WO2015180380A1 - 可调光衰减器 - Google Patents

可调光衰减器 Download PDF

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Publication number
WO2015180380A1
WO2015180380A1 PCT/CN2014/089131 CN2014089131W WO2015180380A1 WO 2015180380 A1 WO2015180380 A1 WO 2015180380A1 CN 2014089131 W CN2014089131 W CN 2014089131W WO 2015180380 A1 WO2015180380 A1 WO 2015180380A1
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Prior art keywords
polarization state
circular polarization
mirror
handed circular
spg
Prior art date
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PCT/CN2014/089131
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English (en)
French (fr)
Inventor
毛崇昌
李岷淳
闵红
Original Assignee
华为技术有限公司
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Application filed by 华为技术有限公司 filed Critical 华为技术有限公司
Priority to EP14893120.7A priority Critical patent/EP3139208B1/en
Priority to JP2016569644A priority patent/JP2017520787A/ja
Publication of WO2015180380A1 publication Critical patent/WO2015180380A1/zh
Priority to US15/360,515 priority patent/US9927678B2/en

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    • 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
    • G02F1/292—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 by controlled diffraction or phased-array beam steering
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/30—Collimators
    • 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
    • G02F1/139—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 based on orientation effects in which the liquid crystal remains transparent
    • G02F1/1393—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 based on orientation effects in which the liquid crystal remains transparent the birefringence of the liquid crystal being electrically controlled, e.g. ECB-, DAP-, HAN-, PI-LC cells
    • 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
    • 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
    • G02F2201/00—Constructional arrangements not provided for in groups G02F1/00 - G02F7/00
    • G02F2201/30—Constructional arrangements not provided for in groups G02F1/00 - G02F7/00 grating
    • 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
    • G02F2201/00—Constructional arrangements not provided for in groups G02F1/00 - G02F7/00
    • G02F2201/34—Constructional arrangements not provided for in groups G02F1/00 - G02F7/00 reflector
    • 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
    • G02F2203/00—Function characteristic
    • G02F2203/07—Polarisation dependent

