WO2015169071A1 - 一种基于液晶光栅的光开关 - Google Patents

一种基于液晶光栅的光开关 Download PDF

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Publication number
WO2015169071A1
WO2015169071A1 PCT/CN2014/090051 CN2014090051W WO2015169071A1 WO 2015169071 A1 WO2015169071 A1 WO 2015169071A1 CN 2014090051 W CN2014090051 W CN 2014090051W WO 2015169071 A1 WO2015169071 A1 WO 2015169071A1
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Prior art keywords
liquid crystal
grating
polarization
input
light
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PCT/CN2014/090051
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English (en)
French (fr)
Inventor
毛崇昌
李岷淳
王思超
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华为技术有限公司
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Priority to EP14891172.0A priority Critical patent/EP3133749B1/en
Priority to JP2017510717A priority patent/JP6345874B2/ja
Publication of WO2015169071A1 publication Critical patent/WO2015169071A1/zh
Priority to US15/346,540 priority patent/US10284931B2/en

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q11/00—Selecting arrangements for multiplex systems
    • H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
    • H04Q11/0005—Switch and router aspects
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/137—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells characterised by the electro-optical or magneto-optical effect, e.g. field-induced phase transition, orientation effect, guest-host interaction or dynamic scattering
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/29—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the position or the direction of light beams, i.e. deflection
    • G02F1/31—Digital deflection, i.e. optical switching
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/25—Arrangements specific to fibre transmission
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J14/00—Optical multiplex systems
    • H04J14/06—Polarisation multiplex systems
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/27—Optical coupling means with polarisation selective and adjusting means
    • G02B6/2706—Optical coupling means with polarisation selective and adjusting means as bulk elements, i.e. free space arrangements external to a light guide, e.g. polarising beam splitters
    • G02B6/2713—Optical coupling means with polarisation selective and adjusting means as bulk elements, i.e. free space arrangements external to a light guide, e.g. polarising beam splitters cascade of polarisation selective or adjusting operations
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/27—Optical coupling means with polarisation selective and adjusting means
    • G02B6/2706—Optical coupling means with polarisation selective and adjusting means as bulk elements, i.e. free space arrangements external to a light guide, e.g. polarising beam splitters
    • G02B6/2713—Optical coupling means with polarisation selective and adjusting means as bulk elements, i.e. free space arrangements external to a light guide, e.g. polarising beam splitters cascade of polarisation selective or adjusting operations
    • G02B6/272—Optical coupling means with polarisation selective and adjusting means as bulk elements, i.e. free space arrangements external to a light guide, e.g. polarising beam splitters cascade of polarisation selective or adjusting operations comprising polarisation means for beam splitting and combining
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/35—Optical coupling means having switching means
    • G02B6/3594—Characterised by additional functional means, e.g. means for variably attenuating or branching or means for switching differently polarized beams
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/42—Coupling light guides with opto-electronic elements
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q11/00—Selecting arrangements for multiplex systems
    • H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
    • H04Q11/0005—Switch and router aspects
    • H04Q2011/0007—Construction
    • H04Q2011/0015—Construction using splitting combining
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q11/00—Selecting arrangements for multiplex systems
    • H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
    • H04Q11/0005—Switch and router aspects
    • H04Q2011/0007—Construction
    • H04Q2011/0026—Construction using free space propagation (e.g. lenses, mirrors)
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q11/00—Selecting arrangements for multiplex systems
    • H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
    • H04Q11/0005—Switch and router aspects
    • H04Q2011/0007—Construction
    • H04Q2011/0035—Construction using miscellaneous components, e.g. circulator, polarisation, acousto/thermo optical
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q11/00—Selecting arrangements for multiplex systems
    • H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
    • H04Q11/0005—Switch and router aspects
    • H04Q2011/0037—Operation
    • H04Q2011/0039—Electrical control
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q11/00—Selecting arrangements for multiplex systems
    • H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
    • H04Q11/0005—Switch and router aspects
    • H04Q2011/0052—Interconnection of switches

Definitions

  • the present invention relates to the field of communications, and in particular, to an optical switch based on a liquid crystal grating.
  • each node of the network needs to perform optical-electrical-to-optical conversion, and still exchanges information by means of electrical signal processing.
  • the electronic components there are shortcomings such as bandwidth limitation, clock offset, severe crosstalk, and high power consumption in adapting to the requirements of high speed and large capacity, thereby causing an "electronic bottleneck" phenomenon in the communication network.
  • AON All Optical Network
  • Optical Cross Connection is the core device in the all-optical network. It is combined with Optical Add-Drop Multiplexer (OADM) and Erbium-doped Optical Fiber Amplifier (EDFA). ), attenuators, optical fibers and other devices and devices form an all-optical network.
  • the OXC exchanges all-optical signals, which interconnect the specified wavelengths at the network nodes, thereby effectively utilizing wavelength resources for wavelength reuse, that is, using a smaller number of wavelengths to interconnect a larger number of network nodes.
  • the OXC can automatically complete operations such as fault isolation, re-routing, and network reconfiguration, so that the service is not interrupted, that is, it has functions such as high-speed optical signal routing and network recovery.
  • OXCs based on Liquid Crystal (LC) and Polarization Beam Splitter (PBS) on the market, as shown in Figure 1, which mainly consists of a light collimator, a beam splitter, a PBS array, and an LC array.
  • the light collimator is used to input and output light
  • the Displaycer is used to convert the input light into the same polarized light and the output end polarized light is coupled into the optical collimator
  • the PBS is used to split and combine the polarized light
  • the LC is used to control the polarization of the light. direction.
  • the polarization direction of the light at each node is controlled by controlling the voltage of the LC array, thereby enabling any one of the input light to be transmitted to the desired output port.
  • the technical solution is difficult to assemble, large in size and high in cost.
  • Embodiments of the present invention provide an optical switch based on a liquid crystal grating, which realizes optical cross-interconnection through a variable polarization grating, and solves the problem that the prior art optical cross-interconnection based on LC and PBS is difficult, bulky, and costly. technical problem.
  • an embodiment of the present invention provides an optical switching apparatus including an input collimator and an output collimator, and further includes: an input polarization beam splitter, an input quarter wave plate, and an output quarter wave plate. And outputting a polarization beam splitter and an N ⁇ N liquid crystal grating array, wherein N is an integer greater than or equal to 2;
  • the input polarization beam splitter is disposed between the input collimator and the input quarter wave plate for splitting an input optical signal from the input collimator into two lights having different polarization directions And outputting the two optical signals having different polarization directions to the input quarter wave plate;
  • the input quarter wave plate is disposed between the input polarization beam splitter and the N x N liquid crystal grating array for receiving the two light having different polarization directions from the input polarization beam splitter a signal, and coupling the two optical signals having different polarization directions into circularly polarized light, and outputting the circularly polarized light to the N ⁇ N liquid crystal grating array;
  • the N ⁇ N liquid crystal grating array is disposed between the input quarter wave plate and the output quarter wave plate for passing through the input quarter of the N ⁇ N liquid crystal grating array a liquid crystal grating corresponding to the wave plate receives the circularly polarized light from the input quarter wave plate, and outputs the circularly polarized light to a selected output quarter wave plate through a selected transmission path; Wherein the selected transmission path is selected by setting a voltage of the liquid crystal grating in the N ⁇ N liquid crystal grating array;
  • the output quarter wave plate is disposed between the N ⁇ N liquid crystal grating array and the output polarization beam splitter for splitting circularly polarized light from the N ⁇ N liquid crystal grating array into two different An optical signal of a polarization direction, and outputting the two optical signals having different polarization directions to the output polarization beam splitter;
  • the output polarization beam splitter is disposed between the output quarter wave plate and the output collimator for separating the two from the output quarter wave plate with different polarization directions
  • An optical signal is coupled into the output collimator.
  • the liquid crystal grating in the N ⁇ N liquid crystal grating array comprises an N ⁇ N variable polarization grating, an N ⁇ N variable polarization grating/liquid crystal panel combination, and an N ⁇ N polymerization.
  • liquid crystal molecules in any of the variable polarization gratings when a voltage applied across the variable polarization grating is less than a first threshold voltage Forming a liquid crystal grating to diffract incident light; when the voltage across the variable polarization grating is greater than or equal to a first threshold voltage, the liquid crystal molecules are caused by voltages across the variable polarization grating The direction of the electric field is deflected and the grating effect disappears;
  • variable polarization grating In the N ⁇ N variable polarization grating, the voltage across the variable polarization grating that does not need to deflect the incident light is set to be greater than or equal to the first threshold voltage; the voltage across the variable polarization grating that needs to deflect the incident light Is set to be smaller than the first threshold voltage; wherein the variable polarization grating that needs to deflect the incident light is corresponding to the input quarter wave plate and corresponds to the output quarter wave plate
  • a variable polarization grating, the variable polarization grating that does not require deflection of incident light is a variable polarization grating of an N x N variable polarization grating array other than the variable polarization grating that requires deflection of incident light.
  • the voltage across the variable polarization grating that needs to deflect the incident light is set to zero.
  • any variable polarization grating when a voltage applied across the variable polarization grating is less than a first threshold voltage, Any variable polarization grating has three diffraction orders of 0, +1 and -1; incident right-handed circularly polarized light is diffracted by any of the variable polarized light to +1, becoming left-handed circular polarization Light; incident left-handed circularly polarized light is diffracted by any of the variable polarized light to a level of -1 to become right-handed circularly polarized light.
  • the circular polarization state of the output signal light is opposite to the circular polarization state of the output crosstalk light;
  • the voltage across the liquid crystal cell controls the polarization state of the optical signal incident on the liquid crystal cell.
  • the output light of any one of the liquid crystal cells is consistent with the polarization state of the input light of any one of the liquid crystal cells;
  • the liquid crystal sheet If the left circularly polarized light is input to any one of the liquid crystal sheets, the liquid crystal sheet outputs right-handed circularly polarized light;
  • any of the liquid crystal cells outputs left-handed circularly polarized light.
  • the output light of any one of the liquid crystal cells is consistent with the polarization state of the input light of the liquid crystal cell
  • the liquid crystal sheet If the left circularly polarized light is input to any one of the liquid crystal sheets, the liquid crystal sheet outputs right-handed circularly polarized light;
  • any of the liquid crystal cells outputs left-handed circularly polarized light.
