Crosstalk suppression method of wavelength selective switch and wavelength selective switch

Abstract

The invention relates to the technical field of optical communication, in particular to a crosstalk suppression method of a wavelength selective switch and the wavelength selective switch, and the method comprises the steps: obtaining the light spot center of incident light on a plurality of pixel points on an LCOS chip; according to the position of the light spot center, calculating a phase modulation amount needing to be superposed on each pixel point; and superposing the phase modulation quantity to the initial phase of the pixel point. By superposing the phase modulation quantity on the initial phase of the pixel point, the phase of the LCOS chip is adjusted, the aberration of the WSS light path is compensated, the port switching function of the WSS module is realized, the crosstalk between adjacent output ports is inhibited, the insertion loss of the output ports is optimized, and the performance of the WSS module is improved under the condition that other elements do not need to be added in the WSS light path. And the index and the performance of the WSS module are effectively improved.

Description

Technical Field

[0001] This invention relates to the field of optical communication technology, and in particular to a method for suppressing crosstalk in a wavelength selective switch and the wavelength selective switch itself. Background Technology

[0002] With the advent of the 5G / F5G era, technologies such as cloud services, data centers, artificial intelligence, and the Internet of Things are booming. Various information and data flows are not only placing increasing demands on network bandwidth but also drastically increasing the data throughput consumed by node switching. To meet the needs of next-generation intelligent network applications, the importance of all-optical switching is growing daily. Among these, the Reconfigurable Optical Add-Drop Multiplexer (ROADM) system, with its core wavelength-selective switch (WSS) module, is currently the mainstream commercial solution for optical fiber communication switching. Its flexible scheduling, large switching capacity, low latency, and low power consumption are increasingly favored by operators and enterprise customers.

[0003] Liquid Crystal on Silicon (LCOS) optical switching chips can achieve optical signal routing and deflection switching by loading different phase grating images. They offer extremely high reliability and are currently the main solution for implementing Flexible Grid Switch (WSS) technology. With the continuous development of all-optical networks and their increasing scale, WSS requires a larger number of ports to support the improved ROADM (Road-Oriented Aspect-Depth) dimensions. This increases the difficulty of WSS optical path design and debugging, leading to some aberrations in the WSS optical path, increased insertion loss at the WSS output ports, and increased crosstalk between adjacent output ports.

[0004] Therefore, overcoming the shortcomings of the existing technology is an urgent problem to be solved in this technical field. Summary of the Invention

[0005] The technical problem to be solved by this invention is that the increased difficulty in the design and debugging of the WSS optical path leads to some aberrations in the WSS optical path, resulting in increased insertion loss at the WSS output port and increased crosstalk between adjacent output ports.

[0006] The present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a method for suppressing crosstalk in a wavelength selective switch, comprising:

[0008] Obtain the center of the incident light spot on several pixels on the LCOS chip;

[0009] The amount of phase modulation that needs to be superimposed on each pixel is calculated based on the position of the light spot center;

[0010] The phase modulation amount is superimposed on the initial phase of the pixel.

[0011] Preferably, obtaining the center of the incident light spot on a plurality of pixels on the LCOS chip specifically includes:

[0012] Calculate the first theoretical insertion loss reduction at the output port when half of the incident light is blocked;

[0013] Starting from the first pixel on the LCOS chip, the phase of each pixel is set to 0, while the phases of the other pixels are set to the initial phase. The first actual insertion loss of the output port is monitored. When the phase of the nth pixel is set to 0, the first actual insertion loss is equal to the first theoretical insertion loss. Then, the position region of the nth pixel is the center of the light spot.

[0014] Preferably, when the wavelength selection switch is a Twin structure wavelength selection switch, the wavelength selection switch includes a first fiber array collimator and a second fiber array collimator. The first fiber array collimator includes a first input port and multiple first output ports, and the second fiber array collimator includes a second input port and multiple second output ports. The first input port corresponds to the first output port, and the second input port corresponds to the second output port. The step of obtaining the center of the incident light spot on several pixels on the LCOS chip includes:

[0015] The plurality of pixels are divided into a first part and a second part to divide the LCOS chip into a first region and a second region. The first region corresponds to the first input port and the first output port, and the second region corresponds to the second input port and the second output port. The total number of pixels is M, the first region corresponds to 1 to m1 pixels, and the second region corresponds to (m1+1) to M pixels.

[0016] Obtain the first spot center of the pixel in the first region, and obtain the second spot center of the pixel in the second region, so as to calculate the phase modulation amount of the pixel in the first region based on the position of the first spot center, and calculate the phase modulation amount of the pixel in the second region based on the position of the second spot center.

[0017] Preferably, obtaining the first spot center of the pixels in the first region and obtaining the second spot center of the pixels in the second region includes:

[0018] Calculate the second theoretical loss reduction of the first output port when the optical signal at the first input port is half blocked; calculate the third theoretical loss reduction of the second output port when the optical signal at the second input port is half blocked.

