Wavelength selective switch and reconfigurable optical add drop multiplexer

Abstract

The invention provides a wavelength selective switch and a reconfigurable optical add-drop multiplexer, and belongs to the technical field of optical communication. The wavelength selection switch comprises an input and output module, a first lens group, a dispersion collimation module and a switching module. The input and output module receives a first optical signal and outputs a second optical signal, the first lens group focuses the second optical signal on a switching plane, and the dispersion collimation module collimates the second optical signal in the switching plane and disperses the second optical signal into a plurality of single-wavelength sub-optical signals on a dispersion plane. The first lens group focuses a plurality of sub-optical signals to the switching module on the switching plane, and the switching module selects different ports in the input and output module for different sub-optical signals to output. By adopting the wavelength selection switch, in a switching plane, an optical signal is focused, collimated and focused in sequence to reach the switching module, so that the appearance height of the wavelength selection switch is effectively compressed on the premise that the total length of an optical path, the deflection angle of the switching module and the spot size of the optical signal on the switching module are not changed.

Description

Technical Field

[0001] The present disclosure relates to the field of optical communication technology, and in particular to a wavelength selection switch and a reconfigurable optical add / drop multiplexer. Background Art

[0002] As the capacity of optical network services continues to increase and the dynamics continue to increase, operators have an increasingly strong demand for the configuration of dynamic service paths. Reconfigurable optical add-drop multiplexers (ROADMs) are key devices that support dynamic service path configuration in optical networks. Operators can remotely control ROADMs through software to expand communication services with greater flexibility. As the core component of ROADMs, wavelength selective switches are also required to have higher-dimensional scheduling capabilities, and the trend of wavelength selective switches evolving to have more ports is becoming increasingly obvious.

[0003] Directly adding ports under the current optical architecture of the wavelength selective switch will inevitably lead to an increase in the device height of the wavelength selective switch. Summary of the invention

[0004] The present disclosure provides a wavelength selective switch and a reconfigurable optical add / drop multiplexer, which effectively compress the device height of the wavelength selective switch without changing the total length of the optical path, the deflection angle of the switching module and the spot size of the optical signal on the switching module.

[0005] In a first aspect, the present disclosure provides a wavelength selective switch, which includes an input-output module, a first mirror group, a dispersion collimation module and a switching module, wherein the input-output module is used to receive a first optical signal and output a second optical signal, wherein the second optical signal is obtained based on the first optical signal, the first mirror group is used to focus the second optical signal on a switching plane, the dispersion collimation module is used to collimate the second optical signal on the switching plane, and disperse the second optical signal into a plurality of sub-optical signals on the dispersion plane, wherein the sub-optical signals are single-wavelength optical signals, the first mirror group is also used to focus the plurality of sub-optical signals on the switching plane to the switching module, and the switching module is used to select different ports in the input-output module for outputting different sub-optical signals.

[0006] In the scheme disclosed in the present disclosure, in the switching plane, after the optical signal is input from the input / output module, it sequentially undergoes focusing, collimation, and focusing to reach the switching module, rather than only undergoing one focusing to reach the switching module, thereby effectively compressing the optical path height without changing the total optical path length, the deflection angle of the switching module, and the spot size of the optical signal on the switching module, and thus compressing the device height of the wavelength selective switch. Moreover, the same lens group is used for the two focusing operations, which can also save the number of devices.

[0007] In an optional manner, the distance between the input-output module and the first mirror group is equal to the focal length of the first mirror group, the focal length of the dispersion collimation module for collimation is equal to the focal length of the first mirror group, and the distance between the first mirror group and the position for dispersion in the dispersion collimation module is equal to twice the focal length of the first mirror group. In this way, assuming that the focal length of the first mirror group is f, the distance from the input-output module to the switching module is 6f, and the wavelength selective switch is a typical "6f" architecture, making the implementation of the wavelength selective switch easy.

[0008] In an optional manner, the wavelength selective switch further includes a second mirror group, the second mirror group is located between the first mirror group and the dispersion collimation module, the distance between the dispersion collimation module and the second mirror group is equal to the focal length of the second mirror group, the second mirror group is used to collimate the second optical signal in the dispersion plane, reflect or transmit the second optical signal to the dispersion collimation module, and the second mirror group is also used to focus multiple sub-optical signals to the switching module in the dispersion plane. In this way, the optical signal is also focused when it reaches the switching module in the dispersion plane.

[0009] In an optional manner, the dispersion collimation module includes a first sub-mirror group and a dispersion unit, the first sub-mirror group is used to collimate the second light signal at the switching plane, and the dispersion unit is used to disperse the second light signal into multiple sub-light signals at the dispersion plane, or the dispersion collimation module is a diffractive optical element phase plate, and the phase step of the diffractive optical element phase plate is determined by the focal length required to be set when the dispersion collimation module performs collimation. In this way, the dispersion collimation module has multiple implementations.

[0010] In an optional manner, when the switching module is sensitive to polarization, the input-output module includes a port unit and a polarization unit, the port unit is used to receive a first optical signal, the polarization unit is used to perform polarization splitting on the first optical signal to obtain a second optical signal, the second optical signal includes two optical signals with the same polarization state, and the polarization state is the same as the polarization state supported by the switching module, so that the loss of the optical signal is relatively small when passing through the switching module, the polarization unit is also used to perform polarization combining on sub-optical signals with the same wavelength received from the switching module to obtain multiple third optical signals, and the port unit is also used to output multiple third optical signals.

[0011] In an optional manner, the switching module is further used to adjust the beam waist positions of the multiple sub-optical signals in the switching plane so that the sub-optical signals with the same wavelength among the multiple sub-optical signals meet the coupling condition when coupling from the switching module back to the port unit; or, the wavelength selective switch further includes a first compensation module, the first compensation module is located between the first mirror group and the switching module, and the first compensation module is used to adjust the beam waist positions of the multiple sub-optical signals in the switching plane so that the sub-optical signals with the same wavelength among the multiple sub-optical signals meet the coupling condition when coupling from the switching module back to the port unit. In this way, since the optical paths of the two sub-optical signals corresponding to the two polarization states are inconsistent, the two sub-optical signals cannot be fully coupled to the output optical fiber when output at the input and output ports. By setting the compensation module to adjust the beam waist positions of the multiple sub-optical signals in the switching plane, the sub-optical signals can meet the coupling condition as much as possible.

[0012] In an optional manner, the wavelength selective switch further includes a second compensation module, the second compensation module is located between the input and output modules and the first mirror group, and the second compensation module is used to perform optical path compensation in the dispersion plane, so that the sub-optical signals with the same wavelength among the multiple sub-optical signals intersect at one point on the switching module. In this way, since the sub-optical signals with the same wavelength intersect at one point on the switching module, the coupling loss is relatively small when the sub-optical signals are output from the port, thereby reducing the insertion loss and polarization-dependent loss.

[0013] In an optional manner, the second compensation module includes N compensation units, the N compensation units have the same thickness in the light transmission direction, and the refractive index corresponds one-to-one with the ports of the port unit; or, the N compensation units have the same refractive index, and the thickness in the light transmission direction corresponds one-to-one with the ports of the port unit.

[0014] In an optional manner, the second compensation module is also used to control the multiple sub-light signals to move along the wavelength direction at the position of the switching module to correct the frequency deviation between the inner and outer ports caused by the conical diffraction on the dispersion collimation module. In this way, the second compensation module can also compensate for the frequency deviation.

[0015] In an optional manner, the wavelength selective switch further includes a third compensation module, the third compensation module is located between the input and output module and the first mirror group, and the third compensation module is used to control the multiple sub-light signals to move along the wavelength direction at the position of the switching module to correct the frequency deviation between the inner and outer ports caused by the conical diffraction on the dispersion collimation module. In this way, since the compensation module is introduced to control the sub-light signals to move along the wavelength direction at the position of the switching module, the frequency deviation between the inner and outer ports caused by the conical diffraction on the dispersion collimation module can be corrected.

[0016] In an optional manner, the third compensation module includes N parallel plates, and the inclination angles of the N parallel plates in the light transmission direction correspond one-to-one to the ports of the port unit.

[0017] In a second aspect, the present disclosure provides a wavelength selective switch, which includes an input-output module, a first mirror group, a dispersion collimation module, a third mirror group and a switching module, wherein the input-output module is used to receive a first optical signal and output a second optical signal, wherein the second optical signal is obtained based on the first optical signal, the first mirror group is used to focus the second optical signal on a switching plane, the dispersion collimation module is used to collimate the second optical signal on a switching plane, and disperse the second optical signal into multiple sub-optical signals on a dispersion plane, wherein the sub-optical signals are single-wavelength optical signals, the third mirror group is used to focus the multiple sub-optical signals on a switching plane to the switching module, and the switching module is used to select different ports in the input-output module for output of different sub-optical signals.

[0018] In the solution disclosed in the present invention, in the switching plane, after the optical signal is input from the input-output module, it is sequentially focused, collimated and focused to reach the switching module, rather than reaching the switching module after only one focusing. This makes it possible to effectively compress the optical path height without changing the total optical path length, the deflection angle of the switching module and the spot size of the optical signal on the switching module, thereby compressing the device height of the wavelength selective switch.

