WO2018214173A1 - 一种波长选择开关、交换引擎及其相位调制方法 - Google Patents

一种波长选择开关、交换引擎及其相位调制方法 Download PDF

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Publication number
WO2018214173A1
WO2018214173A1 PCT/CN2017/086221 CN2017086221W WO2018214173A1 WO 2018214173 A1 WO2018214173 A1 WO 2018214173A1 CN 2017086221 W CN2017086221 W CN 2017086221W WO 2018214173 A1 WO2018214173 A1 WO 2018214173A1
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port
output
along
grating
incident light
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PCT/CN2017/086221
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English (en)
French (fr)
Inventor
毛磊
宗良佳
冯志勇
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华为技术有限公司
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Priority to PCT/CN2017/086221 priority Critical patent/WO2018214173A1/zh
Priority to CN201780089398.2A priority patent/CN110494801B/zh
Publication of WO2018214173A1 publication Critical patent/WO2018214173A1/zh

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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
    • G02F1/31—Digital deflection, i.e. optical switching

Definitions

  • the present application relates to the field of optical communications, and in particular, to a wavelength selective switch, a switching engine, and a phase modulation method thereof.
  • WSS Wavelength Selective Switch
  • ROADM Reconfigurable Optical Add-Drop Multiplexer
  • the MEMS (Micro-Electro-Mechanical System, MEMS)-based WSS is difficult to satisfy the Hitless characteristic when controlling beam deflection to achieve port switching.
  • incident light of different wavelengths is irradiated onto the MEMS mirrors at different positions on the MEMS after being split by the grating, and by controlling the angles of the respective mirrors, different wavelengths can be selected to enter different fiber ports.
  • the MEMS mirror can only rotate in one dimension, the signal light will inevitably sweep the path of port 2 to port 6 during the switching of the mirror rotation. All ports on the port, thus affecting the traffic of port 5 where the wavelength is located, introducing additional switching crosstalk. This situation does not satisfy the Hitless feature, so it is necessary to find a new solution to implement the Hitless feature.
  • liquid crystal on silicon (LCoS)-based WSS offers unparalleled reliability and stability, and LCoS is digitally modulated to support Flex-grid features.
  • LCoS liquid crystal on silicon
  • the deflection of the beam is usually achieved using the phase distribution of the blazed grating arranged along the port distribution direction.
  • Signal light incident on the LCoS panel can be diffracted to different angles by switching stroboscopic gratings of different periods to be coupled to ports at different locations. Therefore, ideally, due to the digital modulation properties of the LCoS, the phase diagram switching process will not affect other ports on the path.
  • LCoS actually achieves phase modulation by rotation of liquid crystal molecules in pixels of each dot.
  • FIG. 3 and FIG. 4 when it is necessary to switch the equivalent phase of the initial state grating A distributed along the port distribution direction to the equivalent phase of the target state grating B distributed along the port distribution direction, it is desirable to distribute along the port distribution direction.
  • the phase diagram of the blazed grating is switched from the initial phase gradient A to the target phase gradient B.
  • the liquid crystal molecules of each pixel on the LCoS panel are also rotated from the initial state to the target state, and the actual electronic device response cannot be completely achieved.
  • liquid crystal molecules at each point will undergo a number of turbulent states during the switching to the next state (as indicated by the dashed line in Fig. 4), and these turbulent states will cause additional transient crosstalk during the switching process. This causes interference to other port services than the target port.
  • the embodiment of the present application provides a wavelength selection switch, a switching engine, and a phase modulation method thereof, which are used to solve the technical problem that it is difficult to satisfy the Hitless characteristic when the LCoS-based WSS performs port switching in the prior art.
  • the present application provides a phase modulation method for a switching engine, the switching engine comprising a liquid crystal on silicon LCOS panel and an LCOS phase modulator, the method being applied to the LCOS phase modulator, the method comprising:
  • the first modulation signal is used to modulate the diffracted light of the incident light to be output along the first port;
  • the second modulation signal is used to modulate the diffracted light of the incident light into a first Output along the output direction and wavelength distribution direction of the first port for a predetermined length of time, output along the output direction of the second port and the wavelength distribution direction for a second set time length; and at the first
  • the intensity of the diffracted light gradually decreases along the output direction of the first port and gradually increases along the wavelength distribution direction within a set length of time; the intensity of the diffracted light during the second set time length
  • the output direction along the second port is gradually increased, and gradually decreases along the wavelength distribution direction.
  • the second modulation signal does not directly modulate the diffracted light of the incident light to be outputted along the output direction of the second port, but modulates the diffracted light of the incident light into an output direction along the first port and
  • the wavelength distribution direction distribution is distributed along the output direction and the wavelength distribution direction of the second port, and finally along the second port; and the intensity of the diffracted light gradually decreases along the output direction of the first port for the first set time length It also gradually increases along the wavelength distribution direction; during the second set time length, the intensity of the diffracted light gradually increases along the wavelength distribution direction as it gradually increases in the output direction of the second port.
  • the second modulated signal gradually shifts the output power of the diffracted light of the incident light to the wavelength distribution direction, and then gradually shifts from the wavelength distribution direction to the output direction of the second port, since the diffracted light of the incident light
  • the output power is transferred to the wavelength distribution direction without causing interference to other ports. Therefore, the present application satisfies the Hitless characteristic when the output port of the incident light can be switched from the first port to the second port according to the second modulation signal.
  • the method further includes: providing a driving signal to the LCOS panel according to the second modulation signal; the driving signal is configured to drive liquid crystal molecules corresponding to the plurality of liquid crystal pixels at the first set time length and And presenting an ordered rotation state in a second set time length, wherein the plurality of liquid crystal pixels form a plurality of states of blazed gratings, wherein the plurality of states of blazed gratings are used to control the diffracted light of the incident light in the a first set time length and an output direction within the second set time length; wherein the plurality of liquid crystal pixels are liquid crystal pixels corresponding to the incident light on the LCOS panel.
  • the liquid crystal molecules corresponding to the plurality of liquid crystal pixels are driven to display an ordered rotation state during the first set time length and the second set time length by providing a driving signal to the LCOS panel.
  • the plurality of liquid crystal pixels are formed into a plurality of blazed gratings, and the blazed gratings of the plurality of states are used to control the output direction of the diffracted light of the incident light for a first set time length and a second set time length to make the incident
  • the output power of the diffracted light of the light is gradually shifted to the wavelength distribution direction, and then gradually transferred from the wavelength distribution direction to the output direction of the second port.
  • the acquiring the second modulated signal includes:
  • phase distribution function of the initial state grating, the phase distribution function of the target state grating, and the preset phase distribution a function of determining a phase distribution function of the N intermediate state gratings; a phase distribution function of the initial state grating; a phase distribution function of the target state grating is a phase distribution function distributed along a port distribution direction, the preset The phase distribution function is a phase distribution function distributed along the wavelength distribution direction;
  • the initial state grating is a blazed grating formed on the LCOS panel when the LCOS phase modulator loads the first modulation signal;
  • the N intermediate state gratings, the target state grating are in the A blazed grating formed successively on the LCOS panel when the LCOS phase modulator loads the second modulated signal.
  • the generated second modulation signal can control the transition of the initial state grating through the plurality of intermediate state gratings to the target state grating, and the plurality of state gratings
  • the function is to gradually attenuate the output power of the incident light along the output direction of the first port, and then gradually increase the output power of the incident light along the output direction of the second port, and gradually attenuate the output of the incident light along the output direction of the first port.
  • the output power of the incident light along the wavelength distribution direction is also gradually increased until the output power of the incident light is all transferred to the wavelength distribution direction, and then the output power of the incident light along the output direction of the second port is gradually increased.
  • the initial state grating is configured to control the diffracted light diffracted by the incident light to be output along an output direction of the first port;
  • the N intermediate gratings are capable of controlling the diffracted light diffracted by the incident light to be output along the output direction and the wavelength distribution direction of the first port, and then along the output direction of the second port and the a wavelength distribution direction output, finally outputting along an output direction of the second port; and during the first set time length, the intensity of the diffracted light is gradually weakened along the output direction of the first port along the wavelength The distribution direction is gradually increased; during the second set time length, the intensity of the diffracted light gradually increases along the wavelength distribution direction as the output direction of the second port gradually increases;
  • the target state grating is configured to control diffracted light that is diffracted by the incident light to be output along an output direction of the second port.
  • phase distribution function of the N intermediate state gratings satisfies the following relationship:
  • N is a positive integer greater than or equal to 3
  • P i (x, y) is the phase distribution function of the ith intermediate state grating
  • P1A(y) is the phase distribution of the initial state grating a function
  • P1B(y) is a phase distribution function of the target state grating
  • P2(x) is the preset phase distribution function
  • a i , b i , c i are respectively P i (x, y), P2 (x), P1B (y) weight coefficient.
  • a specific implementation manner of constructing a phase distribution function of the intermediate state grating is provided, and the LCOS panel is digitally modulated by using three weight coefficients of the selected phase distribution function, so as to adjust the plurality of intermediate state gratings to be stable.
  • the transition compared to the prior art by modifying the beam deflection structure to achieve interference-free switching, does not require any additional hardware, just load the modulation signal required for port switching in the LCOS phase modulator. Yes, it is practical and stable, and it is also beneficial to reduce costs.
  • N is an odd number
  • the preset phase distribution function is a symmetric periodic function.
  • the present application provides a switching engine including an LCOS phase modulator and an LCOS panel, the LCOS phase modulator being electrically connected to the LCOS panel;
  • the LCOS phase modulator is configured to acquire a second modulation signal after determining that the output port of the incident light is switched from the first port to the second port; and switch the loaded first modulation signal to the second modulation signal; And providing a driving signal to the LCOS panel according to the second modulation signal; the first modulation signal is used to modulate the diffracted light of the incident light to be output along the first port; and the second modulation signal is used And dimming the diffracted light of the incident light to output along an output direction and a wavelength distribution direction of the first port for a first set time length, and output along the second port for a second set time length a direction and a direction of the wavelength distribution output; and within the first set time length, the intensity of the diffracted light gradually decreases along the output direction of the first port, and gradually increases along the wavelength distribution direction; During the second set time length, the intensity of the diffracted light gradually increases along the output direction of the second port, and gradually decreases along the wavelength distribution direction.
  • the second modulation signal does not directly modulate the diffracted light of the incident light to be outputted along the output direction of the second port, but modulates the diffracted light of the incident light into an output direction along the first port and
  • the wavelength distribution direction distribution is distributed along the output direction and the wavelength distribution direction of the second port, and finally along the second port; and the intensity of the diffracted light gradually decreases along the output direction of the first port for the first set time length It also gradually increases along the wavelength distribution direction; during the second set time length, the intensity of the diffracted light gradually increases along the wavelength distribution direction as it gradually increases in the output direction of the second port.
  • the second modulated signal gradually shifts the output power of the diffracted light of the incident light to the wavelength distribution direction, and then gradually shifts from the wavelength distribution direction to the output direction of the second port, since the diffracted light of the incident light
  • the output power is transferred to the wavelength distribution direction without causing interference to other ports. Therefore, the present application satisfies the Hitless characteristic when the output port of the incident light can be switched from the first port to the second port according to the second modulation signal.
  • the LCOS panel includes a first substrate, a second substrate, and liquid crystal molecules disposed between the first substrate and the second substrate, and the second substrate is provided with a plurality of rows of liquid crystal pixels ;
  • the LCOS phase modulator is further configured to provide a driving letter to the LCOS panel according to the second modulation signal number;
  • the LCOS panel is configured to acquire the driving signal, and drive the liquid crystal molecules corresponding to the plurality of liquid crystal pixels to be ordered in the first set time length and the second set time length according to the driving signal a state of rotation that causes the plurality of liquid crystal pixels to form a plurality of states of blazed gratings, the plurality of states of blazed gratings for controlling diffracted light of the incident light at the first set time length and the second Setting an output direction within a length of time; wherein the plurality of liquid crystal pixels are liquid crystal pixels corresponding to the incident light on the LCOS panel.
  • the liquid crystal molecules corresponding to the plurality of liquid crystal pixels are driven to display an ordered rotation state during the first set time length and the second set time length by providing a driving signal to the LCOS panel.
  • the plurality of liquid crystal pixels are formed into a plurality of blazed gratings, and the blazed gratings of the plurality of states are used to control the output direction of the diffracted light of the incident light for a first set time length and a second set time length to make the incident
  • the output power of the diffracted light of the light is gradually shifted to the wavelength distribution direction, and then gradually transferred from the wavelength distribution direction to the output direction of the second port.
  • the LCOS phase modulator is specifically configured to:
  • a phase distribution function of the N intermediate state gratings Determining a phase distribution function of the N intermediate state gratings according to a phase distribution function of the initial state grating, a phase distribution function of the target state grating, and a preset phase distribution function; a phase distribution function of the initial state grating, the The phase distribution function of the target state grating is a phase distribution function distributed along the port distribution direction, and the predetermined phase distribution function is a phase distribution function distributed along the wavelength distribution direction;
  • the initial state grating is a blazed grating formed on the LCOS panel when the LCOS phase modulator loads the first modulation signal;
  • the N intermediate state gratings, the target state grating are in the A blazed grating formed successively on the LCOS panel when the LCOS phase modulator loads the second modulated signal.
