JP2008203775A - Wavelength selection switch - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wavelength selection switch which has multiple output ports and high reliability and achieves high-speed switching. <P>SOLUTION: A WDM signal is input to a first array waveguide grating 101. The input WDM signal is wavelength-demultiplexed by the first array waveguide grating 101 and output. Respective output light signals are converted by a first Y cylindrical lens 102 into parallel light signals which are parallel to a Z axis. The respective light signals converted into the parallel light signals pass through a first X cylindrical lens 103 and are converged respectively. Then KTN crystal 104 deflects the respective deflected light signals in a Y-axis direction. The respective deflected light signals pass through one of a second X cylindrical lens 105, a third X cylindrical lens 106, and a second Y cylindrical lens group 109, and are coupled to one of a second array waveguide grating group 110 connected to a selected output port, and wavelength-multiplexed to be output. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a wavelength selective switch, and more particularly to a wavelength selective switch that outputs an optical signal of a selected wavelength among wavelength division multiplexed signals input from an input port to a selected output port.

  In recent years, with the construction of a large-capacity optical communication network that shows rapid progress, wavelength division multiplexing (WDM) communication technology has attracted attention and the spread of facilities for that purpose has been increasing. In a WDM node, a method is generally used in which a path is switched after being converted into an electric signal once without directly controlling an optical signal. However, in the above method, there is a concern that the processing capacity of the node is increased, the communication speed is limited, and the power consumption is increased. For this reason, development of a device that performs path switching while maintaining an optical signal without going through electrical switching, that is, a wavelength selective switch (WSS) or the like, is demanded.

  The operation principle of a general wavelength selective switch is as follows. The WDM signal input from the input optical fiber is incident on the diffraction grating through the lens and is wavelength-demultiplexed, and each wavelength-demultiplexed optical signal is collected again through the lens. A micromirror array and a shutter array are installed at the condensing position. The micromirror array has a configuration capable of adjusting the reflection angle of incident light, and reflects each optical signal at an angle optimized for a target output port. Each of the reflected optical signals enters the diffraction grating through the lens, is wavelength-multiplexed, and then couples to the output fiber through the lens.

  As described above, a micromirror array using an optical micromachine (MEMS: Micro Electro Mechanical Systems) is generally used as the light deflection element. For example, Non-Patent Document 1 describes a micromirror array. The intensity of the output light can be adjusted by controlling the micromirror array so that the light is completely or intentionally incompletely coupled to the output port.

  As described above, the functions of the wavelength selective switch include distributing the optical signal of each wavelength of the WDM signal to an arbitrary output port and adjusting the optical intensity of the optical signal of each wavelength.

J. S. Tsai, et al., Proc. MEMS, 2004, pp. 101-104 Appl. Phys. Lett. 89 (2006) 131115

  By the way, since the deflection angle of the conventional optical deflection element represented by the above-mentioned MEMS is about 10 degrees at most, the position range where the optical signal can be guided is narrow. Therefore, in the case of a wavelength selective switch using such an optical deflection element, the design must be performed according to the deflection angle of the optical deflection element, and the number of output ports is currently limited from 4 to 9 ports.

  In addition, MEMS is an optical deflection method based on the basic principle of mechanically displacing the light reflecting surface, and therefore, failure due to repeated use or impact is likely to occur, and it is difficult to ensure high reliability.

  In addition, in MEMS, the driving time is as slow as 1 millisecond, and it is difficult to cope with a system that requires high-speed operation such as an optical burst switch system and an optical bucket switch system that are expected to be developed in the future.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a wavelength selective switch that realizes multiple output ports, high reliability, and high-speed switching.

  In order to achieve such an object, the present invention provides a wavelength selective switch that outputs an optical signal of a selected wavelength among wavelength division multiplexed signals input from an input port to a selected output port, Wavelength demultiplexing means for wavelength demultiplexing the wavelength division multiplexed signal input from the input port; first optical condensing elements for condensing each optical signal wavelength-demultiplexed by the wavelength demultiplexing means; and Provided in parallel in a direction orthogonal to the path of each optical signal, which deflects each optical signal collected by the first light collecting element toward an output port selected for each optical signal. An electro-optic crystal having at least one electrode; a second light-collecting element for condensing each optical signal deflected by the electro-optic crystal; and each light condensed by the second light-collecting element Wavelength combining signals Characterized in that it comprises a wavelength multiplexing means for outputting the multiplexed optical signal to the output port of said selected.

According to a second aspect of the present invention, in the wavelength selective switch according to the first aspect, the electro-optic crystal is KTa _1-x Nb _x O ₃ (0 <x <1, 0 <y <1). It is characterized by being.

  The invention according to claim 3 is the wavelength selective switch according to claim 1 or 2, further comprising a reflection mirror interposed between the electro-optic crystal and the wavelength multiplexing means, and the input port; The output port is arranged on the same side with respect to an incident surface of each optical signal of the electro-optic crystal.

  According to a fourth aspect of the present invention, in the wavelength selective switch according to the first or second aspect, the input port and the output port are configured so that the optical signal incident surface of the electro-optic crystal The electro-optic crystal is disposed at a position facing each other with the electro-optic crystal interposed therebetween.

  According to a fifth aspect of the present invention, in the wavelength selective switch according to the first or second aspect, each of the wavelength demultiplexing unit and the wavelength demultiplexing unit includes an arrayed waveguide grating.

  According to a sixth aspect of the present invention, in the wavelength selective switch according to the first or second aspect, each of the wavelength demultiplexing unit and the wavelength demultiplexing unit includes a bulk diffraction grating.

According to a seventh aspect of the present invention, in the wavelength selective switch according to the first or second aspect of the present invention, polarization separation that separates each optical signal into two orthogonal polarization components at the front stage of the electro-optic crystal. A polarization element whose polarization direction is not rotated by the first half-wave plate in the subsequent stage of the electro-optic crystal, further comprising an element and a first half-wave plate that rotates one polarization component by 90 degrees It further comprises a second half-wave plate group for rotating the components by 90 degrees, and a polarization beam combining element for combining two orthogonal polarization components.

  In the wavelength selective switch according to claim 1 or 2, the wavelength demultiplexing means is connected to an output port arranged two-dimensionally, and the at least one electrode Each is a panel-type electrode in which a plurality of cells are arranged in a two-dimensional panel shape, and the voltage applied to each of the plurality of cells can be individually controlled.

  The invention according to claim 9 is the wavelength selective switch according to claim 1 or 2, wherein the wavelength demultiplexing means is connected to an output port arranged two-dimensionally, and the at least one electrode Each of these is a strip-shaped electrode in which a plurality of rectangular cells elongated in the optical signal path direction, such as strips, are arranged in parallel, and the voltage applied to each of the plurality of cells is individually controlled. It is possible.

  According to a tenth aspect of the present invention, in the wavelength selective switch according to the first or second aspect, each of the at least one electrode is a rectangular electrode.

The invention according to claim 11 is the wavelength selective switch according to claim 2, wherein each of the at least one electrode has the KTa _1-x Nb _x O ₃ (0 <x <1, 0 <y <1) A rectangular electrode formed using a material that provides the space charge control mode EO effect and a triangular electrode formed using a material that provides the Kerr effect are arranged in the optical signal path direction. It is a composite shape type electrode arranged in a column.

  The invention according to claim 12 is a wavelength selective switch that outputs an optical signal having a wavelength selected from the wavelength division multiplexed signals input from the input port to the selected output port. Wavelength demultiplexing means for demultiplexing the input wavelength division multiplexed signal, a first condensing element for condensing each optical signal wavelength-demultiplexed by the wavelength demultiplexing means, and the first At least one provided in parallel in a direction orthogonal to the path of each optical signal, which deflects each optical signal collected by the condensing element toward an output port selected for each optical signal. An electro-optic crystal having electrodes; a second condensing element that condenses each optical signal deflected by the electro-optic crystal; an optical attenuator through which the second condensing element passes; and the light Each optical signal that passed through the attenuator A third condensing element for condensing light and the respective optical signals collected by the third condensing element are wavelength-multiplexed, and the wavelength-multiplexed optical signal is output to the selected output port. Wavelength multiplexing means, and the optical attenuator cuts off a light path to an output port not involved in switching when the output port is switched from the first output port to the second output port. To do.