[0019] In an optional manner, the distance between the input-output module and the first mirror group is equal to the focal length of the first mirror group, the distance between the first mirror group and the position where the dispersion collimation module performs collimation is equal to twice the focal length of the first mirror group, the focal length of the dispersion collimation module performs collimation is equal to the focal length of the first mirror group, the distance between the position where the dispersion collimation module performs collimation and the third mirror group is twice the focal length of the first mirror group, and the focal length of the third mirror group is equal to the focal length of the first mirror group. In this way, assuming that the focal length of the first mirror group is f, the distance from the input-output module to the switching module is 6f, and the wavelength selective switch is a typical "6f" architecture, making the wavelength selective switch easy to implement.

[0020] In an optional manner, the wavelength selective switch further comprises a second mirror group and a fourth mirror group, wherein the second mirror group is located between the first mirror group and the dispersion collimation module, and the fourth mirror group is located between the dispersion collimation module and the third mirror group, and the second mirror group is used to collimate the second optical signal in the dispersion plane, and the fourth mirror group is used to focus the plurality of sub-optical signals to the switching module in the dispersion plane. In this way, the optical signal is also focused when it reaches the switching module in the dispersion plane.

[0021] In an optional manner, the dispersion collimation module includes a first sub-mirror group and a dispersion unit, the first sub-mirror group is used to collimate the second light signal at the switching plane, and the dispersion unit is used to disperse the second light signal into multiple sub-light signals at the dispersion plane, or the dispersion collimation module is a diffractive optical element phase plate, and the phase step of the diffractive optical element phase plate is determined by the focal length required to be set when the dispersion collimation module performs collimation. In this way, the dispersion collimation module has multiple implementations.

[0022] In an optional manner, when the switching module is sensitive to polarization, the input-output module includes a port unit and a polarization unit, the port unit is used to receive a first optical signal, the polarization unit is used to perform polarization splitting on the first optical signal to obtain a second optical signal, the second optical signal includes two optical signals with the same polarization state, and the polarization state is the same as the polarization state supported by the switching module, so that the loss of the optical signal is relatively small when passing through the switching module, the polarization unit is also used to perform polarization combining on sub-optical signals with the same wavelength received from the switching module to obtain multiple third optical signals, and the port unit is also used to output multiple third optical signals.

[0023] In an optional manner, the switching module is further used to adjust the beam waist positions of the multiple sub-optical signals in the switching plane, so that the sub-optical signals with the same wavelength among the multiple sub-optical signals meet the coupling condition when coupling from the switching module back to the port unit, or the wavelength selective switch further includes a first compensation module, the first compensation module is located between the third mirror group and the switching module, and the first compensation module is used to adjust the beam waist positions of the multiple sub-optical signals in the switching plane, so that the sub-optical signals with the same wavelength among the multiple sub-optical signals meet the coupling condition when coupling from the switching module back to the port unit. In this way, since the optical paths of the two sub-optical signals corresponding to the two polarization states are inconsistent, the two sub-optical signals cannot be fully coupled to the output optical fiber when output at the input and output ports, and the compensation module is set to adjust the beam waist positions of the multiple sub-optical signals in the switching plane, so that the sub-optical signals meet the coupling condition as much as possible.

[0024] In an optional manner, the wavelength selective switch further includes a second compensation module, the second compensation module is located between the input and output modules and the first mirror group, and the second compensation module is used to perform optical path compensation in the dispersion plane, so that the sub-optical signals with the same wavelength among the multiple sub-optical signals intersect at one point on the switching module. In this way, since the sub-optical signals with the same wavelength intersect at one point on the switching module, the coupling loss is relatively small when the sub-optical signals are output from the port, thereby reducing the insertion loss and polarization-dependent loss.

[0025] In an optional manner, the second compensation module is further used to control the position movement of the plurality of sub-optical signals along the wavelength direction at the position of the switching module to correct the frequency deviation between the inner and outer ports caused by conical diffraction on the dispersion collimation module.

[0026] In an optional manner, the wavelength selective switch further includes a third compensation module, the third compensation module is located between the input and output module and the first mirror group, and the third compensation module is used to control the multiple sub-light signals to move along the wavelength direction at the position of the switching module to correct the frequency deviation between the inner and outer ports caused by the conical diffraction on the dispersion collimation module. In this way, since the compensation module is introduced to control the sub-light signals to move along the wavelength direction at the position of the switching module, the frequency deviation between the inner and outer ports caused by the conical diffraction on the dispersion collimation module can be corrected.

[0027] In a third aspect, the present disclosure provides a reconfigurable optical add-drop multiplexer, wherein the reconfigurable optical add-drop multiplexer includes the wavelength selection switch in the first aspect and any optional manner of the first aspect, or the reconfigurable optical add-drop multiplexer includes the wavelength selection switch in the second aspect and any optional manner of the second aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a schematic diagram of a wavelength selective switch in a switching plane in the related art provided by the present disclosure;

[0029] Figure 2 is a schematic diagram of a wavelength selective switch in a switching plane in the related art provided by the present disclosure;

[0030] Figure 3 is a schematic diagram of ROADM networking provided by an exemplary embodiment of the present disclosure;

[0031] Figure 4 is a schematic diagram of an optical path of a wavelength selective switch provided by an exemplary embodiment of the present disclosure;

[0032] Figure 5 is a schematic diagram of an optical path of a wavelength selective switch in a dispersion plane provided by an exemplary embodiment of the present disclosure;

[0033] Figure 6 is a schematic diagram of an optical path of a wavelength selective switch provided by an exemplary embodiment of the present disclosure;

[0034] Figure 7 is a schematic structural diagram of a dispersion unit provided by an exemplary embodiment of the present disclosure;

[0035] Figure 8 is a schematic diagram of an optical path of a wavelength selective switch provided by an exemplary embodiment of the present disclosure;

[0036] Fig. 9 is a schematic diagram of an optical path of a wavelength selective switch provided by an exemplary embodiment of the present disclosure;

[0037] Fig.10 is a schematic diagram of an optical path of a wavelength selective switch provided by an exemplary embodiment of the present disclosure;

[0038] Fig.11 is a schematic diagram of an optical path of a wavelength selective switch provided by an exemplary embodiment of the present disclosure;

[0039] Fig.12 is a schematic diagram of an equivalent optical path in a switching plane provided by an exemplary embodiment of the present disclosure;

[0040] Fig.13is a schematic diagram of an inconsistency of optical paths within a switching plane provided by an exemplary embodiment of the present disclosure;

[0041] Fig.14 is a schematic diagram of the movement of the waist position provided by an exemplary embodiment of the present disclosure;

[0042] Fig.15 is a schematic diagram of the position of a first compensation module provided by an exemplary embodiment of the present disclosure;

[0043] Fig.16 is a structural schematic diagram of a first compensation module provided by an exemplary embodiment of the present disclosure;

[0044] Fig.17 is a schematic diagram of a small spot area in a dispersion plane provided by an exemplary embodiment of the present disclosure;

[0045] Fig.18 is a schematic diagram of the difference in intersection points of optical signals in two polarization states of inner and outer ports provided by an exemplary embodiment of the present disclosure;

[0046] Fig.19 is a schematic diagram of the difference in intersection points of optical signals in two polarization states of inner and outer ports provided by an exemplary embodiment of the present disclosure;

[0047] Fig. 20 is a schematic diagram of polarization-dependent loss of an edge port provided by an exemplary embodiment of the present disclosure;

[0048] Fig.21 is a schematic diagram of the position of a second compensation module provided by an exemplary embodiment of the present disclosure;

[0049] Fig. 22 is a structural schematic diagram of a second compensation module provided by an exemplary embodiment of the present disclosure;

[0050] Fig.23 is a structural schematic diagram of a second compensation module provided by an exemplary embodiment of the present disclosure;

[0051] Fig.24 is a structural schematic diagram of a second compensation module provided by an exemplary embodiment of the present disclosure;

[0052] Fig.25 is a schematic diagram of frequency deviation provided by an exemplary embodiment of the present disclosure;

[0053] Fig.26 is a schematic diagram of the position of a third compensation module provided by an exemplary embodiment of the present disclosure;

[0054] Fig. 27 is a displacement schematic diagram provided by an exemplary embodiment of the present disclosure;

[0055] Fig.28 is a structural schematic diagram of a third compensation module provided by an exemplary embodiment of the present disclosure;

[0056] Fig.29 is a structural schematic diagram of a second compensation module provided by an exemplary embodiment of the present disclosure.

[0057] Illustration

[0058] 1. Input and output module; 2. First mirror group; 3. Dispersion collimation module; 4. Switching module;

[0059] 5. Second lens group; 6. First compensation module; 7. Second compensation module; 8. Third compensation module;

[0060] 11. Port unit; 12. Polarization unit; 31. First sub-mirror group; 32. Dispersion unit;

[0061] 71. Compensation unit; 81. Parallel plate;

[0062] 01, third lens group; 02, fourth lens group. DETAILED DESCRIPTION

[0063] In order to make the objectives, technical solutions and advantages of the present disclosure more clear, the embodiments of the present disclosure will be further described in detail below with reference to the accompanying drawings.

[0064] Some terminology concepts involved in the embodiments of the present disclosure are explained below.