  • the generated second modulation signal can control the transition of the initial state grating through the plurality of intermediate state gratings to the target state grating, and the plurality of state gratings
  • the function is to gradually attenuate the output power of the incident light along the output direction of the first port, and then gradually increase the output power of the incident light along the output direction of the second port, and gradually attenuate the output of the incident light along the output direction of the first port.
  • the output power of the incident light along the wavelength distribution direction is also gradually increased until the output power of the incident light is all transferred to the wavelength distribution direction, and then the output power of the incident light along the output direction of the second port is gradually increased.
  • the initial state grating is configured to control the diffracted light diffracted by the incident light to be output along an output direction of the first port;
  • the N intermediate gratings for controlling diffraction of the incident light to be first output along the output direction and the wavelength distribution direction of the first port, and then along the output direction of the second port and the wavelength a distribution direction output, finally outputting along an output direction of the second port; and a wavelength distribution along the wavelength of the first port when the intensity of the diffracted light gradually decreases along the output direction of the first port for a first set time length
  • the direction is gradually increased; during the second set time length, the intensity of the diffracted light gradually increases along the wavelength distribution direction as the output direction of the second port gradually increases;
  • the target state grating is configured to control the output of the diffracted light diffracted by the incident light along the second port To the output.
  • phase distribution function of the N intermediate state gratings satisfies the following relationship:
  • N is a positive integer greater than or equal to 3
  • P i (x, y) is the phase distribution function of the ith intermediate state grating
  • P1A(y) is the phase distribution of the initial state grating a function
  • P1B(y) is a phase distribution function of the target state grating
  • P2(x) is the preset phase distribution function
  • a i , b i , c i are respectively P i (x, y), P2 (x), P1B (y) weight coefficient.
  • a specific implementation manner of constructing a phase distribution function of the intermediate state grating is provided, and the LCOS panel is digitally modulated by using three weight coefficients of the selected phase distribution function, so as to adjust the plurality of intermediate state gratings to be stable.
  • the transition compared to the prior art by modifying the beam deflection structure to achieve interference-free switching, does not require any additional hardware, just load the modulation signal required for port switching in the LCOS phase modulator. Yes, it is practical and stable, and it is also beneficial to reduce costs.
  • N is an odd number
  • the preset phase distribution function is a symmetric periodic function.
  • the present application provides a wavelength selective switch including at least the switching engine in any of the above embodiments.
  • FIG. 1 is a schematic structural view of a light selection switch in the prior art
  • FIG. 2 is a schematic structural diagram of phase modulation based on LCOS in the prior art
  • FIG. 3 is a schematic diagram showing an equivalent phase structure of an initial state grating A and a target state grating B based on LCOS phase modulation in the prior art;
  • FIG. 4 is a schematic structural diagram of a disorder state of liquid crystal molecules during port switching based on LCOS in the prior art
  • FIG. 5 is a schematic structural diagram of an LCOS-based switching engine in the prior art
  • FIG. 6 is a schematic diagram of an inventive concept of an LCOS-based switching engine according to an embodiment of the present disclosure
  • FIG. 7 is a schematic structural diagram of an LCOS-based switching engine according to an embodiment of the present disclosure.
  • FIG. 8 is a schematic diagram of a spot distribution of diffracted light in a port switching process of an LCOS-based switching engine according to an embodiment of the present disclosure
  • FIG. 9 is a schematic diagram of energy distribution of diffracted light of different transition states in a port switching process of an LCOS-based switching engine according to an embodiment of the present disclosure
  • FIG. 10 is a schematic diagram of comparison between transient interference of a LCOS-based switching engine during port switching and transient interference existing in the prior art according to an embodiment of the present application.
  • a plurality of the present application means two or more.
  • the terms "first”, “second” and the like are used only to distinguish the purpose of description, and are not to be understood as indicating or implying relative importance, nor as an indication. Or suggest the order.
  • the switching engine in this application is an LCoS-based beam deflecting device, which is applied in LCoS-based WSS.
  • the LCoS-based WSS includes at least an optical fiber array, a diffraction grating, a mirror, a switching engine, and other optimized optical signal transmission.
  • Directional device is an LCoS-based beam deflecting device, which is applied in LCoS-based WSS.
  • the LCoS-based WSS includes at least an optical fiber array, a diffraction grating, a mirror, a switching engine, and other optimized optical signal transmission.
  • Directional device is an LCoS-based beam deflecting device, which is applied in LCoS-based WSS.
  • the working principle of the LCoS-based wavelength selective switch is that the optical signal is input from an input port of the optical fiber array, and the optical signal is first incident on the diffraction grating, and the diffraction grating splits the optical signal, and the optical signals of different wavelengths pass through the mirror. After reflection, it is incident on different areas of the LCoS panel as different incident light.
  • incident light of any wavelength is incident on the LCOS panel
  • the spot of the incident light covers the plurality of liquid crystal pixels, and the driving state of the liquid crystal molecules is controlled by controlling the driving signals loaded on the plurality of liquid crystal pixels, thereby controlling the formation on the LCoS panel.
  • the phase distribution of the blazed grating arranged along the distribution direction of the port realizes the deflection of the incident beam by the phase distribution of the blazed grating arranged along the distribution direction of the port, and the deflected beam is coupled to the port at different positions through the reflected optical path.
  • the LCOS phase modulator supplies a driving signal to the LCoS panel according to the loaded modulation signal.
  • the blazed grating formed on the LCoS panel arranged along the port distribution direction controls the trailing edge of the incident light ⁇ 1 deflection
  • the output direction of port A is output; when the LCOS phase modulator supplies the relevant driving signal to the LCoS panel according to the loaded second modulation signal, the blazed grating formed on the LCoS panel arranged along the port distribution direction controls the incident light ⁇ 1 to deflect the trailing edge port
  • the output direction of B is output; when the output port of the incident light ⁇ 1 needs to be switched from port A to port B, the LCOS phase modulator is required to directly switch the loaded first modulated signal to the second modul
  • the blazed grating arranged along the port distribution direction needs to be directly switched from the initial state grating A to the target state grating B.
  • the equivalent phase of the initial state grating A and the target state grating B is shown in Fig. 3, and the initial state grating A is directly switched to
  • the target state grating B is used, the liquid crystal molecules corresponding to the respective pixels on the LCoS panel are also rotated from the initial state to the target state, and The rotation process of the liquid crystal molecules at each pixel cannot be controlled in an orderly manner, and the liquid crystal molecules at each pixel point undergo a state of turbulence in the process of switching from the initial state to the target state, and these disordered states cause the switching process. Additional transient crosstalk in the interference, thereby interfering with optical signals at ports other than the second port.
  • the present application passes between the initial state grating A and the target state grating B formed on the LCoS panel during the switching of the port of the incident light from the first port to the second port.
  • Insert multiple intermediate states The grating realizes the gentle transition of the initial state grating A to the target state grating B, and correspondingly controls the liquid crystal molecules of each pixel on the LCoS panel to rotate from the initial state through a plurality of intermediate states to the target state.
  • the phase distribution of these intermediate gratings is not only distributed along the port, but also distributed along the wavelength distribution direction, for example, in FIG.
  • the intermediate state grating also includes black and white gratings distributed along the wavelength distribution direction.
  • the output power of the incident light along the output direction of the first port is gradually attenuated, and then the incident light is gradually enhanced along the output direction of the second port. Output Power.
  • the output power of the incident light along the wavelength distribution direction is gradually increased until the output power of the incident light is all Transfer to the wavelength distribution direction orthogonal to the port distribution direction, and then gradually increase the output power of the incident light along the output direction of the second port, while gradually attenuating the output power of the incident light along the wavelength distribution direction until the incident light is to be incident.
  • the output power is all transferred to the output direction of the second port to realize the port switching of the incident light.
  • the port distribution direction is perpendicular to the wavelength distribution direction, the diffracted light of the incident light distributed in the wavelength distribution direction during the gradual change process
  • the output power does not affect the output power of the diffracted light distributed in the direction of the port distribution. Therefore, the influence of the optical signal on other ports during the switching process is avoided, and the Hitless characteristic is satisfied when the first port is switched to the second port.
  • the present application provides an exchange engine, as shown in FIG. 7, comprising a liquid crystal liquid crystal LCOS panel and an LCOS phase modulator, the LCOS panel including a first substrate, a second substrate, and a first substrate and a first substrate The liquid crystal molecules between the two substrates, the second substrate is provided with a plurality of rows of liquid crystal pixels; the LCOS phase modulator is electrically connected with the LCOS panel; the LCOS phase modulator is configured to provide a driving signal to the LCOS panel according to the loaded modulation signal; LCOS The panel is used to control the output direction of the diffracted light after the incident light is diffracted by the LCOS panel according to the driving signal provided by the LCOS phase modulator. Based on the drive signal provided by the LCOS phase modulator, the LCOS panel can control the incident light to deflect in different directions.
  • the LCOS phase modulator is mainly configured to acquire a second modulated signal after determining that the output port of the incident light is switched from the first port to the second port; and switch the loaded first modulated signal to the second modulated signal. Providing a driving signal to the LCOS panel according to the second modulated signal.
  • the first modulated signal is used to modulate the diffracted light of the incident light to be output along the first port.
  • the second modulation signal is configured to modulate the diffracted light of the incident light to be output along an output direction and a wavelength distribution direction of the first port for a first set time length, and within a second set time length Outputting along an output direction of the second port and the wavelength distribution direction; and within the first set time length, an intensity of the diffracted light gradually decreases along an output direction of the first port, along the The wavelength distribution direction is gradually increased; during the second set time length, the intensity of the diffracted light gradually increases along the output direction of the second port, and gradually decreases along the wavelength distribution direction.
  • the second modulated signal is a modulated signal that changes with high and low levels over time. As the modulation signal changes, the output direction of the diffracted light of the incident light also changes.
  • the purpose of the second modulated signal is to have a plurality of intermediate states in the output state of the incident light during the process of switching the output port of the incident light from the first port to the second port, in order to ensure that there is no transient interference between the plurality of intermediate states and other ports.
  • the second modulated signal in the present application can first modulate the incident light to have an output along the first port and the wavelength distribution direction, and then modulate the incident light to have an output along the second port and the wavelength distribution direction.
  • the second modulation signal there may be two cases of deformation of the second modulation signal in the present application.
  • One case is to modulate the diffracted light of the incident light into an output direction and a wavelength along the first port for a first set time length. Distribution direction output, and The intensity of the diffracted light gradually decreases along the output direction of the first port, and gradually increases along the wavelength distribution direction; the output direction along the second port and the wavelength distribution direction in the second set time length Outputting, and the intensity of the diffracted light gradually increases along the output direction of the second port, gradually weakens along the wavelength distribution direction until weakened to 0 along the wavelength distribution direction, and is strongest along the output direction of the second port; During the third set time length, it is only output along the output direction of the second port.
  • the formed silicon-based liquid crystal grating includes not only N intermediate gratings but also target gratings.
  • the diffracted light of the incident light is modulated to be output along an output direction and a wavelength distribution direction of the first port for a first set time length, and the intensity of the diffracted light is along the first port
  • the output direction is gradually weakened, gradually increasing along the wavelength distribution direction; outputting along the output direction of the second port and the wavelength distribution direction for a second set time length, and the intensity of the diffracted light is along
  • the output direction of the second port is gradually increased and gradually weakened along the wavelength distribution direction.
  • the formed silicon-based liquid crystal grating includes N intermediate state gratings, excluding the target state grating.
  • the formed silicon-based liquid crystal grating is a target grating.
  • the second modulation signal does not directly modulate the diffracted light of the incident light to output along the output direction of the second port, but modulates the diffracted light of the incident light into an output along the first port.
  • Direction and wavelength distribution direction distribution then distributed along the output direction and wavelength distribution direction of the second port, and finally output along the second port; and within the first set time length, the intensity of the diffracted light gradually increases along the output direction of the first port When weakened, it gradually increases along the wavelength distribution direction; during the second set time length, the intensity of the diffracted light gradually increases along the wavelength distribution direction as it gradually increases in the output direction of the second port.
  • the second modulated signal gradually shifts the output power of the diffracted light of the incident light to the wavelength distribution direction, and then gradually shifts from the wavelength distribution direction to the output direction of the second port, and diffracts the incident light.
  • the output power is transferred to the wavelength distribution direction without causing interference to other ports. Therefore, the present application satisfies the Hitless characteristic when the output port of the incident light can be switched from the first port to the second port according to the second modulation signal.
  • the spot of the incident light covers a plurality of liquid crystal pixels, and the plurality of liquid crystal pixels are referred to as liquid crystal pixels corresponding to the incident light on the LCOS panel.
  • the LCOS phase modulator is further configured to provide a corresponding driving signal to the LCOS panel according to the second modulation signal.
  • the LCOS panel is configured to obtain a driving signal provided by the LCOS phase modulator, and drive the liquid crystal molecules corresponding to the plurality of liquid crystal pixels according to the driving signal to exhibit an orderly rotation state within a first set time length and a second set time length, so that a plurality of liquid crystal pixel shapes are successively formed into a plurality of states of blazed gratings, and a plurality of states of the blazed gratings are used for controlling the output direction of the diffracted light of the incident light for a first set time length and a second set time length to make the incident light
  • the output power of the diffracted light is gradually shifted to the wavelength distribution direction, and then gradually transferred from the wavelength distribution direction to the output direction of the second port.