The invention according to claim 13 is the wavelength selective switch according to claim 12, wherein the electro-optic crystal is KTa _1-x Nb _x O ₃ (0 <x <1, 0 <y <1). It is characterized by being.

  According to the present invention, it is possible to provide a wavelength selective switch that realizes multiple output ports, high reliability, and high-speed switching by using an electro-optic crystal having a large maximum deflection angle as an optical deflection element.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Throughout the drawings, the same reference numerals indicate the same or corresponding parts.

(Embodiment 1)
FIG. 1 shows a configuration of a first embodiment 100 of a wavelength selective switch according to the present invention. FIG. 1A is a plan view, and FIG. 1B is a side view. The wavelength selective switch 100 includes a first arrayed waveguide grating (AWG) 101 having at least one optical fiber connected to the input side, a first Y cylindrical lens 102 having a focal length of fY, and a focal length of fX. A first X cylindrical lens 103, a KTa _1-x Nb _x O ₃ (0 <x <1, 0 <y <1) crystal (hereinafter referred to as a KTN crystal) 104 as an optical deflection element, and A second X cylindrical lens 105 having a focal length of fX, a third X cylindrical lens 106 having a focal length of fX, a liquid crystal optical attenuator 107, and a fourth X cylindrical lens 108 having a focal length of fX. And a second Y cylindrical lens group 109 having a focal length of fY, and a second arrayed waveguide grating group 110, which are arranged in this order. Here, the traveling direction of the optical signal is taken as the Z axis, the horizontal direction with respect to the substrates of the first arrayed waveguide grating 101 and the second arrayed waveguide grating group 110 is taken as the X axis, and the perpendicular direction is taken as the Y axis.

  In such a configuration, the wavelength selective switch 100 according to the first embodiment operates as follows. First, a WDM signal is input to the first arrayed waveguide grating 101 from the input port. The input WDM signal is wavelength-demultiplexed in the first arrayed waveguide grating 101 and output from the substrate of the first arrayed waveguide grating 101. Each output optical signal diverges in the direction perpendicular to the substrate immediately after the output, but as shown in FIG. 1B, the first optical signal arranged at the position fY from the end face of the first arrayed waveguide grating 101 is used. The Y cylindrical lens 102 converts the light into parallel light parallel to the Z-axis direction. Each optical signal converted into parallel light passes through the first X cylindrical lens 103 disposed at the position fX from the end face of the first array waveguide grating 101, and the first array waveguide grating 101 respectively. Is condensed at a position of 2 fX from the end face. The KTN crystal 104 arranged at a position of 2 fX from the end face of the first arrayed waveguide grating 101 has individual electrodes corresponding to the wavelengths of the respective optical signals, and each collected optical signal is transmitted in the Y-axis direction. To deflect. Each deflected optical signal is constituted by a second X cylindrical lens 105 disposed at a position 3fX from the end face of the first arrayed waveguide grating 101 and a third X cylindrical lens 106 disposed at a position 4fX. The light is condensed at the position of the liquid crystal light attenuator 107 disposed at the position of 5 fX through the relay lens system. Each optical signal is finally connected to an output port selected by the KTN crystal 104 via a fourth X cylindrical lens 108 and one of a second Y cylindrical lens group 109. It is coupled to one arrayed waveguide grating in the arrayed waveguide grating group 110, wavelength-multiplexed and output to the output port. Here, the fourth X cylindrical lens 108 and the second arrayed waveguide grating group 110 are disposed at positions 2fX and 3fX in the Z-axis direction from the third X cylindrical lens 106, respectively. The Y cylindrical lens group 109 is disposed at a position fY from the second arrayed waveguide grating group 110.

  The wavelength selective switch 100 according to the present embodiment is characterized by using a KTN crystal 104 having an electrode as an optical deflection element. As will be described later, the KTN crystal 104 can deflect light in accordance with the voltage applied to the electrode, and has a maximum deflection angle larger than that of a conventional optical deflection element. Further, the deflection angle can be switched at high speed according to the applied voltage. Therefore, it is possible to realize a wavelength selective switch that has more output ports than a conventional wavelength selective switch and is capable of high-speed switching operation. Further, unlike the MEMS, the wavelength selective switch 100 according to the present embodiment does not include a mechanical operation when deflecting light, and can obtain high transmittance and high reliability as described later. This will be described in more detail below.

  FIG. 2 shows the first arrayed waveguide grating 101. The first arrayed waveguide grating 101 is connected to the first slab waveguide 201 connected to the input port, the arrayed waveguide 202 connected to the first slab waveguide 201, and the arrayed waveguide 202. And a second slab waveguide 203. The second slab waveguide 203 may or may not be provided. The WDM signal input from the input port passes through the first slab waveguide 201, the arrayed waveguide 202, and the second slab waveguide 203 and is demultiplexed. The arrayed waveguide grating 101 and the first Y cylindrical lens 102 demultiplex the wavelength of the WDM signal, and convert each wavelength-demultiplexed optical signal into an optical signal parallel to the Z-axis direction. This is an exemplary configuration of wavelength demultiplexing means. In the third embodiment, wavelength demultiplexing means having a configuration different from that of the present embodiment will be described.

  The first X cylindrical lens 103 constitutes a first light condensing element that condenses each wavelength-demultiplexed optical signal. It should be noted that the first light collecting element does not necessarily need to be a single lens, and only needs to be able to collect each optical signal.

  FIG. 3 shows details of the electrodes included in the KTN crystal 104. On one side of the KTN crystal 104 parallel to the Z-axis direction, at least one electrode is provided in a direction perpendicular to the optical signal path. Each electrode can be rectangular. In the figure, W is the electrode width, G is the electrode interval, and t is the thickness of the KTN crystal 104. One electrode connected to the ground is provided on the other surface parallel to the Z-axis direction of the KTN crystal 104. However, the shape is not limited to such a shape, and the position corresponding to the above-described rectangular electrode is provided. It is sufficient that a voltage can be applied to the KTN crystal 104.

  When a voltage is applied to the KTN crystal 104 using an electrode having this shape, the refractive index increases in a gradient as the distance from the cathode in the KTN crystal 104 increases, and the optical signal can be deflected in a direction approaching the cathode electrode. The deflection angle can be set according to the voltage applied to the electrode. Therefore, by providing the second arrayed waveguide grating group 110 in which the arrayed waveguide gratings connected to the respective output ports are stacked in the Y-axis direction, the light deflection effect by the KTN crystal 104 is utilized to obtain the wavelength distribution. The output port for each waved optical signal can be selected.

Although titanium (Ti) can be used as an electrode material, a material suitable as an electrode is not limited to titanium Ti. The KTN crystal 104 to be used is a cubic crystal, and the operating temperature is preferably a cubic to tetragonal phase transition temperature. In such a case, the maximum deflection angle is maximized. In this embodiment, a KTN crystal having an electrode such as titanium is used as the light deflecting element. However, the same effect can be obtained if the electrode and the electro-optic crystal have such a refractive index gradient distribution as described above. Note that you can. For example, as such an electro-optic crystal, (Pb, La) (Zr, Tr) O ₃ , K _1-y Li _y Ta _1-x Nb _x O ₃ (0 <x <1, 0 <y <1), LiNbO ₃ , LiTaO ₃ , LilO ₃ , KNbO ₃ , KTiOPO ₄ , BaTiO ₃ , SrTiO ₃ , Ba _1-x Sr _x TiO ₃ (0 <x <1), Ba _1-x Sr _x Nb ₂ O ₆ (0 < _{x <1), Sr 0.75 Ba} 0.25 Nb 2 O 6, Pb 1-y La y Ti 1-x Zr x O 3 (0 <x <1,0 <y <1), Pb (Mg 1/3 Nb 2 _{/ 3) O 3 -PbTiO 3,} KH 2 PO 4, KD 2 PO 4, (NH 4) H 2 PO 4, BaB 2 O 4, LiB 3 O 5, CsLiB 6 O 10, GaAs, CdTe, GaP, ZnS ZnSe, ZnTe, CdS, CdSe, ZnO, etc. are conceivable.