  • any of the polymer polarization grating/liquid crystal panel/polymer polarization grating combination includes: a first polymer polarization grating, a first liquid crystal panel, and a second polymer polarization grating;
  • the first polymer polarization grating and the second polymer polarization grating are both fixed gratings
  • the first polymer polarization grating or the second polymer polarization grating is diffracted to +1 level, and the left circularly polarized light is output; if the left circularly polarized light is input, the first is The polymer polarization grating or the second polymer polarization grating is diffracted to -1 stage, and outputs right-handed circularly polarized light;
  • the first liquid crystal panel is configured to control deflection of an optical signal incident on the liquid crystal panel by setting a voltage across the first liquid crystal panel.
  • the first liquid crystal panel If the left circularly polarized light is input to the first liquid crystal panel, the first liquid crystal panel outputs right circularly polarized light;
  • the first liquid crystal panel If right circularly polarized light is input to the first liquid crystal panel, the first liquid crystal panel outputs left circular polarization Light.
  • the voltage across the first liquid crystal sheet that does not need to deflect the incident light is set to be smaller than the second threshold voltage; the voltage across the first liquid crystal sheet that needs to deflect the incident light is set to be greater than or equal to The second threshold voltage; wherein the first liquid crystal sheet that needs to deflect incident light is a portion corresponding to the input quarter wave plate and corresponding to the output quarter wave plate In the first liquid crystal panel, the first liquid crystal sheet that does not need to deflect incident light is N ⁇ N of the first liquid crystal wafer array except the first liquid crystal that needs to deflect incident light. The first liquid crystal sheet outside the sheet.
  • the first liquid crystal panel If the left circularly polarized light is input to the first liquid crystal panel, the first liquid crystal panel outputs right circularly polarized light;
  • the first liquid crystal panel If right-handed circularly polarized light is input to the first liquid crystal panel, the first liquid crystal panel outputs left-handed circularly polarized light.
  • the voltage across the first liquid crystal sheet that does not need to deflect the incident light is set to be greater than or equal to the second threshold voltage; the voltage across the first liquid crystal sheet that needs to deflect the incident light is set to be smaller than The second threshold voltage; wherein the first liquid crystal sheet that needs to deflect incident light is a portion corresponding to the input quarter wave plate and corresponding to the output quarter wave plate In the first liquid crystal panel, the first liquid crystal sheet that does not need to deflect incident light is N ⁇ N of the first liquid crystal wafer array except the first liquid crystal that needs to deflect incident light. The first liquid crystal sheet outside the sheet.
  • the circular polarization state of the output signal light is opposite to the circular polarization state of the output crosstalk light; wherein, by setting the second liquid crystal The voltage across the sheet controls the polarization state of the optical signal incident on the second liquid crystal cell.
  • the output light of any of the second liquid crystal cells is consistent with the polarization state of the input light
  • the any second liquid crystal sheet outputs right-handed circularly polarized light
  • any of the liquid crystal cells outputs left-handed circularly polarized light.
  • the N ⁇ N second liquid crystal panels are electrically controlled birefringence liquid crystals
  • the output light of the second liquid crystal panel is consistent with the polarization state of the input light
  • the any second liquid crystal sheet outputs right-handed circularly polarized light
  • any of the second liquid crystal chips outputs left-handed circularly polarized light.
  • Embodiments of the present invention provide an optical switching device based on a liquid crystal grating, comprising: an input collimator, an input polarization beam splitter, an input quarter wave plate, an N ⁇ N liquid crystal grating array, and an output quarter wave plate. , output polarization beam splitter, output collimator.
  • the input light passes through the input polarization beam splitter and the input quarter wave plate becomes circularly polarized light.
  • the transmission path of the light is selected by changing the voltage of the liquid crystal grating, outputted to a designated port, coupled to the output collimator via the output quarter wave plate and the output polarization beam splitter.
  • an N ⁇ N optical crossbar function and an add/drop function are implemented.
  • FIG. 1 is a schematic structural view of an optical switching device in the prior art
  • FIG. 2 is a schematic structural view of a liquid crystal grating-based optical switching device according to Embodiment 1 of the present invention
  • FIG. 3 is a schematic structural diagram of an optical switching device based on a variable polarization grating according to Embodiment 2 of the present invention
  • FIG. 4 is a schematic view showing a preparation flow of a variable polarization grating liquid crystal alignment layer
  • FIG. 5 is a schematic view showing the arrangement of liquid crystal molecules when the voltage across the variable polarization grating is 0V;
  • FIG. 6 is a schematic view showing the arrangement of liquid crystal molecules when the voltage across the variable polarization grating is greater than the first threshold voltage
  • Figure 7 is a schematic diagram of the principle of a variable polarization grating
  • FIG. 8 is a schematic diagram showing a specific structure of an optical switching device based on a variable polarization grating/liquid crystal panel according to a third embodiment of the present invention.
  • FIG. 9 is a schematic view showing the principle of vertically arranging a VA type liquid crystal panel
  • Figure 10 is a schematic diagram of a variable polarization grating/liquid crystal combination principle
  • FIG. 11 is a schematic diagram showing the specific structure of an optical switching device based on a polymer polarization grating/liquid crystal panel/polymer polarization grating combination according to Embodiment 4 of the present invention
  • FIG. 12 is a schematic view showing a manufacturing process of a polymer polarization grating
  • Figure 13 is a schematic diagram of the principle of a polymer polarization grating
  • FIG. 14 is a schematic diagram showing the specific structure of an optical switching device based on a polymer polarization grating/liquid crystal panel/polymer polarization grating/liquid crystal panel combination according to Embodiment 5 of the present invention
  • Embodiments of the present invention provide an optical switching device based on a liquid crystal grating, comprising: an input collimator, an input polarization beam splitter, an input quarter wave plate, a liquid crystal grating, an output quarter wave plate, and an output polarization splitting And output collimator.
  • the input light passes through the input polarization beam splitter and the input quarter wave plate becomes circularly polarized light.
  • the transmission path of the light is selected by changing the voltage of the liquid crystal grating, outputted to a designated port, coupled to the output collimator via the output quarter wave plate and the output polarization beam splitter. Further, an N ⁇ N optical crossbar function and an add/drop function are implemented.
  • the liquid crystal grating-based optical switching device in the embodiment of the present invention includes: an input collimator 101, an input polarization beam splitter 201, an input quarter wave plate 301, an N ⁇ N liquid crystal grating 4 array, The quarter wave plate 302, the output polarization beam splitter 202, and the output collimator 102 are output.
  • N is an integer greater than or equal to 2.
  • the input collimator 101 is configured to receive an optical signal input from the optical fiber, and the input collimator 101 is an incident port of the peripheral optical signal, and the optical signal enters the input collimator 101 through the input optical fiber, and the input collimator 101 inputs the input.
  • the light signals are beam shaped such that their beam waists become larger and the divergence angle becomes smaller, allowing these input optical signals to travel longer distances in free space.
  • An input polarization beam splitter 201 is disposed between the input collimator 101 and the input quarter wave plate 301 for splitting the input optical signal from the input collimator 101 into optical signals having two different polarization directions, and The two optical signals having different polarization directions are output to the input quarter wave plate 301.
  • the polarization beam splitter 201 can be realized by various techniques, for example, by a birefringent crystal, a polarizing multilayer film, a polymer film, a quartz glass etching, or the like.
  • the input quarter wave plate 301 is disposed between the input polarization beam splitter 201 and the liquid crystal grating 4 for receiving the two optical signals having different polarization directions from the polarization beam splitter 201 and converting them into a circle
  • the polarized light is output to the array of N x N liquid crystal gratings 4 .
  • the corresponding liquid crystal grating receives the circularly polarized light from the input quarter wave plate 301, and outputs the circularly polarized light to the selected output quarter wave plate 302 through the selected transmission path;
  • the selected transmission path is selected by setting the voltage of the liquid crystal grating in the array of N x N liquid crystal gratings 4.
  • An output quarter wave plate 302 is disposed between the array of N x N liquid crystal gratings 4 and the output polarization beam splitter 202 for receiving circularly polarized light from the array of N x N liquid crystal gratings 4 and modulating the circularly polarized light It is converted into two optical signals having different polarization directions, and the two optical signals having different polarization directions are output to the polarization beam splitter 202.
  • the output polarization beam splitter 202 is disposed between the output quarter wave plate 302 and the output collimator 102 for performing the two optical signals having different polarization directions from the output quarter wave plate 302.
  • the polarization is coupled and output to the output collimator 102.
  • the output polarization beam splitter 202 is implemented in the same manner as the input polarization beam splitter 201, and will not be described herein.
  • the output collimator 102 is configured to receive an optical signal output by the output polarization beam splitter 202, and couple the received optical signal into an optical fiber for output.
  • the embodiment of the invention provides an optical switching device based on a liquid crystal grating, comprising: an input collimator 101, an input polarization beam splitter 201, an input quarter wave plate 301, an N ⁇ N liquid crystal grating 4 array, and an output quadrant.
  • the transmission path of the optical signal is selected by changing the voltage of the liquid crystal grating so that the optical signal is output to the selected output.
  • the optical switching device has a simple structure, a small size, and a low cost.
  • variable polarization grating-based optical switching device includes: an input collimator 101, an input polarization beam splitter 201, an input quarter-wave plate 301, and an N ⁇ N variable.
  • the input collimator 101 is configured to receive an optical signal input from the optical fiber, beam-shape the optical signal input by the optical fiber, and output the optical signal to the input polarization beam splitter 201. Specifically, it has been described in detail in the first embodiment of the present invention shown in FIG. 2 above, and is not described here.
  • An input polarization beam splitter 201 is configured to split the input optical signal from the input collimator 101 into two optical signals having different polarization directions, and output the optical signals having two different polarization directions to the input quarter Wave plate 301. Specifically, it has been described in detail in the first embodiment of the present invention shown in FIG. 2 above, and is not described here.
  • Input a quarter wave plate 301 for receiving two optical signals having different polarization directions from the input polarization beam splitter 201, and converting the same into circularly polarized light, and outputting the circularly polarized light to N ⁇ N
  • An array of N x N variable polarization gratings 401 is placed in the input quarter wave plate 301 and the output quarter Between the wave plates 302, for receiving circularly polarized light from the input quarter wave plate 301, the transmission path of the light is selected by changing the voltage of the array of N ⁇ N variable polarization gratings 401, and output to the selected output four.