  • the blazed grating formed on the LCOS panel is an initial state grating according to the relevant driving signal provided by the LCOS phase modulator; the initial state grating is used to control the incident light to be diffracted.
  • the diffracted light is output in the output direction of the first port.
  • the blazed grating formed on the LCOS panel is N intermediate gratings and target gratings.
  • the diffracted light for controlling the diffraction of the incident light is first output along the output direction and the wavelength distribution direction of the first port, and then output along the output direction and the wavelength distribution direction of the second port, and finally along the second port Output direction output; and in the first setting Within a certain length of time, the intensity of the diffracted light gradually increases along the wavelength distribution direction as it gradually decreases along the output direction of the first port; during the second set time length, the intensity of the diffracted light gradually increases along the output direction of the second port. It also gradually weakens along the wavelength distribution direction; the target state grating, which is used to control the diffracted light diffracted by the incident light, is output along the output direction of the second port.
  • the LCOS phase modulator switches the loaded first modulated signal to the second modulated signal, and provides a corresponding to the LCoS panel based on the second modulated signal.
  • the driving signal controls the liquid crystal molecules of the corresponding pixel on the LCoS panel to rotate from the initial state through a plurality of intermediate states to the target state, and then the initial state grating formed on the LCoS panel smoothly transitions to the target state through the plurality of intermediate state gratings.
  • the output power is all transferred to the wavelength distribution direction, and then gradually increases the incident light along the second port.
  • the LCOS phase modulator acquires the second modulated signal, including: determining a phase distribution function of the N intermediate state gratings according to a phase distribution function of the initial state grating, a phase distribution function of the target state grating, and a preset phase distribution function
  • the phase distribution function of the initial state grating, the phase distribution function of the target state grating is a phase distribution function distributed along the port distribution direction
  • the preset phase distribution function is a phase distribution function distributed along the wavelength distribution direction; according to the N intermediate state gratings
  • the phase distribution function and the phase distribution function of the target state grating generate a second modulated signal.
  • the generated second modulation signal can control the transition of the initial state grating through the plurality of intermediate state gratings to the target state grating, and the plurality of state gratings
  • the function is to gradually attenuate the output power of the incident light along the output direction of the first port, and then gradually increase the output power of the incident light along the output direction of the second port, and gradually attenuate the output of the incident light along the output direction of the first port.
  • the output power of the incident light along the wavelength distribution direction is also gradually increased until the output power of the incident light is all transferred to the wavelength distribution direction, and then the output power of the incident light along the output direction of the second port is gradually increased.
  • the second modulated signal may also be a modulated signal that is pre-stored in the LCOS phase modulator and has an index relationship with the switching process, such that after determining that the output port of the incident light is switched from the first port to the second port, The LCOS phase modulator directly reads the second modulated signal and switches the loaded first modulated signal to the second modulated signal.
  • phase distribution function of the N intermediate state gratings satisfies the following relationship:
  • N is a positive integer greater than or equal to 3
  • P i (x, y) is the phase distribution function of the ith intermediate state grating
  • P1A(y) is the phase distribution function of the initial state grating
  • P1B(y) is the phase distribution function of the target grating
  • P2(x) is the preset phase distribution function
  • a i , b i , c i are P i (x, y), P2 (x), P1B, respectively.
  • a specific implementation manner of constructing a phase distribution function of the intermediate state grating is provided, and the LCOS panel is digitally modulated by using three weight coefficients of the selected phase distribution function, so as to adjust the plurality of intermediate state gratings to be stable.
  • the transition compared to the prior art by modifying the beam deflection structure to achieve interference-free switching, does not require any additional hardware, just load the modulation signal required for port switching in the LCOS phase modulator. Yes, it is practical and stable, and it is also beneficial to reduce costs.
  • P2(x) is a phase distribution function corresponding to the black and white grating, that is, a square wave function shown in FIG. 6.
  • P2(x) is a phase distribution function corresponding to a sine grating or a cosine grating.
  • phase modulation method of the present application is described by taking the selected P2(x) as the phase distribution function of the black and white grating as an example.
  • the port distribution direction on the LCoS is referred to as the X direction
  • the port distribution direction is denoted as the Y direction
  • the phase distribution function of the initial state grating corresponding to the initial output port is P1A(y)
  • the target corresponding to the target output port B The phase distribution function of the state grating is P1B(y).
  • the phase distribution function P2(x) of N intermediate-state gratings is selected.
  • the phase distribution function of P1A(y) and P1B(y) remains unchanged throughout the switching process; P2(x) selects the symmetric periodic function distributed along the wavelength distribution direction, so as to realize the position of the spot distribution without changing the distribution direction of the original port.
  • P2(x) can A symmetric periodic function such as a black-and-white grating or a sinusoidal grating is selected; the function period can be selected according to the actual wavelength channel width, and the period does not change during the entire switching process.
  • the gradual process of the output power of the diffracted light when the incident light is diffracted at the N intermediate gratings formed on the LCoS includes:
  • Figure 8(a) shows the initial state of the selection.
  • the distribution direction of the diffracted spot is the port distribution direction, and the position of the diffracted spot with the strongest intensity can be regarded as the first port position.
  • this intermediate state the position of the spot distributed in the direction of the port distribution is unchanged, but in A diffractive spot is also distributed on both sides of the port distribution direction, and the diffracted spot on both sides of the port distribution direction can be regarded as a diffracted spot in the wavelength distribution direction, the spot intensity in the port distribution direction is attenuated, and the diffracted spot on both sides of the port distribution direction is The intensity is weak.
  • this intermediate state the position of the spot in the existing port distribution direction is unchanged, and both sides of the port distribution direction are The position of the diffracted spot is also unchanged, but the intensity of the spot in the direction of the port distribution is almost attenuated to zero, and the intensity of the diffracted spot on both sides of the port distribution direction is enhanced as compared with FIG. 8(b).
  • the position of the spot in the distribution direction of the port is shifted along the direction of the port distribution, the position of the diffracted spot distributed on both sides of the port distribution direction is unchanged, and the intensity of the diffracted spot distributed on both sides of the port distribution direction is the strongest, and the distribution of the port distribution direction is strong.
  • the spot intensity is weak.
  • the spot position in the port distribution direction is unchanged, and the port distribution direction is The diffracted spot on both sides disappears, and the intensity of the diffracted spot in the port distribution direction is the strongest, and the position of the diffracted spot with the strongest intensity is shifted downward as compared with FIG. 8(a).
  • the gradual change process of the diffraction spot shown in FIG. 8(a) to FIG. 8(f) is to gradually attenuate the output power of the incident light along the output direction of the first port, and then gradually enhance the incident light along the second port.
  • the output power is up until the output power of the incident light is all transferred to the output direction of the second port, so that the output port of the incident light is switched from the first port to the second port without causing signal interference to other ports.
  • the above-mentioned intermediate state regulation process does not control the energy distribution of the diffraction spot by adjusting the period of P2(x), but selects P2 according to the requirements of the specific application scenario (such as the bandwidth of the wavelength channel and the return loss angle in the optical path).
  • the period size then keep the period of P2(x) unchanged, and adjust the weight ratio of P2(x) to achieve a gentle transition; as P2(x) takes up a larger proportion of weight, it is originally located at the port.
  • the intensity of the diffracted spot on A is gradually attenuated. When the intensity of the diffracted spot on port A is completely attenuated, the switching to the target port B is performed.
  • the crosstalk distribution of the switching is shown in Fig.
  • the intermediate state selection is as continuous and gentle as possible, and thus there is a certain requirement for the adjusted granularity and the adjustment range, and the granularity refers to the power between each two intermediate states. Amount of attenuation.
  • the attenuation states of the diffracted light energy distributed along the port direction are selected to be four states at 0 dB, 5 dB, 5.04 dB, and 15 dB, respectively, and the diffracted light is at the port.
  • the energy distribution in the distribution direction is measured. It can be seen from Fig.
  • the energy of the diffracted light of each order distributed along the port distribution direction is synchronously reduced, because the original port A part of the diffracted light energy distributed in the distribution direction is dispersed to both sides, and the diffracted light dispersed to both sides does not introduce additional crosstalk to the diffracted light in the direction of the port distribution.
  • the attenuation of the diffracted light can be as small as 0.04 dB, and the maximum attenuation of the diffracted light can be as much as 15 dB. Therefore, the diffracted light energy distributed along the port direction is here.
  • the process of gradually attenuating to zero in the attenuation range is a process in which the energy distribution of the diffracted light diffracted by the incident light in the initial state grating A is gradually attenuated into a matte state by a plurality of transition states of quasi-continuously varying states.
  • the port is switched.
  • the energy of the diffracted light that is controlled along the wavelength distribution direction is gradually attenuated, the diffracted light energy distributed along the port direction is gradually increased, and the peak of the energy of the diffracted light is gradually distributed at the second port position.
  • FIG. 10(a) shows the case where the initial state grating A (period of 10 pixels) is directly switched to the target state grating B (period of 20 pixels), and the intensity detector is fixed to the negative first order diffraction of the grating A during the actual measurement. Position, if the position is also the negative second-order diffraction position of the target state grating B, the measured transient crosstalk intensity is about 6 dB as shown by the dashed box in Fig. 10(a).
  • the power quasi-continuous dynamic regulation of the wavelength selective switch can be realized, and the adjustment granularity of the power quasi-continuous dynamic regulation can reach 0.04 dB, and the adjustment range can reach 0.04 db to 15 db.
  • the phase modulation method provided by the present application can control the orderly rotation of liquid crystal molecules on the LCoS panel during port switching, so as to form a series of gratings from the initial state grating to the target state grating on the LCoS panel.
  • the gently transitioning intermediate state gratings regularly modulate the energy distribution of the diffracted light of the incident light by these intermediate gratings, thereby solving the transient crosstalk problem existing in the port switching in the WSS.
  • the adjustable range of the intermediate state grating is large.
  • P2(x) mainly modulates the effective pixels distributed along the wavelength distribution direction
  • the number of effective pixels in the wavelength distribution direction may be less than 10 as the wavelength interval in the WSS becomes smaller and smaller in the future.
  • the phase modulation method of the present application controls that the period of P2(x) is kept constant during the port switching process, and only the weight coefficient of P2(x) needs to be adjusted.
  • the embodiment of the present invention provides a phase modulation method of a switching engine, which is used to solve the technical problem that the LCoS-based WSS in the prior art has difficulty in satisfying the Hitless feature when performing port switching.
  • the method and the device It is based on the same inventive concept. Since the principles of the method and the device for solving the problem are similar, the implementation of the device and the method can be referred to each other, and the repeated description will not be repeated.
  • phase modulation method of the switching engine provided by the present application is applied to the LCOS phase modulator in the foregoing embodiment, and specifically includes:
  • Step 101 After determining that the output port of the incident light is switched from the first port to the second port, acquiring a second modulation signal;
  • Step 102 Switch the loaded first modulated signal to a second modulated signal.
  • the first modulated signal is used to modulate the diffracted light of the incident light to be output along the first port;
  • the second modulated signal is used to modulate the diffracted light of the incident light to be along the first set length of time
  • An output direction and a wavelength distribution direction output of a port are output along an output direction of the second port and the wavelength distribution direction for a second set time length; and within the first set time length, the The intensity of the diffracted light gradually decreases along the output direction of the first port, and gradually increases along the wavelength distribution direction; the intensity of the diffracted light is along the output of the second port during the second set time length
  • the direction gradually increases and gradually decreases in the direction of the wavelength distribution.
  • the second modulated signal is a modulated signal that changes with high and low levels over time. As the modulation signal changes, the output direction of the diffracted light of the incident light also changes.
  • the purpose of the second modulated signal is to have a plurality of intermediate states in the output state of the incident light during the process of switching the output port of the incident light from the first port to the second port, in order to ensure that there is no transient interference between the plurality of intermediate states and other ports.
  • the second modulated signal in the present application can first modulate the incident light to have an output along the first port and the wavelength distribution direction, and then modulate the incident light to have an output along the second port and the wavelength distribution direction.
  • the second modulation signal there may be two cases of deformation of the second modulation signal in the present application.
  • One case is to modulate the diffracted light of the incident light into an output direction and a wavelength along the first port for a first set time length.
  • a distribution direction output and the intensity of the diffracted light gradually decreases along the output direction of the first port, gradually increases along the wavelength distribution direction; along the output direction of the second port in the second set time length
  • the wavelength distribution direction is output, and the intensity of the diffracted light gradually increases along the output direction of the second port, and gradually decreases along the wavelength distribution direction until it is weakened to 0 along the wavelength distribution direction, and the output along the second port
  • the direction is the strongest; in the third set time length, only the output direction of the second port is output.
  • the formed silicon-based liquid crystal grating includes not only N intermediate gratings but also target gratings.
  • the diffracted light of the incident light is modulated to be output along an output direction and a wavelength distribution direction of the first port for a first set time length, and the intensity of the diffracted light is along the first port
  • the output direction is gradually weakened, gradually increasing along the wavelength distribution direction; outputting along the output direction of the second port and the wavelength distribution direction for a second set time length, and the intensity of the diffracted light is along
  • the output direction of the second port is gradually increased and gradually weakened along the wavelength distribution direction.