[0019] Starting from the first pixel, the phase of each pixel is set to 0, while the phases of the other pixels are set to the initial phase. The second actual insertion loss of the first output port is monitored. When the phase of the n1th pixel is set to 0, the second actual insertion loss is equal to the second theoretical insertion loss. Then, the location region of the n1th pixel is the center of the first spot.

[0020] Starting from the (m1+1)th pixel, the phase of each pixel is set to 0, while the phases of the other pixels are set to the initial phase. The third actual insertion loss of the second output port is monitored. When the phase of the n2th pixel is set to 0, the third actual insertion loss is equal to the third theoretical insertion loss. Therefore, the position region of the n2th pixel is the center of the second spot.

[0021] Preferably, the step of calculating the phase modulation amount to be superimposed on each pixel based on the position of the light spot center specifically includes:

[0022] The phase modulation amount superimposed on each pixel is calculated according to the following formula.

[0023]

[0024] Where x is the position of the pixel point, x center λ is the position of the center of the light spot, λ is the wavelength of the light, f is the focal length of the lens, and d is the pixel size.

[0025] Preferably, the lens focal length is determined as follows: a small lens is placed in front of the LCOS chip, such that the focal point of the small lens coincides with the center of the light spot, and the lens focal length is the focal length of the small lens; after determining the lens focal length, the small lens is removed.

[0026] Preferably, the method further includes obtaining the initial phase of each pixel, wherein the initial phase is calculated using the following methods:

[0027] Obtain the position of the pixel and the number of pixels in one raster period;

[0028] The initial phase is obtained by multiplying the position of the pixel by 2π and then dividing by the number of pixels in one grating period.

[0029] In a second aspect, the present invention provides a wavelength selective switch applicable to the crosstalk suppression method of the wavelength selective switch described in the first aspect, comprising: an optical fiber array collimator 1, a focusing lens 2, an LCOS chip 3, and a driving circuit 4; wherein the focusing lens 2 is disposed between the optical fiber array collimator 1 and the LCOS chip 3;

[0030] The fiber array collimator 1 includes an input port 10 and multiple output ports 11. The input port 10 is used to output the collimated optical signal, and the output ports 11 are used to collimate the optical signal deflected by the LCOS chip 3.

[0031] The driving circuit 4 is used to adjust the phase of each pixel on the LCOS chip 3 according to the crosstalk suppression method of the wavelength selection switch as described in the first aspect.

[0032] Preferably, the number of fiber array collimators 1 is 2, specifically including a first fiber array collimator 12 and a second fiber array collimator 13. The first fiber array collimator 12 includes a first input port 120 and multiple first output ports 121, and the second fiber array collimator 13 includes a second input port 130 and multiple second output ports 131. The first fiber array collimator 12 and the second fiber array collimator 13 share one LCOS chip 3.

[0033] The wavelength selection switch further includes a first lens 20 and a second lens 21. The first lens 20 is disposed between the first fiber array collimator 12 and the LCOS chip 3, and the second lens 21 is disposed between the second fiber array collimator 13 and the LCOS chip 3.

[0034] Preferably, the fiber array collimator 1 includes multiple fiber arrays and multiple collimating lenses, with each of the multiple fiber arrays and multiple collimating lenses coupled together.

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention adjusts the phase of the LCOS chip by superimposing the initial phase of the pixel with the phase modulation amount, without adding other components in the WSS optical path, to compensate for the aberrations of the WSS optical path, realize the port switching function of the WSS module, suppress the crosstalk between adjacent ports of the output port, optimize the insertion loss of the output port, and effectively improve the performance and specifications of the WSS module. Attached Figure Description

[0036] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments of the present invention will be briefly described below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0037] Figure 1 This is a schematic diagram of the overall structure of a wavelength selective switch provided in an embodiment of the present invention;

[0038] Figure 2 This is a schematic diagram illustrating how optical path aberrations in a wavelength selective switch lead to increased insertion loss at the output port and increased crosstalk between adjacent ports.

[0039] Figure 3 This is a schematic diagram of adding a small lens to a wavelength selective switch according to an embodiment of the present invention;

[0040] Figure 4 This is a schematic diagram of a wavelength selective switch with dual inputs and dual outputs provided in an embodiment of the present invention;

[0041] Figure 5 This is a schematic diagram of the overall process of a crosstalk suppression method for a wavelength selective switch provided in an embodiment of the present invention;

[0042] Figure 6 This is a schematic diagram of step 1 of a crosstalk suppression method for a wavelength selective switch provided in an embodiment of the present invention;

[0043] Figure 7 This is a schematic diagram showing the position of the light spot center in a crosstalk suppression method for a wavelength selective switch provided in an embodiment of the present invention;

[0044] Figure 8 This is a schematic diagram of a method for confirming the center position of a light spot in a TWin structure, which is a crosstalk suppression method for a wavelength selective switch provided in an embodiment of the present invention.