Definitions

  • Embodiments of the present invention relate to the field of optical technologies, and in particular, to a tunable optical attenuator.
  • VOA Variable Optical Attenuator
  • MEMS Micro Electro Mechanical Systems
  • LC Liquid Crystal
  • the MEMS-based VOA controls the attenuation of light by the tilt angle of the MEMS micromirror, which is small in size but poor in shock resistance.
  • the VOA based on the LC+ wedge technology uses a birefringent wedge, so it is bulky, costly, and has a problem of difficulty in alignment of the optical path.
  • the embodiment of the invention provides a tunable optical attenuator for solving the problem that the existing tunable optical attenuator has poor seismic resistance, large volume and high cost.
  • an embodiment of the present invention provides a tunable optical attenuator, including:
  • a collimator for adjusting a voltage of electrodes at both ends of the liquid crystal layer of the SPG, wherein:
  • the collimator, the SPG and the mirror are placed in sequence;
  • the collimator is configured to receive incident light and output the incident light to the SPG;
  • the SPG is configured to emit the incident light to the mirror after being diffracted once;
  • the SPG is further configured to perform a diffraction of the light beam reflected back by the mirror and then emit the obtained diffracted light;
  • the collimator is further configured to receive the diffracted light and output the diffracted light.
  • the SPG when the voltage controller adjusts a voltage across the SPG to a low voltage or a zero voltage, the SPG is configured to perform the diffraction of the incident light and then output the The mirror includes:
  • the SPG performs a +1-order diffraction of the left-handed circular polarization state in the incident light to become a right-handed circular polarization state, and then emits the image to the mirror;
  • the SPG performs a -1st order diffraction of the right circular polarization state of the incident light to become a left circular polarization state, and then exits to the mirror;
  • the mirror is configured to reflect the right-handed circular polarization state/left-hand circular polarization state of the received incident light into a left-handed circular polarization state/right-handed circular polarization state, and then emitted to the SPG;
  • the SPG is further configured to: after diffracting the light beam reflected back by the mirror, to emit the obtained diffracted light to the collimator, including:
  • the SPG converts the left-handed circular polarization state reflected back by the mirror into a right-handed circular polarization state and emits in a direction parallel to the optical axis;
  • the SPG converts the right-handed circular polarization state reflected back by the mirror into a left-handed circular polarization state and emits in a direction parallel to the optical axis;
  • the SPG is used to diffract the incident light to be emitted to the mirror, including:
  • the SPG performs a 0-order diffraction of the left-handed circular polarization state/right-handed circular polarization state in the incident light, and then exits to the mirror;
  • the mirror is configured to directly reflect the diffracted light emitted by the SPG after 0-order diffraction to the collimator.
  • a 1/4 wave plate is further disposed between the SPG and the mirror,
  • the voltage controller adjusts the voltage across the SPG to a low voltage or a zero voltage
  • the SPG is used to diffract the incident light to be emitted to the mirror, including:
  • the SPG emits a left-handed circular polarization state in the incident light to a right-handed circular polarization state after being subjected to a +1st-order diffraction state, and then exits the mirror through the quarter-wave plate;
  • the SPG emits a right-handed circular polarization state in the incident light to a left-handed circular polarization state, and then exits the mirror through the quarter-wave plate;
  • the 1/4 wave plate and the mirror are used to receive the right circular polarization state of the incident light /
  • the left-handed circular polarization state is reflected to the right-handed circular polarization state/left-handed circular polarization state and is emitted to the SPG;
  • the SPG is further configured to: after diffracting the light beam reflected back by the mirror, and diffract the obtained diffracted light, comprising:
  • the SPG performs a +1 order diffraction on the left-handed circular polarization state reflected by the mirror, and then becomes a right-handed circular polarization state and obliquely exits at a certain angle;
  • the SPG converts the right-handed circular polarization state reflected back by the mirror into a left-handed circular polarization state and obliquely exits at a certain angle
  • the SPG is used to diffract the incident light to be emitted to the mirror, including:
  • the SPG performs a 0-order diffraction of the left-handed circular polarization state/right-handed circular polarization state in the incident light, and then exits to the mirror;
  • the mirror is configured to directly reflect the diffracted light emitted by the SPG after 0-order diffraction to the collimator.
  • a liquid crystal component LC is further disposed between the SPG and the 1/4 wave plate, the voltage The controller is also operative to regulate the voltage across the electrodes of the LC for achieving wavelength dependent loss compensation.
  • an embodiment of the present invention provides a tunable optical attenuator, including:
  • a collimator for adjusting the voltage of the electrodes at both ends of the LC, wherein:
  • the collimator, PPG, LC, and mirror are placed in sequence;
  • the collimator is configured to receive incident light and output the incident light to the PPG;
  • the PPG is configured to emit the incident light once and then exit the mirror and reach the mirror through the LC;
  • the LC is used to change the polarization state of the beam as the voltage changes
  • the PPG is further configured to reflect the light beam that is reflected back by the mirror and change the polarization state by the LC, and then diffract the obtained diffracted light;
  • the collimator is further configured to receive the diffracted light and output the diffracted light.
  • the LC is an electrically controlled birefringence ECB type LC, and the voltage controller adjusts a voltage across the ECB type LC to a low voltage or a zero voltage.
  • the ECB-type LC is a quarter-wave plate, and the PPG is used to diffract the incident light and then exit the lens and reach the mirror through the LC, including:
  • the PPG performs a +1-order diffraction of the left circular polarization state of the incident light to become a right-handed circular polarization state, and then exits the lens and reaches the mirror through the LC;
  • the PPG emits a right-handed circular polarization state in the incident light to a left-handed circular polarization state, and then exits the lens and reaches the mirror through the LC;
  • the LC and the mirror are configured to reflect the right-handed circular polarization state/left-handed circular polarization state of the received incident light into a right-handed circular polarization state/left-handed circular polarization state, and then emitted to the PPG;
  • the PPG is further used to reflect the reflected light back and reflect the polarization state of the light beam by the LC, and then diffract the obtained diffracted light, including:
  • the PPG converts the left-handed circular polarization state reflected back by the mirror into a right-handed circular polarization state and obliquely exits at a certain angle
  • the PPG converts the right-handed circular polarization state reflected back by the mirror into a left-handed circular polarization state and obliquely exits at a certain angle
  • the ECB-type LC When the voltage controller adjusts the voltage across the ECB-type LC to be a high voltage, the ECB-type LC is similar to a wave plate having a phase difference of 0, and the PPG is used to diffract the incident light and emit it. Reaching the mirror via the LC includes:
  • the PPG performs a +1-order diffraction of the left circular polarization state of the incident light to become a right-handed circular polarization state, and then exits the lens and reaches the mirror through the LC;
  • the PPG emits a right-handed circular polarization state in the incident light to a left-handed circular polarization state, and then exits the lens and reaches the mirror through the LC;
  • the LC and the mirror are configured to reflect the right-handed circular polarization state/left-handed circular polarization state of the received incident light into a left-handed circular polarization state/right-handed circular polarization state, and then emitted to the PPG;
  • the PPG is further used to reflect the reflected light back and reflect the polarization state of the light beam by the LC, and then diffract the obtained diffracted light, including:
  • the PPG converts the left-handed circular polarization state reflected back by the mirror into a right-handed circular polarization state and emits in a direction parallel to the optical axis;
  • the PPG converts the right-handed circular polarization state reflected back by the mirror into a left-handed circular polarization state to emit in a direction parallel to the optical axis.
  • a 1/4 wave plate is further disposed between the ECB type LC and the mirror.
  • the LC is a vertically aligned VA type LC.
  • the collimator and the A PPG is further disposed between the PPGs, and the incident light output by the collimator sequentially generates ⁇ 1st order diffraction and m1 order diffraction respectively when passing through two PPGs;
  • the LC is an electrically controlled birefringence ECB type LC, and the PPG and the mirror are sequentially disposed with the PPG and a 1/4 wave plate, wherein the voltage controller adjusts the voltage across the ECB type LC to a high voltage, the ECB type LC does not adjust the polarization state of the light;
  • the voltage controller adjusts the voltage across the ECB type LC to be a low voltage or a zero voltage
  • the ECB type LC adjusts the polarization state of the light as a 1/2 wave plate
  • the tunable optical attenuator provided by the embodiment of the invention uses the three-order diffraction of the SPG, combined with the collimator and the mirror, and the voltage controller adjusts the voltage across the SPG to change between a low voltage or a zero voltage to a high voltage.
  • the diffraction occurs twice in the whole process, so the VOA has a large dynamic range and can be adjusted in the range of 0 to 40 dB. Since the embodiment of the present invention adjusts the voltage of the SPG by the voltage controller to adjust the diffraction efficiency of the SPG, the VOA of the embodiment of the present invention has the advantage of good reliability compared with the mechanical adjustment in the prior art, and by adopting the SPG.
  • the VOA of the embodiment of the present invention is small in size and low in cost.
  • 1 is a schematic diagram of polarization states of incident light before and after being diffracted by SPG;
  • FIG. 2 is a schematic diagram showing polarization states of incident light before and after being diffracted by PPG;
  • Embodiment 3 is a schematic structural view of Embodiment 1 of a VOA of the present invention.
  • Figure 4 is a schematic diagram showing the attenuation when the voltage across the SPG is low voltage or zero voltage
  • Figure 5 is a schematic diagram showing the attenuation when the voltage across the SPG is a high voltage
  • Embodiment 2 of a VOA according to the present invention is a schematic structural view of Embodiment 2 of a VOA according to the present invention.
  • Figure 7 is a schematic structural view of a third embodiment of a VOA according to the present invention.
  • FIG. 8 is a schematic diagram showing the structure and working principle of the fourth embodiment of the VOA of the present invention.
  • FIG. 9 is a schematic diagram showing the structure and working principle of the fifth embodiment of the VOA of the present invention.
  • FIG. 10 is a schematic diagram showing the structure and working principle of Embodiment 6 of the VOA of the present invention.
  • FIG. 11 is a schematic diagram showing the structure and working principle (LC heightening voltage) of Embodiment 7 of the VOA of the present invention.
  • Figure 12 is a schematic diagram showing the structure and operation principle (LC plus low voltage or zero voltage) of Embodiment 7 of the VOA of the present invention.
  • Embodiments of the present invention provide a tunable optical attenuator that uses a liquid crystal based grating: a Switchable Polarization Grating (SPG) and a Polymer Polarization Grating (PPG).
  • a liquid crystal component Liquid Crystal, hereinafter referred to as LC
  • LC Liquid Crystal
  • PPG Polymer Polarization Grating
  • the structure and manufacturing process of SPG are very close to the production of traditional LC wafers.
  • the main difference lies in the fabrication of liquid crystal alignment layer.
  • the liquid crystal alignment layer of the SPG is formed by exposing the polymer layer by two UV-coherent polarized lights, one of which is right-handed polarized light and the other of which is left-handed polarized light.
  • the LC is injected between the two glass substrates, the LC molecular orientations are aligned in a hologram pattern formed by the alignment layer after exposure.
  • no voltage is applied, the LC forms a liquid crystal grating that diffracts the incident light.
  • the LC molecules When the power supply at both ends of the SPG is higher than a certain threshold voltage, the LC molecules start to deflect toward the electric field. When the voltage is high enough, the LC molecules are arranged according to the direction of the electric field, and the grating effect almost completely disappears.
  • FIG. 1 is a schematic diagram of the polarization state before and after incident light is diffracted by SPG. As shown in Figure 1, when the voltage across the SPG is increased by VH, incident light of any polarization is diffracted to level 0 after SPG, polarization state and propagation.
  • the direction is unchanged; when zero voltage or low voltage VL is applied across the SPG, the left circular polarization state is diffracted to +1 level, becomes a right circular polarization state, and the right circular polarization state is diffracted to -1 level, becoming Left-handed circular polarization.
  • the probability ⁇ of the left-handed circular polarization and the right-handed circular polarization of the incident light being diffracted to the 0th and ⁇ 1th levels are as follows:
  • ⁇ n is the birefringence of SPG
  • d is the thickness of the liquid crystal
  • ⁇ is the wavelength of light
  • PPG is exposed by a pair of curable liquid crystal layers.
  • PPG is prepared by first coating a photopolymer material on a glass substrate, then exposing it with two beams of coherent light to form a hologram, and then coating the curable liquid crystal on the photosensitive layer, and then using uniform UV light to the liquid crystal layer. Exposure, thereby curing it, at which time the liquid crystal molecules form a fixed grating in accordance with the hologram pattern of the photosensitive layer.
  • PPG is a fixed grating, so it is impossible to change its diffraction efficiency by applying a voltage.
  • PPG has only two diffraction orders of ⁇ 1 order.
  • Figure 2 is a schematic diagram of the polarization state before and after incident light is diffracted by PPG.
  • the left-handed circular polarization state is diffracted to +1 order and becomes a right-handed circular polarization state.
  • the right-handed circular polarization state is diffracted to -1 level, becoming a left-handed circular polarization state, and PPG has only two light output directions.
  • the VOA of this embodiment may include: a collimator 11, an SPG 12, a mirror 13 and a voltage for adjusting electrodes at both ends of the liquid crystal layer of the SPG 12.
  • the voltage controller 14 in which the collimator 11, the SPG 12 and the mirror 13 are placed in sequence, and the optical path alignment is performed after the three are sequentially placed, wherein the mirror 13 and the optical path are placed strictly perpendicularly.
  • Both the SPG 12 and the mirror 13 are disposed perpendicular to the optical path, and the voltage controller 14 can be disposed, for example, between the electrodes at both ends of the liquid crystal layer of the SPG 12.
  • the collimator 11 is for receiving incident light and outputting the incident light to the SPG 12.