  • the formed silicon-based liquid crystal grating includes N intermediate state gratings, excluding the target state grating.
  • the formed silicon-based liquid crystal grating is a target grating.
  • the method further includes: providing a driving signal to the LCOS panel according to the second modulation signal; wherein the driving signal provided to the LCOS panel is used to drive the liquid crystal molecules corresponding to the plurality of liquid crystal pixels in the first set time length and the Having an ordered rotation state within a set length of time, the plurality of liquid crystal pixels form a blazed grating of a plurality of states, and the blazed gratings of the plurality of states are used for controlling the diffracted light of the incident light for a first set time length and the second The output direction within the length of time is set; wherein, the plurality of liquid crystal pixels are liquid crystal pixels corresponding to the incident light on the LCOS panel.
  • acquiring the second modulated signal includes:
  • the phase distribution function of the initial state grating, the phase distribution function of the target state grating, and the preset phase distribution function the phase distribution function of the N intermediate state gratings is determined; the phase distribution function of the initial state grating and the phase distribution of the target state grating The function is a phase distribution function distributed along the distribution direction of the port, and the preset phase distribution function is a phase distribution function distributed along the wavelength distribution direction;
  • the initial state grating is a blazed grating formed on the LCOS panel when the LCOS phase modulator loads the first modulation signal; the N intermediate state gratings and the target state grating are successively applied to the LCOS panel when the LCOS phase modulator loads the second modulation signal A blazed grating formed.
  • An initial state grating for controlling diffracted light diffracted by incident light to be output along an output direction of the first port
  • the diffracted light for controlling the diffraction of the incident light is first output along the output direction and the wavelength distribution direction of the first port, and then output along the output direction and the wavelength distribution direction of the second port, and finally along the second port Output direction output; and the intensity of the diffracted light gradually increases along the wavelength distribution direction as the intensity of the diffracted light gradually decreases along the output direction of the first port for the first set time length; the intensity of the diffracted light during the second set time length As the output direction of the second port gradually increases, it gradually decreases along the wavelength distribution direction;
  • the target state grating is used to control the diffracted light diffracted by the incident light to be output along the output direction of the second port.
  • phase distribution function of the N intermediate state gratings satisfies the following relationship:
  • N is a positive integer greater than or equal to 3
  • P i (x, y) is the phase distribution function of the ith intermediate state grating
  • P1A(y) is the phase distribution function of the initial state grating
  • P1B(y) is the phase distribution function of the target grating
  • P2(x) is the preset phase distribution function
  • a i , b i , c i are P i (x, y), P2 (x), P1B, respectively.
  • N is an odd number
  • the preset phase distribution function is a symmetric periodic function, and the period of the preset phase distribution function is according to the The wavelength bandwidth of the incident light is determined.

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Abstract

一种波长选择开关、交换引擎及其相位调制方法，该方法包括：在确定将入射光的输出端口由第一端口切换为第二端口时，获取第二调制信号；将加载的第一调制信号切换为第二调制信号；第一调制信号用于将入射光的衍射光调制成沿第一端口输出；第二调制信号用于将入射光的衍射光调制成在第一设定时间长度内沿第一端口的输出方向和波长分布方向输出，在第二设定时间长度内沿第二端口的输出方向和波长分布方向输出；并且在第一设定时间长度内，衍射光的强度沿第一端口的输出方向逐渐减弱、沿波长分布方向逐渐增强；在第二设定时间长度内，衍射光的强度沿第二端口的输出方向逐渐增强、沿波长分布方向逐渐减弱。

Description

一种波长选择开关、交换引擎及其相位调制方法 技术领域
本申请涉及光通信领域，尤其涉及一种波长选择开关、交换引擎及其相位调制方法。
背景技术
随着网络流量和带宽的飞速增长，运营商对于底层的波分网络的智能调度功能的需求越来越迫切，这导致ROADM逐渐为越来越多的高端运营商的网络所采用。网络中引入ROADM后，运营商可以快速的提供波长级的业务，便于进行网络规划，降低运营费用，便于维护，降低维护成本。
而波长选择开关(Wavelength selective switch，WSS)作为可重构光分插复用器(Reconfigurable Optical Add-Drop Multiplexer，ROADM)中重要的波长调度单元模块，其性能指标直接影响了整个网络的各项性能。近年来，对于WSS进行光交换的性能有了新的要求，要求在进行端口切换的过程中，不会对目标端口以外的其他端口产生影响，此即Hitless特性。
现有技术中，基于微机电系统MEMS(Micro-Electro-Mechanical System，MEMS)的WSS在控制光束偏转来实现端口切换时很难满足Hitless特性。如图1所示，不同波长的入射光，在经过光栅分光后照射至MEMS上不同位置的MEMS反射镜上，通过控制各个反射镜的角度，可以选择让不同的波长进入不同的光纤端口。如果此时希望某一波长由端口2切换至端口6，由于MEMS反射镜只能在一个维度上旋转，此时在反射镜旋转的切换过程中势必会使信号光扫过端口2至端口6路径上的所有端口，从而对波长所在的端口5的业务产生影响，引入额外的切换串扰。这种情况即不满足Hitless特性，因而需要寻求新的解决方案来实现Hitless特性。
相比较模拟式的MEMS芯片来说，基于硅基液晶(liquidcrystal on silicon，LCoS)的WSS在可靠性和稳定性上具有无可比拟的优势，并且LCoS为数字调制，可支持Flex-grid特性。当利用基于LCoS的WSS进行端口切换时，实际上是通过切换加载在LCoS面板上的相位图像来实现的。对于一维端口切换的情况，如图2所示，通常使用沿端口分布方向排布的闪耀光栅的相位分布来实现光束的偏转。通过切换不同周期的闪耀光栅即可将入射至LCoS面板上的信号光衍射至不同角度，从而耦合至不同位置的端口中。因此，理想情况下，由于LCoS的数字调制属性，在相位图的切换过程是不会对路径上的其他端口产生影响的。
然而，LCoS实际上是借助各点像素中的液晶分子旋转实现位相调制的。如图3和图4所示，当需要将沿端口分布方向分布的初始态光栅A的等效相位切换为沿端口分布方向分布的目标态光栅B的等效相位时，希望沿端口分布方向分布的闪耀光栅的相位图由初始相位梯度A切换至目标相位梯度B，此时LCoS面板上的各像素点的液晶分子同样会从初始状态旋转至目标状态，而由于实际的电子器件响应无法达到完全一致，因而各点液晶分子在切换至下一个状态的过程中，会经历若干紊乱的状态(如图4中虚线所示)，而这些紊乱的状态即会造成切换过程中的额外瞬态串扰，从而对于除了目标端口以外的其他端口业务产生干扰。
因此，基于LCoS的WSS进行端口切换时，也很难满足Hit less特性。目前已经公开的论文与专利中尚未有涉及基于LCoS交换引擎的Hitless解决方案。
发明内容
本申请实施例提供了一种波长选择开关、交换引擎及其相位调制方法，用以解决现有技术中基于LCoS的WSS进行端口切换时存在的很难满足Hitless特性的技术问题。
第一方面，本申请提供一种交换引擎的相位调制方法，所述交换引擎包括硅基液晶LCOS面板和LCOS相位调制器，所述方法应用于所述LCOS相位调制器，所述方法包括：
在确定将入射光的输出端口由第一端口切换为第二端口之后，获取第二调制信号；
将加载的第一调制信号切换为所述第二调制信号；