[0045] Figure 9 This is a schematic diagram of step 112 of a crosstalk suppression method for a wavelength selective switch provided in an embodiment of the present invention;

[0046] Figure 10 This is a schematic diagram showing the positions of the centers of two light spots in a crosstalk suppression method for a wavelength selective switch provided in an embodiment of the present invention;

[0047] Figure 11 This is a schematic diagram of step 2 of a crosstalk suppression method for a wavelength selective switch provided in an embodiment of the present invention;

[0048] Figure 12This is a schematic diagram of step 3 of a crosstalk suppression method for a wavelength selective switch provided in an embodiment of the present invention;

[0049] Figure 13 This is a schematic diagram of the initial phase acquisition method of a crosstalk suppression method for a wavelength selective switch provided in an embodiment of the present invention;

[0050] Figure 14 This is a schematic diagram illustrating the method for calculating the diffraction angle of a crosstalk suppression method for a wavelength selective switch provided in an embodiment of the present invention.

[0051] Figure 15 This is a schematic diagram of the initial phase of an LCOS chip for a crosstalk suppression method for a wavelength selective switch provided in an embodiment of the present invention;

[0052] Figure 16 This is a schematic diagram of the insertion loss of the output port and the crosstalk between adjacent ports before modulation of a crosstalk suppression method for a wavelength selective switch provided in an embodiment of the present invention.

[0053] Figure 17 This is a schematic diagram of the superimposed phase modulation amount of a crosstalk suppression method for a wavelength selective switch provided in an embodiment of the present invention;

[0054] Figure 18 This is a schematic diagram of an optimized phase diagram of a crosstalk suppression method for a wavelength selective switch provided in an embodiment of the present invention.

[0055] Figure 19 This is a schematic diagram of the optimized output port insertion loss and adjacent port crosstalk of a wavelength selective switch crosstalk suppression method provided in an embodiment of the present invention.

[0056] Figure 20 This is a schematic diagram of the initial phase of an LCOS chip containing two modules, which is a method for suppressing crosstalk in a wavelength selective switch according to an embodiment of the present invention.

[0057] Figure 21 This is a schematic diagram of the phase modulation amount superimposed on the first module in a crosstalk suppression method for a wavelength selective switch provided in an embodiment of the present invention;

[0058] Figure 22 This is a schematic diagram of the phase modulation amount superimposed on the second module in a crosstalk suppression method for a wavelength selective switch provided in an embodiment of the present invention;

[0059] Figure 23 This is a schematic diagram of the phase modulation amount superimposed on the first and second modules of a crosstalk suppression method for a wavelength selective switch provided in an embodiment of the present invention.

[0060] Figure 24This is a phase diagram showing the optimized two modules of a crosstalk suppression method for a wavelength selective switch provided in an embodiment of the present invention. Detailed Implementation

[0061] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0062] Unless the context otherwise requires, throughout the specification and claims, the term "comprising" is interpreted as openly inclusive, meaning "including, but not limited to." In the description of the specification, terms such as "one embodiment," "some embodiments," "exemplary embodiment," "example," "specific example," or "some examples" are intended to indicate that a particular feature, structure, material, or characteristic associated with that embodiment or example is included in at least one embodiment or example of this disclosure. The illustrative representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics mentioned may be included in any suitable manner in any one or more embodiments or examples; that is, although they may be incorporated into embodiments or examples using the above terms for reasons such as order and position, it does not limit them to be incorporated in combination by a single embodiment or example.

[0063] In the description of this invention, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this disclosure and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this disclosure.

[0064] In the description of this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of embodiments of this disclosure, unless otherwise stated, "a plurality of" means two or more. Furthermore, for example, the description may use the prefix "A" or "B" to describe the same type of nouns as two independent entities. In this case, the corresponding features defined with "A" and "B" are used only to distinguish between similar entities and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features.

[0065] In describing some embodiments, the terms "coupled," "coupled," and "connected," and their derivative expressions, may be used. For example, the term "connected" may be used in describing some embodiments to indicate that two or more components have direct physical or electrical contact with each other. Similarly, the term "coupled" may be used in describing some embodiments to indicate that two or more components have direct physical or electrical contact. However, the terms "connected" or "coupled" may also refer to two or more components that do not have direct contact with each other but still cooperate or interact with each other, such as "optical coupling," "wireless connection," etc. The embodiments disclosed herein are not necessarily limited to the scope of this invention.

[0066] In the description of this invention, the expression “A and / or B” (where A and B are used to formally represent specific features) will be used. The corresponding expression includes the following three combinations: only A, only B, and a combination of A and B.