  • variable polarization grating in an array of N ⁇ N variable polarization gratings 401 is very close to that of a conventional liquid crystal (LC).
  • the main difference is the fabrication of the liquid crystal alignment layer.
  • the alignment layer of the Nematic LC is typically brushed with a nylon cloth to the polymer layer on the glass surface or exposed to a single beam.
  • the liquid crystal alignment layer of the SPG is formed by exposing two layers of ultraviolet light-coherent polarized light to the polymer layer, as shown in FIG. 4(b), wherein one beam is right-handed polarized light. And the other bundle is left-handed polarized light.
  • the liquid crystal alignment layer includes a glass substrate, a photo alignment layer and an electrode.
  • the alignment of the liquid crystal molecules is arranged in a hologram pattern formed by the alignment layer after exposure.
  • FIG. 5 when no voltage is applied across the SPG, the liquid crystal molecules form a liquid crystal grating, which can diffract the incident light.
  • FIG. 6 when the voltage across the SPG is greater than or equal to the first threshold voltage Vth , the liquid crystal molecules are deflected toward the electric field, and the grating effect disappears.
  • the first threshold voltage is determined by the structure of the selected liquid crystal molecules and the variable polarization grating.
  • any variable polarization grating of N ⁇ N variable polarization gratings when any voltage applied across the variable polarization grating is less than a first threshold voltage, any of the variable polarization gratings Liquid crystal molecules form a liquid crystal grating to diffract incident light; when the voltage across the variable polarization grating is greater than or equal to a first threshold voltage, the liquid crystal molecules are directed to both ends of the variable polarization grating The direction of the electric field caused by the voltage is deflected, and the grating effect disappears;
  • variable polarization gratings In N ⁇ N variable polarization gratings, the voltage across the variable polarization grating that does not need to deflect the incident light is set to be greater than or equal to the first threshold voltage; the ends of the variable polarization grating that need to deflect the incident light The voltage is set to be less than the first threshold voltage; wherein the variable polarization grating that needs to deflect the incident light is corresponding to the input quarter wave plate and corresponds to the output quarter wave plate
  • the variable polarization grating that does not require deflection of incident light is a variable polarization grating in an N ⁇ N variable polarization grating array other than the variable polarization grating that needs to deflect incident light .
  • SPG has only three orders of magnitude, +1 and -1.
  • the polarizing beam splitter and the quarter-wave plate can decompose the incident light into left-handed circularly polarized light and right-handed circularly polarized light, and then left-handed circularly polarized light and right-handed circularly polarized light are respectively diffracted by SPG.
  • ⁇ 1 level as shown in Figure 7.
  • the incident light of any polarization state does not change after the SPG, and the propagation direction does not change; when the voltage across the SPG is less than the first threshold voltage V th
  • V 0 V
  • the right-handed circularly polarized light is diffracted to the +1 order to become a left-handed circularly polarized light
  • the left-handed circularly polarized light is diffracted to the -1st order to become a right-handed circularly polarized light.
  • ports C1, C2, C3, and C4 are incident ports; ports O1, O2, O3, and O4 are output ports; if C1-O3 is to be implemented, C2- O1, C3-O2, C4-O4 are cross-connected, and the SPG voltage needs to be set according to Table 1.
  • C1-O3 it is only necessary to apply a zero voltage to the SPG at the intersection of C1 and O3, and the remaining SPGs are boosted.
  • the high voltage is greater than or equal to the threshold voltage Vth .
  • Table 1 shows the SPG voltage settings for C1-O3, C2-O1, C3-O2, and C4-O4
  • the 4x4 optical switching device has an add-drop function.
  • the ports A1, A2, A3, and A4 are plug-in ports for inserting one or more wavelengths into the optical path; D1.
  • the D2, D3, and D4 ports are drop ports for separating one or more wavelengths from the optical path.
  • C1-O2, C2-O3, C3-D3, C4-O1, A4-O4 functions wherein C3 is sent to the Drop port D3, and A4 is added to the output port O4, and the SPG is set according to Table 2.
  • the voltage can be achieved.
  • Table 2 shows the SPG voltage settings for C1-O2, C2-O3, C3-D3, C4-O1, and A4-O4
  • An output polarization beam splitter 202 is provided for receiving optical signals from the two different polarization directions for polarization coupling and outputting to the output collimator 102.
  • the output polarization beam splitter 202 can be implemented by various techniques, such as by a birefringent crystal, a polarizing multilayer film, a polymer film, quartz glass etching, or the like. Specifically, it has been described in detail in the first embodiment of the present invention shown in FIG. 2 above, and is not described here.
  • the output collimator 102 is configured to receive an optical signal from the output polarization beam splitter 202 and couple the received optical signal into an optical fiber for output. Specifically, it has been described in detail in the first embodiment of the present invention shown in FIG. 2 above, and is not described here.
  • Embodiments of the present invention provide an optical switching device based on a liquid crystal grating, comprising: an input collimator 101, an input polarization beam splitter 201, an input quarter wave plate 301, an array of N ⁇ N variable polarization gratings 401, and an output.
  • the transmission path of the optical signal is selected by setting the voltage of the variable polarization grating 401 such that the optical signal is output to the selected output.
  • the optical switching device has a simple structure, a small size, and a low cost.
  • FIG. 8 is a schematic diagram showing the specific structure of an optical switching device based on a variable polarization grating/liquid crystal panel according to a third embodiment of the present invention.
  • a variable polarization grating/liquid crystal panel-based optical switching device includes: an input collimator 101, an input polarization beam splitter 201, an input quarter wave plate 301, and an N ⁇ The N variable polarization grating 401 / the liquid crystal panel 402 array, the output quarter wave plate 302, the output polarization beam splitter 202, and the output collimator 102.
  • This embodiment is similar to the second embodiment except that a liquid crystal panel 402 is added after each variable polarization grating 401 to form a variable polarization grating 401 / liquid crystal panel 402 combination.
  • a liquid crystal panel 402 is added after each variable polarization grating 401 to form a variable polarization grating 401 / liquid crystal panel 402 combination.
  • the liquid crystal panel 402 is mainly used to control the polarization state of light in the optical switching device of this embodiment.
  • the alignment method of the liquid crystal panel may be an electrically controlled birefringence (ECB) type or a vertical alignment (VA) type.
  • ECB electrically controlled birefringence
  • VA vertical alignment
  • V th2 is a second threshold voltage
  • the second threshold voltage V th2 is determined by the structure of the liquid crystal molecules and the liquid crystal cell in the liquid crystal cell.
  • the working principle of the VA type liquid crystal is that when the applied voltage is greater than or equal to the second threshold voltage Vth2 , the left-handed circularly polarized light is input, and the output is right-handed circularly polarized light, right.
  • the output When the circularly polarized light is input, the output is left-handed circularly polarized light.
  • the polarization directions of the signal light and the crosstalk light are the same. Therefore, in the second embodiment, cross-talk from other SPGs is coupled into the signal optical channel, thereby reducing the signal. Noise ratio.
  • a liquid crystal panel LC402 is added after the SPG sheet. As shown in FIG. 10, by setting the liquid crystal panel voltage, the circular polarization state of the crosstalk light can always be opposite to the circular polarization state of the signal light. Thus, after outputting the quarter-wave plate, the polarization state of the crosstalk light is perpendicular to the polarization state of the signal light, thereby being blocked by the output beam splitter. In this way, the signal to noise ratio can be greatly improved.
  • the combination of N ⁇ N variable polarization gratings and liquid crystal chips can realize the N ⁇ N optical cross function and have the function of Add/Drop.
  • the output path is selected by setting the voltages of the variable polarization grating and the liquid crystal panel, thereby implementing the optical cross function and the Add/Drop function. Specifically, it is described in detail in Embodiment 2 of the present invention in FIG. 3 above, and is not described herein.
  • Embodiments of the present invention provide an optical switching device based on a variable polarization grating/liquid crystal panel, comprising: an input collimator 101, an input polarization beam splitter 201, an input quarter wave plate 301, and an N ⁇ N variable polarization.
  • the transmission path of the optical signal is selected by setting the voltage of the N x N variable polarization grating 401 / liquid crystal panel 402 array such that the optical signal is output to the selected output.
  • Such an optical switching device The structure is simple, the size is small, and the cost is low.
  • the polarization state of the crosstalk light is perpendicular to the polarization state of the signal light, thereby being blocked by the output beam splitter. In this way, the signal to noise ratio can be greatly improved.
  • an optical switching device based on a polymer polarization grating/liquid crystal panel/polymer polarization grating combination according to Embodiment 4 of the present invention includes: an input collimator 101, an input polarization beam splitter 201, and an input quarter.
  • variable polarization grating 401 is replaced by a combination of a polymer polarization grating 4031 / a liquid crystal panel 402 / a polymer polarization grating 4032, wherein "/" represents two devices before and after "/" In the optical transmission path, the optical signal is output to the liquid crystal 402 via the polymer polarization grating 4031 and then output to the polymer polarization grating 4032.
  • FIG. 12 the manufacturing process of Polymer Polarization Grating (PPG) is as shown in FIG. 12, firstly, a photopolymer material (photo-alignment material) is coated on a glass substrate (as shown in FIG. 12(a). Show), then expose it with two beams of coherent light to form a hologram (as shown in Figure 12 (b)), and then apply polymerizable liquid crystal on the photosensitive layer (as shown in Figure 12 (c)), and then The polymerizable liquid crystal is exposed to uniform UV light to cure it, and the liquid crystal molecules are arranged in accordance with the hologram pattern of the photosensitive layer to form a fixed grating (as shown in Fig. 12(d)).
  • PPG Polymer Polarization Grating
  • PPG is a fixed grating, so it is not possible to change its performance by applying a voltage.
  • the right-handed circularly polarized light is diffracted to the +1st order to become a left-handed circularly polarized light
  • the left-handed circularly polarized light is diffracted to the -1st order, and becomes a right-handed circularly polarized light. Therefore PPG has only two light output directions.
  • the liquid crystal panel 402 is for controlling the deflection of the optical signal incident on the liquid crystal panel 402 by setting the voltage across the liquid crystal panel 402.
