WO2024011521A1

WO2024011521A1 - Wavelength selective switch and light beam modulation method

Info

Publication number: WO2024011521A1
Application number: PCT/CN2022/105778
Authority: WO
Inventors: 闻远辉; 卢特安; 宗良佳
Original assignee: 华为技术有限公司
Priority date: 2022-07-14
Filing date: 2022-07-14
Publication date: 2024-01-18

Abstract

A WSS and a light beam modulation method, which improve the isolation of output ports (102), and reduce the crosstalk of output ports (102). The WSS comprises: a port module (10), a dispersion module (20), a lens module (30), an SLM (40) and a controller (50). The port module (10) comprises an input port (101) and a plurality of output ports (102). The dispersion module (20) is used for splitting into a plurality of sub-wavelength light beams wavelength-multiplexed beams coming from the input port (101). The lens module (30) is used for respectively guiding the plurality of sub-wavelength light beams to different regions of the SLM (40). The SLM (40) is used for separately modulating the plurality of sub-wavelength light beams, and the plurality of sub-wavelength light beams modulated are sequentially transmitted to the plurality of output ports (102) by means of the lens module (30) and the dispersion module (20). The controller (50) is used for adjusting a phase distribution corresponding to pixel points on the SLM (40). After being modulated by the SLM (40), the sub-wavelength light beams form light beams of a plurality of diffraction orders; the light field distribution of a light beam of a target diffraction order is matched with a light field mode supported by said output ports (102); and the light field distribution of a light beam of at least one diffraction order is different from the light field distribution of the light beam of the target diffraction order.

Description

A wavelength selective switch and beam modulation method

Technical field

The present application relates to the field of optical communications, and in particular to a wavelength selective switch and a beam modulation method.

Background technique

In the field of optical communications, Reconfigurable Optical Add-Drop Multiplexer (ROADM) is an important device used in optical fiber communication networks to realize automatic path scheduling and control of signals at the optical layer. Among them, the wavelength selective switch (WSS) is the core device of ROADM, and its mainstream switching engine is the spatial light modulator (SLM) based on liquid crystal on silicon (LCOS) technology.

In WSS, after the multiplexed signal from the input port is dispersed by the grating, different wavelengths are spread along the dispersion direction and projected onto different areas of the SLM. Then, by loading phase gratings with different periods in different areas of the SLM, the beams of corresponding wavelengths are deflected along different diffraction angles and finally output from different target ports, thereby realizing the wavelength selective routing function.

However, due to the control pixel discretization of the LCOS device, the fringe field effect existing between pixels, and the elastic interaction between liquid crystal molecules, there is a certain deviation between the actual phase grating morphology and the ideal blazed grating that achieves beam deflection, so it will Other grating diffraction orders are produced. This means that while the incident beam is deflected along the target direction, part of the energy will be diffracted to other directions and eventually coupled to the non-target port output, causing crosstalk at the non-target output port and seriously affecting the performance of the optical communication system.

Contents of the invention

Embodiments of the present application provide a wavelength selective switch and a beam modulation method, which improves the isolation of the output port and reduces crosstalk at the output port.

In a first aspect, embodiments of the present application provide a WSS. WSS includes: port component, dispersion component, lens component, SLM and controller. The port component includes input port and multiple output ports. Specifically, the dispersion component is used to decompose the combined beam from the input port into multiple sub-wavelength beams, and guide the multiple sub-wavelength beams to the lens assembly. The lens assembly is used to direct multiple sub-wavelength beams to different areas of the SLM. The controller is used to adjust the phase distribution corresponding to the pixels on the SLM. SLM is used to separately modulate multiple sub-wavelength beams. The sub-wavelength beam is modulated by SLM to form multiple diffraction order beams. The light field distribution of the target diffraction order beam matches the light field mode supported by the output port. The light field distribution of at least one diffraction order beam matches the light field distribution of the target diffraction order beam. The light field distribution of the target diffraction order beam is different. The lens assembly is also used to guide the modulated multiple sub-wavelength beams to the dispersion assembly. The dispersion component is also used to combine the modulated multiple sub-wavelength beams and transmit them to multiple output ports.

In this implementation, the light field distribution of the light beam of the target diffraction order matches the light field mode supported by the output port, that is, the light beam of the target diffraction order can be efficiently coupled to the output port. For other crosstalk diffraction order beams, the light field distribution is different from the light field distribution of the target diffraction order beam, which will cause the light spot to be dispersed to varying degrees, making it difficult to couple into the output port, thereby improving the isolation of the output port. degree, reducing crosstalk at the output port.

In some possible implementations, the light field distribution includes the intensity distribution of the light field and/or the phase distribution of the light field. The different light field distribution of the light beam may be caused by at least one of the following factors. For example, the beam types can be different. For another example, the size of the beams may be different. For another example, the relative positions of the light beam and the output port may be different. In this implementation, a variety of factors affecting light field distribution are provided, which expands the application scenarios of this solution.

In some possible implementations, matching the light field distribution of the light beam of the target diffraction order with the light field mode supported by the output port can be manifested in that the coupling efficiency of the light beam of the target diffraction order coupled into the output port is greater than or equal to the threshold value. Based on this, the coupling efficiency of light beams of other crosstalk diffraction orders coupled into the output port is less than the threshold, which improves the isolation of the output port and reduces crosstalk at the output port.