  • the SPG 12 is used to diffract incident light to the mirror 13 once, and the SPG 12 is also used to diffract the light beam reflected back from the mirror 13 to emit the diffracted light.
  • the collimator 11 is also for receiving diffracted light and outputting the diffracted light.
  • the voltage controller 14 adjusts the voltage across the SPG 12 to change between a low voltage or a zero voltage to a high voltage VH.
  • FIG. 4 shows that the voltage across the SPG is a low voltage or zero.
  • Schematic diagram of the attenuation at voltage as shown in Fig. 4, after the incident light is emitted from the collimator and reaches SPG12, the left-handed circular polarization state in the incident light is subjected to a +1 order diffraction by SPG12 and becomes a right-handed circular polarization state. The mirror, when reflected light returns to SPG12, forms a left-handed circular polarization state.
  • the right-handed circular polarization state in the incident light is diffracted by the SPG12 to a left-handed circular polarization state, and after passing through the mirror, the reflected light returns to the SPG12 to form a right-handed circular polarization state. Then, the -1st order diffraction is performed again on the SPG12, and when it is emitted into the left-handed circular polarization state, the parallel light is emitted in the direction opposite to the incident light.
  • the SPG12 has a large diffraction angle, the return light will be far from the axis and cannot enter the collimator 11, and the attenuation of the light is maximized.
  • Figure 5 shows the attenuation diagram when the voltage across the SPG is high. As shown in Figure 5, the incident light is diffracted to level 0 regardless of the polarization state, and is directly from the mirror. It is reflected back to the collimator 11 for output, at which point the attenuation of the VOA is minimal.
  • the distribution ratio of the incident light to the 0th order and the ⁇ 1th order also changes with the voltage, see equations (1) and (2) above.
  • the attenuation value of VOA decreases as the voltage increases.
  • the VOA provided in this embodiment utilizes three levels of diffraction of the SPG, combined with the collimator and the inverse The mirror, the voltage controller adjusts the voltage across the SPG to change between low voltage or zero voltage to high voltage. During the whole process, two effective diffractions are generated. Therefore, the VOA has a large dynamic range and can reach a range of 0 to 40 dB. Tune. Since the embodiment of the present invention adjusts the voltage of the SPG by the voltage controller to adjust the diffraction efficiency of the SPG, the VOA of the embodiment of the present invention has the advantage of good reliability compared with the mechanical adjustment in the prior art, and by adopting the SPG. In combination with the structural features of the collimator and the mirror, the VOA of the embodiment of the present invention is small in size and low in cost.
  • FIG. 6 is a schematic structural view of the second embodiment of the VOA of the present invention. As shown in FIG. 6, on the basis of the VOA shown in FIG. 3, a quarter-wave plate 15 is further disposed between the SPG and the mirror 13.
  • the detailed working principle is as follows:
  • the voltage across the SPG 12 is a low voltage or a zero voltage
  • the left circular polarization state in the incident light is subjected to a +1 order diffraction by the SPG 12 and becomes a right circular polarization state.
  • the reflected light After passing through the mirror and the 1/4 wave plate, the reflected light returns to the SPG12 to form a right-handed circular polarization state.
  • another -1 order diffraction is performed on the SPG 12, and when it is turned into a left-handed circular polarization state, it will be obliquely inclined at a certain angle and will not enter the collimator 11.
  • the right-handed circular polarization state in the incident light is diffracted by the SPG12 to a left-handed circular polarization state.
  • the reflected light After passing through the mirror and the quarter-wave plate, the reflected light returns to the SPG12 to form a left-handed circular polarization state.
  • another +1 order diffraction is performed on the SPG12, and when it is turned into a right-handed circular polarization state, it will be obliquely inclined at a certain angle, and will not enter the collimator 11, and the VOA attenuation reaches the maximum at this time.
  • the incident light is diffracted to the 0th order regardless of the polarization state, and is directly reflected back from the mirror back to the collimator 11 for output.
  • the distribution ratio of the incident light to the 0th order and the ⁇ 1th order also changes with the voltage, see equations (1) and (2) above.
  • the attenuation value of VOA decreases as the voltage increases.
  • the light that finally returns to the collimator is the SPG twice-order diffracted light.
  • the polarization state of the incident light can be decomposed into P-polarized light and S-polarized light. After the P-polarized light is diffracted by the 0th order, it passes through the mirror and the 1/4 wave plate, and returns to the SPG to become the S-polarization state; while the S-polarization state is the opposite, after the 0-order diffraction, the mirror and the quarter-wave When the slice returns to SPG, it will become P-polarized. Therefore, the final entry into the collimator is exactly two orthogonal The product of the 0th order diffraction efficiency of the polarization state. For any input light polarization state, the diffraction efficiency is the same, thus achieving automatic compensation of the PDL.
  • the 0th order diffraction efficiency of the SPG is wavelength dependent.
  • WDL wavelength dependent loss
  • FIG. 7 is a schematic structural diagram of Embodiment 3 of the VOA of the present invention.
  • an LC 16 is further disposed between the variable polarization grating and the 1/4 wave plate.
  • the voltage controller 14 is used to adjust the voltage across the SPG 12 and across the LC16. Specifically, the o/e optical path difference produced by the LC, the phase difference between the long and short wavelengths Different, so the LC itself will produce WDL. Selecting the long and short axis directions of the LC and the wave plate, the WDL of the LC is offset to some other parts of the WDL to achieve WDL compensation.
  • the specific working principle is as follows: the right-handed/left-handed circular polarization state after the first diffraction of SPG, after LC, 1/4 wave plate and mirror return to SPG, it is right-handed/left-handed circular polarization, SPG will be m1 level. Perform a second diffraction and slant out.
  • the phase difference produced by the LC and the waveplate is not equal to ⁇ /2, the light returning to the SPG will not be a complete right-handed/left-handed polarization state, but a part of the left-handed/right-handed polarization state. And this part of the incident light will occur ⁇ 1 order diffraction parallel exit, coupled back to the output fiber, as a complement to the 0-order light, to achieve WDL compensation.
  • the light energy output efficiency can be calculated by the following formula (3):
  • the factor Indicates the light energy of two zero-order diffractions,
  • the factor embodies the role of the LC by extracting a portion of the obliquely emitted light energy as part of the WDL compensation light.
  • ⁇ n 1 , ⁇ n 2 are the birefringence difference of SPG and LC, respectively
  • d 1 d 2 is the thickness of the liquid crystal layer of SPG and LC, respectively
  • ⁇ L is the optical path difference of the wave plate
  • ⁇ is the wavelength of light
  • A is ⁇
  • FIG. 8 is a schematic diagram showing the structure and working principle of the fourth embodiment of the VOA of the present invention.
  • the VOA of the embodiment may include: a collimator 21, a PPG 22, an LC 23, a mirror 24, and a voltage for adjusting the voltage across the LC 23 .
  • Voltage controller 25 wherein:
  • the collimator 21, the PPG 22, the LC 23, and the mirror 24 are sequentially placed. As shown in FIG. 8, the PPG 22, the LC 23, and the mirror 24 are all disposed perpendicular to the optical path, and after the four are sequentially placed, the optical path is aligned, and the mirror 24 is disposed. It is placed strictly perpendicular to the light path.
  • the collimator 21 is for receiving incident light and outputting the incident light to the PPG 2.
  • the PPG 22 is used to diffract the incident light once and then exits through the LC23 to the mirror 24, which is used to change the polarization state of the beam as the voltage changes.
  • the PPG 22 is also used to reflect the mirror 24 back and change the polarization state through the LC23. After the light beam is once diffracted, the obtained diffracted light is emitted.
  • the collimator 21 is further configured to receive the diffracted light and output the diffracted light.
  • the LC23 may be an electrically controlled birefringence (ECB) type LC or a vertical alignment (VA) type LC.
  • ECB electrically controlled birefringence
  • VA vertical alignment
  • the voltage controller 14 adjusts the voltage across the ECB type LC to change between a low voltage or a zero voltage to a high voltage VH, as shown in FIG. The phase difference of the light, thereby adjusting the polarization state of the light.
  • the incident light of the left-handed circular polarization state and the right-handed circular polarization state is respectively diffracted to ⁇ 1 level, and is emitted in a right-handed circular polarization state and a left-handed circular polarization state, when the voltage across the LC is At 0, the ECB type LC is a quarter-wave plate that changes the polarization state of the light.
  • the light When the light returns to the PPG through the mirror and LC, the light becomes a right-handed circular polarization state and a left-handed circular polarization state, respectively.
  • the second diffraction on the PPG is m1 level, and the diffracted light will be obliquely emitted at a large angle. Enter the collimator and the output fiber, at which point the VOA attenuation is maximized.
  • the ECB type LC corresponds to a wave plate having a phase difference of zero.
  • the light reflected back to the PPG by the mirror will be a left-handed circular polarization state and a right-handed circular polarization state.
  • the second time is diffracted on the PPG and is emitted in the horizontal direction by ⁇ 1 steps, returning to the collimator and the output fiber. VOA attenuation is minimal.
  • the attenuation of the light by the VOA can be controlled by adjusting the voltage applied across the LC.
  • ⁇ n is the birefringence difference of LC
  • d is the thickness of the liquid crystal layer of LC
  • ⁇ is the wavelength of light. Since only one order diffraction occurs on the PPG after changing the polarization state of the light by controlling the LC, the dynamic range of the VOA in this embodiment is adjustable from 0 to 25 dB.
  • FIG. 9 is a schematic diagram showing the structure and working principle of the fifth embodiment of the VOA of the present invention. As shown in FIG. 9, a quarter-wave plate 26 is disposed between the ECB-type LC and the mirror 24, and the incident light is diffracted to ⁇ 1. The probability ⁇ of the level is as shown in the following formula (5):
  • ⁇ n is the birefringence difference of LC
  • d is the thickness of the liquid crystal layer of LC
  • ⁇ L is the optical path difference of the wave plate
  • ⁇ is the wavelength of light
  • the dynamic range of the VOA in this embodiment is adjustable from 0 to 25 dB.
  • the Bright type VOA in this embodiment has a WDL of 0.7 dB or less within the range of 0 to 20 dB attenuation, and can meet the requirements of the optical communication system for the high-end Bright type VOA.
  • the voltage controller 14 adjusts the voltage across the VA type LC to change between a low voltage or a zero voltage to a high voltage VH, and the probability that the incident light is diffracted to ⁇ 1 level is as follows: Formula (6):
  • ⁇ n is the birefringence difference of LC
  • d is the thickness of the liquid crystal layer of LC
  • ⁇ is the wavelength of light
  • the dynamic range of the VOA is adjustable from 0 to 25 dB.
  • WDL ⁇ 0.6dB@IL 0 ⁇ 15dB, which meets the requirements of optical communication systems for high-end Bright VOA.
  • the VOA provided in this embodiment utilizes two levels of diffraction of the PPG, combined with the LC, the collimator, and the mirror.
  • the voltage controller adjusts the voltage across the LC to change between a low voltage or a zero voltage to a high voltage.
  • the VOA has 0. ⁇ 25dB dynamic range, because the embodiment of the present invention adjusts the voltage across the LC by the voltage controller to adjust the diffraction efficiency of the PPG, compared with the mechanical adjustment in the prior art, the VOA of the embodiment of the invention has the advantages of good reliability.
  • the VOA of the embodiment of the invention is small in size and low in cost.
  • FIG. 10 is a schematic view showing the structure and working principle of the sixth embodiment of the VOA of the present invention. As shown in FIG. 10, on the basis of the embodiment shown in FIG. 8, the collimator 21 and the polymer are provided. A polarization grating 28 is further disposed between the polarization gratings 22.
  • the LC is an ECB type LC, which can constitute a large dynamic range Bright type VOA. Further, if a quarter-wave plate is added between the PPG 2 and the mirror, the Bright type VOA can be changed to the Dark type VOA.
  • the working principle is as follows: When light is incident from the collimator to the PPG 28, the left-handed circular polarization state and the right-handed circular polarization state in the incident light are respectively diffracted to ⁇ 1 order, and the exit is a right-handed circular polarization state/left-hand circular polarization state. In the PPG 22, m1 order diffraction is respectively generated, and the left-handed circular polarization state/right-handed circular polarization state is emitted in the direction of the parallel optical axis.
  • the ECB type LC adjusts the polarization state of the light as a quarter-wave plate.
  • the light is returned to the PPG 22 by the mirror, it is still a left-handed circular polarization state/right-handed circular polarization state.
  • the ⁇ 1 and m1 diffractions occur in PPG28 and PPG22, respectively, and the light is directly reflected back into the collimator and the output fiber, at which point the VOA attenuation is minimal.
  • the dynamic range of the VOA is 0 to 35 dB.
  • FIG. 11 is a schematic diagram of the structure and working principle (LC heightening voltage) of the VOA embodiment 7 of the present invention
  • FIG. 11 For the structure and working principle (LC plus low voltage or zero voltage) of the VOA embodiment of the present invention, as shown in FIG. 11 and FIG. 12, the LC is an ECB type LC, and the PPG 30 is sequentially disposed between the LC 23 and the mirror. And 1/4 wave plate 31.
  • the left-handed circular polarization state and the right-handed circular polarization state component in the incident light are respectively diffracted to ⁇ 1 order, and the exit is a right-handed circular polarization state/left-handed circular polarization state.
  • the ECB type LC does not adjust the polarization state of the light, and the light reaches the PPG 30 in a right-handed circular polarization state/left-handed circular polarization state, and m1 order diffraction occurs, and the left-hand circular polarization state/ The right circular polarization state is emitted at an angle parallel to the direction of the optical axis.
  • the PPG 30 When returning to the PPG 30 through the 1/4 wave plate and the mirror, it is still a left-handed circular polarization state/right-handed circular polarization state.
  • the ECB type LC adjusts the polarization state of the light as a 1/2 wave plate, and the light reaches the PPG 30 in a left-handed circular polarization state/right-handed circular polarization state, and a ⁇ 1 reflection occurs again. , exiting at a large angle, will no longer be able to return to the collimator 21, at which point the VOA attenuation is greatest.
  • the second-stage PPG is also subjected to two-time diffraction, and the IL can reach 0 to 35 dB.
  • the aforementioned program can be stored in a computer readable storage medium.
  • the program when executed, performs the steps including the foregoing method embodiments; and the foregoing storage medium includes various media that can store program codes, such as a ROM, a RAM, a magnetic disk, or an optical disk.