[0067] As used in this invention, “about,” “approximately,” or “approximately” includes the stated value and the average value within an acceptable range of deviation from a particular value, wherein the acceptable range of deviation is determined by a person skilled in the art taking into account the measurement under discussion and the error associated with the measurement of the particular quantity (i.e., the limitations of the measurement system).

[0068] Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0069] Example 1:

[0070] Embodiment 1 of the present invention provides a wavelength selective switch, applicable to the crosstalk suppression method for wavelength selective switches described in subsequent solutions, such as... Figure 1 As shown, it includes: an optical fiber array collimator 1, a focusing lens 2, an LCOS chip 3, and a driving circuit 4; the focusing lens 2 is disposed between the optical fiber array collimator 1 and the LCOS chip 3; the optical fiber array collimator 1 includes an input port 10 and multiple output ports 11, the input port 10 is used to output the collimated optical signal, and the output ports 11 are used to collimate the optical signal deflected by the LCOS chip 3; the driving circuit 4 is used to adjust the phase of each pixel on the LCOS chip 3 according to the crosstalk suppression method of the wavelength selective switch described below.

[0071] The fiber array collimator 1 includes multiple fiber arrays and multiple collimating lenses (not shown in the figure). The multiple fibers in the fiber array are coupled to the multiple collimating lenses one by one. The input port of one fiber is used as input port 10, and the output ports of the other fibers are used as output ports 11. Light is input from the input port, passes through the collimating lens and the focusing lens 2 to the LCOS chip 3, and after diffraction by the phase grating on the LCOS chip 3, it is incident on one of the output ports.

[0072] In practical application scenarios, such as Figure 2 As shown, due to optical aberrations in the WSS optical path, the focal point of the incident beam after being converged by focusing lens 2 does not fall on LCOS chip 3. The light diffracted back by LCOS chip 3 is deflected at a certain angle and cannot be incident directly on the target output port, reducing coupling efficiency. Some light energy may be transferred to adjacent ports of other output ports, resulting in higher insertion loss at the output port and greater crosstalk between adjacent output ports. Therefore, to calibrate this aberration without modulating the phase grating of LCOS chip 3, a lens needs to be added in front of LCOS chip 3 to make the focal point of the incident light fall back on LCOS chip 3, such as... Figure 3 As shown, a small lens 5 can be disposed between the focusing lens 2 and the LCOS chip 3. The focal point of the small lens 5 falls on the LCOS chip 3. The small lens 5 is used to perform secondary focusing of the light signal converged by the focusing lens 2.

[0073] To achieve aberration calibration without adding new components to the wavelength selective switch, the scheme described later in this embodiment of the invention employs a phase modulation amount superimposed on the initial phase of the phase grating. This effectively functions as placing a small lens 5 within the wavelength selective switch to focus the optical signal. The driving circuit 4 applies different voltages to different pixels of the LCOS chip 3, with different voltages corresponding to different phase modulation amounts, forming a phase grating. The incident light undergoes diffraction after passing through the LCOS chip 3, thus deflecting at a certain angle. It then passes through the focusing lens 2 and the fiber array collimator 1 before exiting from the corresponding output port, realizing the port switching function of the WSS.

[0074] In general, a wavelength selective switch may include one input port, multiple output ports, and an LCOS chip 3. In this embodiment of the invention, when the wavelength selective switch is a Twin-structure wavelength selective switch, the wavelength selective switch includes two sets of fiber array collimators 1, and the two sets of fiber array collimators 1 share one LCOS chip 3. For example... Figure 4As shown, the number of fiber array collimators 1 is two, specifically including a first fiber array collimator 12 and a second fiber array collimator 13. The first fiber array collimator 12 includes a first input port 120 and multiple first output ports 121, and the second fiber array collimator 13 includes a second input port 130 and multiple second output ports 131. The first fiber array collimator 12 and the second fiber array collimator 13 share a single LCOS chip 3. A first lens 20 is disposed in the optical path of the first fiber array collimator 12, and a second lens 21 is disposed in the optical path of the second fiber array collimator 13. The first lens 20 is disposed between the first fiber array collimator 12 and the LCOS chip 3, and the second lens 21 is disposed between the second fiber array collimator 13 and the LCOS chip 3. When determining the position of the light spot center, the LCOS chip 3 is divided into two equal regions. One region diffracts the optical signal of the first fiber array collimator 12, and the other region diffracts the optical signal of the second fiber array collimator 13.

[0075] Based on the wavelength selective switch provided by the above solution, this embodiment of the invention also provides a crosstalk suppression method for the wavelength selective switch, such as... Figure 5 As shown, it includes:

[0076] In step 1, the center of the incident light spot on several pixels on the LCOS chip 3 is obtained.