[0065] 1. Dispersion plane refers to the plane formed by the wavelength direction and the light transmission direction. The wavelength direction refers to the direction in which the sub-light signals are arranged when the dispersion device disperses the multi-wavelength light signal into sub-light signals of different wavelengths in space. The wavelength direction is also called the dispersion direction. The light transmission direction refers to the direction in which the light signal is transmitted to the dispersion device. The wavelength direction is defined as the Y direction, and the light transmission direction is defined as the Z direction. The wavelength direction and the light transmission direction are perpendicular to each other. The dispersion plane is the plane formed by the Y direction and the Z direction.

[0066] 2. Switching plane refers to the plane formed by the switching direction and the light transmission direction. The switching direction refers to the direction of port arrangement in the wavelength selective switch, also known as the port direction or switching direction. The switching direction is defined as the X direction, which is perpendicular to the wavelength direction and the light transmission direction. The light transmission direction is defined as the Z direction. The switching plane is the plane formed by the X direction and the Z direction.

[0067] 3. The "2f" / "4f" architecture of the wavelength selective switch refers to the total length of the optical path from the starting plane S0 to the switching plane of the switching module in the switching plane is "2f" and "4f" respectively. Among them, the starting plane S0 refers to the starting plane of the main optical path of the wavelength selective switch, the switching plane refers to the switching plane of the optical signal on the switching module, and f refers to the focal length of the lens system in the switching direction.

[0068] A scheme of the related art is described below.

[0069] Related technology 1, the wavelength selective switch includes an access optical path part and a main optical path part. The access optical path part includes a port and a first lens, the main optical path part includes a second lens and a third lens, a dispersion device and a switching module, the focal length of the second lens and the third lens is f, the distance between the second lens and the third lens is "2f", and the main optical path part forms a "4f" architecture in the switching plane. Figure 1 A schematic diagram of the optical path of the wavelength selective switch in the switching plane is provided. Figure 1 The dotted line in the figure represents a dispersion device. Since the dispersion device works on the dispersion plane, it is drawn as a dotted line. The same principle applies to the following text and will not be described one by one.

[0070] Related technology 2, the wavelength selective switch includes a port, a lens, a dispersion device and a switching module. The focal length of the lens is f, and the wavelength selective switch forms a "2f" architecture in the switching plane. Figure 2 A schematic diagram of the optical path of the wavelength selective switch in the switching plane is provided.

[0071] from Figure 1 and Figure 2 It can be seen that, assuming the total length of the optical path is 4f, the deflection angle θ on the switching module, the spot size is expressed as ω, and it can be obtained through similar triangle calculation that the port height of the "2f" architecture is twice the port height of the "4f" architecture, which is not conducive to port expansion. Although the "4f" architecture has advantages in optical height and is conducive to port expansion, the overall optical path of the wavelength selective switch is relatively long due to the increase in the access optical path part. Considering that the increase in the number of ports of the wavelength selective switch can achieve higher-dimensional scheduling capabilities and establish more cross-connections, the number of ports required for the current wavelength selective switch has increased, and it is necessary to provide a wavelength selective switch that can compress the port height as much as possible without increasing the total length of the overall optical path.

[0072] The application scenario of the wavelength selective switch is described below.

[0073] The wavelength selective switch is applied to ROADM, which is applied to various optical network systems, such as wavelength division multiplexing (WDM) system, optical transport network (OTN) or other optical network systems. The ROADM is a ROADM on the trunk line. Figure 3 , ROADM is used for mesh networking. When mesh networking is used, the high port number of wavelength selective switches means higher-dimensional scheduling capabilities and the ability to establish more cross-connections.

[0074] The wavelength selective switch in the disclosed embodiment is a 1×N wavelength selective switch (ie, 1 input port and N output ports). Since the optical path is reversible, the 1×N wavelength selective switch can also be used as an N×1 wavelength selective switch.

[0075] The following describes a wavelength selective switch provided by an embodiment of the present disclosure, and takes a 1×N wavelength selective switch as an example for description of the solution.

[0076] In the embodiments of the present disclosure, generally speaking, there are two architectures of the wavelength selective switch. The first architecture is: in the switching plane, the same mirror group is used for focusing twice, in the dispersion plane, the same mirror group is used for collimation and focusing, and the dispersion unit used for dispersion is a reflective type. The second architecture is: in the switching plane, two mirror groups are used for focusing twice, in the dispersion plane, two mirror groups are used for collimation and focusing, one of the two mirror groups is used for collimation, and the other mirror group is used for focusing, and the dispersion unit used for dispersion is a transmissive type. The two architectures of the wavelength selective switch are described below.

[0077] 1. The first architecture of wavelength selective switch.

[0078] Figure 4 A schematic diagram of the optical path of a wavelength selective switch is provided. Figure 4, the wavelength selective switch comprises an input-output module 1, a first mirror group 2, a dispersion collimation module 3, a switching module 4 and a second mirror group 5. Among them, the first mirror group 2 is located between the input-output module 1 and the second mirror group 5, the first mirror group 2 is also located between the switching module 4 and the second mirror group 5, the second mirror group 5 is located between the first mirror group 2 and the dispersion collimation module 3, the dispersion collimation module 3 is located at the focal plane of the second mirror group 5, and the switching module 4 is located at the focal plane of the first mirror group 2 and at the focal plane of the second mirror group 5. The first mirror group 2 has a focusing function in the switching plane, and is equivalent to a parallel plate in the dispersion plane, and does not play a lens role. For example, the first mirror group 2 is a cylindrical lens. The dispersion collimation module 3 has a dispersion function in the dispersion plane and a collimation function in the switching plane. The second mirror group 5 has a collimation function and a focusing function in the dispersion plane, and is equivalent to a parallel plate in the switching plane, and does not play a lens role. For example, the second mirror group 5 is a cylindrical lens.

[0079] One side of the port in the input / output module 1 is connected to an optical fiber for receiving a first optical signal. The input / output module 1 outputs a second optical signal, which is obtained based on the first optical signal. Both the first optical signal and the second optical signal are multi-wavelength optical signals. Figure 4 It is shown in FIG. 1 that the second optical signal includes optical signals of two wavelengths. The second optical signal is incident on the first mirror group 2, and the first mirror group 2 focuses the second optical signal on the switching plane. Assuming that the input and output module 1 inputs optical signals through multiple ports, the optical signals input from multiple ports will be focused to one point. The second optical signal is incident on the second mirror group 5, and the second mirror group 5 collimates the second optical signal in the dispersion plane, converting the second optical signal into parallel light. The collimated second optical signal is transmitted by the second mirror group 5 and output to the dispersion collimation module 3. The dispersion collimation module 3 collimates the second optical signal in the switching plane, converting the second optical signal into parallel light. The dispersion collimation module 3 disperses the second optical signal into multiple sub-optical signals in the dispersion plane, and each sub-optical signal is a single-wavelength optical signal. Multiple sub-optical signals are incident on the second mirror group 5, and the second mirror group 5 focuses the multiple sub-optical signals on the switching module 4 in the dispersion plane. After passing through the second mirror group 5, the multiple sub-optical signals are incident on the first mirror group 2, and the first mirror group 2 focuses the multiple sub-optical signals on the switching plane to the switching module 4. In the wavelength direction, multiple sub-optical signals are arranged in a row on the switching module 4. The switching module 4 controls the multiple sub-optical signals to reflect at different deflection angles in the switching plane, so that the multiple sub-optical signals pass through the first mirror group 2, the second mirror group 5 and the dispersion collimation module 3 twice and reach the input-output module 1. Different ports in the input-output module 1 output different sub-optical signals. In addition, the switching module 4 can adjust the attenuation of the sub-optical signals of different wavelengths so that the power of the optical signals of each wavelength is balanced.

[0080] exist Figure 4In the wavelength selective switch shown, within the switching plane, the optical signal is sequentially focused, collimated and focused to reach the switching module 4, so that the device height of the wavelength selective switch is effectively compressed without changing the total length of the optical path, the deflection angle of the switching module 4 and the spot size of the optical signal on the switching module 4.

[0081] In an optional manner, in order to further fold the optical path and compress the size of the optical path, the second mirror group 5 is set to a concave reflector structure, that is, the light signal passing through the second mirror group 5 is reflected and output from the second mirror group 5. Figure 5 A schematic diagram of the optical path of the wavelength selective switch in the dispersion plane is provided. Figure 5 and Figure 4 The difference between the optical signal transmission is: Figure 4 The optical signal passing through the second mirror group 5 is transmitted and output from the second mirror group 5. Figure 5 The optical signal passing through the second mirror group 5 is reflected and output from the second mirror group 5 .

[0082] It should be noted that in Figure 5 Only one concave reflective surface is shown in the figure. In fact, the second lens group 5 can also be a multi-lens combination including one reflective surface to achieve aberration correction.

[0083] In an optional manner, the dispersion collimation module 3 is a diffractive optical element (DOE) phase plate, and the phase step of the diffractive optical element phase plate is determined by the focal length required to be set when the dispersion collimation module 3 performs collimation. For example, the dispersion function in the dispersion collimation module 3 is implemented by a grating, and the grating substrate is pre-processed into a diffractive optical element phase plate, and then the grating lines are engraved to achieve the required dispersion function. In the case where the dispersion collimation module 3 is a diffractive optical element phase plate, when the dispersion collimation module 3 collimates the second optical signal, the second optical signal is dispersed into multiple sub-optical signals at the same time.

