. On the other hand, when the second liquid crystal switch that deflects the y-axis is arranged at the rear stage of the first liquid crystal switch that changes the order and deflects the x-axis, the second liquid crystal depends on the deflection operation state of the first liquid crystal switch. The incident position of the optical signal with respect to the liquid crystal element of the switch changes in the x-axis direction (wavelength axis direction). For this reason, it is impossible to match the x coordinate of each pixel of the first liquid crystal switch and the x coordinate of each pixel of the second liquid crystal switch regardless of the deflection operation state of the first liquid crystal switch. Become.

  In the present invention, when the WSS is composed of two liquid crystal switches, a liquid crystal switch that deflects to the x axis is disposed after the liquid crystal switch that deflects to the y axis. It was found that even if a plurality of liquid crystal switches are stacked, if the liquid crystal switch that deflects in the x-axis is finally arranged, the pixels can match the x coordinate of each pixel of the plurality of liquid crystal switches.

  In the present invention, a liquid crystal switch that deflects in the x-axis direction can be used as the last-stage liquid crystal switch, and therefore, one AWG substrate 10 'can include two AWGs. As a result, the number of output side AWGs 10 'can be reduced, and the stack mounting process of the output side AWG substrate can be simplified, so that a multi-port WSS can be provided at low cost.

  In this embodiment, an example of a 1 × 4 wavelength selective switch is shown for convenience of explanation. However, if the light traveling direction is reversed and the input / output direction is also reversed, four inputs and one output (4 × 1) are provided. It is also possible to operate as a wavelength selective switch.

  The present invention can also be implemented as a 1 × 2 or 2 × 1 WSS, omitting the first liquid crystal switch and the output-side AWG substrate 10 ′-2.

Alternatively, the first liquid crystal switch is cascaded in N stages (N is an integer of 2 or more), and the number of stacks of the output side AWG substrate 10 ′ is 2 ^N stages, thereby 1 × (2 · 2 ^N ) or ( It is also possible to provide a 2 · 2 ^N ) × 1 wavelength selective switch. And / or by making one AWG for a part of the stacked output-side AWG substrate 10 ′, for example, 1 × M (M is an integer of 3 or more) such as 1 × 3 or 3 × 1 It can also be implemented as a WSS.

DESCRIPTION OF SYMBOLS 10 Input side AWG board | substrate 10 'Output side AWG board | substrate 20, 20' Cylindrical lens 30 Polarization separation part 30 'Polarization coupling part 41, 41' Condensing lens 550,550 'Liquid crystal element 900,900' Polarization separation crystal, Wedge-type birefringent crystal

Claims (7)

An optical signal is inputted from one input port and separated into a plurality of optical signals of different wavelengths, and the optical signals are changed to two desired output ports by changing the optical axis. A wavelength selective switch having one input port and two output ports that combine and output optical signals of respective wavelengths corresponding to the respective output ports and output from the respective output ports,
A spectroscopic unit that splits an optical signal incident on the input port into a plurality of optical signals having different wavelengths and emits the optical signal at an emission angle corresponding to the wavelength;
Condensing means for condensing the optical signals spectrally separated for each wavelength by the spectroscopic means;
Spatial deflecting means for changing the direction or position of the optical axis for each of the optical signals collected by the light collecting means;
Combining optical signals whose optical axis direction or position has been changed by the spatial deflecting means and emitting from either of the two output ports;
The two spectral planes of the multiplexing means are in the same plane,
The spatial deflecting means includes a liquid crystal element that changes the polarization state of the signal light arranged in order from the condensing means, and each optical axis of the optical signal in the same plane corresponding to the polarization state of the signal light. A wavelength selective switch characterized by comprising polarization separation means for changing the direction or position of the light. Optical signals are input from one input port and separated into a plurality of optical signals having different wavelengths, and M (M is 3 or more) by changing the optical axis for the optical signals of each wavelength. A wavelength selective switch having one input port and M output ports for combining optical signals of respective wavelengths corresponding to the respective output ports and outputting from the respective output ports. Because
A spectroscopic unit that splits an optical signal incident on the input port into a plurality of optical signals having different wavelengths and emits the optical signal at an emission angle corresponding to the wavelength;
Condensing means for condensing the optical signals spectrally separated for each wavelength by the spectroscopic means;
Spatial deflecting means for changing the direction or position of the optical axis for each of the optical signals collected by the light collecting means;
Combining each of the optical signals whose direction or position of the optical axis has been changed by the spatial deflecting means and emitting from any one of the M output ports,
At least two of the M spectral planes of the multiplexing means are in the same plane, and at least one of the M spectral planes of the multiplexing means is the at least one of the spectral planes. It is in a different plane from the two spectroscopic planes,
The space deflection unit is arranged in order from the light collecting unit side,
A combination of one or more first liquid crystal elements and first polarization separation means for changing the direction or position of each optical axis of the optical signal in a direction not included in the same plane;
A combination of a pair of second liquid crystal elements that change the direction or position of each optical axis of the optical signal in the same plane and the second polarization separation means. Select wavelength switch.   3. The wavelength selective switch according to claim 1, wherein the spectroscopic unit and the multiplexing unit are configured using an arrayed waveguide diffraction grating.   4. The wavelength selective switch according to claim 1, wherein the liquid crystal element has a function of rotating a polarization plane of a transmitted optical signal by 0 degree or 90 degrees. 5.   The wavelength selective switch according to any one of claims 1 to 4, wherein the polarization separation means is configured using a wedge-type birefringent crystal.   5. The wavelength selective switch according to claim 1, wherein the polarization separation means is configured using a polarization separation crystal.   7. The wavelength selective switch according to claim 1, wherein the optical signal travels in a reverse direction, inputs light from the plurality of output ports, and outputs light from the optical input ports. Feature wavelength selective switch.

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