其中，所述第一调制信号用于将所述入射光的衍射光调制成沿所述第一端口输出；所述第二调制信号用于将所述入射光的衍射光调制成在第一设定时间长度内沿所述第一端口的输出方向和波长分布方向输出，在第二设定时间长度内沿所述第二端口的输出方向和所述波长分布方向输出；并且在所述第一设定时间长度内，所述衍射光的强度沿所述第一端口的输出方向逐渐减弱、沿所述波长分布方向逐渐增强；在所述第二设定时间长度内，所述衍射光的强度沿所述第二端口的输出方向逐渐增强、沿所述波长分布方向逐渐减弱。
上述实施例中，第二调制信号的作用并不是直接将入射光的衍射光调制成沿第二端口的输出方向输出，而是将入射光的衍射光调制成先沿第一端口的输出方向和波长分布方向分布，再沿第二端口的输出方向和波长分布方向分布，最后沿第二端口输出；并且在第一设定时间长度内，衍射光的强度沿第一端口的输出方向逐渐减弱时还沿波长分布方向逐渐增强；在第二设定时间长度内，衍射光的强度沿第二端口的输出方向逐渐增强时还沿波长分布方向逐渐减弱。因此，第二调制信号使入射光的衍射光的输出功率先逐渐转移到波长分布方向上，然后再逐渐从波长分布方向上全部转移到第二端口的输出方向上，由于将入射光的衍射光的输出功率转移到波长分布方向上，不会对其他端口产生干扰，因此，本申请根据第二调制信号能够将入射光的输出端口由第一端口切换到第二端口时，满足Hitless特性。
进一步的，还包括：根据所述第二调制信号，向所述LCOS面板提供驱动信号；所述驱动信号用于驱动多个液晶像素对应的液晶分子在所述第一设定时间长度和所述第二设定时间长度内呈现有序的旋转状态，使所述多个液晶像素形成多个状态的闪耀光栅，所述多个状态的闪耀光栅用于控制所述入射光的衍射光在所述第一设定时间长度和所述第二设定时间长度内的输出方向；其中，所述多个液晶像素为所述LCOS面板上与所述入射光对应的液晶像素。
上述实施例中，通过向所述LCOS面板提供驱动信号，驱动多个液晶像素对应的液晶分子在所述第一设定时间长度和所述第二设定时间长度内呈现有序的旋转状态，使所述多个液晶像素形成多个状态的闪耀光栅，多个状态的闪耀光栅用于控制入射光的衍射光在第一设定时间长度和第二设定时间长度内的输出方向，使入射光的衍射光的输出功率先逐渐转移到波长分布方向上，然后再逐渐从波长分布方向上全部转移到第二端口的输出方向上。
一种可能的实现方式中，所述获取第二调制信号，包括：
根据初始态光栅的相位分布函数，目标态光栅的相位分布函数，以及预设的相位分布 函数，确定所述N个中间态光栅的相位分布函数；所述初始态光栅的相位分布函数、所述目标态光栅的相位分布函数是沿端口分布方向分布的相位分布函数，所述预设的相位分布函数是沿所述波长分布方向分布的相位分布函数；
根据所述N个中间态光栅的相位分布函数和所述目标态光栅的相位分布函数，生成所述第二调制信号；
其中，所述初始态光栅是在所述LCOS相位调制器加载所述第一调制信号时所述LCOS面板上形成的闪耀光栅；所述N个中间态光栅、所述目标态光栅是在所述LCOS相位调制器加载所述第二调制信号时所述LCOS面板上先后形成的闪耀光栅。
上述实施例中，通过构造两个正交维度的相位分布函数，使得生成的第二调制信号能控制初始态光栅经过多个中间态光栅平缓过渡到目标态光栅的过程中，多个态光栅的作用是先逐渐衰减入射光沿第一端口的输出方向的输出功率，然后逐渐增强入射光沿第二端口的输出方向上的输出功率，并且在逐渐衰减入射光沿第一端口的输出方向的输出功率时，还逐渐增强入射光沿波长分布方向上的输出功率，直到将入射光的输出功率全部转移到波长分布方向上，然后开始逐渐增强入射光沿第二端口的输出方向上的输出功率，并且在逐渐增强入射光沿第二端口的输出方向上的输出功率时，还逐渐衰减入射光沿波长分布方向上的输出功率，直至将入射光的输出功率全部转移到第二端口的输出方向上，实现在不对其他端口产生信号干扰的情况下将入射光的输出端口由第一端口切换到第二端口。
进一步的，所述初始态光栅，用于控制所述入射光发生衍射的衍射光沿所述第一端口的输出方向输出；
所述N个中间态光栅能，用于控制所述入射光发生衍射的衍射光先沿所述第一端口的输出方向和波长分布方向输出，再沿所述第二端口的输出方向和所述波长分布方向输出，最后沿所述第二端口的输出方向输出；并且在第一设定时间长度内，所述衍射光的强度沿所述第一端口的输出方向逐渐减弱时还沿所述波长分布方向逐渐增强；在第二设定时间长度内，所述衍射光的强度沿所述第二端口的输出方向逐渐增强时还沿所述波长分布方向逐渐减弱；
所述目标态光栅，用于控制所述入射光发生衍射的衍射光沿所述第二端口的输出方向输出。
一种可能的实现方式中，所述N个中间态光栅的相位分布函数满足以下关系式：
Pi(x,y)＝ai*P1A(y)+bi*P2(x)+ci*P1B(y)
其中，1≤i≤N，N为大于或等于3的正整数，Pi(x,y)为第i个中间态光栅的相位分布函数，P1A(y)为所述初始态光栅的相位分布函数，P1B(y)为所述目标态光栅的相位分布函数，P2(x)为所述预设的相位分布函数，ai，bi，ci分别为Pi(x,y)、P2(x)、P1B(y)所占的权重系数。
上述实施例中，提供了一种构造中间态光栅的相位分布函数的具体实现方式，利用选择的相位分布函数的三个权重系数来对LCOS面板进行数字调制，以便调整多个中间态光栅呈现平稳的过渡，相比现有技术中通过对光束偏转结构的进行改造来实现无干扰切换来说，不需要增加任何的额外硬件，只需在LCOS相位调制器中加载端口切换所需的调制信号即可，实用性强，稳定性高，还有利于降低成本。
一种可能的实现方式中，若N为奇数，则：
当i小于
Figure PCTCN2017086221-appb-000001
时，ai+bi＝1，ci＝0且ai由大变小，bi由小变大；
当i等于
Figure PCTCN2017086221-appb-000002
时，ai＝0，bi＝1，ci＝0；
当i大于
Figure PCTCN2017086221-appb-000003
时，ai＝0，bi+ci＝1，且bi由大变小，ci由小变大。
一种可能的实现方式中，若N为偶数，则：
当i小于
Figure PCTCN2017086221-appb-000004
时，ai+bi＝1，ci＝0且ai由大变小，bi由小变大；
当i等于
Figure PCTCN2017086221-appb-000005
和
Figure PCTCN2017086221-appb-000006
时，ai＝0，bi＝1，ci＝0；
当i大于
Figure PCTCN2017086221-appb-000007
时，ai＝0，bi+ci＝1，且bi由大变小，ci由小变大。
一种可能的实现方式中，所述预设的相位分布函数为对称周期函数。
第二方面，本申请提供一种交换引擎，所述交换引擎包括LCOS相位调制器和LCOS面板，所述LCOS相位调制器与所述LCOS面板电连接；
所述LCOS相位调制器，用于在确定将入射光的输出端口由第一端口切换为第二端口之后，获取第二调制信号；将加载的第一调制信号切换为所述第二调制信号；根据所述第二调制信号，向所述LCOS面板提供驱动信号；所述第一调制信号用于将所述入射光的衍射光调制成沿所述第一端口输出；所述第二调制信号用于将所述入射光的衍射光调制成在第一设定时间长度内沿所述第一端口的输出方向和波长分布方向输出，在第二设定时间长度内沿所述第二端口的输出方向和所述波长分布方向输出；并且在所述第一设定时间长度内，所述衍射光的强度沿所述第一端口的输出方向逐渐减弱、沿所述波长分布方向逐渐增强；在所述第二设定时间长度内，所述衍射光的强度沿所述第二端口的输出方向逐渐增强、沿所述波长分布方向逐渐减弱。
上述实施例中，第二调制信号的作用并不是直接将入射光的衍射光调制成沿第二端口的输出方向输出，而是将入射光的衍射光调制成先沿第一端口的输出方向和波长分布方向分布，再沿第二端口的输出方向和波长分布方向分布，最后沿第二端口输出；并且在第一设定时间长度内，衍射光的强度沿第一端口的输出方向逐渐减弱时还沿波长分布方向逐渐增强；在第二设定时间长度内，衍射光的强度沿第二端口的输出方向逐渐增强时还沿波长分布方向逐渐减弱。因此，第二调制信号使入射光的衍射光的输出功率先逐渐转移到波长分布方向上，然后再逐渐从波长分布方向上全部转移到第二端口的输出方向上，由于将入射光的衍射光的输出功率转移到波长分布方向上，不对其他端口产生干扰，因此，本申请根据第二调制信号能够将入射光的输出端口由第一端口切换到第二端口时，满足Hitless特性。
进一步的，所述LCOS面板包括第一基板、第二基板和设置在所述第一基板和所述第二基板之间的液晶分子，所述第二基板上设置有由多行所列液晶像素；
所述LCOS相位调制器，还用于根据所述第二调制信号，向所述LCOS面板提供驱动信 号；
所述LCOS面板，用于获取所述驱动信号；根据所述驱动信号驱动多个液晶像素对应的液晶分子在所述第一设定时间长度和所述第二设定时间长度内呈现有序的旋转状态，使所述多个液晶像素形成多个状态的闪耀光栅，所述多个状态的闪耀光栅用于控制所述入射光的衍射光在所述第一设定时间长度和所述第二设定时间长度内的输出方向；其中，所述多个液晶像素为所述LCOS面板上与所述入射光对应的液晶像素。
上述实施例中，通过向所述LCOS面板提供驱动信号，驱动多个液晶像素对应的液晶分子在所述第一设定时间长度和所述第二设定时间长度内呈现有序的旋转状态，使所述多个液晶像素形成多个状态的闪耀光栅，多个状态的闪耀光栅用于控制入射光的衍射光在第一设定时间长度和第二设定时间长度内的输出方向，使入射光的衍射光的输出功率先逐渐转移到波长分布方向上，然后再逐渐从波长分布方向上全部转移到第二端口的输出方向上。
一种可能的实现方式中，所述LCOS相位调制器，具体用于：
根据初始态光栅的相位分布函数，目标态光栅的相位分布函数，以及预设的相位分布函数，确定所述N个中间态光栅的相位分布函数；所述初始态光栅的相位分布函数、所述目标态光栅的相位分布函数是沿端口分布方向分布的相位分布函数，所述预设的相位分布函数是沿所述波长分布方向分布的相位分布函数；
根据所述N个中间态光栅的相位分布函数和所述目标态光栅的相位分布函数，生成所述第二调制信号；
其中，所述初始态光栅是在所述LCOS相位调制器加载所述第一调制信号时所述LCOS面板上形成的闪耀光栅；所述N个中间态光栅、所述目标态光栅是在所述LCOS相位调制器加载所述第二调制信号时所述LCOS面板上先后形成的闪耀光栅。
上述实施例中，通过构造两个正交维度的相位分布函数，使得生成的第二调制信号能控制初始态光栅经过多个中间态光栅平缓过渡到目标态光栅的过程中，多个态光栅的作用是先逐渐衰减入射光沿第一端口的输出方向的输出功率，然后逐渐增强入射光沿第二端口的输出方向上的输出功率，并且在逐渐衰减入射光沿第一端口的输出方向的输出功率时，还逐渐增强入射光沿波长分布方向上的输出功率，直到将入射光的输出功率全部转移到波长分布方向上，然后开始逐渐增强入射光沿第二端口的输出方向上的输出功率，并且在逐渐增强入射光沿第二端口的输出方向上的输出功率时，还逐渐衰减入射光沿波长分布方向上的输出功率，直至将入射光的输出功率全部转移到第二端口的输出方向上，实现在不对其他端口产生信号干扰的情况下将入射光的输出端口由第一端口切换到第二端口。
进一步的，所述初始态光栅，用于控制所述入射光发生衍射的衍射光沿所述第一端口的输出方向输出；
所述N个中间态光栅，用于控制所述入射光发生衍射的衍射光先沿所述第一端口的输出方向和波长分布方向输出，再沿所述第二端口的输出方向和所述波长分布方向输出，最后沿所述第二端口的输出方向输出；并且在第一设定时间长度内，所述衍射光的强度沿所述第一端口的输出方向逐渐减弱时还沿所述波长分布方向逐渐增强；在第二设定时间长度内，所述衍射光的强度沿所述第二端口的输出方向逐渐增强时还沿所述波长分布方向逐渐减弱；
所述目标态光栅，用于控制所述入射光发生衍射的衍射光沿所述第二端口的输出方 向输出。
一种可能的实现方式中，所述N个中间态光栅的相位分布函数满足以下关系式：
Pi(x,y)＝ai*P1A(y)+bi*P2(x)+ci*P1B(y)
其中，1≤i≤N，N为大于或等于3的正整数，Pi(x,y)为第i个中间态光栅的相位分布函数，P1A(y)为所述初始态光栅的相位分布函数，P1B(y)为所述目标态光栅的相位分布函数，P2(x)为所述预设的相位分布函数，ai，bi，ci分别为Pi(x,y)、P2(x)、P1B(y)所占的权重系数。
上述实施例中，提供了一种构造中间态光栅的相位分布函数的具体实现方式，利用选择的相位分布函数的三个权重系数来对LCOS面板进行数字调制，以便调整多个中间态光栅呈现平稳的过渡，相比现有技术中通过对光束偏转结构的进行改造来实现无干扰切换来说，不需要增加任何的额外硬件，只需在LCOS相位调制器中加载端口切换所需的调制信号即可，实用性强，稳定性高，还有利于降低成本。
一种可能的实现方式中，若N为奇数，则：
当i小于
Figure PCTCN2017086221-appb-000008
时，ai+bi＝1，ci＝0且ai由大变小，bi由小变大；
当i等于
Figure PCTCN2017086221-appb-000009
时，ai＝0，bi＝1，ci＝0；
当i大于
Figure PCTCN2017086221-appb-000010
时，ai＝0，bi+ci＝1，且bi由大变小，ci由小变大。
一种可能的实现方式中，若N为偶数，则：
当i小于
Figure PCTCN2017086221-appb-000011
时，ai+bi＝1，ci＝0且ai由大变小，bi由小变大；
当i等于
Figure PCTCN2017086221-appb-000012
和
Figure PCTCN2017086221-appb-000013