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Abstract

一种可调光衰减器，包括准直器（11）、可变偏振光栅（12）、反射镜（13）和用于调节可变偏振光栅（12）的液晶层两端电压的电压控制器（14），其中准直器（11）、可变偏振光栅（12）和反射镜（13）依次放置，准直器（11）用于接收入射光，并将入射光输出至可变偏振光栅（12），可变偏振光栅（12）用于将入射光进行一次衍射后射出到反射镜（13），可变偏振光栅（12）还用于将反射镜（13）反射回的光束进行一次衍射后，将得到的衍射光输出，准直器（11）还用于接收衍射光，并将衍射光输出。该可调光衰减器具有很大的动态可调范围，具有可靠性好、体积小及成本特的特点。

Description

可调光衰减器 技术领域
本发明实施例涉及光学技术领域，尤其涉及一种可调光衰减器。
背景技术
可调光衰减器(Variable Optical Attenuator,VOA)在光通信中具有广泛的应用，其主要功能是用来动态控制光信号的衰减度，是光网络中不可或缺的关键器件。可调光衰减器一般要求衰减范围大、精度高、稳定性好、体积小，同时成本低廉。目前，在光通信系统中，实现高端可调光衰减器的技术主要有两种：微机电系统(Micro Electro Mechanical systems，简称：MEMS)技术和液晶(Liquid Crystal，简称：LC)+光楔技术。
基于MEMS技术的VOA是通过MEMS微反射镜的倾角来控制光的衰减幅度，其体积虽小，但是抗震性差。基于LC+光楔技术的VOA由于采用了双折射光楔，因此体积大、成本高，而且存在光路对准困难的问题。
发明内容
本发明实施例提供一种可调光衰减器，用以解决现有的可调光衰减器存在抗震性差、体积大以及成本高的问题。
第一方面，本发明实施例提供一种可调光衰减器，包括：
准直器、可变偏振光栅SPG、反射镜和用于调节所述SPG的液晶层两端电极的电压的电压控制器，其中：
所述准直器、SPG和反射镜依次放置；
所述准直器用于接收入射光，并将所述入射光输出至所述SPG；
所述SPG用于将所述入射光进行一次衍射后射出到所述反射镜；
所述SPG还用于将所述反射镜反射回的光束进行一次衍射后，将得到的衍射光射出；
所述准直器还用于接收所述衍射光，并将所述衍射光输出。
在第一方面的第一种可能的实施方式中，所述电压控制器调节所述SPG两端的电压为低电压或零电压时，所述SPG用于将所述入射光进行一次衍射后射出到所述反射镜，包括：
所述SPG将所述入射光中的左旋圆偏振态进行一次+1级衍射后变为右旋圆偏振态后射出到所述反射镜；和，
所述SPG将所述入射光中的右旋圆偏振态进行一次-1级衍射后变为左旋圆偏振态后射出到所述反射镜；
所述反射镜用于将接收到的所述入射光中的右旋圆偏振态/左旋圆偏振态反射为左旋圆偏振态/右旋圆偏振态后射出到所述SPG；
所述SPG还用于将所述反射镜反射回的光束进行一次衍射后，将得到的衍射光射出至所述准直器，包括：
所述SPG将所述反射镜反射回的左旋圆偏振态进行一次+1级衍射后变为右旋圆偏振态以平行光轴的方向射出；和，
所述SPG将所述反射镜反射回的右旋圆偏振态进行一次-1级衍射后变为左旋圆偏振态以平行光轴的方向射出；
所述电压控制器调节所述SPG两端的电压为高电压时，所述SPG用于将所述入射光进行一次衍射后射出到所述反射镜，包括：
所述SPG将所述入射光中的左旋圆偏振态/右旋圆偏振态进行一次0级衍射后射出到所述反射镜；
所述反射镜用于将所述SPG进行一次0级衍射后射出的衍射光直接反射回所述准直器。
结合第一方面或第一方面的第一种可能的实施方式，在第一方面的第二种可能的实施方式中，所述SPG与所述反射镜之间还设置有一1/4波片，所述电压控制器调节所述SPG两端的电压为低电压或零电压时，所述SPG用于将所述入射光进行一次衍射后射出到所述反射镜，包括：
所述SPG将所述入射光中的左旋圆偏振态进行一次+1级衍射后变为右旋圆偏振态后经过所述1/4波片射出到所述反射镜；和，
所述SPG将所述入射光中的右旋圆偏振态进行一次-1级衍射后变为左旋圆偏振态后经过所述1/4波片射出到所述反射镜；
所述1/4波片和反射镜用于将接收到的所述入射光中的右旋圆偏振态/ 左旋圆偏振态反射为右旋圆偏振态/左旋圆偏振态后射出到所述SPG；
所述SPG还用于将所述反射镜反射回的光束进行一次衍射后，将得到的衍射光射出，包括：
所述SPG将所述反射镜反射回的左旋圆偏振态进行一次+1级衍射后变为右旋圆偏振态以一定角度斜射出；和，
所述SPG将所述反射镜反射回的右旋圆偏振态进行一次-1级衍射后变为左旋圆偏振态以一定角度斜射出；
所述电压控制器调节所述SPG两端的电压为高电压时，所述SPG用于将所述入射光进行一次衍射后射出到所述反射镜，包括：
所述SPG将所述入射光中的左旋圆偏振态/右旋圆偏振态进行一次0级衍射后射出到所述反射镜；
所述反射镜用于将所述SPG进行一次0级衍射后射出的衍射光直接反射回所述准直器。
结合第一方面的第二种可能的实施方式，在第一方面的第三种可能的实施方式中，所述SPG与所述1/4波片之间还设置有一液晶部件LC，所述电压控制器还用于调节所述LC两端电极的电压，所述LC用于实现波长相关损耗补偿。
第二方面，本发明实施例提供一种可调光衰减器，包括：
准直器、聚合物偏振光栅PPG、液晶部件LC、反射镜和用于调节所述LC两端电极的电压的电压控制器，其中：
所述准直器、PPG、LC、反射镜依次放置；
所述准直器用于接收入射光，并将所述入射光输出至所述PPG；
所述PPG用于将所述入射光进行一次衍射后射出并经所述LC到达所述反射镜；
所述LC用于随着电压的变化改变光束的偏振态；
所述PPG还用于将所述反射镜反射回并通过所述LC改变偏振态的光束进行一次衍射后，将得到的衍射光射出；
所述准直器还用于接收所述衍射光，并将所述衍射光输出。
在第二方面的第一种可能的实施方式中，所述LC为电控双折射率ECB型LC，所述电压控制器调节所述ECB型LC两端的电压为低电压或零电压 时，所述ECB型LC为1/4波片，所述PPG用于将所述入射光进行一次衍射后射出并经所述LC到达所述反射镜，包括：
所述PPG将所述入射光中的左旋圆偏振态进行一次+1级衍射后变为右旋圆偏振态后射出并经所述LC到达所述反射镜；和，
所述PPG将所述入射光中的右旋圆偏振态进行一次-1级衍射后变为左旋圆偏振态后射出并经所述LC到达所述反射镜；
所述LC和反射镜用于将接收到的所述入射光中的右旋圆偏振态/左旋圆偏振态反射为右旋圆偏振态/左旋圆偏振态后射出到所述PPG；
所述PPG还用于将所述反射镜反射回并通过所述LC改变偏振态的光束进行一次衍射后，将得到的衍射光射出，包括：
所述PPG将所述反射镜反射回的左旋圆偏振态进行一次+1级衍射后变为右旋圆偏振态以一定角度斜射出；和，
所述PPG将所述反射镜反射回的右旋圆偏振态进行一次-1级衍射后变为左旋圆偏振态以一定角度斜射出；
所述电压控制器调节所述ECB型LC两端的电压为高电压时，所述ECB型LC类似于相位差为0的波片，所述PPG用于将所述入射光进行一次衍射后射出并经所述LC到达所述反射镜，包括：
所述PPG将所述入射光中的左旋圆偏振态进行一次+1级衍射后变为右旋圆偏振态后射出并经所述LC到达所述反射镜；和，
所述PPG将所述入射光中的右旋圆偏振态进行一次-1级衍射后变为左旋圆偏振态后射出并经所述LC到达所述反射镜；
所述LC和反射镜用于将接收到的所述入射光中的右旋圆偏振态/左旋圆偏振态反射为左旋圆偏振态/右旋圆偏振态后射出到所述PPG；
所述PPG还用于将所述反射镜反射回并通过所述LC改变偏振态的光束进行一次衍射后，将得到的衍射光射出，包括：
所述PPG将所述反射镜反射回的左旋圆偏振态进行一次+1级衍射后变为右旋圆偏振态以平行光轴的方向射出；和，
所述PPG将所述反射镜反射回的右旋圆偏振态进行一次-1级衍射后变为左旋圆偏振态以以平行光轴的方向射出。
结合第二方面的第一种可能的实施方式，在第二方面的第二种可能的实 施方式中，所述ECB型LC与所述反射镜之间还设置有一1/4波片。
结合第二方面，在第二方面的第三种可能的实施方式中，所述LC为垂直排列VA型LC。
结合第二方面至第二方面的第三种可能的实施方式中任一项所述的可调光衰减器，在第二方面的第四种可能的实施方式中，所述准直器与所述PPG之间还设置有一PPG，所述准直器输出的入射光依次经过两个PPG时，分别产生一次±1级衍射和m1级衍射；
经过所述反射镜和LC反射回的光依次经过两个PPG时，分别产生一次m1级衍射和±1级衍射。
结合第二方面，在第二方面的第五种可能的实施方式中，所述LC为电控双折射率ECB型LC，所述ECB型LC与所述反射镜之间还依次设置有一PPG和一1/4波片，所述电压控制器调节所述ECB型LC两端的电压为高电压时，所述ECB型LC不调整光的偏振态；
所述电压控制器调节所述ECB型LC两端的电压为低电压或零电压时，所述ECB型LC作为1/2波片调整光的偏振态；
所述准直器输出的入射光依次经过两个PPG时，分别产生一次±1级衍射和m1级衍射；
经过所述反射镜和1/4波片反射回的光依次经过两个PPG时，分别产生一次m1级衍射和±1级衍射。
本发明实施例提供的可调光衰减器，利用SPG的三个级次的衍射，结合准直器和反射镜，电压控制器调节SPG两端的电压在低电压或零电压～高电压之间变化，整个过程中产生了2次衍射，因此VOA具有很大的动态范围，可达到0～40dB范围可调。由于本发明实施例是通过电压控制器调节SPG两端的电压进而调节SPG的衍射效率，相比较现有技术中的机械调节，本发明实施例的VOA具有可靠性好的优点，而且，通过采用SPG结合准直器和反射镜的结构特点，本发明实施例的VOA体积小、成本低。