[0084] Alternatively, see Figure 6 The optical path diagram of the wavelength selective switch is shown in FIG. Figure 4 The dispersion collimation module 3 in the embodiment specifically includes a first sub-mirror group 31 and a dispersion unit 32. The first sub-mirror group 31 is arranged at the position of the dispersion unit 32, or arranged on the optical path where the second optical signal is incident to the dispersion unit 32. The second optical signal is incident to the first sub-mirror group 31. After passing through the first sub-mirror group 31, the second optical signal is incident to the dispersion unit 32. The dispersion unit 32 disperses the second optical signal into a plurality of sub-optical signals on the dispersion plane. The dispersion unit 32 is a reflective grating. For example, see Figure 7, the dispersion unit 32 is a reflective prism composed of a prism and a reflective grating. Multiple sub-light signals are reflected by the dispersion unit 32 to the first sub-mirror group 31, and each sub-light signal passes through the first sub-mirror group 31 and becomes a parallel light beam at the switching plane to achieve collimation. In other words, collimation is achieved only after passing through the first sub-mirror group 31 twice.

[0085] In an optional manner, the switching module 4 is a micro-electro-mechanical system (MEMS) or liquid crystal on silicon (LCOS).

[0086] In an optional manner, when the switching module 4 is insensitive to the polarization state of the optical signal, the second optical signal is the first optical signal. When the switching module 4 is LCOS, LCOS is relatively sensitive to the polarization state of the optical signal. In order to reduce the loss of the optical signal on the switching module 4, the polarization state of the optical signal incident on the LCOS is the P polarization state, and the second optical signal is obtained by polarization splitting the first optical signal. Figure 8 As shown in the optical path schematic diagram of the wavelength selective switch, the input-output module 1 includes a port unit 11 and a polarization unit 12. The port unit 11 includes N ports, which are arranged in a line in the switching direction. The polarization unit 12 includes a polarization beam splitter unit and a 1 / 2 wave plate.

[0087] The port unit 11 receives a first optical signal from one of the ports, and the first optical signal is incident on the polarization unit 12. The polarization beam splitting subunit performs polarization beam splitting on the first optical signal to obtain two optical signals, and the polarization states of the two optical signals are P polarization state and S polarization state, respectively. The 1 / 2 wave plate converts the optical signal in S polarization state into an optical signal in P polarization state. In this way, the second optical signal output by the polarization unit 12 includes two optical signals, and both optical signals are in P polarization state. The two optical signals are incident on the first mirror group 2, and the first mirror group 2 focuses the two optical signals at the switching plane. The two optical signals are incident on the second mirror group 5, and the second mirror group 5 collimates the two optical signals at the dispersion plane to convert the two optical signals into parallel light. The collimated two optical signals are transmitted or reflected by the second mirror group 5 and output to the dispersion collimation module 3. The dispersion collimation module 3 collimates the two optical signals at the switching plane to convert the two optical signals into parallel light. The dispersion collimation module 3 disperses two optical signals in the dispersion plane to obtain multiple sub-optical signals, and there are two sub-optical signals of the same wavelength in the multiple sub-optical signals. When dispersing the two optical signals, the dispersion collimation module 3 reflects them at the same time, so that the multiple sub-optical signals are incident on the second mirror group 5, and the second mirror group 5 focuses and transmits the multiple sub-optical signals to the switching module 4 in the dispersion plane. After passing through the second mirror group 5, the multiple sub-optical signals are incident on the first mirror group 2, and the first mirror group 2 focuses the multiple sub-optical signals to the switching module 4 in the switching plane. In the wavelength direction, the multiple sub-optical signals are arranged in a row on the switching module 4, and the sub-optical signals with the same wavelength are located at the same position. The sub-optical signals with the same wavelength correspond to the two sub-optical signals of the P polarization state of the wavelength. In the switching plane, the switching module 4 applies voltage to the pixel point where the sub-light signal is located, changes the refractive index of the corresponding liquid crystal to change the phase, so that multiple sub-light signals are reflected at different deflection angles, so that multiple sub-light signals pass through the first mirror group 2, the second mirror group 5 and the dispersion collimation module 3 twice, and reach the input and output module 1. For the two sub-light signals of each wavelength, the 1 / 2 wave plate converts the polarization state of one of the sub-light signals into the S polarization state, and the polarization beam splitting subunit polarizes the sub-light beams of the two polarization states to obtain the third light signal of the wavelength. In this way, for each wavelength, a third light signal can be obtained. Multiple third light signals are output from different ports of the port unit 11.

[0088] Among them, in the polarization unit 12, the device for splitting the first optical signal into two optical signals is a polarization beam splitter prism or the like.

[0089] It should be noted that, in the case where the second optical signal includes two optical signals, assuming that the first optical signal includes an optical signal of a first wavelength, the two optical signals of the first wavelength are respectively recorded as A and B. When B returns from the LCOS to the input-output module 1, it follows the path of A from the input-output module 1 to the LCOS, but the height direction is different. When A returns from the LCOS to the input-output module 1, it follows the path of B from the input-output module 1 to the LCOS, but the height direction is different.

[0090] in addition, Figure 8 is Figure 4 Based on the description above, the case where the input / output module 1 includes the port unit 11 and the polarization unit 12 can also be applied Figure 5 and Figure 6 The wavelength selective switch shown.

[0091] Optionally, in the case where the second optical signal includes two optical signals, the first sub-mirror group 31 includes a mirror unit C and a mirror unit D, the mirror unit C and the mirror unit D correspond to the two optical signals respectively, the mirror unit C is used to collimate one of the optical signals in the P polarization state, and the mirror unit D is used to collimate the other optical signal in the P polarization state.

[0092] 2. The second architecture of wavelength selective switch.

[0093] Fig. 9 A schematic diagram of the optical path of a wavelength selective switch is provided. Fig. 9 The wavelength selective switch comprises an input-output module 1, a first mirror group 2, a dispersion collimation module 3, a third mirror group 01, a switching module 4, a second mirror group 5 and a fourth mirror group 02. The first mirror group 2 is located between the input-output module 1 and the second mirror group 5, the dispersion collimation module 3 is located between the second mirror group 5 and the fourth mirror group 02, the fourth mirror group 02 is located between the dispersion collimation module 3 and the third mirror group 01, and the third mirror group 01 is located between the fourth mirror group 02 and the switching module 4. The dispersion collimation module 3 is located at the focal plane of the second mirror group 5, the switching module 4 is located at the focal plane of the third mirror group 01, and is located at the focal plane of the fourth mirror group 02. The first mirror group 2 and the third mirror group 01 have a focusing function in the switching plane, and are equivalent to parallel plates in the dispersion plane, and do not act as lenses. The dispersion collimation module 3 has a dispersion function in the dispersion plane and a collimation function in the switching plane. The second mirror group 5 has a collimation function in the dispersion plane, and is equivalent to a parallel plate in the switching plane, and does not act as a lens. The fourth lens group 02 has a focusing function in the dispersion plane and is equivalent to a parallel plate in the switching plane and does not function as a lens.

[0094] One side of the port in the input-output module 1 is connected to an optical fiber for receiving a first optical signal. The input-output module 1 outputs a second optical signal, which is obtained based on the first optical signal. The first optical signal and the second optical signal are multi-wavelength optical signals. The second optical signal is incident on the first mirror group 2, and the first mirror group 2 focuses the second optical signal on the switching plane. The second optical signal is incident on the second mirror group 5, and the second mirror group 5 collimates the second optical signal in the dispersion plane, converting the second optical signal into parallel light. The collimated second optical signal is transmitted by the second mirror group 5 and output to the dispersion collimation module 3. The dispersion collimation module 3 collimates the second optical signal in the switching plane, converting the second optical signal into parallel light. The dispersion collimation module 3 disperses the second optical signal in the dispersion plane to obtain multiple sub-optical signals, each of which is a single-wavelength optical signal. Multiple sub-optical signals are incident on the fourth mirror group 02, and the fourth mirror group 02 focuses and transmits multiple sub-optical signals to the switching module 4 in the dispersion plane. After passing through the fourth mirror group 02, the multiple sub-light signals are incident on the third mirror group 01, and the third mirror group 01 focuses the multiple sub-light signals on the switching plane to the switching module 4. In the wavelength direction, the multiple sub-light signals are arranged in a row on the switching module 4. The switching module 4 controls the multiple sub-light signals to be reflected at different deflection angles in the switching plane, so that the multiple sub-light signals pass through the third mirror group 01, the fourth mirror group 02, the dispersion collimation module 3, the second mirror group 5 and the first mirror group 2, and reach the input-output module 1. Different ports in the input-output module 1 output different sub-light signals. In addition, the switching module 4 can adjust the attenuation of the sub-light signals of different wavelengths, so that the power of the optical signals of each wavelength is balanced.

[0095] In an optional manner, the dispersion collimation module 3 is the diffractive optical element phase plate described above.