In some possible implementations, the beam of the target diffraction order is a Gaussian beam, the beam of the target diffraction order has the same beam waist size as the Gaussian mode supported by the output port, and the beam waist is located at the output port. The beam of at least one diffraction order is a non-Gaussian beam, or the beam of at least one diffraction order has a different beam waist size from the Gaussian mode supported by the output port, or the beam waist of at least one diffraction order deviates from the output port. . Therefore, only the beam of the target diffraction order can be well coupled into the output port that supports Gaussian mode. Beams of other diffraction orders are difficult to couple into the output port, which improves the isolation of the output port and reduces crosstalk at the output port.

In some possible implementations, the controller specifically adjusts the phase distribution corresponding to the pixels on the SLM based on the beam deflection phase, disturbance phase and compensation phase. Among them, the beam deflection phase acts on the deflection direction adjustment of each sub-wavelength beam, the disturbance phase acts on the phase modulation corresponding to each diffraction order, and the compensation phase is used to compensate for the disturbance phase. The perturbation phase and the compensation phase corresponding to the target diffraction order cancel each other, and the perturbation phase and the compensation phase corresponding to at least one diffraction order cannot cancel each other. In other words, for the beam of the target diffraction order, it can be regarded that only the beam deflection phase plays a role. For beams of other diffraction orders, since the disturbance phase and the compensation phase cannot cancel each other, the light field distribution of the beams of other diffraction orders is different from the light field distribution of the beam of the target diffraction order.

In this embodiment, the perturbation phase and the compensation phase are introduced based on the traditional beam deflection phase. Among them, for the target diffraction order beam, the disturbance phase and the compensation phase can be completely offset to maintain the original ideal spot shape, match the light field mode supported by the output port, and can be efficiently coupled to the output port. For beams of other crosstalk diffraction orders, since the disturbance phase and the compensation phase cannot be offset, the light spot will be dispersed to varying degrees, which is different from the light field distribution of the target diffraction order, making it difficult to couple into the output port, thereby improving the output. The port isolation reduces crosstalk at the output port. Moreover, the controller can dynamically adjust the distribution characteristics of the disturbance phase and the compensation phase according to actual needs to control the light field distribution form of the crosstalk light, so that it can be suitable for different application scenarios and has higher flexibility. In addition, this solution is implemented through special encoding by SLM on a conventional equal-focal optical system. It does not require a specific optical path design or the introduction of additional hardware, so it is easier to implement and lower cost.

In some possible implementations, the beam deflection phase has a functional relationship with the perturbation phase or the compensation phase. This embodiment provides a specific implementation method for adjusting the phase distribution corresponding to pixels on the SLM, which enhances the practicality of this solution.

In some possible implementations, the phase distribution corresponding to the pixels on the SLM can be expressed as φ(x), φ(x)=f[G(x)-D(x)]+C(x), or, φ (x)=f[G(x)-C(x)]+D(x), where G(x) represents the beam deflection phase, D(x) represents the disturbance phase, C(x) represents the compensation phase, f [G(x)-D(x)] represents the function associated with G(x)-D(x), f[G(x)-C(x)] represents the function associated with G(x)-C(x) The function.

In some possible implementations, the disturbance phase and the compensation phase satisfy the quadratic phase distribution, which enhances the realizability of this solution. Moreover, this implementation method is suitable for scenarios where all output ports have crosstalk. It is necessary to make the disturbance phase and compensation phase corresponding to each diffraction order except the target diffraction order have different degrees of mismatch, so as to have different degrees of mismatch with the target diffraction order. The different light field distribution makes it difficult for light of all diffraction orders except the target diffraction order to be coupled to the output port.

In some possible implementations, the perturbation phase and the compensation phase satisfy the binary grating phase distribution, which enhances the scalability of this solution. Moreover, this implementation is suitable for scenarios where some output ports have crosstalk. It can be adjusted in a targeted manner so that the disturbance phase and the compensation phase corresponding to some specified diffraction orders in addition to the target diffraction order have different degrees of mismatch, thereby having the following advantages: The light field distribution is different from the target diffraction order, and the light achieving this part of the specified diffraction order is difficult to couple to the output port.

In some possible implementations, the beam deflection phase is a phase grating with periodic distribution to facilitate beam deflection.

In a second aspect, embodiments of the present application provide a beam modulation method. The method includes the following steps. First, adjust the phase distribution corresponding to the pixels on the spatial light modulator SLM. Furthermore, the input multiple sub-wavelength beams are modulated respectively by SLM. The sub-wavelength beams are modulated by SLM to form beams of multiple diffraction orders. The light field distribution of the target diffraction order beam is consistent with the light field supported by the output port. Mode matching, the light field distribution of the beam of at least one diffraction order is different from the light field distribution of the beam of the target diffraction order.

In some possible implementations, adjusting the phase distribution corresponding to the pixels on the spatial light modulator SLM includes: adjusting the phase distribution corresponding to the pixels on the SLM according to the beam deflection phase, the disturbance phase and the compensation phase. Among them, the beam deflection phase acts on the deflection direction adjustment of each sub-wavelength beam, the disturbance phase acts on the phase modulation corresponding to each diffraction order, and the compensation phase is used to compensate for the disturbance phase. The perturbation phase and the compensation phase corresponding to the target diffraction order cancel each other, and the perturbation phase and the compensation phase corresponding to at least one diffraction order cannot cancel each other.

In some possible implementations, the beam deflection phase has a functional relationship with the perturbation phase or the compensation phase.