  A relay lens system constituted by the second X cylindrical lens 105 and the third X cylindrical lens 106 is a second condensing element that condenses each optical signal deflected by the KTN crystal 104. It should be noted that the second condensing element does not necessarily need to be such a relay lens system as long as each optical signal can be condensed.

  The liquid crystal light attenuator 107 is a twisted nematic liquid crystal sandwiched between two polarizers, temporarily interrupts the light path when switching the output port, and allows light to pass again after the switching is completed. The light is blocked by applying a voltage to the light incident surface of the liquid crystal light attenuator 107 and the electrodes provided on the surface facing the incident surface. The wavelength selective switch according to the present embodiment can deflect each optical signal wavelength-demultiplexed with respect to only the stacking direction of the arrayed waveguide grating constituting the second arrayed waveguide grating 110, that is, the Y-axis direction. Therefore, when switching an output port to two or more ports away from a certain port, light passes through ports that are interposed between those ports but are not involved in port switching, and light leaks to other ports. appear. This phenomenon is called “hit”. The liquid crystal optical attenuator 107 realizes this avoidance measure or reduction measure, that is, “hitless”. The liquid crystal light attenuator 107 can have a structure including a liquid crystal as described above, but any principle of liquid crystal may be used as long as the element has an equivalent function. Note that a vessel may be used. Further, the liquid crystal optical attenuator 107 does not need to be provided next to the second condensing element on the optical signal path, and is provided between the KTN crystal 104 and the second arrayed waveguide grating group 110. Note that this is fine.

  In addition, if “hitless” is realized by providing the liquid crystal optical attenuator 107, leakage light at the time of output port switching can be avoided and the reliability of the wavelength selective switch 100 can be further improved. The wavelength selective switch according to this embodiment using the KTN crystal 104 does not include a mechanical operation at the time of light deflection, unlike the wavelength selective switch using MEMS as an optical deflection element. Note that it is expensive. FIG. 4 shows a wavelength selective switch 400 that does not include the liquid crystal optical attenuator 107. In such a wavelength selective switch 400, each optical signal deflected by the KTN crystal 104 is converted into a relay lens system constituted by the second X cylindrical lens 105 and the third X cylindrical lens 106, and the second Y cylindrical lens. Coupled to one array waveguide grating of the second array waveguide grating group 110 connected to the output port selected by the KTN crystal 104 via one of the groups 109, Wave and output to the output port.

  The fourth X cylindrical lens 108 is a third condensing element that condenses each optical signal that has passed through the liquid crystal optical attenuator 107. It should be noted that the third condensing element does not necessarily need to be a single lens, and only needs to be able to condense each optical signal. Note that the wavelength selective switch 400 without the liquid crystal optical attenuator 107 described above does not need to include the third condensing element.

  The second arrayed waveguide grating group 110 is formed by stacking a plurality of arrayed waveguide gratings in the Y-axis direction. Each arrayed waveguide grating can have a structure in which a slab waveguide and an arrayed waveguide are connected in the same manner as the first arrayed waveguide grating 101. Each optical signal collected by the third light collecting element (in the embodiment 400 that does not include the liquid crystal optical attenuator 107, each optical signal collected by the second light collecting element) is the second Y The light is converted into parallel light parallel to the Z-axis direction by one of the cylindrical lens groups 109. Then, it is coupled to one arrayed waveguide grating of the second arrayed waveguide grating group 110 connected to the output port selected by the KTN crystal 104, and wavelength-multiplexed. The second Y cylindrical lens group 109 and the second second arrayed waveguide grating group 110 convert each optical signal deflected toward the output port selected by the KTN crystal 104 into an optical signal parallel to the Z-axis direction. The wavelength combining unit for converting the signal into the wavelength and combining the wavelengths is an exemplary configuration of the wavelength combining unit. In the third and fifth embodiments, wavelength multiplexing means different from the present embodiment will be described.

The following example illustrates the construction and experimental results of the specific examples. Each arrayed waveguide grating constituting the first arrayed waveguide grating 101 and the second arrayed waveguide grating group 110 was produced on a silicon substrate using quartz glass as a base material. In the second arrayed waveguide grating group 110, 16 arrayed waveguide gratings were stacked, and the number of output ports was set to 16. The KTN crystal 104 had an electrode width W of 200 μm, an electrode interval G of 100 μm, and a thickness t of 100 μm. The electrode width and electrode interval of the liquid crystal optical attenuator 107 were also set to 200 μm and 100 μm, respectively. Further, each lens was arranged with fX = 50 mm and fY = 6 mm. In this design, the deflection angle by the KTN crystal 104 is 15 degrees at the maximum, and this value can be realized only by using KTN as an optical deflection element. The performance of the wavelength selective switch according to the present embodiment described below can be obtained in the same manner by using parameters similar to those of the present embodiment, and need not be limited to the same parameters as those of the present embodiment. .

  FIG. 5 shows the characteristics of the wavelength selective switch according to this embodiment. This graph shows the experimental results of outputting 41-channel WDM signals to different output ports for every 16 channels. In this example, a maximum transmittance of −5 dB was realized for each output port, and high performance was confirmed.

  FIG. 6 shows the switching operation characteristics of the wavelength selective switch according to this embodiment. This graph is an experimental result of a change in light intensity when the optical signal path is changed from the output port 1 to the output port 2. Assuming that the light intensity before switching at the output port 1 is 1, and the switching time is from when the light intensity at the output port 1 becomes 0.9 to when the light intensity at the output port 2 becomes 0.9, The switching time is only 5 μs, and a high-speed switching operation is realized. In MEMS, compare with the drive time of about 1 millisecond.

  As described above, the wavelength selective switch according to the present embodiment is a wavelength selective switch that outputs an optical signal of a selected wavelength among wavelength division multiplexed signals input from an input port to a selected output port. A wavelength demultiplexing unit for demultiplexing the wavelength division multiplexed signal input from the input port; a first condensing element for condensing each optical signal wavelength-demultiplexed by the wavelength demultiplexing unit; Each optical signal collected by one light collecting element is deflected toward an output port selected for each optical signal, and is provided in parallel in a direction orthogonal to the path of each optical signal. An electro-optic crystal having an electrode; a second condensing element that condenses each optical signal deflected by the electro-optic crystal; an optical attenuator through which the second condensing element passes; and an optical attenuator Each optical signal that passes through Wavelength multiplexing that combines the wavelength of the third light collecting element that collects light and each optical signal collected by the third light collecting element, and outputs the wavelength-combined optical signal to the selected output port The optical attenuator is characterized in that when the output port is switched from the first output port to the second output port, the optical path to the output port not involved in the switching is interrupted.

  Further, in a form that does not include a liquid crystal optical attenuator, the wavelength selective switch according to the present embodiment outputs an optical signal having a wavelength selected from the wavelength division multiplexed signals input from the input port to the selected output port. And a wavelength demultiplexing unit that demultiplexes the wavelength division multiplexed signal input from the input port, and a first optical unit that condenses each optical signal demultiplexed by the wavelength demultiplexing unit. The light condensing elements and the respective light signals collected by the first light condensing elements are deflected toward the output ports selected for the respective optical signals, and are parallel to each other in the direction orthogonal to the path of each optical signal. An electro-optic crystal having at least one electrode provided on the first, a second light-collecting element for condensing each optical signal deflected by the electro-optic crystal, and a second light-collecting element. Wavelength of each optical signal And, characterized in that it comprises a wavelength multiplexing means for outputting the selected output port optical signal wavelength-multiplexed.