  • the liquid crystal panel 402 may be an ECB type liquid crystal, or a VA type liquid crystal, an ECB type liquid crystal, and a VA type liquid crystal. Specifically, it is described in detail in the third embodiment of the present invention, and is not described herein.
  • the N ⁇ N PPG/LC/PPG combination can realize an N ⁇ N optical crossbar function.
  • the liquid crystal cell is a VA type liquid crystal, and an ECB type liquid crystal can also be used.
  • the voltage applied to the liquid crystal panel is greater than or equal to the second threshold, the polarization direction of the light is changed, so that the emitted light is deflected.
  • the 4 ⁇ 4 optical crossbar function and the Add/Drop function can be realized.
  • the liquid crystal panel 402 is a VA type liquid crystal film, then:
  • the voltage across the liquid crystal panel 402 that does not need to deflect the incident light is set to be smaller than the second threshold voltage; the voltage across the liquid crystal panel 402 that needs to deflect the incident light is set to be greater than or equal to the second threshold voltage;
  • the liquid crystal panel 402 that needs to deflect the incident light is a liquid crystal panel corresponding to the input quarter wave plate 301 and corresponding to the output quarter wave plate 302, and the liquid crystal wafer 402 that does not need to deflect the incident light It is a liquid crystal cell 402 other than the liquid crystal panel 402 which needs to deflect the incident light in the array of N x N liquid crystal cells 402.
  • the liquid crystal chip 402 is an ECB type liquid crystal film, then:
  • the voltage across the liquid crystal panel 402 that does not need to deflect the incident light is set to be greater than or equal to the second threshold voltage; the voltage across the liquid crystal panel 402 that needs to deflect the incident light is set to be less than the second threshold voltage;
  • the liquid crystal panel 402 that needs to deflect the incident light is a liquid crystal panel corresponding to the input quarter wave plate 301 and corresponding to the output quarter wave plate 302, and the liquid crystal wafer 402 that does not need to deflect the incident light It is a liquid crystal cell other than the liquid crystal panel 402 which needs to deflect the incident light in the array of N ⁇ N liquid crystal chips 402.
  • C1, C2, C3, C4 ports are incident ports; O1, O2, O3, O4 ports are output ports; only need to set the liquid crystal voltage according to Table 3, Cross-linking of C1-O3, C2-O1, C3-O2, C4-O4 can be achieved.
  • Table 3 shows the voltage settings of the LC array of C1-O3, C2-O1, C3-O2, C4-O4
  • the system can realize the optical cross-switch function and Add/Drop function at the same time.
  • the ports A1, A2, A3 and A4 are plug-in ports for inserting one or more wavelengths into the optical path; D1, D2, D3
  • the D4 port is a drop port for separating one or more wavelengths from the optical path.
  • the function of each port is described in detail in the second embodiment, and details are not described herein again.
  • the voltage of the LC array can be set according to Table 3.
  • Table 3 shows the voltage settings of the LC array of C1-O3, C2-O4, C3-D3, C4-O2, and A1-O1
  • Embodiments of the present invention provide an optical switching device based on a polymer polarization grating/liquid crystal panel/polymer polarization grating, comprising: an input collimator 101, an input polarization beam splitter 201, an input quarter wave plate 301, and a PPG4031. /LC402/PPG4032, output quarter wave plate 302, output polarization beam splitter 202, and output collimator 102.
  • the transmission path of the optical signal is selected by setting the voltage of the liquid crystal panel 402 so that the optical signal is output to the selected output terminal.
  • the optical switching device has a simple structure, a small size, and a low cost.
  • FIG. 14 is a schematic structural diagram of an optical switching device based on PPG/LC/PPG/LC according to Embodiment 5 of the present invention. As shown in FIG. 14, the optical switching based on PPG/LC/PPG/LC according to Embodiment 5 of the present invention is shown.
  • the device comprises: an input collimator 101, an input polarization beam splitter 201, an input quarter wave plate 301, an N ⁇ NPPG4031/LC4021/PPG4032/LC4022 array, an output quarter wave plate 302, and an output polarization beam splitter 202.
  • the collimator 102 is output.
  • This embodiment is similar to the fourth embodiment except that a liquid crystal cell 4022 is added after each of the polymer polarization grating 4031/liquid crystal panel 4021/polymer polarization grating 4032 to form a polymer polarization grating 4031/liquid crystal 4021/polymer polarization.