In some possible implementations, the phase distribution corresponding to the pixels on the SLM is expressed as φ(x), φ(x)=f[G(x)-D(x)]+C(x), or, φ( x)=f[G(x)-C(x)]+D(x), where G(x) represents the beam deflection phase, D(x) represents the disturbance phase, C(x) represents the compensation phase, f[ G(x)-D(x)] represents the function associated with G(x)-D(x), f[G(x)-C(x)] represents the function associated with G(x)-C(x) function.

In some possible implementations, the disturbance phase and the compensation phase satisfy a quadratic phase distribution.

In some possible implementations, the perturbation phase and the compensation phase satisfy a binary grating phase distribution.

In some possible implementations, the beam deflection phase is a phase grating with periodic distribution.

In the embodiment of the present application, the disturbance phase and the compensation phase are introduced on the basis of the traditional beam deflection phase. Among them, for the target diffraction order beam, the disturbance phase and the compensation phase can be completely offset to maintain the original ideal spot shape, match the light field mode supported by the output port, and can be efficiently coupled to the output port. For beams of other crosstalk diffraction orders, since the disturbance phase and the compensation phase cannot be offset, the light spot will be dispersed to varying degrees, which is different from the light field distribution of the target diffraction order, making it difficult to couple into the output port, thereby improving the output. The port isolation reduces crosstalk at the output port. Moreover, the controller can dynamically adjust the distribution characteristics of the disturbance phase and the compensation phase according to actual needs to control the light field distribution form of the crosstalk light, so that it can be suitable for different application scenarios and has higher flexibility. In addition, this solution is implemented through special encoding by SLM on a conventional equal-focal optical system. It does not require a specific optical path design or the introduction of additional hardware, so it is easier to implement and lower cost.

Description of drawings

Figure 1 is a schematic structural diagram of WSS in an embodiment of the present application;

Figure 2 is several schematic diagrams of light field distribution of light beams in embodiments of the present application;

Figure 3 is a schematic diagram of the transmission of sub-beams of different diffraction orders in the embodiment of the present application;

Figure 4 is a first morphological difference diagram between a special encoded grating and a traditional encoded grating in the embodiment of the present application;

Figure 5 is a first schematic diagram of the diffraction light field distribution in the embodiment of the present application;

Figure 6 is a second morphological difference diagram between a special encoded grating and a traditional encoded grating in the embodiment of the present application;

Figure 7 is a second schematic diagram of the diffraction light field distribution in the embodiment of the present application;

Figure 8 is a schematic flow chart of the first beam modulation method provided by the embodiment of the present application;

FIG. 9 is a schematic flowchart of the second beam modulation method provided by an embodiment of the present application.

Detailed ways

Embodiments of the present application provide a wavelength selective switch and a beam modulation method. The light field distribution of the beam of the target diffraction order matches the light field mode supported by the output port, that is, the beam of the target diffraction order can be efficiently coupled to the output port. For other crosstalk diffraction order beams, the light field distribution is different from the light field distribution of the target diffraction order beam, which will cause the light spot to be dispersed to varying degrees, making it difficult to couple into the output port, thereby improving the isolation of the output port. degree, reducing crosstalk at the output port.

It should be noted that the terms "first", "second", etc. in the description, claims and drawings of this application are used to distinguish similar objects, but do not limit a specific order or sequence. It is to be understood that the above terms are interchangeable under appropriate circumstances so that the embodiments described herein can be practiced in sequences other than those described herein. Furthermore, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units need not be limited to those steps or units that are expressly listed, but may include steps or units that are not expressly listed or that are not specific to the process, method, product, or device. Other steps or units inherent to the equipment.

The beam modulation method provided in the embodiment of this application is beam modulation realized by a spatial light modulator (Spatial Light Modulator, SLM). SLM is a type of optical device that modulates the light field wavefront. Among them, the spatial light modulator based on Liquid Crystal on Silicon (LCOS) technology has flexible light field control, repeatable erasing and high resolution. Features have been widely used in many fields. Specifically, this beam modulation method is mainly used in scenarios involving beam deflection, such as wavelength selective switch (WSS), radar scanning or space optical communication. The following takes the application scenario of WSS as an example to introduce in detail.

Figure 1 is a schematic structural diagram of a WSS in an embodiment of the present application. As shown in FIG. 1 , the WSS includes a port component 10 , a dispersion component 20 , a lens component 30 , a spatial light modulator 40 and a controller 50 . The port component 10 includes an input port 101 and a plurality of output ports 102 . Specifically, the input port 101 inputs a combined light beam including multiple wavelengths. For example, the combined light beam includes a total of n wavelengths λ1, λ2...λn. The dispersion component 20 can decompose the multiplexed beam from the input port 101 into multiple sub-wavelength beams along the dispersion direction as shown in FIG. 1 , so that the multiple sub-wavelength beams are spatially separated. The lens assembly 30 is used to guide the plurality of sub-wavelength beams to different areas of the spatial light modulator 40 respectively. The spatial light modulator 40 modulates the input multiple sub-wavelength beams respectively according to the phase distribution loaded by the controller 50, so that the deflection direction of each sub-wavelength beam can be changed. The modulated plurality of sub-wavelength light beams are sequentially transmitted to the plurality of output ports 102 through the lens assembly 30 and the dispersion assembly 20 . The port assembly 10, the lens assembly 30 and the spatial light modulator 40 constitute an isofocal optical system. It should be understood that the deflection direction of the light beam is also the port direction, so that the deflection direction of each sub-wavelength light beam can be adjusted to transmit it to the corresponding output port. The dispersion direction is usually perpendicular to the port direction. Multiple modulation areas can be divided along the dispersion direction on the SLM to separately modulate the incident multiple sub-wavelength beams. After the modulated sub-wavelength light beam is incident on the dispersion component 20, the dispersion component 20 is also used to combine the incident sub-wavelength light beam along the dispersion direction and then output it.