时，ai＝0，bi＝1，ci＝0；
当i大于
Figure PCTCN2017086221-appb-000014
时，ai＝0，bi+ci＝1，且bi由大变小，ci由小变大。
一种可能的实现方式中，所述预设的相位分布函数为对称周期函数。
第二方面，本申请提供一种波长选择开关，至少包括上述任一实施例中的交换引擎。
附图说明
图1为现有技术中的一种光选择开关的结构示意图；
图2为现有技术中的一种基于LCOS的相位调制的结构示意图；
图3为现有技术中的一种基于LCOS的相位调制的初始态光栅A和目标态光栅B的等效相位结构示意图；
图4为现有技术中的一种基于LCOS的端口切换时液晶分子的紊乱状态的结构示意图；
图5为现有技术中的一种基于LCOS的交换引擎的结构示意图；
图6为本申请实施例提供的一种基于LCOS的交换引擎的发明构思示意图；
图7为本申请实施例提供的一种基于LCOS的交换引擎的结构示意图；
图8为本申请实施例提供的一种基于LCOS的交换引擎在端口切换过程中的衍射光的光斑分布示意图；
图9为本申请实施例提供的一种基于LCOS的交换引擎在端口切换过程中不同过渡态的衍射光的能量分布示意图；
图10为本申请实施例提供的一种基于LCOS的交换引擎在端口切换过程中的瞬态干扰与现有技术中存在的瞬态干扰的对比示意图。
具体实施方式
下面将结合附图对本申请实施例作进一步地详细描述。
本申请中的多个，是指两个或两个以上。另外，需要理解的是，在本申请的描述中，“第一”、“第二”等词汇，仅用于区分描述的目的，而不能理解为指示或暗示相对重要性，也不能理解为指示或暗示顺序。
本申请中的交换引擎是基于LCoS的光束偏转装置，应用在基于LCoS的WSS中，基于LCoS的WSS至少包括光纤阵列，衍射光栅、反射镜、交换引擎之外，还可包括其他优化光信号传输方向的装置。
本申请基于LCoS的波长选择开关的工作原理是：光信号由光纤阵列的一个输入端口输入，光信号首先入射到衍射光栅，衍射光栅对光信号进行分波，不同波长的光信号经过反射镜的反射后，作为不同的入射光入射到LCoS面板的不同区域。当任意波长的入射光入射在LCOS面板上时，入射光的光斑覆盖多个液晶像素，通过控制加载在多个液晶像素上的驱动信号，来控制液晶分子的旋转状态，进而控制LCoS面板上形成的沿端口分布方向排布的闪耀光栅的相位分布，通过沿端口分布方向排布的闪耀光栅的相位分布来实现入射光束的偏转，偏转后的光束通过反射光路耦合至不同位置的端口中。
参照图5，假如LCoS面板上加载的驱动信号由LCOS相位调制器提供，LCOS相位调制器根据加载的调制信号向LCoS面板提供驱动信号。对于任意波长的入射光λ1，当LCOS相位调制器根据加载的第一调制信号向LCoS面板提供相关驱动信号时，LCoS面板上形成的沿端口分布方向排布的闪耀光栅控制入射光λ1偏转后沿端口A的输出方向输出；当LCOS相位调制器根据加载的第二调制信号向LCoS面板提供相关驱动信号时，LCoS面板上形成的沿端口分布方向排布的闪耀光栅控制入射光λ1偏转后沿端口B的输出方向输出；当该入射光λ1的输出端口需要由端口A切换到端口B时，需要LCOS相位调制器将加载的第一调制信号直接切换成第二调制信号，此时LCoS面板上形成的沿端口分布方向排布的闪耀光栅需要由初始态光栅A直接切换为目标态光栅B，初始态光栅A和目标态光栅B的等效相位参见图3，在将初始态光栅A直接切换为目标态光栅B时，对应LCoS面板上的各像素点的液晶分子同样会从初始状态旋转至目标状态，而由于各像素点的液晶分子的旋转过程无法有序控制，导致各像素点的液晶分子在从初始状态切换至目标状态的过程中，会经历若干紊乱的状态，而这些紊乱的状态即会造成切换过程中的额外瞬态串扰，从而对于除了第二端口以外的其他端口的光信号产生干扰。
为了解决这一问题，如图6所示，本申请在入射光的端口由第一端口向第二端口的切换过程中，通过在LCoS面板上形成的初始态光栅A与目标态光栅B之间插入多个中间态 光栅，来实现初始态光栅A向目标态光栅B的平缓过渡，相应的控制LCoS面板上各像素点的液晶分子从初始状态经过多个中间态有序旋转至目标状态。同时，为了不使这些中间态光栅不对现有端口分布方向上的入射光产生串扰，这些中间态光栅的相位分布并不只是沿端口分布方向，还要沿波长分布方向分布，例如，图6中的中间态光栅中还包括沿波长分布方向分布的黑白光栅。通过对这些中间态光栅分别沿端口分布方向和波长分布方向的相位进行调制，先逐渐衰减入射光沿第一端口的输出方向的输出功率，然后逐渐增强入射光沿第二端口的输出方向上的输出功率。为了保证入射光总的输出功率不损失，在逐渐衰减入射光沿第一端口的输出方向的输出功率时，还逐渐增强入射光沿波长分布方向上的输出功率，直到将入射光的输出功率全部转移到与端口分布方向正交的波长分布方向上，然后开始逐渐增强入射光沿第二端口的输出方向上的输出功率，同时逐渐衰减入射光沿波长分布方向上的输出功率，直至将入射光的输出功率全部转移到第二端口的输出方向上，实现入射光的端口切换，因端口分布方向与波长分布方向是垂直正交的，这一渐变过程中入射光在波长分布方向分布的衍射光输出功率不会对端口分布方向上分布的衍射光的输出功率产生影响，因此，避免了切换过程中对其它端口上的光信号的影响，第一端口切换到第二端口时满足Hitless特性。
基于上述发明构思，本申请提供了一种交换引擎，如图7所示，包括硅基液晶LCOS面板和LCOS相位调制器，LCOS面板包括第一基板、第二基板和设置在第一基板和第二基板之间的液晶分子，第二基板上设置有由多行所列液晶像素；LCOS相位调制器与LCOS面板电连接；LCOS相位调制器用于根据加载的调制信号向LCOS面板提供驱动信号；LCOS面板用于根据LCOS相位调制器提供的驱动信号控制入射光在LCOS面板发生衍射后的衍射光的输出方向。根据LCOS相位调制器提供的驱动信号，LCOS面板可以控制入射光朝不同的方向偏转。
本申请中，LCOS相位调制器，主要用于在确定将入射光的输出端口由第一端口切换为第二端口之后，获取第二调制信号；将加载的第一调制信号切换为第二调制信号；根据第二调制信号，向LCOS面板提供驱动信号。
其中，第一调制信号，用于将入射光的衍射光调制成沿第一端口输出。
其中，第二调制信号，用于将所述入射光的衍射光调制成在第一设定时间长度内沿所述第一端口的输出方向和波长分布方向输出，在第二设定时间长度内沿所述第二端口的输出方向和所述波长分布方向输出；并且在所述第一设定时间长度内，所述衍射光的强度沿所述第一端口的输出方向逐渐减弱、沿所述波长分布方向逐渐增强；在所述第二设定时间长度内，所述衍射光的强度沿所述第二端口的输出方向逐渐增强、沿所述波长分布方向逐渐减弱。
需要说明的是，第二调制信号是一个随时间有高低电平变化的调制信号。随着调制信号的变化，入射光的衍射光的输出方向也发生变化。第二调制信号的目的是使入射光的输出端口由第一端口切换到第二端口的过程中入射光的输出状态存在多个中间态，为了保证多个中间态对其他端口不存在瞬态干扰，本申请中的第二调制信号能够先将入射光调制成沿第一端口和波长分布方向有输出，再将入射光调制成沿第二端口和波长分布方向有输出。
具体的，本申请中第二调制信号的变形可以有两种情况，一种情况是将入射光的衍射光调制成：在第一设定时间长度内沿所述第一端口的输出方向和波长分布方向输出，并且 所述衍射光的强度沿所述第一端口的输出方向逐渐减弱、沿所述波长分布方向逐渐增强；在第二设定时间长度内沿所述第二端口的输出方向和所述波长分布方向输出，并且所述衍射光的强度沿所述第二端口的输出方向逐渐增强、沿所述波长分布方向逐渐减弱，直至沿波长分布方向减弱为0，沿第二端口的输出方向最强；在第三设定时间长度内，只沿第二端口的输出方向输出。在第二调制信号的调制下，形成的硅基液晶光栅不仅包括N个中间态光栅，还包括目标态光栅。
另一种情况是将入射光的衍射光调制成：在第一设定时间长度内沿所述第一端口的输出方向和波长分布方向输出，并且所述衍射光的强度沿所述第一端口的输出方向逐渐减弱、沿所述波长分布方向逐渐增强；在第二设定时间长度内沿所述第二端口的输出方向和所述波长分布方向输出，并且所述衍射光的强度沿所述第二端口的输出方向逐渐增强、沿所述波长分布方向逐渐减弱。在第二调制信号的调制下，形成的硅基液晶光栅包括N个中间态光栅，不包括目标态光栅。在加载完第二调制信号之后，还需要加载第三调制信号，第三调制信号用于将入射光的衍射光调制成沿第二端口输出。在第三调制信号的调制下，形成的硅基液晶光栅为目标态光栅。
与现有技术相比，第二调制信号的作用并不是直接将入射光的衍射光调制成沿第二端口的输出方向输出，而是将入射光的衍射光调制成先沿第一端口的输出方向和波长分布方向分布，再沿第二端口的输出方向和波长分布方向分布，最后沿第二端口输出；并且在第一设定时间长度内，衍射光的强度沿第一端口的输出方向逐渐减弱时还沿波长分布方向逐渐增强；在第二设定时间长度内，衍射光的强度沿第二端口的输出方向逐渐增强时还沿波长分布方向逐渐减弱。因此，第二调制信号使入射光的衍射光的输出功率先逐渐转移到波长分布方向上，然后再逐渐从波长分布方向上全部转移到第二端口的输出方向上，将入射光的衍射光的输出功率转移到波长分布方向上，不对其他端口产生干扰，因此，本申请根据第二调制信号能够将入射光的输出端口由第一端口切换到第二端口时，满足Hitless特性。
当任意波长的入射光入射到LCOS面板时，入射光的光斑覆盖多个液晶像素，这多个液晶像素称为LCOS面板上与入射光对应的液晶像素。
进一步的，LCOS相位调制器，还用于根据第二调制信号，向LCOS面板提供相应的驱动信号。LCOS面板，用于获取LCOS相位调制器提供的驱动信号；根据驱动信号驱动多个液晶像素对应的液晶分子在第一设定时间长度和第二设定时间长度内呈现有序的旋转状态，使多个液晶像素形先后成多个状态的闪耀光栅，多个状态的闪耀光栅用于控制入射光的衍射光在第一设定时间长度和第二设定时间长度内的输出方向，使入射光的衍射光的输出功率先逐渐转移到波长分布方向上，然后再逐渐从波长分布方向上全部转移到第二端口的输出方向上。
本申请中，在LCOS相位调制器加载第一调制信号时，根据LCOS相位调制器提供的相关驱动信号，LCOS面板上形成的闪耀光栅为初始态光栅；初始态光栅，用于控制入射光发生衍射的衍射光沿第一端口的输出方向输出。
在LCOS相位调制器加载第二调制信号时，根据LCOS相位调制器提供的相关驱动信号，LCOS面板上先后形成的闪耀光栅为N个中间态光栅、目标态光栅。N个中间态光栅，用于控制入射光发生衍射的衍射光先沿第一端口的输出方向和波长分布方向输出，再沿第二端口的输出方向和波长分布方向输出，最后沿第二端口的输出方向输出；并且在第一设 定时间长度内，衍射光的强度沿第一端口的输出方向逐渐减弱时还沿波长分布方向逐渐增强；在第二设定时间长度内，衍射光的强度沿第二端口的输出方向逐渐增强时还沿波长分布方向逐渐减弱；目标态光栅，用于控制入射光发生衍射的衍射光沿第二端口的输出方向输出。
因此，在确定将入射光的输出端口由第一端口切换为第二端口之后，LCOS相位调制器将加载的第一调制信号切换为第二调制信号，基于第二调制信号，向LCoS面板提供相应的驱动信号，控制LCoS面板上对应像素点的液晶分子从初始状态经过多个中间态有序旋转至目标状态，进而在LCoS面板上形成的初始态光栅经过多个中间态光栅平缓过渡到目标态光栅，并且在初始态光栅经过多个中间态光栅平缓过渡到目标态光栅的过程中，多个态光栅的作用是先逐渐衰减入射光沿第一端口的输出方向的输出功率，然后逐渐增强入射光沿第二端口的输出方向上的输出功率，并且在逐渐衰减入射光沿第一端口的输出方向的输出功率时，还逐渐增强入射光沿波长分布方向上的输出功率，直到将入射光的输出功率全部转移到波长分布方向上，然后开始逐渐增强入射光沿第二端口的输出方向上的输出功率，并且在逐渐增强入射光沿第二端口的输出方向上的输出功率时，还逐渐衰减入射光沿波长分布方向上的输出功率，直至将入射光的输出功率全部转移到第二端口的输出方向上，实现在不对其他端口产生信号干扰的情况下将入射光的输出端口由第一端口切换到第二端口。
进一步的，LCOS相位调制器获取第二调制信号，包括：根据初始态光栅的相位分布函数，目标态光栅的相位分布函数，以及预设的相位分布函数，确定N个中间态光栅的相位分布函数；初始态光栅的相位分布函数、目标态光栅的相位分布函数是沿端口分布方向分布的相位分布函数，预设的相位分布函数是沿波长分布方向分布的相位分布函数；根据N个中间态光栅的相位分布函数和目标态光栅的相位分布函数，生成第二调制信号。
上述实施例中，通过构造两个正交维度的相位分布函数，使得生成的第二调制信号能控制初始态光栅经过多个中间态光栅平缓过渡到目标态光栅的过程中，多个态光栅的作用是先逐渐衰减入射光沿第一端口的输出方向的输出功率，然后逐渐增强入射光沿第二端口的输出方向上的输出功率，并且在逐渐衰减入射光沿第一端口的输出方向的输出功率时，还逐渐增强入射光沿波长分布方向上的输出功率，直到将入射光的输出功率全部转移到波长分布方向上，然后开始逐渐增强入射光沿第二端口的输出方向上的输出功率，并且在逐渐增强入射光沿第二端口的输出方向上的输出功率时，还逐渐衰减入射光沿波长分布方向上的输出功率，直至将入射光的输出功率全部转移到第二端口的输出方向上，实现在不对其他端口产生信号干扰的情况下将入射光的输出端口由第一端口切换到第二端口。
需要说明的是，第二调制信号也可以是预先存储在LCOS相位调制器中的与切换进程存在索引关系的调制信号，这样在确定将入射光的输出端口由第一端口切换为第二端口之后，LCOS相位调制器直接读取第二调制信号，并将加载的第一调制信号切换为第二调制信号。
进一步的，N个中间态光栅的相位分布函数满足以下关系式：
Pi(x,y)＝ai*P1A(y)+bi*P2(x)+ci*P1B(y)