[0096] Alternatively, see Fig.10 The optical path schematic diagram of the wavelength selective switch shown in the figure, the dispersion collimation module 3 includes a first sub-mirror group 31 and a dispersion unit 32, and the first sub-mirror group 31 is arranged at the position of the dispersion unit 32, or is arranged on the optical path where the second optical signal is incident to the dispersion unit 32. The second optical signal is incident on the first sub-mirror group 31, and the first sub-mirror group 31 collimates the second optical signal in the switching plane to convert the second optical signal into parallel light. After the second optical signal is collimated by the first sub-mirror group 31, it is incident on the dispersion unit 32, and the dispersion unit 32 disperses the second optical signal in the dispersion plane to obtain multiple sub-optical signals. The dispersion unit 32 is a transmission type grating.

[0097] In an optional manner, when the switching module 4 is insensitive to the polarization state of the optical signal, the second optical signal is the first optical signal. When the switching module 4 is an LCOS, the LCOS is relatively sensitive to the polarization state of the optical signal. In order to reduce the loss of the optical signal on the switching module 4, the polarization state of the optical signal incident on the LCOS is a P polarization state. The input-output module 1 includes a port unit 11 and a polarization unit 12. The port unit 11 includes N ports, and the N ports are arranged in a row in the switching direction. The polarization unit 12 includes a polarization beam splitter unit and a 1 / 2 wave plate, see Fig.11 Schematic diagram of the optical path of the wavelength selective switch shown.

[0098] The port unit 11 receives a first optical signal from one of the ports, and the first optical signal is incident on the polarization unit 12. The polarization beam splitting subunit performs polarization beam splitting on the first optical signal to obtain two optical signals, and the polarization states of the two optical signals are P polarization state and S polarization state, respectively. The 1 / 2 wave plate converts the optical signal in S polarization state into an optical signal in P polarization state. In this way, the second optical signal output by the polarization unit 12 includes two optical signals, and both optical signals are in P polarization state. The two optical signals are incident on the first mirror group 2, and the first mirror group 2 focuses the two optical signals at the switching plane. The two optical signals are incident on the second mirror group 5, and the second mirror group 5 collimates the two optical signals at the dispersion plane to convert the two optical signals into parallel light. The collimated two optical signals are transmitted by the second mirror group 5 and output to the dispersion collimation module 3. The dispersion collimation module 3 collimates the two optical signals at the switching plane to convert the two optical signals into parallel light. The dispersion collimation module 3 disperses two optical signals in the dispersion plane to obtain multiple sub-optical signals, and there are two sub-optical signals of the same wavelength in the multiple sub-optical signals. When the dispersion collimation module 3 disperses the two optical signals, it transmits the multiple sub-optical signals at the same time, so that the multiple sub-optical signals are incident on the fourth mirror group 02, and the fourth mirror group 02 focuses and transmits the multiple sub-optical signals in the dispersion plane to the switching module 4. After passing through the fourth mirror group 02, the multiple sub-optical signals are incident on the third mirror group 01, and the third mirror group 01 focuses the multiple sub-optical signals on the switching plane to the switching module 4. In the wavelength direction, the multiple sub-optical signals are arranged in a row on the switching module 4, and the sub-optical signals with the same wavelength are located at the same position. In the switching plane, the switching module 4 applies voltage to the pixel point where the sub-light signal is located, changes the refractive index of the corresponding liquid crystal to change the phase, so that multiple sub-light signals are reflected at different deflection angles, so that multiple sub-light signals pass through the third mirror group 01, the fourth mirror group 02, the dispersion collimation module 3, the second mirror group 5 and the first mirror group 2, and reach the input and output module 1. For the two sub-light signals of each wavelength, the 1 / 2 wave plate converts the polarization state of one of the sub-light signals into the S polarization state, and the polarization beam splitting subunit polarizes the sub-light beams of the two polarization states to obtain the third light signal of the wavelength. In this way, for each wavelength, a third light signal can be obtained. Multiple third light signals are output from different ports of the port unit 11.

[0099] Among them, in the polarization unit 12, the device for splitting the first optical signal into two optical signals is a polarization beam splitter prism or the like.

[0100] It should be noted that LCOS Figure 8 The role played by Fig.11 The role played by it is the same as that played by the above, so I will not repeat it here.

[0101] Optionally, in the case where the second optical signal includes two optical signals, the first sub-mirror group 31 includes a mirror unit C and a mirror unit D, the mirror unit C and the mirror unit D correspond to the two optical signals respectively, the mirror unit C is used to collimate one of the optical signals in the P polarization state, and the mirror unit D is used to collimate the other optical signal in the P polarization state.

[0102] For the above two structures, in the first structure, the distance between the input-output module 1 and the first lens group 2 is equal to the focal length of the first lens group 2, that is, the input-output module 1 is located at the focal plane of the first lens group 2. The focal length of the dispersion collimation module 3 for collimation is equal to the focal length of the first lens group 2, and the distance between the first lens group 2 and the position of dispersion in the dispersion collimation module 3 is equal to twice the focal length of the first lens group 2. In this way, Figure 4 and Figure 5 In the wavelength selective switch shown, the total length of the optical path from the input-output module 1 to the switching module 4 in the switching plane is “6f”. The wavelength selective switch is a “6f” architecture, where f is the focal length of the first mirror group 2 .

[0103] In the second architecture, the distance between the input-output module 1 and the first lens group 2 is equal to the focal length of the first lens group 2, that is, the input-output module 1 is located on the focal plane of the first lens group 2. The distance between the first lens group 2 and the position where the dispersion collimation module 3 performs collimation is equal to twice the focal length of the first lens group 2. The focal length of the dispersion collimation module 3 for collimation is equal to the focal length of the first lens group 2. The distance between the position where the dispersion collimation module 3 performs collimation and the third lens group 01 is twice the focal length of the first lens group 2. The focal length of the third lens group 01 is equal to the focal length of the first lens group 2.

[0104] It should be noted that the focal length for collimation is the focal length of the element for collimation, and the position for collimation is the position where the element for collimation is located. For example, the dispersion collimation module 3 includes a first sub-mirror group 31 and a dispersion unit 32, the focal length for collimation is the focal length of the first sub-mirror group 31, and the position for collimation is the position where the first sub-mirror group 31 is located.

[0105] Fig.12 The equivalent optical path diagrams in the switching plane under the two architectures are provided. Fig.12, assuming that the focal length of the first lens group 2 is f, the total length of the optical path from the input-output module 1 to the switching module 4 is 6f, which can be called a "6f" architecture, the deflection angle of the switching module 4 is θ, the total length of the optical path is 6f, and the spot size is ω. Fig.12 and Figure 2 It can be seen that through similar triangle calculation, it can be obtained that, while maintaining the same total optical path length, deflection angle and light spot on the switching module 4 as the "2f" architecture, the optical height of the "6f" architecture is compressed to 1 / 3 of the "2f" architecture, and the optical height of the "4f" architecture is 1 / 2 of the optical height of the "2f" architecture. It can be seen that among the three optical architectures, the "6f" architecture has the most compact structure, the highest integration, and is most conducive to port expansion.

[0106] In an optional manner, in the above two architectures, the first lens group 2 , the second lens group 5 and the first sub-lens group 31 each include one lens or multiple lenses.

[0107] For the above two architectures, when the second optical signal includes two optical signals, there may be problems such as poor coupling effect, insertion loss, polarization-related loss and frequency deviation. The embodiments of the present disclosure also provide improvement methods, which are explained below.

[0108] 1. Improve the problem of poor coupling effect.

[0109] In the case where the second optical signal includes two optical signals, in the switching direction, after the second optical signal is reflected or transmitted by the dispersion unit 32, the Gaussian beam is transformed into a small light spot, which is sensitive to the optical path. At the position of the dispersion unit 32, the optical paths of the two optical signals are inconsistent, resulting in that they cannot be at the waist position at the same time when they are incident on the switching module 4 in the switching plane. In order to achieve complete coupling of the two optical signals at the port of the input and output module 1, it is necessary to make the waist of the sub-optical signals with the same wavelength in the switching plane mirrored on the switching plane as much as possible. The switching plane refers to the plane where the two optical signals are incident on the switching module 4. In addition, the optical path difference between each wavelength in the two optical signals is also different, resulting in the inability to make the optical signals of all wavelengths in the two optical signals mirrored on the switching plane of the switching module 4. For example, Fig.13 A schematic diagram of the inconsistency of the optical path length in the switching plane is provided, see Fig.13 , the two optical signals are represented as A and B. The second optical signal includes optical signals of three wavelengths. The optical signals of the three wavelengths are represented by white circles, black circles and shaded circles respectively. The wavelengths represented by white circles, black circles and shaded circles gradually increase. The optical path differences of the sub-optical signals of each wavelength are inconsistent. Fig.13The optical path difference between the two medium-wavelength long sub-optical signals is the largest, resulting in poor coupling of the long-wavelength optical signal, which causes large wavelength-related losses. When the long-wavelength optical signal returns from the switching plane to the port of the input / output module 1 for output, the light spot is diffused and the port isolation becomes poor. It should be noted that Fig.13 This is just an example, used to illustrate that the coupling effect may be different if the wavelength is different.