In some possible implementations, the implementation form of the port component 10 includes but is not limited to an optical fiber array, a waveguide array, etc., and may be a one-dimensional array or a two-dimensional array. The implementation forms of the dispersion component 20 include but are not limited to gratings, prisms, etc. The implementation forms of the lens assembly 30 include but are not limited to ball lenses, cylindrical lenses, curved mirrors, etc. The spatial light modulator 40 may specifically use an LCOS array. The LCOS array has a pixelated modulation area, and the deflection direction of each sub-wavelength light beam can be changed by modulating the pixels in the corresponding wavelength area. Specifically, after a certain sub-wavelength beam is injected into the spatial light modulator 40, the spatial light modulator 40 can transmit the entire sub-wavelength beam to the output port 102 without loss by changing the deflection direction of the sub-wavelength beam, or make the sub-wavelength beam transmit to the output port 102 without loss. The wavelength beam cannot be transmitted to the output port 102 , or part of the sub-wavelength beam can be transmitted to the output port 102 . The port assembly 10 and the spatial light modulator 40 are located at the front focal plane and the rear focal plane of the lens assembly 30, respectively.

It should be understood that the optical path design in the WSS shown in Figure 1 is just an example, and other optical path designs can also be used in practical applications, so that various commonly used optical path designs in WSS can be adapted. For example, the WSS may also use a transmissive dispersion component 20 . Furthermore, in a possible implementation, the port assembly 10 and the spatial light modulator 40 are respectively located on the front focal plane and the rear focal plane of the lens assembly 30 to form an equifocal optical system.

It should be noted that the spatial light modulator specifically adjusts the phase distribution corresponding to each pixel point according to the beam deflection phase loaded by the controller 50 to adjust the deflection direction of each sub-wavelength beam. The beam deflection phase may be a phase grating with periodic distribution, such as a zigzag distributed blazed grating, a rectangular distributed binary grating, etc. After the sub-wavelength beam irradiates the phase grating, it will be diffracted and propagate in various directions. The propagation direction follows the following grating equation: p(sinφ+sinθ)=nλ. Among them, p is the grating period, φ is the incident angle of the beam, θ is the exit angle of the diffracted light, λ is the wavelength of the incident beam, and n is any integer. Different n corresponds to different diffraction orders. Generally, +1 order diffraction light is commonly used. That is to say, each sub-wavelength beam has multiple diffraction orders, and light of different diffraction orders propagates in different directions. For example, part of the sub-wavelength beam with wavelength λ1 is transmitted toward the specified target output port, while the other part of the light is diffracted in other directions, causing crosstalk at non-target output ports.

To this end, in the embodiment of the present application, the phase modulation encoding method of the spatial light modulator 40 can be adjusted through the controller 50, and the disturbance phase and the compensation phase can be further introduced on the basis of the beam deflection phase, so that the light of the target diffraction order can be maintained The original ideal light spot shape can be efficiently coupled to the target output port, while the beams of other diffraction orders will be dispersed to varying degrees and have different light field distributions from the target diffraction order, making it difficult to couple into the output port to avoid affecting other beams. Crosstalk on non-intended output ports.

Specifically, the sub-wavelength beam is modulated by the spatial light modulator 40 to form a beam of multiple diffraction orders, wherein the light field distribution of the target diffraction order beam matches the light field mode supported by the output port. The light field distribution of at least one other diffraction order beam is different from the light field distribution of the target diffraction order beam. That is to say, the light field distribution of at least one other diffraction order beam is different from the light field mode supported by the output port. match. Therefore, the beam of the target diffraction order can be efficiently coupled to the output port, while the beam of at least one other diffraction order is difficult to couple into the output port. In a possible implementation, whether the light field distribution of the light beam matches the light field mode supported by the output port can be judged by the coupling efficiency of the light beam coupled into the output port. For example, the coupling efficiency of the target diffraction order beam coupled into the output port is greater than or equal to the threshold, which matches the light field mode supported by the output port. For another example, the coupling efficiency of light beams of other diffraction orders coupled into the output port is less than the threshold and does not match the light field mode supported by the output port. Among them, the threshold here can be flexibly set according to the actual application scenario, for example, it can be 60%, and there is no specific limit here.

It should be noted that the light field distribution of the light beam includes the intensity distribution of the light field and/or the phase distribution of the light field. The different light field distribution of the light beam may be caused by at least one of the following factors. For example, the beam types can be different. For another example, the size of the beams may be different. For another example, the relative position of the light beam and the output port may be different, which is represented by whether the light beam is aligned with the output port.