  • the grating 4032/liquid crystal 4022 is combined.
  • the liquid crystal film can be selected from the VA type or the ECB type liquid crystal.
  • the working principle of the VA type liquid crystal and the ECB type liquid crystal is described in detail in the third embodiment, and details are not described herein again.
  • the principle of suppressing crosstalk light is similar to that of the third embodiment, such that the polarization direction of the crosstalk light is opposite to the polarization direction of the signal light, thereby being intercepted by the polarization beam splitter 202 at the output end. Therefore, the signal to noise ratio of the system can be greatly improved.
  • Embodiments of the present invention provide an optical switching device based on a variable polarization grating/liquid crystal panel, comprising: an input collimator 101, an input polarization beam splitter 201, an input quarter wave plate 301, and an N ⁇ N PPG4031/LC4021. /PPG4032/LC4022 array, output quarter wave plate 302, output polarization beam splitter 202, output collimator 102.
  • the transmission path of the optical signal is selected by setting the voltage of the LC4021 so that the optical signal is output to the selected output.
  • the optical switching device has the advantages of simple structure, small size and low cost.
  • the polarization state of the crosstalk light is perpendicular to the polarization state of the signal light, thereby being blocked by the output beam splitter. In this way, the signal to noise ratio can be greatly improved.

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Abstract

本发明实施例提供了一种基于液晶光栅的光交换装置，包括：输入准直器101、输入偏振分光器201、输入四分之一波片301、液晶光栅4、输出四分之一波片302、输出偏振分光器202、输出准直器102。通过改变液晶光栅的电压，来选择光信号的传输路径，使得光信号输出至选定输出端。这种光交换装置结构简单、尺寸小、成本低。

Description

[根据细则37.2由ISA制定的发明名称]　一种基于液晶光栅的光开关 技术领域
本发明涉及通信领域，尤其涉及一种基于液晶光栅的光开关。
背景技术
在以波分复用技术(Wavelength Division Multiplexing,WDM)为基础的现有通信网络中，网络的各个节点要完成光-电-光的转换，仍以电信号处理信息的方式进行交换。其中的电子件在适应高速、大容量的需求上，存在着诸如带宽限制、时钟偏移、严重串话、高功耗等缺点，由此产生了通信网中的“电子瓶颈”现象。为了解决这个问题，人们提出了全光网(All Optical Network,AON)的概念，全光网以其良好的透明性、波长路由特性、兼容性和可扩展性，已成为下一代高速宽带网络的首选。
光交叉连接(Optical Cross Connection,OXC)是全光网中的核心器件，它与光分插复用器(Optical Add-Drop Multiplexer,OADM)、掺饵光纤放大器(Erbium-doped Optical Fiber Amplifier,EDFA)、衰减器、光纤等器件和设备组成了全光网络。OXC交换的是全光信号，它在网络节点处，对指定波长进行互连，从而有效地利用波长资源，实现波长重用，也就是使用较少数量的波长，互连较大数量的网络节点。当光纤中断或业务失效时，OXC能够自动完成故障隔离、重新选择路由和网络重新配置等操作，使业务不中断，即它具有高速光信号的路由选择、网络恢复等功能。
目前市场上有基于液晶(Liquid Crystal,LC)和偏振分光器(Polarization Beam Splitter,PBS)的OXC，如图1所示，主要由光准直器、分束器displacer、PBS阵列、LC阵列组成。光准直器用于输入和输出光，Displaycer用于将输入光转变为同一偏振光和将输出端偏振光耦合进光准直器，PBS用于分、合偏振光，LC用于控制光的偏振方向。通过控制LC阵列的电压来控制光在每一节点的偏振方向，从而实现将任意一束输入光传输到所要求的输出端口。该技术方案装配难度大、体积大、成本高。
发明内容
本发明实施例提供了一种基于液晶光栅的光开关，通过可变偏振光栅实现光交叉互连，解决了现有技术基于LC和PBS的光交叉互连装配难度大、体积大、成本高的技术问题。
第一方面，本发明实施例提供了一种光交换装置，包括输入准直器、输出准直器，还包括：输入偏振分光器、输入四分之一波片、输出四分之一波片、输出偏振分光器和N×N液晶光栅阵列，其中，N为大于或等于2的整数；
所述输入偏振分光器置于所述输入准直器与所述输入四分之一波片之间，用于将来自所述输入准直器的输入光信号分成两个具有不同偏振方向的光信号，并将所述两个具有不同偏振方向的光信号输出至所述输入四分之一波片；
所述输入四分之一波片置于所述输入偏振分光器与所述N×N液晶光栅阵列之间，用于接收来自所述输入偏振分光器的所述两个具有不同偏振方向的光信号，并将所述两个具有不同偏振方向的光信号耦合成圆偏振光，将所述圆偏振光输出到所述N×N液晶光栅阵列；
所述N×N液晶光栅阵列置于所述输入四分之一波片与所述输出四分之一波片之间，用于通过N×N液晶光栅阵列中与所述输入四分之一波片对应的液晶光栅接收来自所述输入四分之一波片的所述圆偏振光，并将所述圆偏振光通过选定的传输路径输出至选定的输出四分之一波片；其中，所述选定的传输路径是通过设置N×N液晶光栅阵列中液晶光栅的电压来选择的；
所述输出四分之一波片置于所述N×N液晶光栅阵列与所述输出偏振分光器之间，用于将来自所述N×N液晶光栅阵列的圆偏振光分成两个具有不同偏振方向的光信号，并将所述两个具有不同偏振方向的光信号输出至所述输出偏振分光器；
所述输出偏振分光器置于所述输出四分之一波片与所述输出准直器之间，用于将来自所述输出四分之一波片的所述两个具有不同偏振方向的光信号耦合进所述输出准直器。
在第一方面的第一种可能的实现方式中，所述N×N液晶光栅阵列中液晶光栅包括N×N可变偏振光栅、N×N可变偏振光栅/液晶片组合、N×N聚合 物偏振光栅/液晶片/聚合物偏振光栅组合、或N×N聚合物偏振光栅/液晶片/聚合物偏振光栅/液晶片组合。
结合第一方面，或者第一种可能的实现方式中的任意一种可能的实现方式，在第二种可能的实现方式中，
对于N×N个可变偏振光栅中任一可变偏振光栅，当所述任一可变偏振光栅两端所加电压小于第一阈值电压时，所述任一可变偏振光栅中的液晶分子形成液晶光栅，对入射光进行衍射；当所述任一可变偏振光栅两端电压大于或等于第一阈值电压时，所述液晶分子向由所述任一可变偏振光栅两端电压造成的电场方向偏转，光栅效应消失；
在N×N可变偏振光栅中，不需要对入射光进行偏转的可变偏振光栅两端电压被设置为大于或等于第一阈值电压；需要对入射光进行偏转的可变偏振光栅两端电压被设置为小于第一阈值电压；其中，所述需要对入射光进行偏转的可变偏振光栅为与所述输入四分之一波片对应并且与所述输出四分之一波片对应的可变偏振光栅，所述不需要对入射光进行偏转的可变偏振光栅为N×N可变偏振光栅阵列中除所述需要对入射光进行偏转的可变偏振光栅之外的可变偏振光栅。
结合第一方面第二种可能的实现方式，在第三种可能的实现方式中，所述需要对入射光进行偏转的可变偏振光栅两端电压被设置为零。
结合第一方面第二种或第三种可能的实现方式中，在第四种可能的实现方式中，当所述任一可变偏振光栅两端所加电压小于第一阈值电压时，所述任一可变偏振光栅有0级、+1级和-1级三个衍射级次；入射的右旋圆偏振光被所述任一可变偏振光衍射到+1级，变成左旋圆偏振光；入射的左旋圆偏振光被所述任一可变偏振光衍射到-1级，变成右旋圆偏振光。
结合第一方面第二到第四种中任意一种可能的实现方式，在第五种可能的实现方式中，输出信号光的圆偏振态与输出串扰光的圆偏振态相反；其中，通过设置所述液晶片两端的电压来控制入射所述液晶片的光信号的偏振态。
结合第一方面第五种可能的实现方式，在第六种可能的实现方式中，
当任一液晶片所加电压小于第二阈值电压时，所述任一液晶片的输出光与所述任一液晶片的输入光偏振态一致；
当所述任一液晶片所加电压大于或等于第二阈值电压时，
若左旋圆偏振光输入所述任一液晶片，则所述任一液晶片输出右旋圆偏振光；
若右旋圆偏振光输入所述任一液晶片，则所述任一液晶片输出左旋圆偏振光。
结合第一方面第五种可能的实现方式，在第七种可能的实现方式中，
当任一液晶片所加电压大于或等于第二阈值电压时，所述任一液晶片的输出光与所述液晶片的输入光偏振态一致；
当所述任一液晶片所加电压小于第二阈值电压时，
若左旋圆偏振光输入所述任一液晶片，则所述任一液晶片输出右旋圆偏振光；
若右旋圆偏振光输入所述任一液晶片，则所述任一液晶片输出左旋圆偏振光。
结合第一方面，或者第一种可能的实现方式中的任意一种可能的实现方式，在第八种可能的实现方式中，任一聚合物偏振光栅/液晶片/聚合物偏振光栅组合包括：第一聚合物偏振光栅、第一液晶片和第二聚合物偏振光栅；
所述第一聚合物偏振光栅与第二聚合物偏振光栅均为固定光栅；
若输入右旋圆偏振光，则被所述第一聚合物偏振光栅或第二聚合物偏振光栅衍射到+1级，输出左旋圆偏振光；若输入左旋圆偏振光，则被所述第一聚合物偏振光栅或第二聚合物偏振光栅衍射到-1级，输出右旋圆偏振光；