  By using an electro-optic crystal such as a KTN crystal having an electrode as the light deflection element, light can be deflected according to the voltage applied to the electrode, and the maximum deflection angle is larger than that of a conventional light deflection element. can do. Further, the electro-optic crystal can switch the deflection angle according to the applied voltage at high speed. Further, unlike MEMS, in addition to not including a mechanical operation when deflecting light, high transmittance can be obtained, so that reliability is high. Therefore, according to the present embodiment, it is possible to provide a wavelength selective switch that realizes multi-port, high reliability, and high-speed switching.

  Furthermore, in the embodiment provided with the optical attenuator, it is possible to avoid the leakage light at the time of switching the output port and further improve the reliability of the wavelength selective switch.

  Also, by using an arrayed waveguide grating as the wavelength demultiplexing means and wavelength multiplexing means, the collimating lens installed in the immediate vicinity of the input / output fiber required in the wavelength selective switch realized using the bulk diffraction grating is omitted. Therefore, it is possible to simplify the mounting of the wavelength selective switch and reduce the cost. A wavelength selective switch realized using a bulk diffraction grating will be described in a third embodiment.

  In this embodiment, the left side of FIG. 1 is an input port and the right side is an output port. However, the light input port and the output port are reversed, and light is input from the right output port side and output from the left side. Of course it is good.

(Embodiment 2)
FIG. 7 shows a configuration of a second embodiment 700 of the wavelength selective switch according to the present invention. FIG. 7A is a plan view, and FIG. 7B is a side view. The wavelength selective switch 700 includes an arrayed waveguide grating group 701 connected to at least one input port and at least one output port, a Y cylindrical lens group 702 having a focal length of fY, and a first lens having a focal length of fX. A first X cylindrical lens 703, a liquid crystal optical attenuator 704, a second X cylindrical lens 705 having a focal length of fX, a third X cylindrical lens 706 having a focal length of fX, and an optical deflection element. A KTN crystal 707 and a reflection mirror 708 are provided, and these are arranged in this order. Here, the traveling direction of the optical signal is taken as the Z axis, the direction horizontal to the substrate of the arrayed waveguide grating group 701 is taken as the X axis, and the perpendicular direction is taken as the Y axis. A significant difference from the first embodiment is that a reflection mirror 708 is inserted after the wavelength division multiplexed signal passes through the KTN crystal 707, and is reflected by this mirror and guided to the output port.

  In such a configuration, the wavelength selective switch 700 according to the second embodiment operates as follows. First, a WDM signal is input to the arrayed waveguide grating group 701 from the input port. The input WDM signal is wavelength-demultiplexed in the arrayed waveguide grating group 701 and output from the substrate of the arrayed waveguide grating group 701. Each output optical signal diverges in the direction perpendicular to the substrate immediately after output, but as shown in FIG. 7B, a Y cylindrical lens group disposed at a position fY from the end face of the arrayed waveguide grating group 701. It is converted into parallel light parallel to the Z-axis direction by one of 702. Each optical signal converted into parallel light passes through a first X cylindrical lens 703 disposed at a position fX from the end face of the arrayed waveguide grating group 701, and 2 fX from the end face of the arrayed waveguide grating group 701. The light is condensed at the position of the liquid crystal light attenuator 704 disposed at the position. Each optical signal that has passed through the liquid crystal optical attenuator 704 is second X cylindrical lens 705 disposed at a position 3fX from the end face of the arrayed waveguide grating group 701, and a third X cylindrical lens disposed at a position 4fX. The light is condensed at a position of 5 fX through a relay lens system configured by 706. A KTN crystal 707 disposed at a position of 5 fX from the end face of the arrayed waveguide grating group 701 has individual electrodes corresponding to the wavelengths of the respective optical signals, and deflects each collected optical signal in the Y-axis direction. To do. Each deflected optical signal is folded back by the reflection mirror 708 provided adjacent to the KTN crystal 707 and is incident on the KTN crystal 707 again. Each optical signal that has passed through the KTN crystal 707 again passes through the relay lens system constituted by the second X cylindrical lens 705 and the third X cylindrical lens 706, the liquid crystal optical attenuator 704, and the first X cylindrical lens 703. Pass again in order. Then, each optical signal is connected to an output port selected by the KTN crystal 707 via one of the Y cylindrical lens groups 702, and one array waveguide grating of the arrayed waveguide grating group 701. Are combined and wavelength-multiplexed.

  The wavelength selective switch 700 according to the present embodiment is characterized by using a KTN crystal 707 having an electrode as an optical deflection element. As described in the first embodiment, the KTN crystal 707 can deflect light according to the voltage applied to the electrode, and has a maximum deflection angle larger than that of a conventional optical deflection element. Further, the deflection angle can be switched at high speed according to the applied voltage. Therefore, it is possible to realize a wavelength selective switch that has more output ports than a conventional wavelength selective switch and is capable of high-speed switching operation. Furthermore, unlike the MEMS, the wavelength selective switch 700 according to the present embodiment does not include a mechanical operation when deflecting light, and has a high transmittance as described in the example of the first embodiment. High reliability. In addition, since the wavelength selective switch 700 according to the present embodiment transmits the KTN crystal 707 twice by including the reflection mirror 708, a deflection angle of 30 degrees that is twice the maximum deflection angle of the KTN crystal 707 is possible. In addition, further multi-ports can be realized. For example, when an arrayed waveguide grating similar to the wavelength selective switch according to the first embodiment is used, the number of output ports can be doubled to 32 ports, but the thickness of the planar optical circuit (PLC) substrate is When the arrayed waveguide grating is stacked with a configuration of 1 mm and a distance between the substrates of 0.5 mm, the number of output ports can be set to 100, and a highly selective wavelength selective switch is realized. .

  Also, since the input optical signal is transmitted twice through the liquid crystal optical attenuator 704, it is possible to set a large extinction ratio of the output optical signal to the input optical signal. As a result, it is possible to further reduce crosstalk due to leaked light to the output port not involved in output port switching during hitless operation, and the reliability as a wavelength selective switch is improved.

  Further, since the input port and the output port are arranged on the same side with respect to the incident surface of each optical signal of the KTN crystal 707, the X cylindrical lens, the Y cylindrical lens, the optical attenuator, and the arrayed waveguide grating are shared. This greatly contributes to the reduction of member costs and the improvement of the simplicity of optical axis alignment. Although FIG. 7 shows the wavelength selective switch 700 in which the members are made common, it is not necessary to make the common. Each component will be described below.

  The arrayed waveguide grating group 701 is formed by stacking a plurality of arrayed waveguide gratings in the Y-axis direction. Each arrayed waveguide grating can have a structure in which a slab waveguide and an arrayed waveguide are connected, similarly to the first arrayed waveguide grating 101 of the first embodiment. The second slab waveguide 203 may or may not be provided. The WDM signal input from the input port passes through the slab waveguide and the array waveguide and is demultiplexed. The arrayed waveguide grating connected to the input port in the arrayed waveguide grating group 701 and the Y cylindrical lens corresponding to such an arrayed waveguide grating in the Y cylindrical lens group 702 can demultiplex the WDM signal. Thus, wavelength demultiplexing means for converting each wavelength-demultiplexed optical signal into an optical signal parallel to the Z-axis direction is configured, which is an exemplary configuration of the wavelength demultiplexing means. The arrayed waveguide grating connected to the output port in the arrayed waveguide grating group 701 and the Y cylindrical lens corresponding to the arrayed waveguide grating in the Y cylindrical lens group 702 are formed by the KTN crystal 707. Each of the optical signals deflected toward the selected output port is converted into an optical signal parallel to the Z-axis direction, and constitutes wavelength multiplexing means for wavelength multiplexing. It is an exemplary configuration.

  The first X cylindrical lens 703, the second X cylindrical lens 705, and the third X cylindrical lens 706, which are the light condensing elements, are not limited to these, and as described in the first embodiment, the function of condensing light. Anything that fulfills

  The KTN crystal 707 having an electrode, which is an electro-optic crystal, can have the same configuration as the KTN crystal 104 described in Embodiment 1, and can operate on the same principle to switch the deflection angle. It should be noted that the electro-optic crystal includes those other than the KTN crystal as described in the first embodiment.