其中，1≤i≤N，N为大于或等于3的正整数，Pi(x,y)为第i个中间态光栅的相位分布函数，P1A(y)为初始态光栅的相位分布函数，P1B(y)为目标态光栅的相位分布函数，P2(x)为预设的相位分布函数，ai，bi，ci分别为Pi(x,y)、P2(x)、P1B(y)所占的权重系 数。
上述实施例中，提供了一种构造中间态光栅的相位分布函数的具体实现方式，利用选择的相位分布函数的三个权重系数来对LCOS面板进行数字调制，以便调整多个中间态光栅呈现平稳的过渡，相比现有技术中通过对光束偏转结构的进行改造来实现无干扰切换来说，不需要增加任何的额外硬件，只需在LCOS相位调制器中加载端口切换所需的调制信号即可，实用性强，稳定性高，还有利于降低成本。
可选的，本申请中，P2(x)为黑白光栅对应的相位分布函数，即图6中所示的方波函数。
可选的，本申请中，P2(x)为正弦光栅或余弦光栅对应的相位分布函数。
可选的，对于上述关系式，若N为奇数，则：
当i小于
Figure PCTCN2017086221-appb-000015
时，ai+bi＝1，ci＝0且ai由大变小，bi由小变大；
当i等于
Figure PCTCN2017086221-appb-000016
时，ai＝0，bi＝1，ci＝0；
当i大于
Figure PCTCN2017086221-appb-000017
时，ai＝0，bi+ci＝1，且bi由大变小，ci由小变大。
可选的，对于上述关系式，若N为偶数，则：
当i小于
Figure PCTCN2017086221-appb-000018
时，ai+bi＝1，ci＝0且ai由大变小，bi由小变大；
当i等于
Figure PCTCN2017086221-appb-000019
和
Figure PCTCN2017086221-appb-000020
时，ai＝0，bi＝1，ci＝0；
当i大于
Figure PCTCN2017086221-appb-000021
时，ai＝0，bi+ci＝1，且bi由大变小，ci由小变大。
本申请中，以选取的P2(x)为黑白光栅的相位分布函数为例，说明本申请的相位调制方法。
如图6所示，当WSS中的LCoS上的某个波长通道需要进行端口切换时，需要将端口分布方向分布的光栅A直接切换至目标态光栅B，为了防止切换过程中的瞬态串扰，需要寻找一系列介于AB之间的中间过渡态。基于此出发点，不改变沿端口分布方向分布的光栅A的相位分布函数，而是在A的相位分布函数的表达式上叠加一个沿波长分布方向分布的黑白光栅的相位分布函数。如果将LCoS上的波长分布方向记为X方向，端口分布方向记为Y方向，此时与初始输出端口对应的初始态光栅的相位分布函数为P1A(y)，与目标输出端口B对应的目标态光栅的相位分布函数为P1B(y)。进行端口切换时，选取N个中间态光栅的相位分布函数P2(x)，对于任一个中间态i(1≤i≤N)，其相位分布满足Pi(x,y)＝ai*P1A(y)+bi*P2(x)+ci*P1B(y)；ai,bi与ci为振幅项，调节ai,bi与ci系数即可调节P1A(y)、P2(x)、P1B(y)的权重比。P1A(y)与P1B(y)的相位分布函数在整个切换过程中保持不变；P2(x)选取沿波长分布方向分布的对称周期函数，从而实现不改变原端口分布方向上光斑分布位置的衰减效应；中间态选取过程中保持P2(x)光栅周期不变，通过调控光栅振幅系数a1与a2以控制权重比，进而得到一系列极小颗粒度的准连续 中间态；P2(x)可以选取黑白光栅或正弦光栅等对称周期性函数；该函数周期可根据实际波长通道宽度选取，在整个切换过程中周期不再变化。
如图8(a)至图8(f)所示，在端口切换过程中，入射光在LCoS上形成的N个中间态光栅处发生衍射时衍射光的输出功率的渐变过程包括：
图8(a)为选取的初始态，在此初始态，衍射光斑的分布方向为端口分布方向，并且强度最大的衍射光斑位置可以视为第一端口位置。
图8(b)为选取的ai由大变小，bi由小变大，ci＝0时的一个中间态，在此中间态，端口分布方向上分布的光斑位置不变，但是在端口分布方向两侧也分布有衍射光斑，端口分布方向两侧的衍射光斑可以视为波长分布方向的衍射光斑，端口分布方向上的光斑强度有所衰减，而且端口分布方向两侧的衍射光斑的强度较弱。
图8(c)为选取的ai接近0，bi接近1，ci＝0时的一个中间态，在此中间态，已有端口分布方向上的光斑位置不变，端口分布方向两侧的衍射光斑位置也不变，但端口分布方向上的光斑强度几乎衰减为0，端口分布方向两侧的衍射光斑的强度与图8(b)相比有所增强。
图8(d)为选取的ai＝0，bi由大变小，ci由小变大且bi接近1时的一个中间态，在此中间态，与图8(c)相比，已有端口分布方向上的光斑位置沿端口分布方向发生偏移，端口分布方向两侧分布的衍射光斑位置不变，端口分布方向两侧分布的衍射光斑的强度最强，端口分布方向分布的光斑强度较弱。
图8(e)为选取的ai＝0，bi由大变小，ci由小变大，bi小于ci时的一个中间态，在此中间态，与图8(d)相比，已有端口分布方向上的光斑位置不变，端口分布方向两侧分布的衍射光斑位置不变，但端口分布方向两侧分布的衍射光斑的强度衰减，端口分布方向分布的光斑强度增强。
图8(f)为选取的ai＝0，bi＝0，ci＝1的目标态，与图8(e)相比，已有端口分布方向上的光斑位置不变，端口分布方向两侧的衍射光斑消失，端口分布方向上的衍射光斑的强度最强，并且和图8(a)相比，强度最大的衍射光斑位置向下偏移，此时强度最大的衍射光斑位置为第二端口位置。
上述如图8(a)至图8(f)所示的衍射光斑的渐变过程即为：先逐渐衰减入射光沿第一端口的输出方向的输出功率，然后逐渐增强入射光沿第二端口的输出方向上的输出功率，并且在逐渐衰减入射光沿第一端口的输出方向的输出功率时，还逐渐增强入射光沿波长分布方向上的输出功率，直到将入射光的输出功率全部转移到波长分布方向上，然后开始逐渐增强入射光沿第二端口的输出方向上的输出功率，并且在逐渐增强入射光沿第二端口的输出方向上的输出功率时，还逐渐衰减入射光沿波长分布方向上的输出功率，直至将入射光的输出功率全部转移到第二端口的输出方向上，实现在不对其他端口产生信号干扰的情况下将入射光的输出端口由第一端口切换到第二端口。
上述中间态的调控过程，不是通过调控P2(x)的周期大小来控制衍射光斑的能量分布，而是根据具体应用场景的需求(如波长通道的带宽大小，光路中回损角度大小)选取P2(x)的周期大小，然后保持P2(x)的周期不变，调控P2(x)所占的权重比实现平缓过渡；随着P2(x)所占权重比例越来越大，原本位于端口A上的衍射光斑强度逐渐衰减，当端口A上的衍射光斑强度被完全衰减后，再进行向目标端口B的切换，图8(a)向图8(c)调控过程中，切换的串扰分布于端口分布方向以外的位置。图8(d)向图8(f)的调控过 程中，随着P2(x)所占权重比例越来越小，位于端口分布方向以外的衍射光斑强度逐渐衰减，位于端口B上的衍射光斑强度逐渐增强。
本申请中，端口切换过程中很重要的一点是中间态选取要尽可能的连续且平缓，因而对于调节的颗粒度和调节范围有一定的要求，颗粒度是指每两个中间态间的功率衰减量。
在沿端口方向分布的衍射光能量逐渐衰减为0的过程中，选取沿端口方向分布的衍射光能量的衰减量分别为0dB、5dB、5.04dB和15dB时的四个状态，对衍射光在端口分布方向上的能量分布进行了测量，参照图9可以看出：通过调控中间态权重比的方式，沿端口分布方向分布的各个级次的衍射光的能量均同步降低，这是因为原有端口分布方向所分布的衍射光能量有一部分被分散到了两侧，分散到两侧的衍射光不会对端口分布方向上的衍射光引入额外的串扰。根据图9所示的测量结果，可以看出，衍射光的衰减量的颗粒度最小可以达到0.04dB，衍射光的最大衰减量可达15dB，因此，在沿端口方向分布的衍射光能量在此衰减范围内逐渐衰减为0的过程，就是入射光在初始态光栅A出发生衍射的衍射光的能量分布经过准连续变化的多个过渡态逐渐衰减为消光状态的过程。在初始态光栅A连续的衰减为消光状态以后，再进行端口的切换。进行端口切换时，控制沿波长分布方向的衍射光的能量逐渐衰减，沿端口方向分布的衍射光能量逐渐增强，并且衍射光的能量的峰值逐渐分布在第二端口位置处。
在此基础之上，对于本申请中Hitless的实际效果进行了测量。图10(a)为由初始态光栅A(周期10个像素)直接切换至目标态光栅B(周期20个像素)时的情况，实际测量过程中强度探测器固定于光栅A的负1级衍射位置，假如该位置同时也是目标态光栅B的负二级衍射位置，此时如图10(a)中虚线方框所示，测得的瞬态串扰强度大约为6dB。借助本申请上述实施例在初始态光栅A和目标态光栅B中间插入多个中间态光栅的切换方案，保持强度探测器的位置不变，重复了上述实验，实验结果参见图10(b)。通过图10(b)可以看出，在初始态光栅A、各个中间态光栅、目标态光栅B的切换过程之中不再有瞬态串扰的出现，实现了Hitless特性。
从上述实施例可以看出，相对于现有技术，可以实现波长选择开关的功率准连续动态调控，功率准连续动态调控的调节颗粒度可以达到0.04dB，调节范围可以达到0.04db～15db。基于这种功率准连续调控特性，本申请提供的相位调制方法能够控制LCoS面板上的液晶分子在端口切换过程中有序的旋转，以便在LCoS面板上形成一系列由初始态光栅向目标态光栅平缓过渡的中间态光栅，通过这些中间态光栅对入射光的衍射光的能量分布进行有规律的调制，进而解决了WSS中的端口切换时存在的瞬态串扰问题。
本申请中，在选取中间态光栅时，由于P2(x)的权重系数可灵活变化，因此，中间态光栅的可调范围很大。此外，由于P2(x)主要是调制沿波长分布方向上分布的有效像素，而随着未来WSS中的波长间隔越来越小，波长分布方向上的有效像素的数量可能在10个以内。为了适应未来极少像素的情形，本申请的相位调制方法控制在端口切换过程中保持P2(x)的周期不变，仅需调节P2(x)的权重系数即可。
与现有解决端口串扰的技术方案相比，本申请提供的交换引擎中，由于LCOS面板支持数字调制模式，不需要增加任何的额外硬件，只需在LCOS相位调制器中加载端口切换所需的调制信号即可，实用性强，成本低。
本申请实施例提供一种交换引擎的相位调制方法，用以解决现有技术中存在的基于LCoS的WSS进行端口切换时存在的难以满足Hitless特性的技术问题。其中，方法和装置 是基于同一发明构思的，由于方法及装置解决问题的原理相似，因此装置与方法的实施可以相互参见，重复之处不再赘述。
本申请提供的一种交换引擎的相位调制方法，应用于前述实施例中的LCOS相位调制器，具体包括：
步骤101，在确定将入射光的输出端口由第一端口切换为第二端口之后，获取第二调制信号；
步骤102，将加载的第一调制信号切换为第二调制信号；
其中，第一调制信号用于将入射光的衍射光调制成沿第一端口输出；第二调制信号用于将所述入射光的衍射光调制成在第一设定时间长度内沿所述第一端口的输出方向和波长分布方向输出，在第二设定时间长度内沿所述第二端口的输出方向和所述波长分布方向输出；并且在所述第一设定时间长度内，所述衍射光的强度沿所述第一端口的输出方向逐渐减弱、沿所述波长分布方向逐渐增强；在所述第二设定时间长度内，所述衍射光的强度沿所述第二端口的输出方向逐渐增强、沿所述波长分布方向逐渐减弱。
需要说明的是，第二调制信号是一个随时间有高低电平变化的调制信号。随着调制信号的变化，入射光的衍射光的输出方向也发生变化。第二调制信号的目的是使入射光的输出端口由第一端口切换到第二端口的过程中入射光的输出状态存在多个中间态，为了保证多个中间态对其他端口不存在瞬态干扰，本申请中的第二调制信号能够先将入射光调制成沿第一端口和波长分布方向有输出，再将入射光调制成沿第二端口和波长分布方向有输出。
具体的，本申请中第二调制信号的变形可以有两种情况，一种情况是将入射光的衍射光调制成：在第一设定时间长度内沿所述第一端口的输出方向和波长分布方向输出，并且所述衍射光的强度沿所述第一端口的输出方向逐渐减弱、沿所述波长分布方向逐渐增强；在第二设定时间长度内沿所述第二端口的输出方向和所述波长分布方向输出，并且所述衍射光的强度沿所述第二端口的输出方向逐渐增强、沿所述波长分布方向逐渐减弱，直至沿波长分布方向减弱为0，沿第二端口的输出方向最强；在第三设定时间长度内，只沿第二端口的输出方向输出。在第二调制信号的调制下，形成的硅基液晶光栅不仅包括N个中间态光栅，还包括目标态光栅。
另一种情况是将入射光的衍射光调制成：在第一设定时间长度内沿所述第一端口的输出方向和波长分布方向输出，并且所述衍射光的强度沿所述第一端口的输出方向逐渐减弱、沿所述波长分布方向逐渐增强；在第二设定时间长度内沿所述第二端口的输出方向和所述波长分布方向输出，并且所述衍射光的强度沿所述第二端口的输出方向逐渐增强、沿所述波长分布方向逐渐减弱。在第二调制信号的调制下，形成的硅基液晶光栅包括N个中间态光栅，不包括目标态光栅。在加载完第二调制信号之后，还需要加载第三调制信号，第三调制信号用于将入射光的衍射光调制成沿第二端口输出。在第三调制信号的调制下，形成的硅基液晶光栅为目标态光栅。
步骤102之后，还包括：根据第二调制信号，向LCOS面板提供驱动信号；其中，向LCOS面板提供的驱动信号，用于驱动多个液晶像素对应的液晶分子在第一设定时间长度和第二设定时间长度内呈现有序的旋转状态，使多个液晶像素形成多个状态的闪耀光栅，多个状态的闪耀光栅用于控制入射光的衍射光在第一设定时间长度和第二设定时间长度内的输出方向；其中，多个液晶像素为LCOS面板上与入射光对应的液晶像素。
一种可能的实现方式中，获取第二调制信号，包括：