[0077] The LCOS chip 3 has multiple pixels arranged to form a phase grating. By adjusting the phase of the pixels, aberrations are compensated.

[0078] In step 2, the amount of phase modulation that needs to be superimposed on each pixel is calculated based on the position of the center of the light spot.

[0079] In step 3, the phase modulation amount is superimposed on the initial phase of the pixel.

[0080] The initial phase mainly depends on the position of the pixel, and the method for determining the initial phase is described below.

[0081] In addition to the steps described above, after calculating the phase modulation amount and the initial phase, the method further includes: obtaining the light field after the incident light is modulated by the LCOS chip 3 based on the initial phase and the phase modulation amount.

[0082] This invention compensates for aberrations in the WSS optical path by superimposing phase modulation on the initial phase of the pixels, without adding other components to the WSS optical path. This enables the port switching function of the WSS module, suppresses crosstalk between adjacent output ports, optimizes the insertion loss of the output ports, and effectively improves the specifications and performance of the WSS module.

[0083] Before performing phase modulation on each pixel of the phase grating, it is first necessary to find the center of the incident light spot on the LCOS chip 3, and determine the amount of phase modulation superimposed on each pixel based on the spot center. The principle of determining the spot center is as follows: the light spot on the LCOS chip 3 from the input port is the energy distribution area of ​​the light. When the spot is partially blocked, the light power passing through the LCOS chip 3 will decrease.

[0084] In optical systems, insertion loss refers to the reduction in optical power caused by the introduction of a component. In this embodiment, the insertion loss is due to the phase of some pixels on the LCOS chip 3 being set to 0, causing these pixels to be unable to deflect light, resulting in a reduction in output optical power. In the LCOS chip 3, each pixel can independently control its phase, thereby achieving modulation of the light wavefront. When the phase of a pixel is set to 0, that pixel has no deflecting effect on the light, and the light will pass directly without deflection. When half of the light spot area is blocked, since the light spot radius is proportional to the light amplitude, when half of the light spot is blocked, the light spot radius is halved, and the light amplitude is also halved. Since the light intensity is proportional to the square of the light amplitude, when the light amplitude is halved, the light intensity becomes 1 / 4 of the original, which can be expressed by the formula I = kA. 2 Where I is the light intensity, A is the light amplitude, and k is a proportionality coefficient related to the properties of the light wave and environmental conditions. Then, according to the formula for insertion loss (dB)... Where P out P is the output power of light. in The input power of light. (Based on the aforementioned light intensity becoming 1 / 4 of the original), the insertion loss (dB) will decrease by 6dB when half of the light spot is blocked.

[0085] Based on the above theory, in step 1, when there is one input port and multiple output ports, the process of obtaining the center of the incident light spot on several pixels of the LCOS chip 3 is as follows: Figure 6 As shown, it specifically includes:

[0086] In step 101, the first theoretical insertion loss at the output port is calculated when half of the incident light is blocked.

[0087] The first theoretical loss is 6dB.

[0088] In step 102, starting from the first pixel on the LCOS chip 3, the phase of each pixel is set to 0, while the phases of the other pixels are set to the initial phase. The first actual insertion loss of the output port 11 is monitored. When the phase of the nth pixel is set to 0, the first actual insertion loss is equal to the first theoretical insertion loss. Then, the position region of the nth pixel is the center of the light spot.

[0089] That is, the position X of the center of the light spot center =n.

[0090] See Figure 7 As shown, firstly, the phase of the first pixel is set to 0, and the phases of the other pixels are the initial phases; then, the phase of the second pixel is set to 0 (at this time, the phase of the first pixel is still 0), and the phases of the other pixels are the initial phases, and so on. When the phase of the 217th pixel is set to 0, the first actual insertion loss is equal to the first theoretical insertion loss, and the position area corresponding to the 217th pixel is the center of the light spot.

[0091] When the wavelength selection switch is a Twin structure wavelength selection switch, the wavelength selection switch includes a first fiber array collimator 12 and a second fiber array collimator 13. The first fiber array collimator 12 includes a first input port 120 and multiple first output ports 121. The second fiber array collimator 13 includes a second input port 130 and multiple second output ports 131. The first input port 120 corresponds to the first output port 121, and the second input port 130 corresponds to the second output port 131. The process of obtaining the center of the incident light spot on several pixels on the LCOS chip 3 is as follows: Figure 8 As shown, it specifically includes:

[0092] In step 111, the plurality of pixels are divided into a first part and a second part to divide the LCOS chip 3 into a first region and a second region. The first region corresponds to the first input port 120 and the first output port 121, and the second region corresponds to the second input port 130 and the second output port 131. The total number of pixels is M, the first region corresponds to 1 to m1 pixels, and the second region corresponds to (m1+1) to M pixels.