  The liquid crystal optical attenuator 704, which is an optical attenuator, can have the same configuration as the liquid crystal optical attenuator 107 described in the first embodiment, and operates on the same principle to enable a “hitless” operation. It should be noted that embodiments without the liquid crystal light attenuator 704 are possible as described in the first embodiment.

  In this embodiment, the reflection mirror 708 is provided adjacent to the KTN crystal 707. However, if the reflection mirror 708 is provided between the KTN crystal 707, which is an electro-optic crystal, and the wavelength multiplexing means, the maximum deflection angle is increased. Note that this can be done.

  As described above, the wavelength selective switch according to the present embodiment is a wavelength selective switch that outputs an optical signal of a selected wavelength among wavelength division multiplexed signals input from an input port to a selected output port. A wavelength demultiplexing unit for demultiplexing the wavelength division multiplexed signal input from the input port; a first condensing element for condensing each optical signal wavelength-demultiplexed by the wavelength demultiplexing unit; Each optical signal collected by one light collecting element is deflected toward an output port selected for each optical signal, and is provided in parallel in a direction orthogonal to the path of each optical signal. An electro-optic crystal having electrodes, a second condensing element for condensing each optical signal deflected by the electro-optic crystal, and wavelength multiplexing for each optical signal condensed by the second condensing element Wavelength-multiplexed light Wavelength combining means for outputting a signal to the selected output port, and a reflection mirror interposed between the electro-optic crystal and the wavelength combining means, wherein the input port and the output port are the electro-optic crystal. The optical signals are arranged on the same side with respect to the light incident surface.

(Embodiment 3)
FIG. 8 shows the configuration of a third embodiment 800 of a wavelength selective switch according to the present invention. The wavelength selective switch 800 is a wavelength selective switch that outputs an optical signal having a selected wavelength among the wavelength division multiplexed signals input from the input port to the selected output port, and the wavelength division multiplexed input from the input port. A wavelength demultiplexing means for demultiplexing the signal, a first condensing element (X cylindrical lens 803) for condensing each optical signal wavelength-demultiplexed by the wavelength demultiplexing means, and a first condensing Electricity having at least one electrode provided in parallel in a direction orthogonal to the path of each optical signal, which deflects each optical signal collected by the element toward an output port selected for each optical signal. An optical crystal (KTN crystal 804), a second condensing element (X cylindrical lenses 805 and 806) for condensing each optical signal deflected by the electro-optic crystal, and a second An optical attenuator (liquid crystal optical attenuator 807) through which the condensing element passes, a third condensing element (X cylindrical lens 808) that condenses each optical signal that has passed through the optical attenuator, and a third concentrator. Wavelength multiplexing means for wavelength-multiplexing each optical signal collected by the optical element and outputting the wavelength-multiplexed optical signal to the selected output port, and the optical attenuator includes the first output port. When switching from the output port to the second output port, the optical path to the output port not involved in the switching is blocked, which is the same as in the first embodiment. Elements in parentheses are elements that constitute each component in the present embodiment. The present embodiment is different from the wavelength selective switch 100 according to the first embodiment in that a bulk diffraction grating is provided as the wavelength demultiplexing unit and the wavelength multiplexing unit.

  In such a configuration, the wavelength selective switch 800 according to the third embodiment operates as follows. First, a WDM signal is input from the input port to the first bulk diffraction grating 802 as collimated light by a collimating lens 801 installed in the immediate vicinity of the input optical fiber. The input WDM signal is reflected at a different angle for each wavelength in the first bulk diffraction grating 802 and demultiplexed. Each optical signal subjected to wavelength demultiplexing passes through the first X cylindrical lens 803 and is condensed from the first X cylindrical lens 803 to the position of fX. The KTN crystal 804 disposed at the position fX from the first X cylindrical lens 803 has individual electrodes corresponding to the wavelengths of the respective optical signals, and deflects each collected optical signal in the Y-axis direction. . Each of the deflected optical signals is composed of a second X cylindrical lens 805 disposed at a position 2fX from the first X cylindrical lens 803 and a third X cylindrical lens 806 disposed at a position 3fX. The light is condensed at the position of the liquid crystal light attenuator 807 disposed at the position of 4 fX via the lens system. Each optical signal is finally incident on the second bulk diffraction grating 809 via the fourth X cylindrical lens 808. The light is reflected by the second bulk type diffraction grating 809 at an angle corresponding to the wavelength, finally collected by the condenser lens 810, and coupled to the output port configured by the optical fiber array 812.

  The wavelength selective switch 800 according to the present embodiment is characterized by using a KTN crystal 804 having an electrode as an optical deflection element. As described in the first embodiment, the KTN crystal 804 can deflect light according to the voltage applied to the electrode, and has a maximum deflection angle larger than that of a conventional optical deflection element. Further, the deflection angle can be switched at high speed according to the applied voltage. Therefore, it is possible to realize a wavelength selective switch that has more output ports than a conventional wavelength selective switch and is capable of high-speed switching operation. Furthermore, unlike the MEMS, the wavelength selective switch 800 according to the present embodiment does not include a mechanical operation when deflecting light, and has high transmittance as described in the example of the first embodiment. High reliability. In addition, in the wavelength selective switch 800 according to the present embodiment, the wavelength demultiplexing unit includes the collimating lens 801 and the first bulk diffraction grating 802, and the wavelength multiplexing unit includes the second bulk diffraction grating 809 and the collecting unit. Since the optical lens 812 is used and the optical fiber array 812 is used as the output port, it is possible to reduce the interval between the output ports, greatly contribute to the miniaturization of the wavelength selective switch, and an array type waveguide grating is provided. Compared with the case where the wavelength demultiplexing means and the wavelength multiplexing means are used, it is possible to further increase the number of ports.

  As a bulk type diffraction grating, in addition to a blazed diffraction grating having a sawtooth groove as shown in FIG. 8, a holographic diffraction grating having a sinusoidal groove and a laminar diffraction grating having a rectangular groove are provided. It should be noted that any bulk diffraction grating can be used. In particular, when a holographic diffraction grating is used, since the diffraction efficiency is high, it is possible to realize a wavelength selective switch with less insertion loss.

  It should be noted that an embodiment without the liquid crystal optical attenuator 807 is possible as in the first embodiment.

(Embodiment 4)
FIG. 9 shows the configuration of a fourth embodiment 900 of a wavelength selective switch according to the present invention. FIG. 9A is a plan view, and FIG. 9B is a side view. The wavelength selective switch 900 includes a first arrayed waveguide grating (AWG) 101 having at least one optical fiber connected to the input side, a first Y cylindrical lens 102 having a focal length of fY, and a focal length of fX. A first X cylindrical lens 103, a KTN crystal 104 as a light deflection element, a second X cylindrical lens 105 with a focal length of fX, and a third X cylindrical lens 106 with a focal length of fX, , A liquid crystal optical attenuator 107, a fourth X cylindrical lens 108 having a focal length of fX, a second Y cylindrical lens group 109 having a focal length of fY, and a second arrayed waveguide grating group 110. These are arranged in this order. Then, the polarization separation element 901 is between the first Y cylindrical lens 102 and the first X cylindrical lens 103, and the first half-wave plate 902 is the first X cylindrical lens 103 and the KTN crystal 104. Between the liquid crystal optical attenuator 107 and the fourth X cylindrical lens 108, and the polarization beam combining element 904 between the fourth X cylindrical lens 108 and the second X cylindrical lens 108. It is inserted between the Y cylindrical lens 109. Here, the traveling direction of the optical signal is taken as the Z axis, the horizontal direction with respect to the substrates of the first arrayed waveguide grating 101 and the second arrayed waveguide grating group 110 is taken as the X axis, and the perpendicular direction is taken as the Y axis.