[0110] In order to improve the problem of poor port isolation and large wavelength-related loss, for optical signals with wavelengths with poor coupling effects, a lens with a switching direction is added at or near the switching plane to move the beam waist position in the switching plane so that the beam waist position meets the coupling conditions as much as possible. For example, Fig.14 A schematic diagram of the movement of the beam waist position is provided, with a beam waist radius of 1000um, a beam waist distance of 1000mm from the lens (misalignment will introduce 0.5dB insertion loss), and a lens focal length of 5100mm. The beam waist can be moved to the lens (ie, close to the exchange plane) through the lens.

[0111] In one example, the wavelength selective switch further includes a first compensation module 6, Fig.15 A schematic diagram of the position of the first compensation module 6 is provided. Fig.15 Only part of the optical path is shown, see Fig.15 In the first architecture of the wavelength selective switch, the first compensation module 6 is located between the first mirror group 2 and the switching module 4, and is close to the switching module 4. In the second architecture of the wavelength selective switch, the first compensation module 6 is located between the third mirror group 01 and the switching module 4, and is close to the switching module 4. The first compensation module 6 applies different lens effects to the sub-optical signals of different wavelengths according to the beam waist misalignment, and adjusts the beam waist positions of multiple sub-optical signals in the switching plane, so that when the sub-optical signals with the same wavelength are coupled from the switching module 4 back to the port unit 11, the coupling condition is met. The coupling condition is that the coupling effect meets certain requirements. When the coupling effect meets certain requirements, the beam waist positions of the sub-optical signals with the same wavelength in the switching plane are close to or completely mirrored on the switching plane. Fig.16 A schematic diagram of the structure of the first compensation module 6 is provided, and different wavelengths correspond to different lens effects. Optionally, the first compensation module 6 is configured as a diffractive optical element phase plate, and the phase step is determined by the focal length distribution required to be set.

[0112] In another example, the switching module 4 loads a phase diagram and adjusts the beam waist positions of multiple sub-optical signals in the switching plane, so that when the sub-optical signals with the same wavelength are coupled from the switching module 4 back to the port unit 11, the coupling condition is met. The coupling condition is that the coupling effect meets certain requirements. When the coupling effect meets certain requirements, the beam waist of the sub-optical signals with the same wavelength in the switching plane is close to a mirror image or completely a mirror image on the switching plane. Compared with the first compensation module 6, the switching module 4 adjusts the beam waist position by loading a phase diagram, can be adjusted dynamically, and has a better effect.

[0113] It should be noted that when the beam waist of the sub-light signal with the same wavelength in the switching plane is mirrored on the switching plane, the coupling effect at the port is the best. However, in practice, due to errors and other reasons, it may not be completely mirrored. As long as the optical path difference of the two polarization states of the light beam is not too large, or the performance degradation is within an acceptable range, it will be fine. In addition, the "coupling" here refers to the coupling of the sub-light signal to the port and the output from the optical fiber connected to the port.

[0114] Thus, in the switching plane, the beam waist position is adjusted by the first compensation module 6 or the switching module 4, so that the sub-optical signals with the same wavelength can be well coupled at the ports of the input and output module 1, thereby improving port isolation.

[0115] 2. Improve insertion loss and polarization-related loss.

[0116] As the number of ports of a wavelength selective switch increases significantly, the insertion loss (IL) and polarization dependent loss (PDL) will deteriorate significantly as the ports expand outward. Insertion loss refers to the loss of optical power in the optical path due to the intervention of the wavelength selective switch. Polarization dependent loss is used to measure the polarization sensitivity of the wavelength selective switch. It is defined as the ratio of the maximum power to the minimum power of optical signals of different polarization states after passing through the wavelength selective switch, expressed in logarithmic form. Figure 8 Take the wavelength selective switch shown as an example, Fig.17 A schematic diagram of a small spot area of ​​a dispersion plane is provided. In the small spot area, the waist radius of the Gaussian beam is only a dozen microns. The optical path of the optical signal input from the central port of the input-output module 1 to the second mirror group 5 is represented as Ic1+Ic2, and the optical path output from the second mirror group 5 to the switching module 4 is represented as Oc1+Oc2. The optical path of the optical signal input from the edge port of the input-output module 1 to the second mirror group 5 is represented as Im1+Im2, and the optical path output from the second mirror group 5 to the switching module 4 is represented as Om1+Om2. The optical path corresponding to the edge port is longer than the optical path corresponding to the central port. Fig.17The bold line in represents the optical path. When the two sub-optical signals A and B intersect at one point in the switching module 4 in the dispersion direction corresponding to the center port, the sub-optical signals of the two polarization states of the edge port cannot intersect at one point in the switching module 4. A and B represent sub-optical signals of two polarization states with the same wavelength. In this way, the sub-optical signal looped back from the center port in the optical signal input from the center port can achieve optimal coupling. However, when the optical signal input from the center port is switched to the edge port output, since the sub-optical signals of the two polarization states of the edge port cannot intersect at one point in the switching module 4, when returning to the edge port output, they cannot all be output through the edge port, and there will be coupling loss, that is, the insertion loss of the edge port will deteriorate. Fig.18 A schematic diagram of the intersection point difference of the optical signals in the two polarization states of the inner and outer ports is provided. Fig.18 The dashed lines correspond to the center ports, and the solid lines correspond to the edge ports.

[0117] In addition, after the optical signals of the two polarization states are split from the dispersion unit 32, the main light rays of the sub-optical signals of each wavelength have different reverse intersection points, resulting in asymmetry of the two sub-optical signals of each wavelength incident on the switching module 4. Fig.19 In (a), the central port inputs an optical signal. When the sub-optical signals are transmitted to the switching module 4, the intersection of the two sub-optical signals with the same wavelength is close to the switching module 4, or is located at the switching module 4. In this way, when the sub-optical signals are output from the central port, since the ports are completely overlapped, the two sub-optical signals with the same wavelength are completely symmetrical when exchanged, and the coupling is consistent, and there is no problem of polarization-related loss. See Fig.19 In (b), when the optical signal is input from the edge port and the sub-optical signal is transmitted to the switching module 4, the intersection of the two sub-optical signals with the same wavelength is far away from the switching module 4. In this way, when the sub-optical signal is output from the central port, since the ports do not overlap, the sub-optical signals with the same wavelength are asymmetric when exchanged, which may cause the problem of polarization-related loss.

[0118] Fig. 20 A schematic diagram of the polarization-dependent loss at a non-central port is provided, see Fig. 20 , assuming that the two polarization states include A1 polarization state and B1 polarization state, when the first optical signal is input from the center port and the sub-optical signal is output from the edge port, the offset of the first sub-optical signal at the center port and the second sub-optical signal at the non-center port (i.e., the outer port) on the switching module 4 is shown. The first sub-optical signal and the second sub-optical signal are both in the A1 polarization state, but the second sub-optical signal is obtained by converting the optical signal in the B1 polarization state through a 1 / 2 wave plate. Fig. 20: The figure shows the offset of two polarization state sub-optical signals of three wavelengths. The two polarization state sub-optical signals of the first wavelength are offset by heights a1 and b1, respectively. The two polarization state sub-optical signals of the second wavelength are offset by heights a2 and b2, respectively. The two polarization state sub-optical signals of the third wavelength are offset by heights a3 and b3, respectively. The second wavelength is the center wavelength, and a2 is equal to b2. However, for other wavelengths, a1 is not equal to b1, and a3 is not equal to b3, and wavelength-related polarization-related loss will occur. Moreover, as the port continues to move toward the edge port, the difference between a1 and b1 is larger, the difference between a3 and b3 is larger, and the polarization-related loss is larger, that is, port-related polarization-related loss occurs.

[0119] In order to reduce the insertion loss and polarization-dependent loss, the wavelength selective switch further comprises a second compensation module 7. The second compensation module 7, Fig.21 A schematic diagram of the position of the second compensation module 7 is provided. Fig.21 A portion of the optical path is shown. Fig.21 The second compensation module 7 is located between the input-output module 1 and the first mirror group 2. The input-output module 1 outputs the second optical signal, and the second optical signal is incident on the second compensation module 7. The second compensation module 7 performs optical path compensation on the second optical signal in the dispersion plane, so that the sub-optical signals with the same wavelength obtained by the dispersion of the second optical signal intersect at one point on the switching module 4, so that the insertion loss and polarization-related loss can be reduced.

[0120] In one implementation of the second compensation module 7, considering that the wavelengths of the sub-optical signals transmitted by different ports are different, in order to perform compensation for different ports respectively, the second compensation module 7 includes N compensation units 71, and the N compensation units 71 correspond one-to-one to the ports of the port unit 11. There are multiple implementations of the N compensation units 71, and two feasible implementations are provided below.

[0121] Method 1: Fig. 22 A schematic diagram of the structure of N compensation units 71 is provided. Fig. 22 , the N compensation units 71 have the same thickness in the light transmission direction, and the refractive indexes of the N compensation units 71 correspond one-to-one to the ports of the port unit 11. The optical path difference is equal to Δn*d, where n represents the refractive index, Δn represents the difference in refractive index, and d represents the thickness. Since the N compensation units 71 are set with different refractive indices, the optical path differences corresponding to the ports are different, so that different optical path compensation is achieved for each port. Fig. 22 In FIG. 7 , the arrows on each compensation unit 71 indicate the direction of the optical axis.