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一简单地介绍，显而易见地，下面描述中的附图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性的前提下，还可以根据这些附图获得其他的附图。
图1为入射光被SPG衍射前后的偏振态示意图；
图2为入射光被PPG衍射前后的偏振态示意图；
图3为本发明VOA实施例一的结构示意图；
图4为SPG两端的电压为低电压或零电压时的衰减示意图；
图5为SPG两端的电压为高电压时的衰减示意图；
图6为本发明VOA实施例二的结构示意图；
图7为本发明VOA实施例三的结构示意图；
图8为本发明VOA实施例四的结构和工作原理示意图；
图9为本发明VOA实施例五的结构和工作原理示意图；
图10为本发明VOA实施例六的结构和工作原理示意图；
图11为本发明VOA实施例七的结构和工作原理(LC加高电压)示意图；
图12为本发明VOA实施例七的结构和工作原理(LC加低电压或零电压)示意图。
具体实施方式
为使本发明实施例的目的、技术方案和优点更加清楚，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、完整地描述，显然，所描述的实施例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。
本发明实施例提供一种可调光衰减器，采用基于液晶技术的光栅：可变偏振光栅(Switchable Polarization Grating，以下简称：SPG)和聚合物偏振光栅(Polymer Polarization Grating，以下简称：PPG)，结合液晶部件(Liquid Crystal，以下简称：LC)和波片，构成Dark型和Bright型的VOA，本发明实施例提供的VOA有良好的性能，并且具有可靠性好、 体积小及成本低的特点，下面结合附图详细说明。
首先介绍一下SPG的制作和工作原理，SPG的结构和制作工艺与传统LC片的制作很接近，主要差别在于液晶对准层的制作。SPG的液晶对准层是由两束UV相干偏振光对聚合物层曝光而成，其中一束光为右旋偏振光，而另一束为左旋偏振光。当LC被注入两玻璃基板间后，LC分子取向按曝光后在对准层形成的全息图样排列。在不加电压时，LC形成液晶光栅，可对入射光进行衍射。当SPG两端电源高于某个阈值电压时，LC分子开始偏转向电场方向，当电压足够高时，LC分子依据电场方向排列，光栅效应几乎完全消失。
SPG有0级和±1级三个衍射级次，根据入射光的偏振态不同，可以将入射光分解成一束左旋圆偏振态和一束右旋圆偏振态。图1为入射光被SPG衍射前后的偏振态示意图，如图1所示，当SPG两端加高电压VH时，任何偏振态的入射光经过SPG后都被衍射到0级，偏振态和传播方向不变；当SPG两端加零电压或低电压VL时，左旋圆偏振态被衍射到+1级，变成右旋圆偏振态，右旋圆偏振态被衍射到-1级，变成左旋圆偏振态。
在SPG两端所加电压为VL～VH之间的值时，入射光的左旋圆偏振态和右旋圆偏振态被衍射到0级和±1级的概率η分别为如下式所示：
Figure PCTCN2014089131-appb-000001
其中Δn为SPG的双折射率，d为液晶厚度，λ为光的波长。
接着介绍一下PPG的制作和工作原理，PPG由一对可固化液晶层曝光而成。PPG的制作流程是首先将光敏聚合物材料涂在玻璃基板上，然后用两束相干光对其曝光而形成全息图，再将可固化液晶涂在光敏层上，然后用均匀UV光对液晶层曝光，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。PPG为固定光栅，所以不能通过加电压来改变其衍射效率。PPG只有±1级两个衍射级次，图2为入射光被PPG衍射前后的偏振态示意图，如图2所示，左旋圆偏振态被衍射到+1级，变成右旋圆偏振态，右旋圆偏振态被衍射到-1级，变成左旋圆偏振态，PPG只有两个光输出方向。
图3为本发明VOA实施例一的结构示意图，如图3所示，本实施例的VOA可以包括：准直器11、SPG12、反射镜13和用于调节SPG12的液晶层两端电极的电压的电压控制器14，其中，准直器11、SPG12和反射镜13依次放置，三者依次放置后需进行光路对准，其中，反射镜13和光路严格垂直放置。SPG12与反射镜13均以垂直于光路方向设置，电压控制器14例如可设置在SPG12的液晶层两端电极之间。准直器11用于接收入射光，并将入射光输出至SPG12。SPG12用于将入射光进行一次衍射后射出到反射镜13，SPG12还用于将反射镜13反射回的光束进行一次衍射后，将得到的衍射光射出。准直器11还用于接收衍射光，并将衍射光输出。
具体地，电压控制器14调节SPG12两端的电压在低电压或零电压～高电压VH之间变化，SPG12两端的电压为低电压或零电压时，图4为SPG两端的电压为低电压或零电压时的衰减示意图，如图4所示，入射光从准直器射出后到达SPG12后，入射光中的左旋圆偏振态被SPG12进行一次+1级衍射后变为右旋圆偏振态，经过反射镜，反射光回到SPG12时形成左旋圆偏振态。接着在SPG12上再进行一次+1级衍射，变成右旋圆偏振态出射时将以平行光反着入射光的方向出射。SPG12衍射角度较大时，返回光将离轴较远，无法进入准直器11，此时光的衰减达到最大。
入射光中的右旋圆偏振态被SPG12进行一次-1级衍射后变为左旋圆偏振态，经过反射镜，反射光回到SPG12时形成右旋圆偏振态。接着在SPG12上再进行一次-1级衍射，变成左旋圆偏振态出射时将以平行光反着入射光的方向出射。SPG12衍射角度较大时，返回光将离轴较远，无法进入准直器11，此时光的衰减达到最大。
SPG12两端的电压为高电压时，图5为SPG两端的电压为高电压时的衰减示意图，如图5所示，入射光无论何种偏振态，都被衍射到0级，并且从反射镜直接反射回准直器11而输出，这时VOA的衰减最小。
SPG两端的电压为0～VH之间的任意值时，入射光被衍射到0级和±1级的分配比例也随电压改变，见上述式(1)和式(2)。VOA的衰减值就随着电压增大而减小。
本实施例提供的VOA，利用SPG的三个级次衍射，结合准直器和反 射镜，电压控制器调节SPG两端的电压在低电压或零电压～高电压之间变化，整个过程中产生了2次有效衍射，因此VOA具有很大的动态范围，可达到0～40dB范围可调。由于本发明实施例是通过电压控制器调节SPG两端的电压进而调节SPG的衍射效率，相比较现有技术中的机械调节，本发明实施例的VOA具有可靠性好的优点，而且，通过采用SPG结合准直器和反射镜的结构特点，本发明实施例的VOA体积小、成本低。
在上述实施例中，SPG本身可能对不同的偏振光具有不同的衍射效率，从而造成偏振相关损耗(Polarization dependent loss，以下简称：PDL)，为降低PDL，进一步地，还可以包括1/4波片，图6为本发明VOA实施例二的结构示意图，如图6所示，在图3所示VOA的基础上，SPG与反射镜13之间还设置有1/4波片15。详细的工作原理如下：
SPG12两端的电压为低电压或零电压时，入射光从准直器11射出后到达SPG12后，入射光中的左旋圆偏振态被SPG12进行一次+1级衍射后变为右旋圆偏振态，经过反射镜和1/4波片，反射光回到SPG12时形成右旋圆偏振态。接着在SPG12上再进行一次-1级衍射，变成左旋圆偏振态出射时将以一定角度斜射，不会进入准直器11。入射光中的右旋圆偏振态被SPG12进行一次-1级衍射后变为左旋圆偏振态，经过反射镜和1/4波片，反射光回到SPG12时形成左旋圆偏振态。接着在SPG12上再进行一次+1级衍射，变成右旋圆偏振态出射时将以一定角度斜射，不会进入准直器11，此时VOA衰减达到最大。
SPG12两端的电压为高电压时，和图5所示类似，入射光无论何种偏振态，都被衍射到0级，并且从反射镜直接反射回准直器11而输出，这时VOA的衰减最小。
SPG两端的电压为0～VH之间的任意值时，入射光被衍射到0级和±1级的分配比例也随电压改变，见上述式(1)和式(2)。VOA的衰减值就随着电压增大而减小。
在本实施例中，最终回到准直器的光是SPG两次0级衍射的光。入射光的偏振态可分解为P偏光和S偏光。P偏振态的光经0级衍射后，经过反射镜和1/4波片，回到SPG时变成S偏振态；而S偏振态则相反，经过0级衍射，反射镜和1/4波片回到SPG时将变成P偏振态。因此，最终进入准直器的刚好是两种正交 偏振态的0级衍射效率之积。对于任何输入光偏振态，表现出来的衍射效率相同，从而实现了PDL的自动补偿。
在图6所示的VOA中，从式(1)中可以看出，SPG的0级衍射效率与波长相关。当SPG两端电压在0～VH之间时，长波长的0级衍射效率比短波长大，损耗比短波长小，产生了波长相关损耗(Wavelength dependent loss,以下简称：WDL)。为减小WDL，本发明给出另一种VOA结构。
图7为本发明VOA实施例三的结构示意图，如图7所示，在图6所示的VOA的基础上，在可变偏振光栅与1/4波片之间还设置有LC16。此时，电压控制器14用于调节SPG12两端和LC16两端的电压。具体来说，LC产生的o/e光程差，对长短波长的相位差
Figure PCTCN2014089131-appb-000002
不同，因此LC本身会产生WDL。选择LC和波片相反的长短轴方向，使LC的WDL与其他部分WDL形成一定程度抵消，从而可实现WDL补偿。