  In such a configuration, the wavelength selective switch 900 according to the fourth embodiment operates as follows. First, a WDM signal is input to the first arrayed waveguide grating 101 from the input port. The input WDM signal is wavelength-demultiplexed in the first arrayed waveguide grating 101 and output from the substrate of the first arrayed waveguide grating 101. Each output optical signal diverges in the vertical direction of the substrate immediately after the output, but the first Y cylindrical lens 102 disposed at the position fY from the end face of the first arrayed waveguide grating 101 causes the Z-axis direction Is converted into parallel light. Each optical signal converted into parallel light is separated into a TE wave and a TM wave by the polarization separation element 901. Each of the separated TE waves and TM waves passes through the first X cylindrical lens 103 disposed at the position of fX from the end face of the first arrayed waveguide grating 101, and the respective TM waves. The light is condensed at a position of 2 fX from the end face of one arrayed waveguide grating 101. The KTN crystal 104 arranged at a position of 2 fX from the end face of the first arrayed waveguide grating 101 has individual electrodes corresponding to the wavelengths of the respective optical signals, and each condensed TM wave is transmitted in the Y-axis direction. To deflect. Each deflected TM wave is constituted by a second X cylindrical lens 105 disposed at a position of 3 fX from the end face of the first arrayed waveguide grating 101 and a third X cylindrical lens 106 disposed at a position of 4 fX. The light is condensed at the position of the liquid crystal light attenuator 107 disposed at the position of 5 fX through the relay lens system. Next, each TM wave passes through one of the second half-wave plate groups 903 inserted between the liquid crystal optical attenuator 107 and the fourth X cylindrical lens 108, so that the polarization direction is 90. And passes through a polarization beam combining element 904 inserted between the fourth X cylindrical lens 108 and the second Y cylindrical lens group 109. Finally, the array conductor of one of the second arrayed waveguide grating groups 110 connected to the output port selected by the KTN crystal 104 via one of the second Y cylindrical lens group 109. Coupled to the waveguide grating, wavelength combined and output to the output port. Here, the fourth X cylindrical lens 108 and the second arrayed waveguide grating group 110 are disposed at positions 2fX and 3fX in the Z-axis direction from the third X cylindrical lens 106, respectively. The Y cylindrical lens 109 is disposed at a position fY from the second arrayed waveguide grating group 110.

  On the other hand, each TE wave separated by the polarization separation element is rotated by 90 degrees in the polarization direction in the first half-wave plate 902 and converted into a deflection component parallel to the TM polarization. This polarization component sequentially passes through the KTN crystal 104, the second X cylindrical lens 105, the third X cylindrical lens 106, the liquid crystal optical attenuator 107, and the fourth X cylindrical lens 108. Then, it is combined with another polarized wave in the polarization beam combiner 904 and similarly guided to the output port.

  The wavelength selective switch 900 according to this embodiment is characterized by using a KTN crystal 104 having an electrode as an optical deflection element. As described in the first embodiment, the KTN crystal can deflect light according to the voltage applied to the electrode, and has a maximum deflection angle larger than that of a conventional optical deflection element. Further, the deflection angle can be switched at high speed according to the applied voltage. Therefore, it is possible to realize a wavelength selective switch that has more output ports than a conventional wavelength selective switch and is capable of high-speed switching operation. Further, the wavelength selective switch 900 according to the present embodiment does not include a mechanical operation when deflecting light unlike the MEMS, and high transmittance is obtained as described in the example of the first embodiment. High reliability. In addition, the wavelength selective switch 900 according to the present embodiment includes a polarization separation element 901 that separates an optical signal into two orthogonal polarization components, and one polarization in front of the KTN crystal 104 that is an electro-optic crystal. A first half-wave plate 902 that rotates the component by 90 degrees, and a second component that rotates the polarization component whose polarization direction is not rotated by the first half-wave plate by 90 degrees after the electro-optic crystal. By providing a half-wave plate group 903 and a polarization beam combining element 904 that combines two orthogonal polarization components, the polarization of an optical signal when passing through an electro-optic crystal having polarization dependency, such as a KTN crystal. The direction is aligned with one polarization direction (polarization diversity configuration), and the influence of polarization dependency can be eliminated or reduced.

As the polarization separation element 901, a rutile TiO ₂ crystal can be used, and an element having a similar function, such as a YVO ₄ crystal, may be used.

  It should be noted that, as in the first embodiment, an embodiment without the liquid crystal optical attenuator 107 is possible.

(Embodiment 5)
FIG. 10 shows the configuration of a fifth embodiment 1000 of the wavelength selective switch according to the present invention. FIG. 10A is a plan view, and FIG. 10B is a side view. The wavelength selective switch 1000 includes a first arrayed waveguide grating (AWG) 1001 having at least one optical fiber connected to the input side, a first Y cylindrical lens 1002 having a focal length of fY, and a focal length of fX. A first X cylindrical lens 1003, a KTN crystal 1004 as a light deflection element, a second X cylindrical lens 1005 with a focal length of fX, and a second Y cylindrical lens group 1006 with a focal length of fY. And a second arrayed waveguide grating group 1007, which are arranged in this order. Here, the traveling direction of the optical signal is taken as the Z axis, the horizontal direction with respect to the substrates of the first arrayed waveguide grating 1001 and the second arrayed waveguide grating group 1007 is taken as the X axis, and the perpendicular direction is taken as the Y axis. In the present embodiment, a significant difference from the wavelength selective switch 100 according to the first embodiment is that a panel type is used instead of a rectangular type as an electrode of the KTN crystal 1004. The electrodes using strip-type and shape-combined electrodes will be described later in Embodiments 6 and 7.

  In such a configuration, the wavelength selective switch 1000 according to the first embodiment operates as follows. First, a WDM signal is input to the first arrayed waveguide grating 1001 from the input port. The input WDM signal is wavelength-demultiplexed in the first arrayed waveguide grating 1001 and output from the substrate of the first arrayed waveguide grating 1001. Each output optical signal diverges in the direction perpendicular to the substrate immediately after the output, but as shown in FIG. 10B, the first optical signal arranged at the position fY from the end face of the first arrayed waveguide grating 1001. Y cylindrical lens 1002 converts the light into parallel light parallel to the Z-axis direction. Each optical signal converted into the parallel light passes through the first X cylindrical lens 1003 disposed at the position fX from the end face of the first array waveguide grating 1001, and the first array waveguide grating 101. Is condensed at a position of 2 fX from the end face. The KTN crystal 1004 arranged at a position 2fX from the end face of the first arrayed waveguide grating 1001 has a panel-type electrode, and deflects each collected optical signal in the X-axis direction and the Y-axis direction. . Each deflected optical signal passes through one of the second X cylindrical lens 1005 and the second Y cylindrical lens group 1006 disposed at a position 3 fX from the end face of the first arrayed waveguide grating 1001. , Coupled to one array waveguide grating in the second array waveguide grating group 1007 connected to the output port selected by the KTN crystal 1004, wavelength-multiplexed and output to the output port. Here, the second arrayed waveguide grating group 1007 is disposed at the position of fX in the Z-axis direction from the second X cylindrical lens 1005, and the second Y cylindrical lens 1006 has the second array waveguide. The waveguide grating group 1007 is disposed at a position fY.

  The wavelength selective switch 1000 according to the present embodiment uses a KTN crystal 1004 having a panel-type electrode as an optical deflection element. As described in Embodiment 1, the KTN crystal 1004 can deflect light according to the voltage applied to the electrode, and has a maximum deflection angle larger than that of a conventional optical deflection element. Further, the deflection angle can be switched at high speed according to the applied voltage. Therefore, it is possible to realize a wavelength selective switch that has more output ports than a conventional wavelength selective switch and is capable of high-speed switching operation. Furthermore, the wavelength selective switch 1000 according to the present embodiment does not include a mechanical operation when deflecting light, unlike the MEMS, and high transmittance can be obtained as described in the example of the first embodiment. High reliability. In addition, the wavelength selective switch 1000 according to the present embodiment uses a panel type as an electrode of the KTN crystal 1004, deflects an optical signal not only in the Y axis direction but also in the X axis direction, and provides a two-dimensional output. Allows port alignment. This greatly contributes to the miniaturization of the wavelength selective switch, and further increases the number of ports. In addition, since the optical signal can be deflected two-dimensionally, the optical signal can be avoided or reduced without providing an optical attenuator so as to avoid or reduce leakage light to the output port not involved in the switching when the output port is switched. The final cost can be reduced by reducing the material cost and facilitating the alignment technology. This will be described in more detail below.