Figure 2 is several schematic diagrams of light field distribution of light beams in embodiments of the present application. As shown in Example A of Figure 2, the beam of the target diffraction order is a Gaussian beam, and the Gaussian beam has the same beam waist size as the Gaussian mode supported by the output port, and the beam waist of the Gaussian beam is located at the output port, which can be coupled efficiently. input and output ports. It should be understood that in some possible scenarios, the above-mentioned "same girdle size" does not necessarily mean exactly the same, but may also refer to similar girdle sizes. As shown in Example B of Figure 2 , beams of other diffraction orders may be non-Gaussian beams. Compared with Example A, their light field distribution is different from that of Example A due to different beam types. As shown in the C example of Figure 2, the beams of other diffraction orders can be Gaussian beams, but the Gaussian beam has a different beam waist size from the Gaussian mode supported by the output port. Compared with the A example, due to the different beam sizes, its light The field distribution is different from the light field distribution of Example A. As shown in the D example of Figure 2, the beams of other diffraction orders can be Gaussian beams, but the beam waist of the Gaussian beam deviates from the output port. Compared with the A example, the light field distribution is different due to the relative position of the beam and the output port. Light field distribution different from example A. In summary, only the light field distribution of the target diffraction order beam in example A matches the light field mode supported by the output port and can be efficiently coupled into the output port. The light field distribution of the beams of other diffraction orders in examples B, C, or D does not match the light field mode supported by the output port, and it is difficult to couple into the output port.

Based on the above introduction of Figure 2, several possible application scenarios are provided below. Figure 3 is a schematic diagram of the transmission of different diffraction order beams in the embodiment of the present application. As shown in example a of FIG. 3 , if the method provided by this application is not used to adjust the phase modulation encoding method of the spatial light modulator 40 , light of all diffraction orders can be well coupled into the output port, thereby causing crosstalk. As shown in the b example of Figure 3, the beam of the target diffraction order and the beam of the partial crosstalk diffraction order have different beam types. As shown in example c of Figure 3, the beam of the target diffraction order and the beam of the partial crosstalk diffraction order have different beam sizes. As shown in the d example of Figure 3, the beam of the target diffraction order can be aligned with the output port, but the beam of some crosstalk diffraction orders cannot be aligned with the output port. In summary, in examples b, c, and d, the light field distribution of the beam of the target diffraction order matches the light field mode supported by the output port, and can be efficiently coupled into the output port. The beams of some crosstalk diffraction orders do not match the light field modes supported by the output port, and are difficult to couple into the output port.

The following is an introduction to how the controller 50 adjusts the phase distribution corresponding to the pixels on the spatial light modulator 40 .

Specifically, the controller 50 adjusts the phase distribution corresponding to the pixels on the spatial light modulator 40 according to the beam deflection phase, disturbance phase and compensation phase. Among them, the beam deflection phase acts on the deflection direction adjustment of each sub-wavelength beam, the disturbance phase acts on the phase modulation corresponding to each diffraction order, and the compensation phase is used to compensate for the disturbance phase. By designing the distribution of the perturbation phase and the compensation phase, the perturbation phase and the compensation phase corresponding to the target diffraction order in multiple diffraction orders can be canceled out. For example, the perturbation phase is represented by D(x), and the compensation phase is represented by C. (x), then D(x)=-C(x). The disturbance phase and compensation phase corresponding to at least one diffraction order except the target diffraction order cannot cancel each other, that is, D(x)≠-C(x). In other words, different perturbation phases will be introduced for different diffraction orders, and the introduction of perturbation phases will cause the original ideal form of light spot to be dispersed to varying degrees. At the same time, a compensation phase will be introduced to compensate for the disturbance phase. The disturbance phase and compensation phase corresponding to the target diffraction order cancel each other out. Then the spot of the target diffraction order will still maintain its original ideal shape and can be coupled to the target output. port. The disturbance phase and compensation phase corresponding to at least one other diffraction order cannot cancel each other. The light spot of this part of the diffraction order will be dispersed and have a different light field distribution from the target diffraction order, making it difficult to couple to the output port.

In a possible implementation, the beam deflection phase has a functional relationship with the disturbance phase or the compensation phase.

Specifically, the phase distribution corresponding to the pixels on the spatial light modulator is expressed as φ(x). φ(x)=f[G(x)-D(x)]+C(x), or φ(x)=f[G(x)-C(x)]+D(x). Among them, G(x) represents the beam deflection phase, D(x) represents the disturbance phase, C(x) represents the compensation phase, f[G(x)-D(x)] represents the relationship between G(x)-D(x) The associated function, f[G(x)-C(x)] represents the function associated with G(x)-C(x). That is to say, φ(x)=f[G(x)-D(x)]+C(x) can be regarded as having a functional relationship between the beam deflection phase G(x) and the disturbance phase D(x). φ(x)=f[G(x)-C(x)]+D(x) can be regarded as having a functional relationship between the beam deflection phase G(x) and the compensation phase C(x). In a possible implementation, the above functional relationship may use a remainder function. For example, φ(x)=mod[G(x)-D(x),2π]+C(x). The above-mentioned beam deflection phase G(x) may be a blazed grating, for example, G(x)=mod(2πx/T, 2π), where T is the grating period.

It should be noted that the disturbance phase and compensation phase can adopt a variety of distribution forms. Two specific phase distribution forms are provided below.

Phase distribution form 1: The disturbance phase and the compensation phase satisfy the quadratic phase distribution.

Taking the above-mentioned Embodiment 1 as an example, the disturbance phase and the compensation phase may be secondary phase distributions with a lens function. For example: C(x)=-D(x)=mod(c x^2,2π), where c is a constant coefficient, which can be equivalent to different focal lengths of the lens. Figure 4 is a first morphological difference diagram between a special encoding grating and a traditional encoding grating in the embodiment of the present application. As shown in Figure 4, compared with the traditional periodic grating that only combines the beam deflection phase, the grating formed by introducing the disturbance phase and the compensation phase for encoding based on the traditional periodic grating can be called a special encoding grating. Through comparison, it can be seen that this special encoded grating has similar period hopping characteristics to traditional periodic gratings, so that beam deflection can be achieved. In addition, this special encoded grating has an overall envelope of the secondary phase.