[0093] In step 112, the first spot center of the pixel in the first region is obtained, and the second spot center of the pixel in the second region is obtained, so as to calculate the phase modulation amount of the pixel in the first region based on the position of the first spot center, and calculate the phase modulation amount of the pixel in the second region based on the position of the second spot center.

[0094] In one embodiment, when the LCOS chip has 1200 pixels, the phase grating formed by the first 600 pixels is used to selectively deflect the optical signal from the first input port 120 to a certain first output port 121; the phase grating formed by the last 600 pixels is used to selectively deflect the optical signal from the second input port 130 to a certain second output port 131. The spot centers of the regions corresponding to the first 600 pixels and the last 600 pixels are determined respectively, and the phase of the pixels is compensated based on their respective spot centers.

[0095] In one embodiment, obtaining the first spot center of the pixels in the first region and obtaining the second spot center of the pixels in the second region, as shown below. Figure 9 As shown, it includes:

[0096] In step 121, the second theoretical loss reduction of the first output port 121 when the optical signal of the first input port 120 is half blocked is calculated; the third theoretical loss reduction of the second output port 131 when the optical signal of the second input port 130 is half blocked is calculated.

[0097] The second and third theoretical losses can be 6dB.

[0098] In step 122, starting from the first pixel, the phase of each pixel is set to 0, and the phases of the other pixels are set to the initial phase. The second actual insertion loss of the first output port is monitored. When the phase of the n1th pixel is set to 0, the second actual insertion loss is equal to the second theoretical insertion loss. Then, the position region of the n1th pixel is the center of the first spot.

[0099] Among them, the center of the first light spot X center1 =n1.

[0100] In step 123, starting from the (m1+1)th pixel, the phase of each pixel is set to 0, while the phases of the other pixels are set to the initial phase. The third actual insertion loss of the second output port is monitored. When the phase of the n2th pixel is set to 0, the third actual insertion loss is equal to the third theoretical insertion loss. Therefore, the position region of the n2th pixel is the center of the second spot.

[0101] Among them, the center of the second spot X center2 =n2.

[0102] See Figure 10 As shown in one embodiment, the center X of the first light spot is confirmed. center1 The second spot center X center2 In the example, the position corresponding to the 211th pixel is the center X of the first light spot. center1 The position corresponding to the 841st pixel is the center X of the second light spot. center2 .

[0103] After obtaining the position of the light spot center, the phase modulation amount superimposed on each pixel is calculated based on the position of the light spot center. The phase modulation amount superimposed on each pixel is calculated according to the following formula.

[0104]

[0105] Where x is the position of the pixel point, x center λ is the position of the center of the light spot, λ is the wavelength of the light, f is the focal length of the lens, and d is the pixel size.

[0106] In one embodiment, the focal length of the lens is determined as follows: a small lens is placed before the LCOS chip, such that the focal point of the small lens coincides with the center of the light spot; the focal length of the small lens is then determined. After determining the focal length, the small lens is removed. In this process, it is first necessary to obtain... Figure 3 The focal length of the small lens 5 is used as the basis to determine the phase compensation amount of each pixel. The method of superimposing the phase modulation amount onto the initial phase of each pixel is used instead of the small lens 5 to avoid adding components.

[0107] Therefore, in step 2 above, the calculation of the required phase modulation amount based on the position of the light spot center is as follows: Figure 11 As shown, it specifically includes:

[0108] In step 201, the focusing lens 2 and the LCOS chip 3 are arranged in sequence, and a small lens 5 is placed between the focusing lens 2 and the LCOS chip 3. The focal point of the small lens 5 is aligned with the center of the light spot to obtain the focal length of the small lens 5.

[0109] In practical applications, the small lens 5 is removed after its focal length is measured. In actual products, the small lens 5 does not exist. Its main purpose is to use the focal length of the small lens 5 to calculate the final phase modulation amount.

[0110] In step 202, the position of each pixel, the position of the center of the light spot, the focal length of the small lens 5, and the wavelength of light are obtained.

[0111] In step 203, the phase modulation amount of each pixel is obtained based on the position of the pixel, the position of the center of the light spot, the focal length of the small lens 5, and the wavelength of the light.

[0112] Specifically, the position x of the pixel and the position x of the center of the light spot center The formula for obtaining the phase modulation amount of each pixel point based on the lens focal length f, pixel size d, and light wavelength λ of the small lens 5 is as follows:

[0113] When the first fiber array collimator 12 and the second fiber array collimator 13 are provided, the formula for the phase modulation amount of the pixels in the first region is: The formula for the phase modulation amount of the pixels in the second region is: The phase modulation amount of the pixels in the first region is combined with the phase modulation amount of the pixels in the second region to obtain the phase modulation amount used to simultaneously modulate the first region and the second region.