具体的工作原理如下：SPG第一次衍射后的右旋/左旋圆偏振态，经过LC，1/4波片和反射镜再回到SPG时为右旋/左旋圆偏光，SPG将以m1级进行第二次衍射，并斜射出去。当LC和波片产生的相位差不等于π/2时，回到SPG的光将不是完全的右旋/左旋偏振态，而夹杂了一部分左旋/右旋偏振态。而这部分夹杂光就会发生±1级衍射平行出射，耦合回输出光纤，作为对0级光的补充，实现了WDL的补偿。
其中，光能输出效率可由下式(3)计算：
Figure PCTCN2014089131-appb-000003
Figure PCTCN2014089131-appb-000004
表示两次0级衍射的光能，
Figure PCTCN2014089131-appb-000005
因子体现了LC的作用，是将斜射出的那一部分光能抽出一部分作为WDL补偿光。式中Δn1，Δn2分别为SPG和LC的双折射率差，d1d2分别为SPG和LC的液晶层厚度，ΔL为波片的光程差，λ是光的波长，A为±1级光与准直器的耦合比例。选择合适参数，只需在LC上施加与SPG相同的电压便可进行全动态范围内的 WDL补偿，无需另外加不同电压值来调节。在这样一组参数下，式(3)的模拟结果显示，VOA在0～30dB衰减范围内，可实现WDL从补偿前的3dB降到0.63dB。
上述实施例都是基于SPG的VOA，下面将详细描述本发明实施例提供的基于PPG的VOA。
图8为本发明VOA实施例四的结构和工作原理示意图，如图8所示，本实施例的VOA可以包括：准直器21、PPG22、LC23、反射镜24和用于调节LC23两端的电压的电压控制器25，其中：
准直器21、PPG22、LC23、反射镜24依次放置，如图8所示，PPG22、LC23和反射镜24均以垂直于光路方向设置，四者依次放置后需进行光路对准，反射镜24和光路严格垂直放置。准直器21用于接收入射光，并将所述入射光输出至PPG2。PPG22用于将入射光进行一次衍射后射出并经LC23到达反射镜24，LC23用于随着电压的变化改变光束的偏振态，PPG22还用于将反射镜24反射回并通过LC23改变偏振态的光束进行一次衍射后，将得到的衍射光射出。准直器21还用于接收所述衍射光，并将所述衍射光输出。
具体地，LC23可以是电控双折射率(Electrically Controlled Birefringence，以下简称：ECB)型LC或垂直排列(Vertical Alignment，以下简称：VA)型LC，
一、当LC23为ECB型的LC时，电压控制器14调节ECB型LC两端的电压在低电压或零电压～高电压VH之间变化，如图8所示，在LC两端加电压可调节光的相位差，从而调节光的偏振态。光从准直器向PPG入射时，左旋圆偏振态和右旋圆偏振态的入射光分别被衍射到±1级，以右旋圆偏振态和左旋圆偏振态射出，当LC两端电压为0时，ECB型LC为1/4波片，可改变光的偏振态。光经过反射镜和LC回到PPG时，光分别成为右旋圆偏振态和左旋圆偏振态，第二次在PPG上发生的衍射就为m1级，衍射光将以较大角度斜射出，不进入准直器和输出光纤，此时VOA衰减达到最大。在LC两端加高电压VH时，ECB型LC相当于相位差为0的波片。经过反射镜反射回到PPG的光将为左旋圆偏振态和右旋圆偏振态，第二次在PPG上发生衍射以±1级以水平方向出射，回到准直器和输出光纤，此时VOA衰减最小。
当LC两端所加电压在0～VH范围内变化，光的衰减值就随着电压增大而 减小。因此，可以通过调节加在LC两端的电压来控制VOA对光的衰减幅度。
入射光被衍射到±1级的概率η如下公式(4)所示：
Figure PCTCN2014089131-appb-000006
式中Δn为LC的双折射率差，d为LC的液晶层厚度，λ是光的波长。由于通过控制LC改变光偏振态后，在PPG上只产生1次衍射，本实施例中的VOA的动态范围为0～25dB可调。
进一步地，当LC为ECB型LC时，在上述实施例的基础上，还可以是，在ECB型LC和反射镜之间加一片1/4波片，则构成Bright型的VOA。图9为本发明VOA实施例五的结构和工作原理示意图，如图9所示，ECB型LC与反射镜24之间还设置有一1/4波片26，此时入射光被衍射到±1级的概率η如下公式(5)所示：
Figure PCTCN2014089131-appb-000007
式中Δn为LC的双折射率差，d为LC的液晶层厚度，ΔL为波片的光程差，λ是光的波长。
本实施例中的VOA的动态范围为0～25dB范围可调。本实施例中的Bright型VOA，在0～20dB衰减范围内，WDL在0.7dB以内，可以满足光通信系统对高端Bright型VOA的要求。
二、当LC23为VA型的LC时，电压控制器14调节VA型LC两端的电压在低电压或零电压～高电压VH之间变化，此时入射光被衍射到±1级的概率η如下公式(6)所示：
Figure PCTCN2014089131-appb-000008
式中Δn为LC的双折射率差，d为LC的液晶层厚度，λ是光的波长。
由于PPG产生1次有效衍射，此时VOA的动态范围为0～25dB可调。WDL<0.6dB@IL＝0～15dB，满足光通信系统对高端Bright型VOA的要求。
本实施例提供的VOA，利用PPG的二个级次衍射，结合LC、准直器和反射镜，电压控制器调节LC两端的电压在低电压或零电压～高电压之间变化，VOA具有0～25dB的动态范围，由于本发明实施例是通过电压控制器调节LC两端的电压进而调节PPG的衍射效率，相比较现有技术中的机械调节，本发明实施例的VOA具有可靠性好的优点，而且，通过采用PPG结合LC、准直器和反射镜的结构特点，本发明实施例的VOA体积小、成本低。
在上述图8和图9所示的实施例的基础上，为进一步扩大VOA的动态范围，可以采用2级PPG，即是在准直器与聚合物偏振光栅之间还设置有一聚合物偏振光栅，可提高VOA的动态范围到0～35dB。结合附图特举一实施例，图10为本发明VOA实施例六的结构和工作原理示意图，如图10所示，在图8所示实施例的基础上，在准直器21与聚合物偏振光栅22之间还设置有一聚合物偏振光栅28，本实施例中LC为ECB型LC，可构成大动态范围的Bright型VOA。进一步地，若在PPG2和反射镜之间加上1/4波片则可将Bright型的VOA变成Dark型VOA。
工作原理如下：当光从准直器向PPG28入射时，入射光中的左旋圆偏振态和右旋圆偏振态分别被衍射到±1级，出射为右旋圆偏振态/左旋圆偏振态。在PPG22又分别产生m1级衍射，左旋圆偏振态/右旋圆偏振态以平行光轴的方向射出。
当LC23加低电压或零电压时，ECB型LC作为1/4波片调整光的偏振态，光再由反射镜返回到PPG22时，仍为左旋圆偏振态/右旋圆偏振态。在PPG28和PPG22分别发生±1和m1级衍射，光直接射回准直器和输出光纤中，此时VOA衰减最小。
当LC23加高电压VH时，光经过LC23后不改变偏振态，光再经过反射镜返回到PPG22时，偏振属性改变，在PPG22和PPG28分别发生m1和±1级衍射，光将离轴较远平行射出，回不到准直器21和输出光纤中，此时VOA衰减最大。
而当LC23两端所加电压在低电压/零电压～VH范围内变化，光的衰减值 就随着电压增大而增大，从而调节了VOA的衰减幅度。
本实施例中由于采用了2级PPG，回到准直器的光经过了2次PPG的衍射，从而可实现大的衰减动态范围，本实施例中VOA的动态范围到0～35dB。
进一步地，在图8所示实施例的基础上，为实现VOA的动态范围到0～35dB以上，图11为本发明VOA实施例七的结构和工作原理(LC加高电压)示意图，图12为本发明VOA实施例七的结构和工作原理(LC加低电压或零电压)示意图，如图11和图12所示，LC为ECB型的LC，LC23与反射镜之间还依次设置有PPG30和1/4波片31。
工作原理如下：
当光从准直器21向PPG22入射时，入射光中的左旋圆偏振态和右旋圆偏振态成分分别被衍射到±1级，出射为右旋圆偏振态/左旋圆偏振态。
如图11所示，当LC23加高电压VH时，ECB型LC不调整光的偏振态，光以右旋圆偏振态/左旋圆偏振态到达PPG30，发生m1级衍射，左旋圆偏振态/右旋圆偏振态以平行光轴的方向的角度射出。再通过1/4波片和反射镜回到PPG30时，仍为左旋圆偏振态/右旋圆偏振态。在PPG30上发生±1级衍射，出射的右旋圆偏振态/左旋圆偏振态到达PPG22时再次衍射到m1级，以平行光轴的方向方向射出，回到输出准直器21。此时VOA衰减最小。
如图12所示，当LC23加低电压VL时，ECB型LC作为1/2波片调整光的偏振态，光以左旋圆偏振态/右旋圆偏振态到达PPG30，再次发生±1级反射，以大角度出射，将不再能够返回到准直器21中，此时VOA衰减最大。
而当LC23两端所加电压在VL～VH范围内变化，光的衰减值就随着电压增大而减小，从而调节了VOA的衰减幅度。此时入射光被衍射到±1级的概率η如下公式(7)所示：
Figure PCTCN2014089131-appb-000009
本实施例中同样采用了2级PPG经过了2次衍射，IL可达0～35dB。
本领域普通技术人员可以理解：实现上述各方法实施例的全部或部分步骤可以通过程序指令相关的硬件来完成。前述的程序可以存储于一计算机可读取存储介质中。该程序在执行时，执行包括上述各方法实施例的步骤；而前述的存储介质包括：ROM、RAM、磁碟或者光盘等各种可以存储程序代码的介质。
最后应说明的是：以上各实施例仅用以说明本发明的技术方案，而非对其限制；尽管参照前述各实施例对本发明进行了详细的说明，本领域的普通技术人员应当理解：其依然可以对前述各实施例所记载的技术方案进行修改，或者对其中部分或者全部技术特征进行等同替换；而这些修改或者替换，并不使相应技术方案的本质脱离本发明各实施例技术方案的范围。