Figure 5 is a first schematic diagram of the diffraction light field distribution in the embodiment of the present application. As shown in Figure 5, based on the phase distribution form shown in Figure 4 above, the traditional periodic grating actually generates There is a certain deviation between the phase grating morphology and the ideal blazed grating that achieves beam deflection. Therefore, in addition to the +1 order diffraction order, other grating diffraction orders that are the same as the +1 order diffraction light field distribution will be produced. The special encoded grating introduces the perturbation phase and the compensation phase with a quadratic phase distribution, and for the +1st diffraction order, the perturbation phase and the compensation phase can cancel each other and retain the original light field distribution, while other crosstalk diffraction Due to the different degrees of mismatch between the disturbance phase and the compensation phase, the orders retain the role of the secondary phase. Therefore, these crosstalk diffraction orders have different degrees of light field dispersion and have different light field distributions from the target diffraction orders. . Through the above phase distribution form, a crosstalk light dispersion effect similar to that of non-equifocal optical design can be achieved. However, compared with non-equifocal optical design, this solution can dynamically select different defocuss through coding to achieve different degrees. The crosstalk light is dispersed, and there is no need to change the existing WSS optical design and assembly, which has more advantages in terms of function and implementation.

Phase distribution form 2: The disturbance phase and the compensation phase satisfy the binary grating phase distribution.

Taking the above-mentioned Embodiment 1 as an example, the disturbance phase and the compensation phase may be binary grating phase distributions. For example:

Among them, n is any integer, p is the grating period,

for any phase value. Figure 6 is a second morphological difference diagram between a special encoding grating and a traditional encoding grating in the embodiment of the present application. As shown in Figure 6, with

For example, compared with the traditional periodic grating that only combines the beam deflection phase, the grating formed by introducing the disturbance phase and the compensation phase for encoding based on the traditional periodic grating can be called a special encoding grating. Through comparison, it can be seen that this special encoded grating has similar period hopping characteristics to traditional periodic gratings, so that beam deflection can be achieved. In addition, this special encoded grating has an overall envelope of binary grating phases.

Figure 7 is a second schematic diagram of the diffraction light field distribution in the embodiment of the present application. As shown in Figure 7, based on the phase distribution form shown in Figure 6 above, the traditional periodic grating actually produces due to the control pixel discretization of the LCOS device, the fringe field effect between pixels and the elastic interaction between liquid crystal molecules. There is a certain deviation between the phase grating morphology and the ideal blazed grating that achieves beam deflection. Therefore, in addition to the +1 order diffraction order, other grating diffraction orders that are the same as the +1 order diffraction light field distribution will be produced. The special encoded grating introduces the perturbation phase and the compensation phase with a quadratic phase distribution, and for the +1st diffraction order, the perturbation phase and the compensation phase can cancel each other and retain the original light field distribution, while other crosstalk diffraction The stages have varying degrees of mismatch due to both the disturbance phase and the compensation phase. Among them, for odd diffraction orders, since there are 0 and

The binary grating is therefore unaffected. For even diffraction orders, since there are 0 and

The binary grating is thus split into two halves and moved to different positions as the period of the binary grating changes.

By comparing the two phase distribution forms introduced above, it can be seen that using the above-mentioned phase distribution form 1 can achieve different degrees of light field dispersion in all diffraction orders except the target diffraction order (+1 diffraction order), as shown in the figure 5 shown. Therefore, the above phase distribution form 1 is suitable for scenarios where all output ports have crosstalk. It is necessary to make the disturbance phase and compensation phase corresponding to each diffraction order except the target diffraction order have different degrees of mismatch, so as to achieve the goal of eliminating the target. Light of all diffraction orders except the diffraction order is difficult to couple to the output port. Using the above-mentioned phase distribution form 2 can achieve different degrees of light field dispersion in other diffraction orders except the target diffraction order (+1 diffraction order), as shown in Figure 7. Therefore, the above phase distribution form 2 is suitable for scenarios where some output ports have crosstalk. It can be adjusted in a targeted manner so that the disturbance phase and compensation phase corresponding to some specified diffraction orders except the target diffraction order have different degrees of mismatch. As a result, the light of this part of the specified diffraction order is difficult to couple to the output port. In summary, the above two phase distribution forms can be flexibly selected according to different needs in practical applications. It should be understood that in practical applications, the disturbance phase and the compensation phase can also adopt other distribution forms besides the two distribution forms introduced above, as long as the optical power distribution and peak intensity position of the crosstalk diffraction order can be adjusted to make it difficult to couple It can be connected to the output port, and there is no specific limit here.

The WSS provided by the embodiment of the present application is introduced above, and the beam modulation method provided by the embodiment of the present application is introduced below.

FIG. 8 is a schematic flowchart of the first beam modulation method provided by the embodiment of the present application. It should be noted that this beam modulation method can be applied in scenarios involving beam deflection including WSS. The beam modulation method includes the following steps.

801. Adjust the phase distribution corresponding to the pixels on the spatial light modulator according to the beam deflection phase, disturbance phase and compensation phase.