[0114] As mentioned in the aforementioned scheme, superimposing a phase modulation amount on the initial phase of the phase grating can achieve the effect of placing a lens in the wavelength selective switch to focus the optical signal. In one embodiment, the initial optical field of the incident light is E0, and the expression of the optical field after passing through the lens is... in This represents the amount of phase modulation of the light by the lens. When the WSS incident light is switched to a specific output port, the initial phase of the LCOS chip is... Therefore, the light field expression after the incident light passes through the lens and then the LCOS chip 3 is: The aforementioned plan has already been described. The calculation method, based on the above formula, will be explained below. The calculation method.

[0115] In step 3, the method further includes obtaining the initial phase of each pixel, wherein the initial phase is calculated using a method such as... Figure 12 As shown, it includes:

[0116] In step 301, the position of the pixel and the number of pixels in a grating period are obtained.

[0117] The phase grating includes multiple grating periods, and one grating period includes multiple pixels.

[0118] In step 302, the initial phase is obtained by multiplying the position of the pixel by 2π and then dividing by the number of pixels in one grating period.

[0119] In the calculation of the initial phase, the formula for the initial phase is derived through the following methods, such as... Figure 13 As shown, it includes:

[0120] In step 311, the diffraction angle of the phase grating, the length of the pixel, the position of the pixel, and the wavelength of light are obtained.

[0121] In step 312, the initial phase is calculated based on the diffraction angle of the phase grating, the length of the pixel, the position of the pixel, and the wavelength of light.

[0122] In the above formula for calculating the initial phase, the method for calculating the diffraction angle of the phase grating is as follows: Figure 14 As shown, it specifically includes:

[0123] In step 321, the length of the pixel and the number of pixels within a phase grating period are obtained.

[0124] In step 322, the length of one phase grating period is obtained based on the length of the pixel and the number of pixels in one phase grating period.

[0125] In step 323, the diffraction secondary of the input optical signal and the optical wavelength are obtained.

[0126] In step 324, the diffraction angle of the phase grating is obtained based on the diffraction secondary of the optical signal, the optical wavelength, and the length of one period of the phase grating.

[0127] In practical applications, based on the diffraction order m of the optical signal, the optical wavelength λ, and the length D of the grating period, the formula for calculating the diffraction angle of the phase grating is D·sinθ=mλ. The light entering the output port of the WSS module is generally the +1st order diffracted light, so m=1 can be set. Of course, in special scenarios, m can be determined according to the actual situation. In the initial phase calculation formula provided in this embodiment, the diffraction order m is 1 used for calculating the diffraction angle θ.

[0128] Assuming a grating period comprises n pixels, and the length of each pixel is d, the length D of the grating period is equal to n × d. Therefore, the formula for calculating the initial phase based on the diffraction angle θ of the phase grating, the size d of each pixel, the position x of each pixel, and the wavelength λ of the light is as follows:

[0129]

[0130] Using the solution provided in the embodiments of the present invention, Figure 15 This is an initial phase diagram of LCOS chip 3 in one embodiment. Figure 16 This is a schematic diagram showing the insertion loss of the output port before modulation and the crosstalk between adjacent ports; after superimposing, such as Figure 17 After the phase modulation amount shown, the phase of each pixel is as follows: Figure 18 As shown, the insertion loss at the output port and the crosstalk between adjacent ports are as follows: Figure 19 As can be seen, insertion loss and crosstalk between adjacent ports have been greatly improved.

[0131] For wavelength selective switches with a Twin structure, such as Figure 20 As shown, this is the initial phase diagram of LCOS chip 3. The phase diagrams of the two modules are superimposed as shown below. Figure 21 and Figure 22 After the phase modulation amount shown, Figure 21 and Figure 22 The combination of phase modulation amounts added to the two modules shown yields the following results. Figure 23 The diagram shows the phase modulation amount used to simultaneously modulate two modules. For example... Figure 24 As shown, this is the phase diagram after optimization by superimposing the phase modulation amount. Compensation in this way can improve insertion loss and crosstalk between adjacent ports.

[0132] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for suppressing crosstalk in a wavelength selective switch, characterized in that, include: Obtain the center of the incident light spot on several pixels on the LCOS chip; The amount of phase modulation that needs to be superimposed on each pixel is calculated based on the position of the light spot center; The phase modulation amount is superimposed on the initial phase of the pixel.

2. The crosstalk suppression method for wavelength selective switches according to claim 1, characterized in that, The process of obtaining the center of the incident light spot on several pixels of the LCOS chip specifically includes: Calculate the first theoretical insertion loss reduction at the output port when half of the incident light is blocked; Starting from the first pixel on the LCOS chip, the phase of each pixel is set to 0, while the phases of the other pixels are set to the initial phase. The first actual insertion loss of the output port is monitored. When the phase of the nth pixel is set to 0, the first actual insertion loss is equal to the first theoretical insertion loss. Then, the position region of the nth pixel is the center of the light spot.