Claims (10)

  1. 一种可调光衰减器，其特征在于，包括：
    准直器、可变偏振光栅SPG、反射镜和用于调节所述SPG的液晶层两端电极的电压的电压控制器，其中：
    所述准直器、SPG和反射镜依次放置；
    所述准直器用于接收入射光，并将所述入射光输出至所述SPG；
    所述SPG用于将所述入射光进行一次衍射后射出到所述反射镜；
    所述SPG还用于将所述反射镜反射回的光束进行一次衍射后，将得到的衍射光射出；
    所述准直器还用于接收所述衍射光，并将所述衍射光输出。
  2. 根据权利要求1所述的可调光衰减器，其特征在于，所述电压控制器调节所述SPG两端的电压为低电压或零电压时，所述SPG用于将所述入射光进行一次衍射后射出到所述反射镜，包括：
    所述SPG将所述入射光中的左旋圆偏振态进行一次+1级衍射后变为右旋圆偏振态后射出到所述反射镜；和，
    所述SPG将所述入射光中的右旋圆偏振态进行一次-1级衍射后变为左旋圆偏振态后射出到所述反射镜；
    所述反射镜用于将接收到的所述入射光中的右旋圆偏振态/左旋圆偏振态反射为左旋圆偏振态/右旋圆偏振态后射出到所述SPG；
    所述SPG还用于将所述反射镜反射回的光束进行一次衍射后，将得到的衍射光射出至所述准直器，包括：
    所述SPG将所述反射镜反射回的左旋圆偏振态进行一次+1级衍射后变为右旋圆偏振态以平行光轴的方向射出；和，
    所述SPG将所述反射镜反射回的右旋圆偏振态进行一次-1级衍射后变为左旋圆偏振态以平行光轴的方向射出；
    所述电压控制器调节所述SPG两端的电压为高电压时，所述SPG用于将所述入射光进行一次衍射后射出到所述反射镜，包括：
    所述SPG将所述入射光中的左旋圆偏振态/右旋圆偏振态进行一次0级衍射后射出到所述反射镜；
    所述反射镜用于将所述SPG进行一次0级衍射后射出的衍射光直接反射 回所述准直器。
  3. 根据权利要求1或2所述的可调光衰减器，其特征在于，所述SPG与所述反射镜之间还设置有一1/4波片，所述电压控制器调节所述SPG两端的电压为低电压或零电压时，所述SPG用于将所述入射光进行一次衍射后射出到所述反射镜，包括：
    所述SPG将所述入射光中的左旋圆偏振态进行一次+1级衍射后变为右旋圆偏振态后经过所述1/4波片射出到所述反射镜；和，
    所述SPG将所述入射光中的右旋圆偏振态进行一次-1级衍射后变为左旋圆偏振态后经过所述1/4波片射出到所述反射镜；
    所述1/4波片和反射镜用于将接收到的所述入射光中的右旋圆偏振态/左旋圆偏振态反射为右旋圆偏振态/左旋圆偏振态后射出到所述SPG；
    所述SPG还用于将所述反射镜反射回的光束进行一次衍射后，将得到的衍射光射出，包括：
    所述SPG将所述反射镜反射回的左旋圆偏振态进行一次+1级衍射后变为右旋圆偏振态以一定角度斜射出；和，
    所述SPG将所述反射镜反射回的右旋圆偏振态进行一次-1级衍射后变为左旋圆偏振态以一定角度斜射出；
    所述电压控制器调节所述SPG两端的电压为高电压时，所述SPG用于将所述入射光进行一次衍射后射出到所述反射镜，包括：
    所述SPG将所述入射光中的左旋圆偏振态/右旋圆偏振态进行一次0级衍射后射出到所述反射镜；
    所述反射镜用于将所述SPG进行一次0级衍射后射出的衍射光直接反射回所述准直器。
  4. 根据权利要求3所述的可调光衰减器，其特征在于，所述SPG与所述1/4波片之间还设置有一液晶部件LC，所述电压控制器还用于调节所述LC两端电极的电压，所述LC用于实现波长相关损耗补偿。
  5. 一种可调光衰减器，其特征在于，包括：
    准直器、聚合物偏振光栅PPG、液晶部件LC、反射镜和用于调节所述LC两端电极的电压的电压控制器，其中：
    所述准直器、PPG、LC、反射镜依次放置；
    所述准直器用于接收入射光，并将所述入射光输出至所述PPG；
    所述PPG用于将所述入射光进行一次衍射后射出并经所述LC到达所述反射镜；
    所述LC用于随着电压的变化改变光束的偏振态；
    所述PPG还用于将所述反射镜反射回并通过所述LC改变偏振态的光束进行一次衍射后，将得到的衍射光射出；
    所述准直器还用于接收所述衍射光，并将所述衍射光输出。
  6. 根据权利要求5所述的可调光衰减器，其特征在于，所述LC为电控双折射率ECB型LC，所述电压控制器调节所述ECB型LC两端的电压为低电压或零电压时，所述ECB型LC为1/4波片，所述PPG用于将所述入射光进行一次衍射后射出并经所述LC到达所述反射镜，包括：
    所述PPG将所述入射光中的左旋圆偏振态进行一次+1级衍射后变为右旋圆偏振态后射出并经所述LC到达所述反射镜；和，
    所述PPG将所述入射光中的右旋圆偏振态进行一次-1级衍射后变为左旋圆偏振态后射出并经所述LC到达所述反射镜；
    所述LC和反射镜用于将接收到的所述入射光中的右旋圆偏振态/左旋圆偏振态反射为右旋圆偏振态/左旋圆偏振态后射出到所述PPG；
    所述PPG还用于将所述反射镜反射回并通过所述LC改变偏振态的光束进行一次衍射后，将得到的衍射光射出，包括：
    所述PPG将所述反射镜反射回的左旋圆偏振态进行一次+1级衍射后变为右旋圆偏振态以一定角度斜射出；和，
    所述PPG将所述反射镜反射回的右旋圆偏振态进行一次-1级衍射后变为左旋圆偏振态以一定角度斜射出；
    所述电压控制器调节所述ECB型LC两端的电压为高电压时，所述ECB型LC类似于相位差为0的波片，所述PPG用于将所述入射光进行一次衍射后射出并经所述LC到达所述反射镜，包括：
    所述PPG将所述入射光中的左旋圆偏振态进行一次+1级衍射后变为右旋圆偏振态后射出并经所述LC到达所述反射镜；和，
    所述PPG将所述入射光中的右旋圆偏振态进行一次-1级衍射后变为左旋圆偏振态后射出并经所述LC到达所述反射镜；
    所述LC和反射镜用于将接收到的所述入射光中的右旋圆偏振态/左旋圆偏振态反射为左旋圆偏振态/右旋圆偏振态后射出到所述PPG；
    所述PPG还用于将所述反射镜反射回并通过所述LC改变偏振态的光束进行一次衍射后，将得到的衍射光射出，包括：
    所述PPG将所述反射镜反射回的左旋圆偏振态进行一次+1级衍射后变为右旋圆偏振态以平行光轴的方向射出；和，
    所述PPG将所述反射镜反射回的右旋圆偏振态进行一次-1级衍射后变为左旋圆偏振态以平行光轴的方向射出。
  7. 根据权利要求6所述的可调光衰减器，其特征在于，所述ECB型LC与所述反射镜之间还设置有一1/4波片。
  8. 根据权利要求5所述的可调光衰减器，其特征在于，所述LC为垂直排列VA型LC。
  9. 根据权利要求5～8任一所述的可调光衰减器，其特征在于，所述准直器与所述PPG之间还设置有一PPG，所述准直器输出的入射光依次经过两个PPG时，分别产生一次±1级衍射和m1级衍射；
    经过所述反射镜和LC反射回的光依次经过两个PPG时，分别产生一次m1级衍射和±1级衍射。
  10. 根据权利要求5所述的可调光衰减器，其特征在于，所述LC为电控双折射率ECB型LC，所述ECB型LC与所述反射镜之间还依次设置有一PPG和一1/4波片，所述电压控制器调节所述ECB型LC两端的电压为高电压时，所述ECB型LC不调整光的偏振态；
    所述电压控制器调节所述ECB型LC两端的电压为低电压或零电压时，所述ECB型LC作为1/2波片调整光的偏振态；
    所述准直器输出的入射光依次经过两个PPG时，分别产生一次±1级衍射和m1级衍射；
    经过所述反射镜和1/4波片反射回的光依次经过两个PPG时，分别产生一次m1级衍射和±1级衍射。
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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3324226A1 (en) * 2016-08-17 2018-05-23 Huawei Technologies Co., Ltd. Optical cross connection apparatus