In this embodiment, by adjusting the phase modulation encoding method of the spatial light modulator, the disturbance phase and the compensation phase are further introduced on the basis of the beam deflection phase. Among them, the beam deflection phase acts on the deflection direction adjustment of each sub-wavelength beam, the disturbance phase acts on the phase modulation corresponding to each diffraction order, and the compensation phase is used to compensate for the disturbance phase. By designing the distribution of the perturbation phase and the compensation phase, the perturbation phase and the compensation phase corresponding to the target diffraction order in multiple diffraction orders can be canceled out, and the light field distribution remains unchanged as in the case where only the beam deflection phase acts. However, the disturbance phase and the compensation phase corresponding to at least one diffraction order other than the target diffraction order cannot cancel each other, and the light field distribution at the output port plane is different from the light field distribution of the target diffraction order. Then, the light spot of the target diffraction order will still maintain its original ideal shape, so that it can be coupled to the target output port. The disturbance phase and compensation phase corresponding to at least one other diffraction order cannot cancel each other, and the light spots of this part of the diffraction order will be dispersed, making it difficult to couple to the output port.

802. Use a spatial light modulator to modulate multiple sub-wavelength beams respectively.

Based on the phase distribution corresponding to each pixel point on the spatial light modulator, the spatial light modulator will separately modulate the incident multiple sub-wavelength beams. While adjusting the deflection direction of the sub-wavelength beam, it will also change each diffraction order of the sub-wavelength beam. corresponding light field distribution. Taking one of the sub-wavelength beams that can cause crosstalk as an example, the spatial light modulator modulates the sub-wavelength beam so that the light of the target diffraction order maintains the original ideal spot shape and can be coupled to the target output port. The light field distribution of at least one other diffraction order is different from the light field distribution of the target diffraction order, making it difficult to couple to the output port.

The beam modulation method provided by the embodiment of the present application will be further introduced below in conjunction with the application scenario of WSS.

FIG. 9 is a schematic flowchart of the second beam modulation method provided by an embodiment of the present application. It should be noted that the structure of WSS and the functions of each module can be referred to the introduction of the embodiment shown in Figure 1 above, and details will not be described again here. The beam modulation method includes the following steps.

901. Measure the optical power of each output port.

Specifically, an optical power detector can be used to measure the optical power of each output port in the WSS.

902. Determine the output port that needs to suppress crosstalk.

The output port that needs to suppress crosstalk can be determined based on the optical power of each output port. For example, an output port whose output optical power is greater than a preset optical power threshold can be identified as an output port that needs to suppress crosstalk.

903. Determine the phase distribution form of the disturbance phase and the compensation phase.

Based on the introduction of the above embodiments, the disturbance phase and the compensation phase can adopt various distribution forms. Therefore, the phase distribution form of the disturbance phase and the compensation phase can be determined according to the diffraction order corresponding to the output port where crosstalk needs to be suppressed. Taking the two phase distribution forms introduced in the above embodiments as an example, when it is necessary to achieve dispersion for all the diffraction orders of crosstalk, the perturbation phase and the compensation phase can be selected as quadratic phase distribution. When it is necessary to achieve dispersion for one or some diffraction orders of crosstalk, To realize dispersion, the disturbance phase and compensation phase can be selected as binary grating phase distribution. For introduction to the quadratic phase distribution and the binary grating phase distribution, please refer to the relevant descriptions of the above embodiments and will not be described again here.

904. Adjust the phase distribution corresponding to the pixels on the spatial light modulator.

According to the phase distribution form of the disturbance phase and the compensation phase, and combined with the beam deflection phase, the phase distribution corresponding to the pixel points on the spatial light modulator is adjusted, thereby re-modulating the light beam incident on the spatial light modulator. For the specific method, please refer to the relevant introduction of step 801 in the embodiment shown in FIG. 8 , and will not be described again here.

905. Determine whether the output port that needs to suppress crosstalk meets the standard. If yes, perform step 906. If not, perform step 903 and step 904.

By measuring the optical power of each output port again, you can determine whether the output port that needs to suppress crosstalk meets the standard. If the standard is met, it means that port crosstalk has been effectively suppressed, and the phase distribution corresponding to the pixels on the current spatial light modulator can be confirmed and maintained. If the standard is not met, it means that there is still large crosstalk at the port, and the

above steps

903 and 904 need to be performed again to readjust the phase distribution corresponding to the pixels on the spatial light modulator.

906. Maintain the phase distribution corresponding to the pixels on the spatial light modulator.

Claims

A wavelength selective switch WSS, characterized in that it includes: a port component, a dispersion component, a lens component, a spatial light modulator SLM and a controller, the port component includes an input port and a plurality of output ports;

The dispersion component is used to decompose the multiplexed beam from the input port into multiple sub-wavelength beams, and guide the multiple sub-wavelength beams to the lens assembly;

The lens assembly is used to guide the plurality of sub-wavelength beams to different areas of the SLM respectively;

The SLM is used to modulate the plurality of sub-wavelength light beams respectively. The sub-wavelength light beams are modulated by the SLM to form multiple diffraction order light beams, wherein the light field distribution of the target diffraction order light beam is consistent with the light field distribution of the target diffraction order light beams. The light field mode supported by the output port is matched, and the light field distribution of the light beam of at least one diffraction order is different from the light field distribution of the light beam of the target diffraction order;

The lens component is also used to guide the modulated multiple sub-wavelength light beams to the dispersion component;

The dispersion component is also used to combine the modulated multiple sub-wavelength beams and transmit them to the multiple output ports;