  The first arrayed waveguide grating group 1001 can have a structure in which a slab waveguide and an arrayed waveguide are connected, similarly to the first arrayed waveguide grating 101 of the first embodiment. The second slab waveguide 203 may or may not be provided. The first arrayed waveguide grating 1001 and the first Y cylindrical lens 1002 wavelength-demultiplex the WDM signal and convert the wavelength-demultiplexed optical signals into optical signals parallel to the Z-axis direction. It constitutes a demultiplexing means and is an exemplary configuration of the wavelength demultiplexing means.

  It should be noted that the first X cylindrical lens 1003 that is a condensing element is not necessarily a single lens, and it is sufficient that each optical signal can be condensed.

  FIG. 11 shows one substrate of the second arrayed waveguide grating group 1007 in which a plurality of substrates are stacked. A plurality of arrayed waveguide gratings are arranged in the X-axis direction on each substrate. Each arrayed waveguide grating includes a first slab waveguide 1101, an arrayed waveguide 1102 connected to the first slab waveguide 1102, and a second slab waveguide 1103 connected to the arrayed waveguide 1102. Prepare. The first slab waveguide 1101 may or may not be provided. The second X cylindrical lens 1005, the second Y cylindrical lens group 1106, and the second arrayed waveguide grating group 1107 are deflected in the X-axis direction and the Y-axis direction toward the output port selected by the KTN crystal 1104. Each of the optical signals is converted into an optical signal parallel to the Z-axis direction to constitute wavelength multiplexing means for wavelength multiplexing, which is an exemplary configuration of the wavelength multiplexing means. The second X cylindrical lens 1005 can also function as a condensing element that condenses each optical signal deflected by the KTN crystal 1004 that is an electro-optic crystal.

  FIG. 12 shows details of an electrode included in the KTN crystal 1004 which is an electro-optic crystal. On one side of the KTN crystal 1004 parallel to the Z-axis direction, at least one electrode is provided in a direction orthogonal to the optical signal path. Each electrode can be a panel type. In the figure, W is the electrode width, G is the electrode interval, and t is the thickness of the KTN crystal 1004. One electrode connected to the ground is provided on the other side parallel to the Z-axis direction of the KTN crystal 1004. However, the shape is not limited to such a shape, and the position corresponding to the rectangular electrode described above is provided. It is sufficient that a voltage can be applied to the KTN crystal 1004. As described in the embodiment, the operation of the KTN crystal 1004 is such that when a voltage is applied to the electrode, the refractive index increases in a slope closer to the cathode in the KTN crystal 1004, and an optical signal is transmitted in the direction approaching the cathode electrode. To deflect.

  FIG. 13 shows the operation of the KTN crystal 1004 having panel type electrodes. Each electrode has a plurality of cells arranged in a two-dimensional panel shape, and each cell can be individually voltage controlled. When deflecting an optical signal only in the Y-axis direction, a voltage is uniformly applied to all cells as shown in FIG. Then, the optical signal is deflected by the space charge control mode EO effect by the KTN crystal 1004. When deflecting in the X-axis direction, a voltage is uniformly applied to cells corresponding to a region that can be approximated to a triangle as shown in FIG. Then, while the light is deflected in the Y-axis direction, a refractive index change caused by the space charge control mode EO effect occurs in the KTN crystal 1004, and the light is also deflected in the X-axis direction via Snell's law. The deflection angle in the X-axis direction depends on the angle of the hypotenuse of the voltage application region approximated to a triangle and the magnitude of the applied voltage.

  Here, the deflection angle in the Y-axis direction depends on the amount of applied voltage and the optical path length in the voltage application region. Therefore, when the voltage is applied in a triangular shape, the optical path length becomes shorter than when the entire surface voltage is applied as shown in FIG. 13A, and a sufficient deflection angle cannot be obtained with respect to the Y-axis direction. There is. As a countermeasure, when a voltage is applied in a triangular shape, a higher voltage may be applied than when a voltage is applied across the entire surface. By applying a higher voltage, the difference in refractive index between the anode and the cathode becomes larger, and the deflection angle in the Y-axis direction can be set larger. That is, by optimizing the approximate triangular shape and applied voltage, it is possible to adjust the light deflection angle in the X-axis direction while maintaining the light deflection angle in the Y-axis direction.

  In addition, a panel-type electrode is disposed on the top of a 100 μm thick KTN, and the deflection angle in the X-axis direction when a voltage of 250 V is applied to a region that can be approximated to a triangle whose hypotenuse is 45 degrees is obtained. According to Non-Patent Document 2, since the deflection angle when a voltage of 250 V is applied is approximately 15 degrees, the refractive index between the voltage application region and the non-application region at the center of the crystal, that is, y = t / 2. The difference Δn = 0.075 is calculated. Based on this value, when Snell's law is used, a polarization angle of about 4.2 degrees is obtained. By setting the angle of the hypotenuse of the triangle that can approximate the voltage application region to ± 45 degrees, a wide angle of up to 8.4 degrees can be obtained. Deflection is possible.

  As described above, the wavelength selective switch according to the present embodiment uses a panel-type electrode in which a plurality of cells are arranged in a two-dimensional panel as an electrode of the electro-optic crystal, and a voltage applied to each cell. The optical signal transmitted through the electro-optic crystal is deflected two-dimensionally by individually controlling.

(Embodiment 6)
FIG. 14 shows the operation of a KTN crystal having strip-shaped electrodes. In the fifth embodiment, an optical signal can be deflected two-dimensionally using a KTN crystal having panel-type electrodes. However, even if the electrodes are strip-shaped, they can be deflected two-dimensionally. Each electrode has a plurality of rectangular cells elongated in the Z-axis direction, such as strips, arranged in parallel in the X-axis direction, and each cell can be individually voltage controlled. In the present embodiment, it is desirable that the beam spot Wo of the monochromatic optical signal in the KTN crystal is sufficiently larger than the width W of the strip, for example, W ₀ > 10 W.

  When deflecting an optical signal only in the Y-axis direction, a voltage is uniformly applied to all cells as shown in FIG. When deflecting in the X-axis direction, the applied voltage amount is gradually increased in the light deflection direction as shown in FIG. Then, a refractive index change is formed stepwise in the X-axis direction, and the optical signal can be deflected in the X-axis direction. A feature of this electrode shape is that the wavefront distortion of the light deflected by KTN hardly occurs.

  As described above, the wavelength selective switch according to the present embodiment is a strip in which a plurality of rectangular cells elongated in the optical signal path direction, such as strips, are arranged in parallel as electrodes of the electro-optic crystal. By using a mold electrode and individually controlling the voltage applied to each cell, the optical signal transmitted through the electro-optic crystal is deflected two-dimensionally.

(Embodiment 7)
FIG. 15 shows the operation of a KTN crystal having a composite shape type electrode. Each electrode includes a rectangular electrode 1501 for deflecting the optical signal in the Y-axis direction and a triangular electrode 1502 for deflecting the optical signal in the X-axis direction. When, for example, titanium is used as the material of the rectangular electrode 1501, the space charge control mode EO effect is exhibited in the electrode portion, so that a refractive index distribution can be formed in the Y-axis direction, and light is deflected in the same direction. It is possible. In addition, when, for example, platinum is used as the material of the triangular electrode 1502, a normal electro-optical effect, that is, the Kerr effect can be exhibited. In the Kerr effect, since the refractive index change in the crystal is uniform in the Y-axis direction, light can be deflected in the X-axis direction by a simple prism effect. In either electrode, a larger deflection angle can be obtained as a higher voltage is applied. In the present embodiment, deflection occurs centrally in the direction of the apex corresponding to the hypotenuse of the triangular electrode 1502 that exhibits the Kerr effect. Therefore, in the seventh embodiment, the deflection angle in the X-axis direction is narrower than that in the fifth and sixth embodiments. However, when this composite-shaped electrode is used, the structure is very simple, and the vertical and horizontal directions are also high. Has a great advantage in that it can be controlled independently.