[0122] Optionally, the N compensation units 71 are implemented using crystal materials. The crystal optical axis is located in the XY plane, the crystal optical axis is perpendicular to the incident light, the directions of the optical axes of the N compensation units 71 are inconsistent, the refractive index is the refractive index of o light when the optical axis is parallel to the polarization direction of the incident light, the refractive index is the refractive index of e light when the optical axis is perpendicular to the polarization direction of the incident light, and the refractive index ranges from the refractive index of o light to the refractive index of e light when the optical axis is between parallel and perpendicular to the polarization direction of the incident light. The N compensation units 71 use liquid crystal sheets, and by controlling the friction orientation process, the distribution of the optical axes of the liquid crystal sheets is controlled, thereby controlling the refractive index of the N compensation units 71.

[0123] Method 2: Fig.23 Another schematic diagram of the structure of N compensation units 71 is provided. Fig.23 , the refractive index of the N compensation units 71 is the same, and the thickness of the N compensation units 71 in the light transmission direction corresponds to the port of the port unit 11 one by one. The optical path difference is equal to n*Δd, where n represents the refractive index and Δd represents the thickness difference. Since the N compensation units 71 are set with different thicknesses, the optical path differences corresponding to each port are different, so that each port realizes different optical path compensation.

[0124] In the second approach, the N compensation units 71 are implemented using crystal materials or other materials.

[0125] In another implementation of the second compensation module 7, the second compensation module 7 is not physically divided into N compensation units 71, but is logically divided into N compensation unit layers, that is, the second compensation module 7 is a whole, but logically the N compensation unit layers correspond to the ports of the port unit 11 one by one, see Fig.24 In the second compensation module 7 shown, the dotted line indicates that the second compensation module 7 is logically divided into N compensation unit layers. The N compensation unit layers have the same thickness in the light transmission direction, and the refractive index corresponds to the port of the port unit one by one, or the N compensation unit layers have the same refractive index, and the thickness corresponds to the port of the port unit one by one in the light transmission direction. Fig.24 In the figure, the arrows on each compensation unit layer indicate the direction of the optical axis.

[0126] It should be noted that in Figure 22 to Figure 24 , 5 ports are shown, 0 represents the center port, 1 and 2 represent two ports above the center port, and -1 and -2 represent two ports below the center port.

[0127] Optionally, in the second compensation module 7, the optical axes of the N compensation units 71 are initially the same, electrodes are set for the N compensation units 71, and voltage is applied to the electrodes to accurately control the rotation of the optical axis of each compensation unit 71, thereby dynamically and accurately configuring the optical path difference of each compensation unit 71, and then adjusting the optical path so that sub-optical signals with the same wavelength in multiple sub-optical signals intersect at one point on the switching module 4.

[0128] Optionally, when the first optical signal is input into the wavelength selective switch from the central port, the ports located at symmetrical positions of the central port have the same refractive index, because the optical paths to be compensated are the same.

[0129] 3. Improve the frequency deviation problem.

[0130] When the first optical signal is input from the edge port to the wavelength selective switch, the first optical signal is obliquely incident on the dispersion unit 32, which will produce conical diffraction. The change in the splitting angle will cause the edge port to have a frequency deviation relative to the center port, and the sub-optical signals with the same wavelength will have a position shift along the wavelength direction on the switching plane of the switching module 4. This phenomenon is called frequency deviation, and as the number of ports of the wavelength selective switch increases significantly, the frequency deviation will significantly deteriorate as the ports expand outward. Fig.25 A schematic diagram of frequency deviation is provided. Fig.25 In the figure, the solid line represents before frequency deviation, and the dotted line represents after frequency deviation.

[0131] Frequency deviation is a position shift in the wavelength direction. If a wavelength shift is introduced before the second optical signal is incident on the second mirror group 5, the shift can be transmitted to the switching plane of the switching module 4 to compensate for the position shift at the switching plane, thereby improving the frequency deviation problem. Exemplarily, in order to improve the frequency deviation problem, in an optional manner, the wavelength selective switch further includes a third compensation module 8, Fig.26 A schematic diagram of the position of the third compensation module 8 is provided. Fig.26 The third compensation module 8 is located between the input-output module 1 and the first mirror group 2. The input-output module 1 outputs the second optical signal, and the second optical signal is incident on the third compensation module 8. The third compensation module 8 controls the multiple sub-optical signals to move along the wavelength direction at the position of the switching module 4 to correct the frequency deviation between the inner and outer ports caused by the conical diffraction on the dispersion collimation module 3.

[0132] Optionally, a parallel plate 81 with a certain angle is used to introduce a wavelength direction offset. Different angles of the parallel plate 81 introduce different wavelength direction offsets. Fig. 27 A schematic diagram of the offset in wavelength direction introduced by the parallel plate 81 is provided. Fig. 27After a beam of light signals passes through the parallel plate 81, the path of the light signal is a solid line, which is offset from that before passing through the parallel plate 81. The dotted line and the solid line represent the displacement introduced by the incident light before the second mirror group 5, which can be transmitted to the switching plane of the switching module 4. Based on this, the third compensation module 8 includes N parallel plates 81, and the inclination angles of the N parallel plates 81 in the light transmission direction correspond to the ports one by one, so that the sub-light signals corresponding to each port have different displacements in the wavelength direction, which can correct the frequency deviation at the switching plane. Fig.28 A schematic structural diagram of N parallel plates 81 is provided.

[0133] The sizes of the N parallel plates 81 are all the same or partially the same.

[0134] It should be noted that, when the second compensation module 7 and the third compensation module 8 exist at the same time, there is no order in the positions of the second compensation module 7 and the third compensation module 8 .

[0135] In an optional manner, the second compensation module 7 can also improve insertion loss, polarization-dependent loss and frequency deviation at the same time. For example, the second compensation module 7 includes N compensation units 71, and the N compensation units 71 are all parallel plates 81. The N parallel plates 81 have the same refractive index, different angles, and different thicknesses in the light transmission direction. The same refractive index and different thicknesses in the light transmission direction can improve insertion loss and polarization-dependent loss, and different angles can improve frequency deviation. In this way, the number of modules can be reduced. Fig.29 A schematic structural diagram of N parallel plates 81 is provided.

[0136] It should be noted that in Fig.28 and Fig.29 , 5 ports are shown, 0 represents the center port, 1 and 2 represent two ports above the center port, and -1 and -2 represent two ports below the center port.

[0137] In an optional manner, the first optical signal is input from the central port of the input / output module 1, and the multiple sub-optical signals are output from any port, or the first optical signal is input from the edge port, and the multiple sub-optical signals are output from any port. Of course, the first optical signal can also be input from other ports, and the multiple sub-optical signals can be output from any port.

[0138] It should be noted that, in the embodiments of the present disclosure, in all optical path schematic diagrams of the wavelength selective switch, only the optical path from the input / output module 1 to the switching module 4 is shown, and the optical path from the switching module 4 to the input / output module 1 is not shown.

[0139] It should also be noted that, in the embodiments of the present disclosure, the inner port among the inner and outer ports refers to the port close to the central port or the central port, and the outer port refers to the port far from the central port.

[0140] The embodiment of the present disclosure further provides a ROADM, which includes the wavelength selective switch described above.

[0141] In the disclosed embodiments, the wavelength selective switch can be made into a wavelength selective switch board, or a wavelength selective switch device, etc.

[0142] In the present disclosure, the terms "first" and "second" are used to distinguish between the same or similar items with substantially the same effects and functions. It should be understood that there is no logical or temporal dependency between "first" and "second", nor is the quantity and execution order limited. It should also be understood that although the following description uses the terms first and second, etc. to describe various elements, these elements should not be limited by the terms. These terms are only used to distinguish one element from another. For example, without departing from the scope of various examples, the first mirror group can be referred to as the second mirror group, and similarly, the second mirror group can be referred to as the first mirror group. Both the first mirror group and the second mirror group can be mirror groups, and in some cases, can be separate and different mirror groups.

[0143] The term "plurality" in the present disclosure means two or more.

[0144] The above description is only an exemplary embodiment of the present disclosure, but the protection scope of the present disclosure is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed in the present disclosure, and these modifications or replacements should be included in the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure should be based on the protection scope of the claims.

Claims

1. A wavelength selective switch, characterized in that: It comprises an input-output module (1), a first mirror group (2), a dispersion collimation module (3) and a switching module (4); The input-output module (1) is used to receive a first optical signal and output a second optical signal, wherein the second optical signal is obtained based on the first optical signal; The first mirror group (2) is used to focus the second light signal at the switching plane; The dispersion collimation module (3) is used to collimate the second optical signal at the switching plane, and disperse the second optical signal into a plurality of sub-optical signals at the dispersion plane, wherein the sub-optical signals are single-wavelength optical signals; The first mirror group (2) is further used to focus the multiple sub-light signals on the switching plane to the switching module (4); The switching module (4) is used to select different ports in the input and output module (1) for outputting different sub-optical signals.