3. The crosstalk suppression method for wavelength selective switches according to claim 1, characterized in that, When the wavelength selection switch is a Twin structure wavelength selection switch, the wavelength selection switch includes a first fiber array collimator and a second fiber array collimator. The first fiber array collimator includes a first input port and multiple first output ports, and the second fiber array collimator includes a second input port and multiple second output ports. The first input port corresponds to the first output port, and the second input port corresponds to the second output port. The step of obtaining the center of the incident light spot on several pixels on the LCOS chip includes: The plurality of pixels are divided into a first part and a second part to divide the LCOS chip into a first region and a second region. The first region corresponds to the first input port and the first output port, and the second region corresponds to the second input port and the second output port. The total number of pixels is M, the first region corresponds to 1 to m1 pixels, and the second region corresponds to (m1+1) to M pixels. Obtain the first spot center of the pixel in the first region, and obtain the second spot center of the pixel in the second region, so as to calculate the phase modulation amount of the pixel in the first region based on the position of the first spot center, and calculate the phase modulation amount of the pixel in the second region based on the position of the second spot center.

4. The crosstalk suppression method for wavelength selective switches according to claim 3, characterized in that, The step of obtaining the first spot center of the pixels in the first region and obtaining the second spot center of the pixels in the second region includes: Calculate the second theoretical loss reduction of the first output port when the optical signal at the first input port is half blocked; calculate the third theoretical loss reduction of the second output port when the optical signal at the second input port is half blocked. Starting from the first pixel, the phase of each pixel is set to 0, while the phases of the other pixels are set to the initial phase. The second actual insertion loss of the first output port is monitored. When the phase of the n1th pixel is set to 0, the second actual insertion loss is equal to the second theoretical insertion loss. Then, the location region of the n1th pixel is the center of the first spot. Starting from the (m1+1)th pixel, the phase of each pixel is set to 0, while the phases of the other pixels are set to the initial phase. The third actual insertion loss of the second output port is monitored. When the phase of the n2th pixel is set to 0, the third actual insertion loss is equal to the third theoretical insertion loss. Therefore, the position region of the n2th pixel is the center of the second spot.

5. The crosstalk suppression method for a wavelength selective switch according to claim 1, characterized in that, The calculation of the phase modulation amount to be superimposed on each pixel based on the position of the light spot center specifically includes: The phase modulation amount superimposed on each pixel is calculated according to the following formula. Where x is the position of the pixel point, x center λ is the position of the center of the light spot, λ is the wavelength of the light, f is the focal length of the lens, and d is the pixel size.

6. The crosstalk suppression method for a wavelength selective switch according to claim 5, characterized in that, The method for determining the focal length of the lens is as follows: A small lens is placed in front of the LCOS chip, such that the focal point of the small lens coincides with the center of the light spot, and the focal length of the lens is the focal length of the small lens; after determining the focal length of the lens, the small lens is removed.

7. The crosstalk suppression method for a wavelength selective switch according to any one of claims 1-6, characterized in that, It also includes obtaining the initial phase of each pixel, and the method for calculating the initial phase includes: Obtain the position of the pixel and the number of pixels in one raster period; The initial phase is obtained by multiplying the position of the pixel by 2π and then dividing by the number of pixels in one grating period.

8. A wavelength selective switch, characterized in that, include: The fiber array collimator (1), focusing lens (2), LCOS chip (3), and driving circuit (4) are provided; the focusing lens (2) is disposed between the fiber array collimator (1) and the LCOS chip (3); The fiber array collimator (1) includes an input port (10) and multiple output ports (11). The input port (10) is used to output the collimated optical signal, and the output ports (11) are used to output the optical signal deflected by the LCOS chip (3). The driving circuit (4) is used to adjust the phase of each pixel on the LCOS chip (3) according to the crosstalk suppression method of the wavelength selection switch as described in any one of claims 1-7.

9. The wavelength selective switch according to claim 8, characterized in that, The number of fiber array collimators (1) is 2, specifically including a first fiber array collimator (12) and a second fiber array collimator (13). The first fiber array collimator (12) includes a first input port (120) and multiple first output ports (121). The second fiber array collimator (13) includes a second input port (130) and multiple second output ports (131). The first fiber array collimator (12) and the second fiber array collimator (13) share a single LCOS chip (3). The wavelength selection switch further includes a first lens (20) and a second lens (21). The first lens (20) is disposed between the first fiber array collimator (12) and the LCOS chip (3), and the second lens (21) is disposed between the second fiber array collimator (13) and the LCOS chip (3).

10. The wavelength selective switch according to claim 8, characterized in that, The fiber array collimator (1) includes a fiber array and multiple collimating lenses, wherein multiple optical fibers in the fiber array are coupled to multiple collimating lenses one by one.

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