  As described above, the wavelength selective switch according to this embodiment includes a rectangular electrode formed using a material that provides a space charge control mode EO effect for the KTN crystal as an electrode of the electro-optic crystal, It is characterized by using a composite-shaped electrode in which triangular electrodes formed using a material that brings about the Kerr effect are arranged in tandem in the optical signal path direction.

It is a figure which shows 1st Embodiment of the wavelength selective switch by this invention. FIG. 3 is a diagram illustrating a first arrayed waveguide grating according to the first embodiment. FIG. 3 is a diagram showing details of an electrode included in the KTN crystal according to the first embodiment. It is a figure which shows the wavelength selective switch of a form which is not provided with the liquid crystal optical attenuator in Embodiment 1. FIG. It is a figure which shows the characteristic of the wavelength selective switch of the Example which concerns on Embodiment 1. FIG. It is a figure which shows the switching operation characteristic of the wavelength selective switch of the Example which concerns on Embodiment 1. FIG. It is a figure which shows 2nd Embodiment of the wavelength selective switch by this invention. It is a figure which shows 3rd Embodiment of the wavelength selective switch by this invention. It is a figure which shows 4th Embodiment of the wavelength selective switch by this invention. It is a figure which shows 5th Embodiment of the wavelength selective switch by this invention. FIG. 10 is a view showing one substrate in a second arrayed waveguide grating group according to the fifth embodiment. It is a figure which shows the detail of the electrode which the KTN crystal which concerns on Embodiment 5 has. FIG. 10 is a diagram illustrating an operation of a KTN crystal having a panel-type electrode according to the fifth embodiment. It is a figure which shows operation | movement of the KTN crystal | crystallization which has a strip-shaped electrode based on Embodiment 6. FIG. It is a figure which shows operation | movement of the KTN crystal | crystallization which has a composite shape type electrode based on Embodiment 7. FIG.

Explanation of symbols

101, 1001 First arrayed waveguide grating 102, 1002 First Y cylindrical lens 103, 703, 803, 1003 First X cylindrical lens 104, 707, 804, 1004 KTN crystal 105, 705, 805, 1005 Second X cylindrical lens 106, 706, 806 Third X cylindrical lens 107, 704, 807 Liquid crystal optical attenuator 108, 808 Fourth X cylindrical lens 109, 1006 Second Y cylindrical lens group 110, 1007 Second array Waveguide grating group 201 First slab circuit 202 Array waveguide 203 Second slab circuit 701 Array waveguide grating group 702 Y cylindrical lens group 708 Reflecting mirror 801 Collimating lens 802 First bulk diffraction grating 80 Second bulk diffraction grating 810 Condensing lens 811 Optical fiber 812 Optical fiber array 901 Polarization separation element 902 First half-wave plate 903 Second half-wave plate group 904 Polarization combining element 1101 First slab circuit 1102 Array waveguide 1103 Second slab circuit 1301, 1401 Cell 1501 Rectangular electrode 1502 Triangular electrode

Claims (13)

A wavelength selective switch that outputs an optical signal of a selected wavelength among wavelength division multiplexed signals input from an input port to a selected output port,
Wavelength demultiplexing means for wavelength demultiplexing the wavelength division multiplexed signal input from the input port;
A first condensing element for condensing each optical signal wavelength-demultiplexed by the wavelength demultiplexing means;
Provided in parallel in a direction orthogonal to the path of each optical signal that deflects each optical signal collected by the first light collecting element toward an output port selected for each optical signal. An electro-optic crystal having at least one electrode;
A second condensing element for condensing each optical signal deflected by the electro-optic crystal,
Wavelength multiplexing means for wavelength-combining each optical signal collected by the second condensing element and outputting the wavelength-multiplexed optical signal to the selected output port. Wavelength selective switch. 2. The wavelength selective switch according to claim 1, wherein the electro-optic crystal is KTa _1-x Nb _x O ₃ (0 <x <1, 0 <y <1).   A reflection mirror interposed between the electro-optic crystal and the wavelength multiplexing means; and the input port and the output port are on the same side with respect to an incident surface of the respective optical signals of the electro-optic crystal. The wavelength selective switch according to claim 1, wherein the wavelength selective switch is arranged.   3. The input port and the output port are arranged at positions facing the incident surface of each optical signal of the electro-optic crystal with the electro-optic crystal interposed therebetween. The wavelength selective switch described in 1.   3. The wavelength selective switch according to claim 1, wherein each of the wavelength demultiplexing unit and the wavelength demultiplexing unit includes an arrayed waveguide grating.   3. The wavelength selective switch according to claim 1, wherein each of the wavelength demultiplexing unit and the wavelength demultiplexing unit includes a bulk diffraction grating. Before the electro-optic crystal,
A polarization separation element that separates each optical signal into two orthogonal polarization components;
A first half-wave plate that rotates one polarization component by 90 degrees, and after the electro-optic crystal,
A second half-wave plate group for rotating a polarization component whose polarization direction is not rotated by the first half-wave plate by 90 degrees;
The wavelength selective switch according to claim 1, further comprising: a polarization beam combining element that combines two orthogonal polarization components. The wavelength demultiplexing means is connected to an output port arranged in two dimensions,
Each of the at least one electrode is a panel-type electrode in which a plurality of cells are arranged in a two-dimensional panel shape,
The wavelength selective switch according to claim 1 or 2, wherein the voltage applied to each of the plurality of cells can be individually controlled. The wavelength demultiplexing means is connected to an output port arranged in two dimensions,
Each of the at least one electrode is a strip-shaped electrode in which a plurality of rectangular cells elongated in the optical signal path direction such as a strip are arranged in parallel,
The wavelength selective switch according to claim 1 or 2, wherein the voltage applied to each of the plurality of cells can be individually controlled.   The wavelength selective switch according to claim 1, wherein each of the at least one electrode is a rectangular electrode. Each of the at least one electrode is formed using a material that provides a space charge control mode EO effect for the KTa _1-x Nb _x O ₃ (0 <x <1, 0 <y <1). 3. The wavelength according to claim 2, wherein the electrode is a composite-shaped electrode in which rectangular electrodes and triangular electrodes formed using a material that brings about the Kerr effect are arranged in tandem in the optical signal path direction. Select switch. A wavelength selective switch that outputs an optical signal of a selected wavelength among wavelength division multiplexed signals input from an input port to a selected output port,
Wavelength demultiplexing means for wavelength demultiplexing the wavelength division multiplexed signal input from the input port;
A first condensing element for condensing each optical signal wavelength-demultiplexed by the wavelength demultiplexing means;
Provided in parallel in a direction orthogonal to the path of each optical signal that deflects each optical signal collected by the first light collecting element toward an output port selected for each optical signal. An electro-optic crystal having at least one electrode;
A second condensing element that condenses each optical signal deflected by the electro-optic crystal, an optical attenuator through which the second condensing element passes,
A third condensing element that condenses each optical signal that has passed through the optical attenuator;
Wavelength multiplexing means for wavelength-multiplexing each optical signal collected by the third condensing element and outputting the wavelength-multiplexed optical signal to the selected output port, and the optical attenuator The wavelength selective switch, wherein when the output port is switched from the first output port to the second output port, the optical path to the output port not involved in the switching is cut off. The electro-optical crystal, the wavelength selective switch according to claim 12, characterized in that the _{KTa 1-x Nb x O 3} (0 <x <1,0 <y <1).

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