所述第一液晶片，用于通过设置所述第一液晶片两端的电压来控制入射所述液晶片的光信号的偏转。
结合第一方面第八种可能的实现方式，在第九种可能的实现方式中，
当所述第一液晶片所加电压大于或等于第二阈值电压时，
若左旋圆偏振光输入所述第一液晶片，则所述第一液晶片输出右旋圆偏振光；
若右旋圆偏振光输入所述第一液晶片，则所述第一液晶片输出左旋圆偏振 光。
不需要对入射光进行偏转的所述第一液晶片两端电压被设置为小于所述第二阈值电压；需要对入射光进行偏转的所述第一液晶片两端电压被设置为大于或等于所述第二阈值电压；其中，所述需要对入射光进行偏转的所述第一液晶片为与所述输入四分之一波片对应并且与所述输出四分之一波片对应的所述第一液晶片，所述不需要对入射光进行偏转的所述第一液晶片为N×N个所述第一液晶片阵列中除所述需要对入射光进行偏转的所述第一液晶片之外的第一液晶片。
结合第一方面第八种可能的实现方式，在第一十种可能的实现方式中，
当所述第一液晶片所加电压小于第二阈值电压时，
若左旋圆偏振光输入所述第一液晶片，则所述第一液晶片输出右旋圆偏振光；
若右旋圆偏振光输入所述第一液晶片，则所述第一液晶片输出左旋圆偏振光。
不需要对入射光进行偏转的所述第一液晶片两端电压被设置为大于或等于所述第二阈值电压；需要对入射光进行偏转的所述第一液晶片两端电压被设置为小于所述第二阈值电压；其中，所述需要对入射光进行偏转的所述第一液晶片为与所述输入四分之一波片对应并且与所述输出四分之一波片对应的所述第一液晶片，所述不需要对入射光进行偏转的所述第一液晶片为N×N个所述第一液晶片阵列中除所述需要对入射光进行偏转的所述第一液晶片之外的第一液晶片。
结合第一方面第八种可能的实现方式，在第一十一种可能的实现方式中，输出信号光的圆偏振态与输出串扰光的圆偏振态相反；其中，通过设置所述第二液晶片两端的电压来控制入射所述第二液晶片的光信号的偏振态。
结合第一方面第一十一种可能的实现方式，在第一十二种可能的实现方式中，
当任一第二液晶片所加电压小于第二阈值电压时，所述任一第二液晶片的输出光与输入光偏振态一致；
当所述任一第二液晶片所加电压大于或等于第二阈值电压时，
若左旋圆偏振光输入所述任一第二液晶片，则所述任一第二液晶片输出右旋圆偏振光；
若右旋圆偏振光输入所述任一液晶片，则所述任一液晶片输出左旋圆偏振光。
结合第一方面第一十一种可能的实现方式，在第一十三种可能的实现方式中，所述N×N个第二液晶片为电控双折射液晶
当任一第二液晶片所加电压大于第或等于二阈值电压时，所述任一第二液晶片的输出光与输入光偏振态一致；
当所述任一第二液晶片所加电压小于第二阈值电压时，
若左旋圆偏振光输入所述任一第二液晶片，则所述任一第二液晶片输出右旋圆偏振光；
若右旋圆偏振光输入所述任一第二液晶片，则所述任一第二液晶片输出左旋圆偏振光。
本发明实施例提供了一种基于液晶光栅的光交换装置，包括：输入准直器、输入偏振分光器、输入四分之一波片、N×N液晶光栅阵列、输出四分之一波片、输出偏振分光器、输出准直器。输入光经过输入偏振分光器和输入四分之一波片后变为圆偏振光。通过改变液晶光栅的电压来选择光的传输路径，输出至指定端口，经过输出四分之一波片和输出偏振分光器而耦合进输出准直器。进而实现N×N光交叉开关功能和光分插复用(Add/Drop)功能。通过设置液晶光栅的电压来选择光传输路径，简化了光交换装置,降低了成本，且器件尺寸小。下面通过具体实施例进行说明。
附图说明
为了更清楚地说明本发明实施例或现有技术中的技术方案，下面将对实施例或现有技术描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本发明的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其他的附图。
图1是现有技术中一种光交换装置的结构示意图；
图2本发明实施例一中的一种基于液晶光栅的光交换装置的结构示意图；
图3是本发明实施例二的一种基于可变偏振光栅的光交换装置的具体结构示意图；
图4是可变偏振光栅液晶对准层的制备流程示意图；
图5是可变偏振光栅两端电压为0V时液晶分子排布示意图；
图6是可变偏振光栅两端电压大于第一阈值电压时液晶分子排布示意图；
图7是可变偏振光栅原理示意图；
图8是本发明实施例三的一种基于可变偏振光栅/液晶片的光交换装置的具体结构示意图；
图9是垂直排列VA型液晶片的原理示意图；
图10是可变偏振光栅/液晶组合原理示意图；
图11是本发明实施例四的一种基于聚合物偏振光栅/液晶片/聚合物偏振光栅组合的光交换装置的具体结构示意图；
图12是聚合物偏振光栅的制作流程示意图；
图13是聚合物偏振光栅原理示意图；
图14是本发明实施例五的一种基于聚合物偏振光栅/液晶片/聚合物偏振光栅/液晶片组合的光交换装置的具体结构示意图；
具体实施方式
下面将结合本发明实施例中的附图，对本发明实施例中的技术方案进行清楚的描述，显然，所描述的实施例仅仅是本发明一部分实施例，而不是全部的实施例。基于本发明中的实施例，本领域普通技术人员在没有作出创造性劳动前提下所获得的所有其他实施例，都属于本发明保护的范围。
本发明实施例提供了一种基于液晶光栅的光交换装置，包括：输入准直器、输入偏振分光器、输入四分之一波片、液晶光栅、输出四分之一波片、输出偏振分光器、输出准直器。输入光经过输入偏振分光器和输入四分之一波片后变为圆偏振光。通过改变液晶光栅的电压来选择光的传输路径，输出至指定端口，经过输出四分之一波片和输出偏振分光器而耦合进输出准直器。进而实现N×N光交叉开关功能和光分插复用(Add/Drop)功能。通过设置液晶光栅的电压来选择光传输路径，简化了光交换装置,降低了成本，且器件尺寸小。下面通 过具体实施例进行说明。
实施例一
图2是本发明实施例一的一种基于液晶光栅的光交换装置的结构示意图。如图所示，本发明实施例中的基于液晶光栅的光交换装置，包括：输入准直器101、输入偏振分光器201、输入四分之一波片301、N×N液晶光栅4阵列、输出四分之一波片302、输出偏振分光器202、输出准直器102。其中，N为大于或等于2的整数。
输入准直器101，用于接收从光纤输入的光信号，输入准直器101是外围光信号的入射端口，光信号经过输入光纤进入到输入准直器101，输入准直器101把输入的光信号进行光束整形，使它们的束腰变大，发散角变小，从而使得这些输入的光信号能在自由空间内传输更远的距离。
输入偏振分光器201，置于输入准直器101与输入四分之一波片301之间，用于对来自输入准直器101的输入光信号分成具有两个不同偏振方向的光信号，并将所述两个具有不同偏振方向的光信号输出至输入四分之一波片301。偏振分光器201可以通过多种技术实现，例如通过双折射晶体、偏振多层膜、高分子膜、石英玻璃刻蚀等来实现。
输入四分之一波片301，置于输入偏振分光器201与液晶光栅4之间，用于接收来自偏振分光器201的所述两个具有不同偏振方向的光信号，并将其转化为圆偏振光，将圆偏振光输出至N×N液晶光栅4阵列。
N×N液晶光栅4阵列，置于输入四分之一波片301和输出四分之一波片302之间，用于通过N×N液晶光栅4阵列中与所述输入四分之一波片对应的液晶光栅接收来自输入四分之一波片301的圆偏振光，并将所述圆偏振光通过选定的传输路径输出至选定的输出四分之一波片302；其中，所述选定的传输路径是通过设置N×N液晶光栅4阵列中液晶光栅的电压来选择的。
输出四分之一波片302，置于N×N液晶光栅4阵列与输出偏振分光器202之间，用于接收来自N×N液晶光栅4阵列的圆偏振光，并将所述圆偏振光转化为两个具有不同偏振方向的光信号，将所述两个具有不同偏振方向的光信号输出至偏振分光器202。
输出偏振分光器202，置于输出四分之一波片302与输出准直器102之间，用于将来自输出四分之一波片302的所述两个具有不同偏振方向的光信号进行偏振耦合并输出至输出准直器102。输出偏振分光器202与输入偏振分光器201实现方式一样，在此不再赘述。
输出准直器102，用于接收输出偏振分光器202输出的光信号，将接收的光信号耦合到光纤中进行输出。
本发明实施例提供了一种基于液晶光栅的光交换装置，包括：输入准直器101、输入偏振分光器201、输入四分之一波片301、N×N液晶光栅4阵列、输出四分之一波片302、输出偏振分光器202、输出准直器102。通过改变液晶光栅的电压，来选择光信号的传输路径，使得光信号输出至选定输出端。这种光交换装置结构简单、尺寸小、成本低。
实施例二
图3是本发明实施例二的一种基于可变偏振光栅的光交换装置的具体结构示意图。如图3所示，本发明实施例二的基于可变偏振光栅的光交换装置，包括：输入准直器101、输入偏振分光器201、输入四分之一波片301、N×N可变偏振光栅401阵列、输出四分之一波302、输出偏振分光器202、输出准直器102。其中：
输入准直器101，用于接收从光纤输入的光信号，把光纤输入的光信号进行光束整形，输出至输入偏振分光器201。具体已在上述图2本发明第一实施例中详述，在此不累述。
输入偏振分光器201，用于对来自输入准直器101的输入光信号分成两个具有不同偏振方向的光信号，并将所述具有两个不同偏振方向的光信号输出至输入四分之一波片301。具体已在上述图2本发明第一实施例中详述，在此不累述。
输入四分之一波片301，用于接收来自输入偏振分光器201的两个具有不同偏振方向的光信号，并将其转化为圆偏振光，将所述圆偏振光输出至N×N可变偏振光栅401阵列。
N×N可变偏振光栅401阵列置于输入四分之一波片301和输出四分之一 波片302之间，用于接收来自输入四分之一波片301的圆偏振光，通过改变N×N可变偏振光栅401阵列的电压来选择光的传输路径，输出至选定的输出四分之一波片302。
在具体应用中，N×N可变偏振光栅401阵列中可变偏振光栅(Switchable Polarization Grating，SPG)的结构和制作工艺与传统液晶片(Liquid Crystal，LC)的制作很接近。主要差别在于液晶对准层的制作。Nematic(向列型)LC的对准层一般用尼龙布对玻璃表面的聚合物层刷擦而成或者用单光束曝光而成。如图4所示，SPG的液晶对准层则是由两束紫外相干偏振光对聚合物层曝光而成，如图4(b)上方的两列光束，其中一束光为右旋偏振光，而另一束为左旋偏振光。液晶对准层如图4包括玻璃基板，光取向层和电极，当液晶被注入两玻璃基板间后，液晶分子取向按曝光后在对准层形成的全息图样排列。如图5所示，在SPG两端不加电压时，液晶分子形成液晶光栅，可对入射光进行衍射。如图6所示，当SPG两端电压大于或等于第一阈值电压Vth时，液晶分子向电场方向偏转，光栅效应消失。其中，所述第一阈值电压由所选液晶分子以及可变偏振光栅的结构决定。
具体的，对于N×N个可变偏振光栅中任一可变偏振光栅，当所述任一可变偏振光栅两端所加电压小于第一阈值电压时，所述任一可变偏振光栅中的液晶分子形成液晶光栅，对入射光进行衍射；当所述任一可变偏振光栅两端电压大于或等于第一阈值电压时，所述液晶分子向由所述任一可变偏振光栅两端电压造成的电场方向偏转，光栅效应消失；
在N×N个可变偏振光栅中，不需要对入射光进行偏转的可变偏振光栅两端电压被设置为大于或等于第一阈值电压；需要对入射光进行偏转的可变偏振光栅两端电压被设置为小于第一阈值电压；其中，所述需要对入射光进行偏转的可变偏振光栅为与所述输入四分之一波片对应并且与所述输出四分之一波片对应的可变偏振光栅，所述不需要对入射光进行偏转的可变偏振光栅为N×N可变偏振光栅阵列中除所述需要对入射光进行偏转的可变偏振光栅之外的可变偏振光栅。