根据初始态光栅的相位分布函数，目标态光栅的相位分布函数，以及预设的相位分布函数，确定N个中间态光栅的相位分布函数；初始态光栅的相位分布函数、目标态光栅的相位分布函数是沿端口分布方向分布的相位分布函数，预设的相位分布函数是沿波长分布方向分布的相位分布函数；
根据N个中间态光栅的相位分布函数和目标态光栅的相位分布函数，生成第二调制信号；
其中，初始态光栅是在LCOS相位调制器加载第一调制信号时LCOS面板上形成的闪耀光栅；N个中间态光栅、目标态光栅是在LCOS相位调制器加载第二调制信号时LCOS面板上先后形成的闪耀光栅。
初始态光栅，用于控制入射光发生衍射的衍射光沿第一端口的输出方向输出；
N个中间态光栅能，用于控制入射光发生衍射的衍射光先沿第一端口的输出方向和波长分布方向输出，再沿第二端口的输出方向和波长分布方向输出，最后沿第二端口的输出方向输出；并且在第一设定时间长度内，衍射光的强度沿第一端口的输出方向逐渐减弱时还沿波长分布方向逐渐增强；在第二设定时间长度内，衍射光的强度沿第二端口的输出方向逐渐增强时还沿波长分布方向逐渐减弱；
目标态光栅，用于控制入射光发生衍射的衍射光沿第二端口的输出方向输出。
可选的，N个中间态光栅的相位分布函数满足以下关系式：
Pi(x,y)＝ai*P1A(y)+bi*P2(x)+ci*P1B(y)
其中，1≤i≤N，N为大于或等于3的正整数，Pi(x,y)为第i个中间态光栅的相位分布函数，P1A(y)为初始态光栅的相位分布函数，P1B(y)为目标态光栅的相位分布函数，P2(x)为预设的相位分布函数，ai，bi，ci分别为Pi(x,y)、P2(x)、P1B(y)所占的权重系数。
可选的，若N为奇数，则：
当i小于
Figure PCTCN2017086221-appb-000022
时，ai+bi＝1，ci＝0且ai由大变小，bi由小变大；
当i等于
Figure PCTCN2017086221-appb-000023
时，ai＝0，bi＝1，ci＝0；
当i大于
Figure PCTCN2017086221-appb-000024
时，ai＝0，bi+ci＝1，且bi由大变小，ci由小变大。
可选的，若N为偶数，则：
当i小于
Figure PCTCN2017086221-appb-000025
时，ai+bi＝1，ci＝0且ai由大变小，bi由小变大；
当i等于
Figure PCTCN2017086221-appb-000026
和
Figure PCTCN2017086221-appb-000027
时，ai＝0，bi＝1，ci＝0；
当i大于
Figure PCTCN2017086221-appb-000028
时，ai＝0，bi+ci＝1，且bi由大变小，ci由小变大。
可选的，预设的相位分布函数为对称周期函数，预设的相位分布函数的周期根据所述 入射光的波长带宽确定。
显然，本领域的技术人员可以对本申请实施例进行各种改动和变型而不脱离本申请实施例的精神和范围。这样，倘若本申请实施例的这些修改和变型属于本申请权利要求及其等同技术的范围之内，则本申请也意图包含这些改动和变型在内。

Claims (17)

  1. 一种交换引擎的相位调制方法，所述交换引擎包括硅基液晶LCOS面板和LCOS相位调制器，所述方法应用于所述LCOS相位调制器，其特征在于，所述方法包括：
    在确定将入射光的输出端口由第一端口切换为第二端口之后，获取第二调制信号；
    将加载的第一调制信号切换为所述第二调制信号；
    其中，所述第一调制信号用于将所述入射光的衍射光调制成沿所述第一端口输出；所述第二调制信号用于将所述入射光的衍射光调制成在第一设定时间长度内沿所述第一端口的输出方向和波长分布方向输出，在第二设定时间长度内沿所述第二端口的输出方向和所述波长分布方向输出；并且在所述第一设定时间长度内，所述衍射光的强度沿所述第一端口的输出方向逐渐减弱、沿所述波长分布方向逐渐增强；在所述第二设定时间长度内，所述衍射光的强度沿所述第二端口的输出方向逐渐增强、沿所述波长分布方向逐渐减弱。
  2. 根据权利要求1所述的方法，其特征在于，还包括：
    根据所述第二调制信号，向所述LCOS面板提供驱动信号；所述驱动信号用于驱动多个液晶像素对应的液晶分子在所述第一设定时间长度和所述第二设定时间长度内呈现有序的旋转状态，使所述多个液晶像素形成多个状态的闪耀光栅，所述多个状态的闪耀光栅用于控制所述入射光的衍射光在所述第一设定时间长度和所述第二设定时间长度内的输出方向；其中，所述多个液晶像素为所述LCOS面板上与所述入射光对应的液晶像素。
  3. 根据权利要求1所述的方法，其特征在于，所述获取第二调制信号，包括：
    根据初始态光栅的相位分布函数，目标态光栅的相位分布函数，以及预设的相位分布函数，确定所述N个中间态光栅的相位分布函数；所述初始态光栅的相位分布函数、所述目标态光栅的相位分布函数是沿端口分布方向分布的相位分布函数，所述预设的相位分布函数是沿所述波长分布方向分布的相位分布函数；
    根据所述N个中间态光栅的相位分布函数和所述目标态光栅的相位分布函数，生成所述第二调制信号；
    其中，所述初始态光栅是在所述LCOS相位调制器加载所述第一调制信号时所述LCOS面板上形成的闪耀光栅；所述N个中间态光栅、所述目标态光栅是在所述LCOS相位调制器加载所述第二调制信号时所述LCOS面板上先后形成的闪耀光栅。
  4. 根据权利要求3所述的方法，其特征在于，
    所述初始态光栅，用于控制所述入射光发生衍射的衍射光沿所述第一端口的输出方向输出；
    所述N个中间态光栅能，用于控制所述入射光发生衍射的衍射光先沿所述第一端口的输出方向和波长分布方向输出，再沿所述第二端口的输出方向和所述波长分布方向输出，最后沿所述第二端口的输出方向输出；并且在第一设定时间长度内，所述衍射光的强度沿所述第一端口的输出方向逐渐减弱时还沿所述波长分布方向逐渐增强；在第二设定时间长度内，所述衍射光的强度沿所述第二端口的输出方向逐渐增强时还沿所述波长分布方向逐渐减弱；
    所述目标态光栅，用于控制所述入射光发生衍射的衍射光沿所述第二端口的输出方向输出。
  5. 根据权利要求3所述的方法，其特征在于，所述N个中间态光栅的相位分布函数 满足以下关系式：
    Pi(x,y)＝ai*P1A(y)+bi*P2(x)+ci*P1B(y)
    其中，1≤i≤N，N为大于或等于3的正整数，Pi(x,y)为第i个中间态光栅的相位分布函数，P1A(y)为所述初始态光栅的相位分布函数，P1B(y)为所述目标态光栅的相位分布函数，P2(x)为所述预设的相位分布函数，ai，bi，ci分别为Pi(x,y)、P2(x)、P1B(y)所占的权重系数。
  6. 根据权利要求5所述的方法，其特征在于，若N为奇数，则：
    当i小于
    Figure PCTCN2017086221-appb-100001
    时，ai+bi＝1，ci＝0且ai由大变小，bi由小变大；
    当i等于
    Figure PCTCN2017086221-appb-100002
    时，ai＝0，bi＝1，ci＝0；
    当i大于
    Figure PCTCN2017086221-appb-100003
    时，ai＝0，bi+ci＝1，且bi由大变小，ci由小变大。
  7. 根据权利要求5所述的方法，其特征在于，若N为偶数，则：
    当i小于
    Figure PCTCN2017086221-appb-100004
    时，ai+bi＝1，ci＝0且ai由大变小，bi由小变大；
    当i等于
    Figure PCTCN2017086221-appb-100005
    和
    Figure PCTCN2017086221-appb-100006
    时，ai＝0，bi＝1，ci＝0；
    当i大于
    Figure PCTCN2017086221-appb-100007
    时，ai＝0，bi+ci＝1，且bi由大变小，ci由小变大。
  8. 根据权利要求4所述的方法，其特征在于，所述预设的相位分布函数为对称周期函数。
  9. 一种交换引擎，其特征在于，所述交换引擎包括LCOS相位调制器和LCOS面板，所述LCOS相位调制器与所述LCOS面板电连接；
    所述LCOS相位调制器，用于在确定将入射光的输出端口由第一端口切换为第二端口之后，获取第二调制信号；将加载的第一调制信号切换为所述第二调制信号；根据所述第二调制信号，向所述LCOS面板提供驱动信号；所述第一调制信号用于将所述入射光的衍射光调制成沿所述第一端口输出；所述第二调制信号用于将所述入射光的衍射光调制成在第一设定时间长度内沿所述第一端口的输出方向和波长分布方向输出，在第二设定时间长度内沿所述第二端口的输出方向和所述波长分布方向输出；并且在所述第一设定时间长度内，所述衍射光的强度沿所述第一端口的输出方向逐渐减弱、沿所述波长分布方向逐渐增强；在所述第二设定时间长度内，所述衍射光的强度沿所述第二端口的输出方向逐渐增强、沿所述波长分布方向逐渐减弱。
  10. 根据权利要求9所述的交换引擎，其特征在于，所述LCOS面板包括第一基板、第二基板和设置在所述第一基板和所述第二基板之间的液晶分子，所述第二基板上设置有由多行所列液晶像素；
    所述LCOS相位调制器，还用于根据所述第二调制信号，向所述LCOS面板提供驱动信 号；
    所述LCOS面板，用于获取所述驱动信号；根据所述驱动信号驱动多个液晶像素对应的液晶分子在所述第一设定时间长度和所述第二设定时间长度内呈现有序的旋转状态，使所述多个液晶像素形成多个状态的闪耀光栅，所述多个状态的闪耀光栅用于控制所述入射光的衍射光在所述第一设定时间长度和所述第二设定时间长度内的输出方向；其中，所述多个液晶像素为所述LCOS面板上与所述入射光对应的液晶像素。
  11. 根据权利要求9所述的交换引擎，其特征在于，所述LCOS相位调制器，具体用于：
    根据初始态光栅的相位分布函数，目标态光栅的相位分布函数，以及预设的相位分布函数，确定所述N个中间态光栅的相位分布函数；所述初始态光栅的相位分布函数、所述目标态光栅的相位分布函数是沿端口分布方向分布的相位分布函数，所述预设的相位分布函数是沿所述波长分布方向分布的相位分布函数；
    根据所述N个中间态光栅的相位分布函数和所述目标态光栅的相位分布函数，生成所述第二调制信号；
    其中，所述初始态光栅是在所述LCOS相位调制器加载所述第一调制信号时所述LCOS面板上形成的闪耀光栅；所述N个中间态光栅、所述目标态光栅是在所述LCOS相位调制器加载所述第二调制信号时所述LCOS面板上先后形成的闪耀光栅。
  12. 根据权利要求11所述的交换引擎，其特征在于，
    所述初始态光栅，用于控制所述入射光发生衍射的衍射光沿所述第一端口的输出方向输出；
    所述N个中间态光栅，用于控制所述入射光发生衍射的衍射光先沿所述第一端口的输出方向和波长分布方向输出，再沿所述第二端口的输出方向和所述波长分布方向输出，最后沿所述第二端口的输出方向输出；并且在第一设定时间长度内，所述衍射光的强度沿所述第一端口的输出方向逐渐减弱时还沿所述波长分布方向逐渐增强；在第二设定时间长度内，所述衍射光的强度沿所述第二端口的输出方向逐渐增强时还沿所述波长分布方向逐渐减弱；
    所述目标态光栅，用于控制所述入射光发生衍射的衍射光沿所述第二端口的输出方向输出。
  13. 根据权利要求11所述的交换引擎，其特征在于，所述N个中间态光栅的相位分布函数满足以下关系式：
    Pi(x,y)＝ai*P1A(y)+bi*P2(x)+ci*P1B(y)
    其中，1≤i≤N，N为大于或等于3的正整数，Pi(x,y)为第i个中间态光栅的相位分布函数，P1A(y)为所述初始态光栅的相位分布函数，P1B(y)为所述目标态光栅的相位分布函数，P2(x)为所述预设的相位分布函数，ai，bi，ci分别为Pi(x,y)、P2(x)、P1B(y)所占的权重系数。
  14. 根据权利要求13所述的交换引擎，其特征在于，若N为奇数，则：
    当i小于
    Figure PCTCN2017086221-appb-100008
    时，ai+bi＝1，ci＝0且ai由大变小，bi由小变大；
    当i等于
    Figure PCTCN2017086221-appb-100009
    时，ai＝0，bi＝1，ci＝0；
    当i大于
    Figure PCTCN2017086221-appb-100010
    时，ai＝0，bi+ci＝1，且bi由大变小，ci由小变大。
  15. 根据权利要求13所述的交换引擎，其特征在于，若N为偶数，则：
    当i小于
    Figure PCTCN2017086221-appb-100011
    时，ai+bi＝1，ci＝0且ai由大变小，bi由小变大；
    当i等于
    Figure PCTCN2017086221-appb-100012
    和
    Figure PCTCN2017086221-appb-100013
    时，ai＝0，bi＝1，ci＝0；
    当i大于
    Figure PCTCN2017086221-appb-100014
    时，ai＝0，bi+ci＝1，且bi由大变小，ci由小变大。
  16. 根据权利要求12所述的交换引擎，其特征在于，所述预设的相位分布函数为对称周期函数。
  17. 一种波长选择开关，其特征在于，至少包括权利要求9至16中任一项所述的交换引擎。
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