The controller is used to adjust the phase distribution corresponding to the pixels on the SLM.
The WSS according to claim 1, characterized in that the light field distribution includes the intensity distribution of the light field and/or the phase distribution of the light field, the light field distribution depends on the beam type, the beam size and/or the beam and the The relative position between the output ports.
The WSS according to claim 1 or 2, characterized in that the coupling efficiency of the target diffraction order light beam coupled into the output port is greater than or equal to a threshold value, and the at least one diffraction order light beam is coupled into the The coupling efficiency of the output port is less than the threshold.
The WSS according to any one of claims 1 to 3, wherein the beam of the target diffraction order is a Gaussian beam, and the beam of the target diffraction order has the same characteristics as the Gaussian mode supported by the output port. The waist size of the waistband is located at the output port;

The at least one diffraction order beam is a non-Gaussian beam, or the at least one diffraction order beam has a different beam waist size from the Gaussian mode supported by the output port, or the at least one diffraction order The beam waist of the beam is offset from the output port.
The WSS according to any one of claims 1 to 4, characterized in that the controller specifically adjusts the phase distribution corresponding to the pixel points on the SLM according to the beam deflection phase, disturbance phase and compensation phase, wherein, the The beam deflection phase acts on the deflection direction adjustment of each sub-wavelength beam, the perturbation phase acts on the phase modulation corresponding to each diffraction order, the compensation phase is used to compensate for the perturbation phase, and the target diffraction order The corresponding disturbance phase and the compensation phase cancel each other, and the disturbance phase and the compensation phase corresponding to the at least one diffraction order cannot cancel each other.
The WSS according to claim 1, wherein the beam deflection phase has a functional relationship with the disturbance phase or the compensation phase.
The WSS according to claim 6, characterized in that the phase distribution corresponding to the pixel points on the SLM can be expressed as φ(x), φ(x)=f[G(x)-D(x)]+C (x), or, φ(x)=f[G(x)-C(x)]+D(x), where G(x) represents the beam deflection phase, and D(x) represents the disturbance phase, the C(x) represents the compensation phase, the f[G(x)-D(x)] represents the function associated with G(x)-D(x), and the f [G(x)-C(x)] represents the function associated with G(x)-C(x).
The WSS according to any one of claims 5 to 7, characterized in that the disturbance phase and the compensation phase satisfy a quadratic phase distribution.
The WSS according to any one of claims 5 to 7, characterized in that the disturbance phase and the compensation phase satisfy a binary grating phase distribution.
The WSS according to any one of claims 5 to 9, wherein the beam deflection phase is a phase grating with periodic distribution.
A beam modulation method, characterized by including:

Adjust the phase distribution corresponding to the pixels on the spatial light modulator SLM;

The input multiple sub-wavelength beams are modulated respectively by the SLM, and the sub-wavelength beams are modulated by the SLM to form multiple diffraction order beams, wherein the light field distribution of the target diffraction order beam is consistent with the The output port supports light field mode matching, and the light field distribution of the light beam of at least one diffraction order is different from the light field distribution of the light beam of the target diffraction order.
The method of claim 11, wherein the light field distribution includes an intensity distribution of the light field and/or a phase distribution of the light field, and the light field distribution depends on the type of light beam, the size of the light beam and/or the relationship between the light field and the light field. The relative position between the output ports.
The method according to claims 11 and 12, characterized in that the coupling efficiency of the target diffraction order light beam coupled into the output port is greater than or equal to a threshold value, and the at least one diffraction order light beam is coupled into the The coupling efficiency of the output port is less than the threshold.
The method according to any one of claims 11 to 13, characterized in that the beam of the target diffraction order is a Gaussian beam, and the beam of the target diffraction order has the same characteristics as the Gaussian mode supported by the output port. The waist size of the waistband is located at the output port;

The beam of at least one diffraction order is a non-Gaussian beam, or the beam of at least one diffraction order has a different beam waist size from the Gaussian mode supported by the output port, or the at least one diffraction order The beam waist of the beam is offset from the output port.
The method according to any one of claims 11 to 14, characterized in that adjusting the phase distribution corresponding to the pixel points on the spatial light modulator SLM includes:

The phase distribution corresponding to the pixel point on the SLM is adjusted according to the beam deflection phase, the perturbation phase and the compensation phase, wherein the beam deflection phase acts on the deflection direction adjustment of each sub-wavelength beam, and the perturbation phase acts on each diffraction order corresponding phase modulation, the compensation phase is used to compensate the perturbation phase, the perturbation phase and the compensation phase corresponding to the target diffraction order cancel each other, and the perturbation phase corresponding to the at least one diffraction order and The compensation phases cannot cancel each other out.
The method of claim 15, wherein the beam deflection phase has a functional relationship with the disturbance phase or the compensation phase.
The method according to claim 16, characterized in that the phase distribution corresponding to the pixel point on the SLM can be expressed as φ(x), φ(x)=f[G(x)-D(x)]+C (x), or, φ(x)=f[G(x)-C(x)]+D(x), where G(x) represents the beam deflection phase, and D(x) represents the disturbance phase, the C(x) represents the compensation phase, the f[G(x)-D(x)] represents the function associated with G(x)-D(x), and the f [G(x)-C(x)] represents the function associated with G(x)-C(x).
The method according to any one of claims 15 to 17, characterized in that the disturbance phase and the compensation phase satisfy a quadratic phase distribution.
The method according to any one of claims 15 to 17, characterized in that the disturbance phase and the compensation phase satisfy a binary grating phase distribution.
The method according to any one of claims 15 to 19, wherein the beam deflection phase is a phase grating with periodic distribution.