2. The wavelength selective switch according to claim 1, characterized in that: The distance between the input-output module (1) and the first lens group (2) is equal to the focal length of the first lens group (2); The focal length of the dispersion collimation module (3) for collimation is equal to the focal length of the first lens group (2); The distance between the first mirror group (2) and the position where dispersion is performed in the dispersion collimation module (3) is equal to twice the focal length of the first mirror group (2).

3. The wavelength selective switch according to claim 1 or 2, characterized in that: The wavelength selective switch further comprises a second mirror group (5), wherein the second mirror group (5) is located between the first mirror group (2) and the dispersion collimation module (3), and the distance between the dispersion collimation module (3) and the second mirror group (5) is equal to the focal length of the second mirror group (5); The second mirror group (5) is used to collimate the second optical signal on the dispersion plane, and reflect or transmit the second optical signal to the dispersion collimation module (3); The second mirror group (5) is also used to focus the multiple sub-light signals on the dispersion plane to the switching module (4).

4. The wavelength selective switch according to any one of claims 1 to 3, characterized in that: The dispersion collimation module (3) comprises a first sub-mirror group (31) and a dispersion unit (32); The first sub-mirror group (31) is used for collimating the second optical signal at the switching plane; The dispersion unit (32) is used to disperse the second optical signal into a plurality of sub-optical signals in the dispersion plane; or The dispersion collimation module (3) is a diffractive optical element phase plate, and the phase steps of the diffractive optical element phase plate are determined by the focal length required to be set when the dispersion collimation module (3) performs collimation.

5. The wavelength selective switch according to any one of claims 1 to 4, characterized in that: The input-output module (1) comprises a port unit (11) and a polarization unit (12); The port unit (11) is used to receive a first optical signal; The polarization unit (12) is used to perform polarization splitting on the first optical signal to obtain a second optical signal, wherein the second optical signal includes two optical signals with the same polarization state; The polarization unit (12) is also used to perform polarization beam combining on the sub-optical signals with the same wavelength received from the switching module (4) to obtain a plurality of third optical signals; The port unit (11) is also used to output the multiple third optical signals.

6. The wavelength selective switch according to claim 5, characterized in that: The switching module (4) is further used to adjust the beam waist positions of the plurality of sub-optical signals in the switching plane so that the sub-optical signals with the same wavelength among the plurality of sub-optical signals meet the coupling condition when they are coupled back from the switching module (4) to the port unit (11); or The wavelength selective switch further comprises a first compensation module (6); The first compensation module (6) is located between the first lens group (2) and the switching module (4); The first compensation module (6) is used to adjust the beam waist positions of the multiple sub-optical signals in the switching plane so that the sub-optical signals with the same wavelength among the multiple sub-optical signals meet the coupling condition when they are coupled from the switching module (4) back to the port unit (11).

7. The wavelength selective switch according to claim 5 or 6, characterized in that: The wavelength selective switch further comprises a second compensation module (7); The second compensation module (7) is located between the input-output module (1) and the first lens group (2); The second compensation module (7) is used to perform optical path compensation on the dispersion plane so that sub-optical signals with the same wavelength among the multiple sub-optical signals intersect at one point on the switching module (4).

8. The wavelength selective switch according to claim 7, characterized in that: The second compensation module (7) comprises N compensation units (71); The N compensation units (71) have the same thickness in the light transmission direction, and their refractive indexes correspond one-to-one to the ports of the port unit (11); or, The N compensation units (71) have the same refractive index, and their thickness in the light transmission direction corresponds one-to-one to the ports of the port unit (11).

9. The wavelength selective switch according to claim 7, characterized in that: The second compensation module (7) is also used to control the multiple sub-light signals to move along the wavelength direction at the position of the switching module (4) to correct the frequency deviation between the inner and outer ports caused by conical diffraction on the dispersion collimation module (3).

10. The wavelength selective switch according to any one of claims 5 to 8, characterized in that: The wavelength selective switch further comprises a third compensation module (8); The third compensation module (8) is located between the input-output module (1) and the first lens group (2); The third compensation module (8) is used to control the multiple sub-light signals to move along the wavelength direction at the position of the switching module (4) to correct the frequency deviation between the inner and outer ports caused by conical diffraction on the dispersion collimation module (3).

11. The wavelength selective switch according to claim 10, characterized in that: The third compensation module (8) comprises N parallel flat plates (81), and the inclination angles of the N parallel flat plates (81) in the light transmission direction correspond one-to-one to the ports of the port unit (11).

12. A wavelength selective switch, characterized in that: It comprises an input-output module (1), a first mirror group (2), a dispersion collimation module (3), a third mirror group (01) and a switching module (4); The input-output module (1) is used to receive a first optical signal and output a second optical signal, wherein the second optical signal is obtained based on the first optical signal; The first mirror group (2) is used to focus the second light signal at the switching plane; The dispersion collimation module (3) is used to collimate the second optical signal at the switching plane, and disperse the second optical signal into a plurality of sub-optical signals at the dispersion plane, wherein the sub-optical signals are single-wavelength optical signals; The third mirror group (01) is used to focus the multiple sub-light signals onto the switching module at the switching plane; The switching module (4) is used to select different ports in the input and output module (1) for outputting different sub-optical signals.

13. The wavelength selective switch according to claim 12, characterized in that: The distance between the input-output module (1) and the first lens group (2) is equal to the focal length of the first lens group (2); The distance between the first lens group (2) and the position where the dispersion collimation module (3) performs collimation is equal to twice the focal length of the first lens group (2); The focal length of the dispersion collimation module (3) for collimation is equal to the focal length of the first lens group (2); The distance between the position where the dispersion collimation module (3) performs collimation and the third lens group (01) is twice the focal length of the first lens group (2); The focal length of the third lens group (01) is equal to the focal length of the first lens group (2).

14. The wavelength selective switch according to claim 12 or 13, characterized in that: The wavelength selective switch further comprises a second mirror group (5) and a fourth mirror group (02); The second mirror group (5) is located between the first mirror group (2) and the dispersion collimation module (3), and the fourth mirror group (02) is located between the dispersion collimation module (3) and the third mirror group (01); The second mirror group (5) is used to collimate the second optical signal in the dispersion plane; The fourth mirror group (02) is used to focus the multiple sub-light signals on the dispersion plane to the switching module (4).

15. The wavelength selective switch according to any one of claims 12 to 14, characterized in that: The dispersion collimation module (3) comprises a first sub-mirror group (31) and a dispersion unit (32); The first sub-mirror group (31) is used for collimating the second optical signal at the switching plane; The dispersion unit (32) is used to disperse the second optical signal into a plurality of sub-optical signals in the dispersion plane; or The dispersion collimation module (3) is a diffractive optical element phase plate, and the phase steps of the diffractive optical element phase plate are determined by the focal length required to be set when the dispersion collimation module (3) performs collimation.

16. The wavelength selective switch according to any one of claims 12 to 15, characterized in that: The input-output module (1) comprises a port unit (11) and a polarization unit (12); The port unit (11) is used to receive a first optical signal; The polarization unit (12) is used to perform polarization splitting on the first optical signal to obtain a second optical signal, wherein the second optical signal includes two optical signals with the same polarization state; The polarization unit (12) is also used to perform polarization beam combining on the sub-optical signals with the same wavelength received from the switching module (4) to obtain a plurality of third optical signals; The port unit (11) is also used to output the multiple third optical signals.

17. The wavelength selective switch according to claim 16, characterized in that: The switching module (4) is further used to adjust the beam waist positions of the plurality of sub-optical signals in the switching plane so that the sub-optical signals with the same wavelength among the plurality of sub-optical signals meet the coupling condition when they are coupled back from the switching module (4) to the port unit (11); or The wavelength selective switch further comprises a first compensation module (6); The first compensation module (6) is located between the third lens group (01) and the switching module (4); The first compensation module (6) is used to adjust the beam waist positions of the multiple sub-optical signals in the switching plane so that the sub-optical signals with the same wavelength among the multiple sub-optical signals meet the coupling condition when they are coupled from the switching module (4) back to the port unit (11).

18. The wavelength selective switch according to claim 16 or 17, characterized in that: The wavelength selective switch further comprises a second compensation module (7); The second compensation module (7) is located between the input-output module (1) and the first lens group (2); The second compensation module (7) is used to perform optical path compensation on the dispersion plane so that sub-optical signals with the same wavelength among the multiple sub-optical signals intersect at one point on the switching module (4).

19. The wavelength selective switch according to claim 18, characterized in that: The second compensation module (7) is also used to control the multiple sub-light signals to move along the wavelength direction at the position of the switching module (4) to correct the frequency deviation between the inner and outer ports caused by conical diffraction on the dispersion collimation module (3).

20. The wavelength selective switch according to any one of claims 16 to 18, characterized in that: The wavelength selective switch further comprises a third compensation module (8); The third compensation module (8) is located between the input-output module (1) and the first lens group (2); The third compensation module (8) is used to control the multiple sub-light signals to move along the wavelength direction at the position of the switching module (4) to correct the frequency deviation between the inner and outer ports caused by conical diffraction on the dispersion collimation module (3).

21. A reconfigurable optical add / drop multiplexer, characterized in that: The reconfigurable optical add / drop multiplexer comprises the wavelength selective switch according to any one of claims 1 to 11, or the wavelength selective switch according to any one of claims 12 to 20.

Images