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP7101954B2 (ja) * 2017-10-30 2022-07-19 株式会社フォトニックラティス 光マトリクススイッチ
CN110208999B (zh) * 2019-05-18 2023-03-24 深圳市麓邦技术有限公司 图像采集方法及系统
CN113253389B (zh) * 2020-02-07 2022-06-14 华为技术有限公司 一种衰减调节方法和可变光衰减器
US20220197043A1 (en) * 2020-12-22 2022-06-23 Facebook Technologies, Llc Three-dimensional beam steering device

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20090073331A1 (en) * 2007-09-11 2009-03-19 Lei Shi Tunable liquid crystal devices, devices using same, and methods of making and using same
CN102725683A (zh) * 2009-12-01 2012-10-10 视瑞尔技术公司 用于调制与相位调制器相互作用的光的相位调制器
CN102866534A (zh) * 2012-10-08 2013-01-09 南京大学 可调光衰减器
CN103091787A (zh) * 2013-01-17 2013-05-08 珠海保税区光联通讯技术有限公司 可调光衰减器及可调光衰减波分复用器
CN103703405A (zh) * 2012-01-30 2014-04-02 华为技术有限公司 波长选择开关的方法和装置

Family Cites Families (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5276747A (en) 1993-01-21 1994-01-04 E-Tek Dynamics, Inc. Polarization-independent optical switch/attenuator
US7312906B2 (en) * 1996-07-12 2007-12-25 Science Applications International Corporation Switchable polymer-dispersed liquid crystal optical elements
US7034979B1 (en) 2001-11-09 2006-04-25 Ezconn Corporation Variable optical attenuator using crystal wedges
JP4382661B2 (ja) * 2002-06-28 2009-12-16 富士通株式会社 反射型可変光偏向器及びそれを用いたデバイス
DE602004023641D1 (de) 2003-11-27 2009-11-26 Asahi Glass Co Ltd Optisches element mit einem flüssigkristall mit optischer isotropie
JP4013892B2 (ja) * 2003-11-28 2007-11-28 旭硝子株式会社 回折素子および光減衰器
JP2005274847A (ja) * 2004-03-24 2005-10-06 Toshiaki Nose 位相分布の形成方法及び回折光学素子
JP2008545149A (ja) * 2005-07-05 2008-12-11 富士フイルム株式会社 液晶表示装置及び液晶プロジェクタ
US7295748B2 (en) 2005-08-08 2007-11-13 Jds Uniphase Corporation Variable optical attenuator with wavelength dependent loss compensation
EP2012173A3 (en) * 2007-07-03 2009-12-09 JDS Uniphase Corporation Non-etched flat polarization-selective diffractive optical elements
JP2009294604A (ja) * 2008-06-09 2009-12-17 Asahi Glass Co Ltd 光変調液晶素子および可変光減衰器
EP2202568B1 (en) * 2008-12-26 2018-09-05 SCREEN Holdings Co., Ltd. Optical modulator
US8064036B2 (en) * 2009-04-30 2011-11-22 Oclaro (North America), Inc. Liquid crystal optical switch configured to reduce polarization dependent loss
WO2011014743A2 (en) * 2009-07-31 2011-02-03 North Carolina State University Beam steering devices including stacked liquid crystal polarization gratings and related methods of operation
JP5195991B2 (ja) * 2010-10-04 2013-05-15 ソニー株式会社 照明装置および表示装置
CN104204926B (zh) * 2012-01-26 2017-08-11 视瑞尔技术公司 具有观察者跟踪功能的显示器

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20090073331A1 (en) * 2007-09-11 2009-03-19 Lei Shi Tunable liquid crystal devices, devices using same, and methods of making and using same
CN102725683A (zh) * 2009-12-01 2012-10-10 视瑞尔技术公司 用于调制与相位调制器相互作用的光的相位调制器
CN103703405A (zh) * 2012-01-30 2014-04-02 华为技术有限公司 波长选择开关的方法和装置
CN102866534A (zh) * 2012-10-08 2013-01-09 南京大学 可调光衰减器
CN103091787A (zh) * 2013-01-17 2013-05-08 珠海保税区光联通讯技术有限公司 可调光衰减器及可调光衰减波分复用器

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3324226A1 (en) * 2016-08-17 2018-05-23 Huawei Technologies Co., Ltd. Optical cross connection apparatus

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EP3139208A4 (en) 2017-06-21
EP3139208B1 (en) 2020-04-29
CN105446048B (zh) 2017-06-20
JP2017520787A (ja) 2017-07-27
EP3139208A1 (en) 2017-03-08
US9927678B2 (en) 2018-03-27
US20170075189A1 (en) 2017-03-16

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