SPG只有0级、+1级和-1级三个衍射级次。根据入射光的偏振态不同，偏振分光器和四分之一波片可以将入射光分解成左旋圆偏振光和右旋圆偏振光， 然后左旋圆偏振光和右旋圆偏振光分别被SPG衍射到±1级，如图7所示。具体的，当SPG两端电压大于或等于第一阈值电压Vth时，任何偏振态的入射光经过SPG后偏振态不变，传播方向不变；当SPG两端电压小于第一阈值电压Vth时，例如，V＝0V，右旋圆偏光被衍射到+1级，变成左旋圆偏光，左旋圆偏光被衍射到-1级，变成右旋圆偏光。
具体的，以4x4光交换装置为例，如图3所示，C1、C2、C3、C4端口为入射端口；O1、O2、O3、O4端口为输出端口；如要实现C1-O3，C2-O1，C3-O2，C4-O4交叉连接，需要按照表1设置SPG电压。例如，要实现C1-O3，只需将位于C1和O3交叉点的SPG加零电压，其余SPG加高电压，具体的，所述高电压大于或等于阈值电压Vth。这样，光从C1的准直器输入，通过两片SPG后传输方向不变，再经过第三片SPG(电压为0V)后被衍射而偏向O3，而后耦合进O3的准直器。从而实现了C1到O3的光传输。
表1实现C1-O3,C2-O1,C3-O2,C4-O4的SPG电压设置
表1 O1 O2 O3 O4
C4 ON ON ON OFF
C3 ON OFF ON ON
C2 OFF ON ON ON
C1 ON ON OFF ON
本4x4光交换装置具有光分插复用(Add-Drop)功能，如图3所示，A1、A2、A3、A4端口为插入端口，用于往光路中插入一个或多个波长；D1、D2、D3、D4端口为分出端口，用于从光路中分出一个或多个波长。例如，要实现C1-O2,C2-O3,C3-D3,C4-O1,A4-O4功能，其中，将C3送到Drop端口D3，同时将A4加入到输出端口O4，按表2设置SPG的电压即可实现。
表2实现C1-O2,C2-O3,C3-D3,C4-O1,A4-O4的SPG电压设置
表2 O1 O2 O3 O4  
C4 OFF ON ON ON D4
C3 ON ON ON ON D3
C2 ON ON OFF ON D2
C1 ON OFF ON ON D1
  A1 A2 A3 A4  
输出四分之一波片302，用于接收来自N×N可变偏振光栅401阵列的光信号，并将其转化为两个具有不同偏振方向的光信号，将所述具有两个不同偏振方向的光信号输出至偏振分光器202。具体已在上述图2本发明第一实施例中详述，在此不累述。
输出偏振分光器202，用于接收来自所述具有两个不同偏振方向的光信号进行偏振耦合并输出至输出准直器102。输出偏振分光器202可以通过多种技术实现，例如通过双折射晶体、偏振多层膜、高分子膜、石英玻璃刻蚀等来实现。具体已在上述图2本发明第一实施例中详述，在此不累述。
输出准直器102，用于接收来自输出偏振分光器202的光信号，将接收的光信号耦合到光纤中进行输出。具体已在上述图2本发明第一实施例中详述，在此不累述。
本发明实施例提供了一种基于液晶光栅的光交换装置，包括：输入准直器101、输入偏振分光器201、输入四分之一波片301、N×N可变偏振光栅401阵列、输出四分之一波片302、输出偏振分光器202、输出准直器102。通过设置可变偏振光栅401的电压，来选择光信号的传输路径，使得光信号输出至选定输出端。这种光交换装置结构简单、尺寸小、成本低。
实施例三
图8是本发明实施例三的一种基于可变偏振光栅/液晶片的光交换装置的具体结构示意图。如图8所示，本发明实施例三的基于可变偏振光栅/液晶片的光交换装置，包括：输入准直器101、输入偏振分光器201、输入四分之一波片301、N×N可变偏振光栅401/液晶片402阵列、输出四分之一波片302、输出偏振分光器202、输出准直器102。
本实施例与实施例二方案类似，只是在每个可变偏振光栅401后增加了一个液晶片402，形成可变偏振光栅401/液晶片402组合。通过对N×N可变偏振光栅401/液晶片402阵列电压的控制，使串扰光的圆偏振态与信号光的圆偏 振态相反。经过输出四分之一波片302后，串扰光的偏振态与信号光的偏振态垂直，从而被输出端的输出偏振分光器所阻断。这样，就可将信噪比大大的提高。
具体的，液晶片402在本实施例的光交换装置中主要是用来控制光的偏振态。可选的，液晶片的对准方法可以是电控双折射(Electrically Controlled Birefringence，ECB)型或垂直排列(Vertical Alignment，VA)型。其中，ECB型液晶，V＜Vth2时，例如，V＝0V，为双折射晶体；V≥Vth2时，无双折射效应。VA型液晶，V＜Vth2时，例如，V＝0V，无双折射效应；V≥Vth2时，为双折射晶体。其中，Vth2为第二阈值电压，第二阈值电压Vth2由液晶片中液晶分子和液晶片的结构所决定。
以VA型为例，如图9所示，VA型液晶的工作原理是，当所加电压大于或等于第二阈值电压Vth2时，左旋圆偏振光输入，则输出为右旋圆偏振光，右旋圆偏振光输入，则输出为左旋圆偏振光。当所加电压小于第二阈值电压时，例如V＝0V，输出光与输入光的偏振态一致。
如图10所示，光经SPG后，信号光和串扰光的偏振方向相同，因而，在实施例二中，来自其他SPG的串扰光(cross-talk)会耦合进信号光通道，从而降低信噪比。本发明实施例在SPG片后加一液晶片LC402，如图10，通过设置液晶片电压，可使串扰光的圆偏振态始终与信号光的圆偏振态相反。这样，经过输出四分之一波片后，串扰光的偏振态与信号光的偏振态垂直，从而被输出分光器所阻断。这样，就可将信噪比大大的提高。
同实施例二方案类似，N×N个可变偏振光栅与液晶片的组合可以实现N×N的光交叉功能，并具有Add/Drop的功能。通过设置可变偏振光栅和液晶片的电压来选择输出路径，进而实现光交叉功能和Add/Drop功能。具体已在上述图3本发明实施例二中详述，在此不累述。
本发明实施例提供了一种基于可变偏振光栅/液晶片的光交换装置，包括：输入准直器101、输入偏振分光器201、输入四分之一波片301、N×N可变偏振光栅401/液晶片402阵列、输出四分之一波片302、输出偏振分光器202、输出准直器102。通过设置N×N可变偏振光栅401/液晶片402阵列的电压，来选择光信号的传输路径，使得光信号输出至选定输出端。这种光交换装置结 构简单、尺寸小、成本低；同时通过设置液晶片的电压，使串扰光的偏振态与信号光的偏振态垂直，从而被输出分光器所阻断。这样，就可将信噪比大大的提高。
实施例四
图11是本发明实施例四的一种基于聚合物偏振光栅/液晶片/聚合物偏振光栅组合的光交换装置的结构示意图。如图11所示，本发明实施例四的基于聚合物偏振光栅/液晶片/聚合物偏振光栅组合的光交换装置，包括：输入准直器101、输入偏振分光器201、输入四分之一波片301、N×N聚合物偏振光栅4031/液晶片402/聚合物偏振光栅4032阵列、输出四分之一波片302、输出偏振分光器202、输出准直器102。
本实施例与实施例二的方案类似，只是将可变偏振光栅401替换成聚合物偏振光栅4031/液晶片402/聚合物偏振光栅4032组合，其中，“/”表示“/”前后两个器件在光传输路径中为紧邻关系，即光信号经聚合物偏振光栅4031输出至液晶402，然后输出至聚合物偏振光栅4032。
在具体应用中，聚合物偏振光栅(Polymer Polarization Grating，PPG)的制作工艺流程如图12所示，首先将光敏聚合物材料(光取向材料)涂在玻璃基板上(如图12(a)所示)，然后用两束相干光对其曝光而形成全息图(如图12(b)所示)，再将可聚合物液晶涂在光敏层上(如图12(c)所示)，然后用均匀UV光对可聚合液晶曝光，从而将其固化，这时液晶分子依照光敏层的全息图型排布而形成一固定光栅(如图12(d)所示)。
PPG为固定光栅，所以不能通过加电压来改变其性能。如图13所示，右旋圆偏光被衍射到+1级，变成左旋圆偏光，左旋圆偏光被衍射到-1级，变成右旋圆偏光。因此PPG只有两个光输出方向。
液晶片402，用于通过设置液晶片402两端的电压来控制入射液晶片402的光信号的偏转。
可选的，液晶片402可以为ECB型液晶、或VA型液晶，ECB型液晶和VA型液晶的原理，具体已在上述图8本发明实施例三中详述，在此不累述。
N×N个PPG/LC/PPG组合可以实现N×N的光交叉开关功能。具体的， 以4×4个PPG/LC/PPG组合为例，如图11所示，其中液晶片为VA型液晶，也可使用ECB型液晶。当液晶片所加电压大于或等于第二阈值时，改变光的偏振方向，从而出射光发生偏转。而当液晶片所加电压小于第二阈值电压时，具体的，所加电压V＝0V，不改变光的偏振方向，从而出射光与光轴平行。这样，通过设置液晶片的电压，就可实现4×4光交叉开关功能和Add/Drop功能。
可选的，液晶片402为VA型液晶片，则：
不需要对入射光进行偏转的液晶片402两端电压被设置为小于第二阈值电压；需要对入射光进行偏转的液晶片402两端电压被设置为大于或等于第二阈值电压；其中，所述需要对入射光进行偏转的液晶片402为与输入四分之一波片301对应并且与输出四分之一波片302对应的液晶片，所述不需要对入射光进行偏转的液晶片402为N×N个液晶片402阵列中除所述需要对入射光进行偏转的液晶片402之外的液晶片402。
可选的，液晶片402为ECB型液晶片，则：
不需要对入射光进行偏转的液晶片402两端电压被设置为大于或等于第二阈值电压；需要对入射光进行偏转的液晶片402两端电压被设置为小于第二阈值电压；其中，所述需要对入射光进行偏转的液晶片402为与输入四分之一波片301对应并且与输出四分之一波片302对应的液晶片，所述不需要对入射光进行偏转的液晶片402为N×N个液晶片402阵列中除所述需要对入射光进行偏转的液晶片402之外的液晶片。
如图11所示4×4个PPG/LC/PPG组合，C1、C2、C3、C4端口为入射端口；O1、O2、O3、O4端口为输出端口；只需要按照表3设置液晶片电压，就可以实现C1-O3，C2-O1，C3-O2，C4-O4的交叉连接。
表3实现C1-O3,C2-O1,C3-O2,C4-O4的LC阵列的电压设置
表3 O1 O2 O3 O4
C4 OFF OFF OFF ON
C3 OFF ON OFF OFF
C2 ON OFF OFF OFF
C1 OFF OFF ON OFF
本系统可同时实现光交叉开关功能和Add/Drop功能，如图11所示，A1、A2、A3、A4端口为插入端口，用于往光路中插入一个或多个波长；D1、D2、D3、D4端口为分出端口，用于从光路中分出一个或多个波长；关于各端口功能具体实施例二中有详细描述，在此不再赘述。例如，要实现C1-O3，C2-O4，C3-D3，C4-O2，A1-O1，可按照表3设置LC阵列的电压。
表3实现C1-O3,C2-O4,C3-D3,C4-O2,A1-O1的LC阵列的电压设置
表4 O1 O2 O3 O4  
C4 OFF ON OFF OFF D4
C3 OFF OFF OFF OFF D3
C2 OFF OFF OFF ON D2
C1 OFF OFF ON OFF D1
  A1 A2 A3 A4  
本发明实施例提供了一种基于聚合物偏振光栅/液晶片/聚合物偏振光栅的光交换装置，包括：输入准直器101、输入偏振分光器201、输入四分之一波片301、PPG4031/LC402/PPG4032、输出四分之一波片302、输出偏振分光器202、输出准直器102。通过设置液晶片402的电压，来选择光信号的传输路径，使得光信号输出至选定输出端。这种光交换装置结构简单、尺寸小、成本低。
实施例五
图14是本发明实施例五的一种基于PPG/LC/PPG/LC的光交换装置的结构示意图，如图14所示，本发明实施例五的基于PPG/LC/PPG/LC的光交换装置，包括：输入准直器101、输入偏振分光器201、输入四分之一波片301、N×NPPG4031/LC4021/PPG4032/LC4022阵列、输出四分之一波片302、输出偏振分光器202、输出准直器102。
本实施例与实施例四方案类似，只是在每个聚合物偏振光栅4031/液晶片4021/聚合物偏振光栅4032后增加了一个液晶片4022，形成聚合物偏振光栅4031/液晶4021/聚合物偏振光栅4032/液晶4022组合。
可选的，液晶片可以选择VA型，也可以选择ECB型液晶，关于VA型液晶和ECB型液晶的工作原理在实施例三中有详细描述，在此不再赘述。抑制串扰光的原理和实施例三类似，使串扰光的偏振方向与信号光的偏振方向相反，从而被输出端的偏振分光器202拦截。因此，系统的信噪比可大大提高。
本发明实施例提供了一种基于可变偏振光栅/液晶片的光交换装置，包括：输入准直器101、输入偏振分光器201、输入四分之一波片301、N×N PPG4031/LC4021/PPG4032/LC4022阵列、输出四分之一波片302、输出偏振分光器202、输出准直器102。通过设置LC4021的电压，来选择光信号的传输路径，使得光信号输出至选定输出端。这种光交换装置结构简单、尺寸小、成本低；同时通过设置LC4022的电压，使串扰光的偏振态与信号光的偏振态垂直，从而被输出分光器所阻断。这样，就可将信噪比大大的提高。
以上所述，仅为本发明的具体实施方式，但本发明的保护范围并不局限于此，任何熟悉本技术领域的技术人员在本发明揭露的技术范围内，可轻易想到变化或替换，都应涵盖在本发明的保护范围之内。因此，本发明的保护范围应以所述权利要求的保护范围为准。

Claims (14)

  1. 一种光交换装置，包括输入准直器、输出准直器，其特征在于，还包括：输入偏振分光器、输入四分之一波片、输出四分之一波片、输出偏振分光器和N×N液晶光栅阵列，其中，N为大于或等于2的整数；
    所述输入偏振分光器置于所述输入准直器与所述输入四分之一波片之间，用于将来自所述输入准直器的输入光信号分成两个具有不同偏振方向的光信号，并将所述两个具有不同偏振方向的光信号输出至所述输入四分之一波片；
    所述输入四分之一波片置于所述输入偏振分光器与所述N×N液晶光栅阵列之间，用于接收来自所述输入偏振分光器的所述两个具有不同偏振方向的光信号，并将所述两个具有不同偏振方向的光信号耦合成圆偏振光，将所述圆偏振光输出到所述N×N液晶光栅阵列；
    所述N×N液晶光栅阵列置于所述输入四分之一波片与所述输出四分之一波片之间，用于通过N×N液晶光栅阵列中与所述输入四分之一波片对应的液晶光栅接收来自所述输入四分之一波片的所述圆偏振光，并将所述圆偏振光通过选定的传输路径输出至选定的输出四分之一波片；其中，所述选定的传输路径是通过设置N×N液晶光栅阵列中液晶光栅的电压来选择的；
    所述输出四分之一波片置于所述N×N液晶光栅阵列与所述输出偏振分光器之间，用于将来自所述N×N液晶光栅阵列的圆偏振光分成两个具有不同偏振方向的光信号，并将所述两个具有不同偏振方向的光信号输出至所述输出偏振分光器；
    所述输出偏振分光器置于所述输出四分之一波片与所述输出准直器之间， 用于将来自所述输出四分之一波片的所述两个具有不同偏振方向的光信号耦合进所述输出准直器。
  2. 如权利要求1所述的光交换装置，其特征在于，所述N×N液晶光栅阵列中液晶光栅包括N×N可变偏振光栅、N×N可变偏振光栅/液晶片组合、N×N聚合物偏振光栅/液晶片/聚合物偏振光栅组合、或N×N聚合物偏振光栅/液晶片/聚合物偏振光栅/液晶片组合。
  3. 如权利要求1或2所述的光交换装置，其特征在于，所述N×N液晶光栅阵列中液晶光栅包括N×N个可变偏振光栅；
    对于N×N个可变偏振光栅中任一可变偏振光栅，当所述任一可变偏振光栅两端所加电压小于第一阈值电压时，所述任一可变偏振光栅中的液晶分子形成液晶光栅，对入射光进行衍射；当所述任一可变偏振光栅两端电压大于或等于第一阈值电压时，所述液晶分子向由所述任一可变偏振光栅两端电压造成的电场方向偏转，光栅效应消失；
    在N×N可变偏振光栅中，不需要对入射光进行偏转的可变偏振光栅两端电压被设置为大于或等于第一阈值电压；需要对入射光进行偏转的可变偏振光栅两端电压被设置为小于第一阈值电压；其中，所述需要对入射光进行偏转的可变偏振光栅为与所述输入四分之一波片对应并且与所述输出四分之一波片对应的可变偏振光栅，所述不需要对入射光进行偏转的可变偏振光栅为N×N可变偏振光栅阵列中除所述需要对入射光进行偏转的可变偏振光栅之外的可变偏振光栅。
  4. 如权利要求3所述的光交换装置，其特征在于，所述需要对入射光进行偏转的可变偏振光栅两端电压被设置为零。
  5. 如权利要求3或4所述的光交换装置，其特征在于，当所述任一可变偏振光栅两端所加电压小于第一阈值电压时，所述任一可变偏振光栅有0级、+1级和-1级三个衍射级次；入射的右旋圆偏振光被所述任一可变偏振光衍射到+1级，变成左旋圆偏振光；入射的左旋圆偏振光被所述任一可变偏振光衍射到-1级，变成右旋圆偏振光。
  6. 如权利要求3-5中任一项所述的光交换装置，其特征在于，所述N×N液晶光栅阵列中光栅液晶还包括N×N个液晶片，每个液晶片与每个可变偏振光栅一一对应形成一个可变偏振光栅/液晶片组合，每个液晶片用于控制入射所述液晶片的光信号的偏振态，使得来自与该液晶片对应的可变偏振光栅的信号光和串扰光经过所述液晶片后，输出信号光的圆偏振态与输出串扰光的圆偏振态相反；其中，通过设置所述液晶片两端的电压来控制入射所述液晶片的光信号的偏振态。
  7. 如权利要求6所述的光交换装置，其特征在于，所述N×N个液晶片为垂直排列型液晶，
    当任一液晶片所加电压小于第二阈值电压时，所述任一液晶片的输出光与所述任一液晶片的输入光偏振态一致；
    当所述任一液晶片所加电压大于或等于第二阈值电压时，
    若左旋圆偏振光输入所述任一液晶片，则所述任一液晶片输出右旋圆偏振光；
    若右旋圆偏振光输入所述任一液晶片，则所述任一液晶片输出左旋圆偏振光。
  8. 如权利要求6所述的光交换装置，其特征在于，所述N×N个液晶片为电控双折射型液晶，
    当任一液晶片所加电压大于或等于第二阈值电压时，所述任一液晶片的输出光与所述液晶片的输入光偏振态一致；
    当所述任一液晶片所加电压小于第二阈值电压时，
    若左旋圆偏振光输入所述任一液晶片，则所述任一液晶片输出右旋圆偏振光；
    若右旋圆偏振光输入所述任一液晶片，则所述任一液晶片输出左旋圆偏振光。
  9. 如权利要求1或2所述的光交换装置，其特征在于，所述N×N液晶光栅阵列中液晶光栅包括N×N聚合物偏振光栅/液晶片/聚合物偏振光栅组合，任一聚合物偏振光栅/液晶片/聚合物偏振光栅组合包括：第一聚合物偏振光栅、第一液晶片和第二聚合物偏振光栅；
    所述第一聚合物偏振光栅与第二聚合物偏振光栅均为固定光栅；
    若输入右旋圆偏振光，则被所述第一聚合物偏振光栅或第二聚合物偏振 光栅衍射到+1级，输出左旋圆偏振光；若输入左旋圆偏振光，则被所述第一聚合物偏振光栅或第二聚合物偏振光栅衍射到-1级，输出右旋圆偏振光；
    所述第一液晶片，用于通过设置所述第一液晶片两端的电压来控制入射所述液晶片的光信号的偏转。
  10. 如权利要求9所述的光交换装置，其特征在于，所述第一液晶片为垂直排列液晶，当所述第一液晶片所加电压小于第二阈值电压时，所述第一液晶片的输出光与输入光偏振态一致；
    当所述第一液晶片所加电压大于或等于第二阈值电压时，
    若左旋圆偏振光输入所述第一液晶片，则所述第一液晶片输出右旋圆偏振光；
    若右旋圆偏振光输入所述第一液晶片，则所述第一液晶片输出左旋圆偏振光；
    不需要对入射光进行偏转的所述第一液晶片两端电压被设置为小于所述第二阈值电压；需要对入射光进行偏转的所述第一液晶片两端电压被设置为大于或等于所述第二阈值电压；其中，所述需要对入射光进行偏转的所述第一液晶片为与所述输入四分之一波片对应并且与所述输出四分之一波片对应的所述第一液晶片，所述不需要对入射光进行偏转的所述第一液晶片为N×N个所述第一液晶片阵列中除所述需要对入射光进行偏转的所述第一液晶片之外的第一液晶片。
  11. 如权利要求9所述的光交换装置，其特征在于，所述第一液晶片为电 控双折射液晶，当所述第一液晶片所加电压大于或等于第二阈值电压时，所述第一液晶片的输出光与输入光偏振态一致；
    当所述第一液晶片所加电压小于第二阈值电压时，
    若左旋圆偏振光输入所述第一液晶片，则所述第一液晶片输出右旋圆偏振光；
    若右旋圆偏振光输入所述第一液晶片，则所述第一液晶片输出左旋圆偏振光；
    不需要对入射光进行偏转的所述第一液晶片两端电压被设置为大于或等于所述第二阈值电压；需要对入射光进行偏转的所述第一液晶片两端电压被设置为小于所述第二阈值电压；其中，所述需要对入射光进行偏转的所述第一液晶片为与所述输入四分之一波片对应并且与所述输出四分之一波片对应的所述第一液晶片，所述不需要对入射光进行偏转的所述第一液晶片为N×N个所述第一液晶片阵列中除所述需要对入射光进行偏转的所述第一液晶片之外的第一液晶片。
  12. 如权利要求9所述的光交换装置，其特征在于，所述N×N液晶光栅阵列中液晶光栅还包括N×N个第二液晶片，每个第二液晶片与每个聚合物偏振光栅/液晶片/聚合物偏振光栅组合形成一个聚合物偏振光栅/液晶片/聚合物偏振光栅/液晶片组合，每个第二液晶片用于控制入射所述第二液晶片的光信号的偏振态，使得来自与该第二液晶片对应的聚合物偏振光栅/液晶片/聚合物偏振光栅的信号光和串扰光经过所述第二液晶片后，输出信号光的圆偏振态与输出串扰光的圆偏振态相反；其中，通过设置所述第二液晶片两端的 电压来控制入射所述第二液晶片的光信号的偏振态。
  13. 如权利要求12所述的光交换装置，其特征在于，所述N×N个第二液晶片为垂直排列液晶，
    当任一第二液晶片所加电压小于第二阈值电压时，所述任一第二液晶片的输出光与输入光偏振态一致；
    当所述任一第二液晶片所加电压大于或等于第二阈值电压时，
    若左旋圆偏振光输入所述任一第二液晶片，则所述任一第二液晶片输出右旋圆偏振光；
    若右旋圆偏振光输入所述任一液晶片，则所述任一液晶片输出左旋圆偏振光。
  14. 如权利要求12所述的光交换装置，其特征在于，所述N×N个第二液晶片为电控双折射液晶
    当任一第二液晶片所加电压大于第或等于二阈值电压时，所述任一第二液晶片的输出光与输入光偏振态一致；
    当所述任一第二液晶片所加电压小于第二阈值电压时，
    若左旋圆偏振光输入所述任一第二液晶片，则所述任一第二液晶片输出右旋圆偏振光；
    若右旋圆偏振光输入所述任一第二液晶片，则所述任一第二液晶片输出左旋圆偏振光。
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