A wavelength selective switch

Abstract

The application discloses a wavelength selective switch and belongs to the technical field of optical communication. In view of the problems of the prior art, such as the large space occupied by the switch lens, the large process development difficulty caused by the position and angle of the switch lens needing to be adjusted in combination with other optical elements, and the like, the application provides a wavelength selective switch, a second lens is connected to one side of a prism to form a self-focusing dispersion prism grating, the second lens is arranged in sequence along the incident direction of a polarized light beam, the diffraction grating is arranged on one side of the self-focusing lens to form a second lens, and the self-focusing lens and the diffraction grating are arranged in sequence along the incident direction of the polarized light beam. Thus, the self-focusing dispersion prism grating is used in the WSS optical system structure to separate the polarized light beam by wavelength, the switch lens is not needed, and the optical path adjustment in combination with other optical elements is not needed, so that the WSS optical system structure is simpler.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical communication technology, more particularly, to a wavelength selective switch. BACKGROUND

[0002] Reconfigurable optical add-drop multiplexer (ROADM) can realize optical signal switching, attenuation or blocking of any wavelength or wavelength combination in any communication port in optical communication network, and is the core optical switching device for flexible scheduling of optical communication network. Wavelength selective switch (WSS) is the core module for realizing the function of ROADM system, and is mainly divided into WSS based on liquid crystal on silicon (LCoS) technology, liquid crystal (LC) technology and micro-electro-mechanical system (MEMS) technology according to technical principle, wherein the WSS based on LCoS technology has the characteristics of flexible grid configuration, i.e. the communication center frequency and bandwidth can be flexibly set, and therefore gradually becomes the mainstream of market application.

[0003] The main principle of WSS based on LCoS technology is to use a dispersion grating to focus different wavelengths of light to different positions on the surface of LCoS by imaging method for spatial separation, so as to process each wavelength individually, and the LCoS surface is an elliptical light spot, the long axis direction is the switch direction, and the short axis direction is the wavelength arrangement direction. In order to realize switching of each wavelength in different ports of WSS, the LCoS forms a phase diffraction grating in the long axis direction (switch direction) of the light spot, and the energy is concentrated in one diffraction order and output to the corresponding WSS port. In the prior art, the switch lens distance of most WSS optical system structures is close to the wave plate and prism grating or optical path, the switch lens occupies a large space, and other structural parts need to be left with a certain safety margin of light aperture to reduce, which is not conducive to the miniaturization of WSS; in addition, the position and angle of the switch lens need to be adjusted in combination with other optical elements, including adjustment of position and angle, which also increases the difficulty and cost of process development.

[0004] According to retrieval, Chinese patent application, application number 201811330506.3, published on November 9, 2018, discloses a wavelength selective switch. The wavelength selective switch comprises: a fiber array, a concave grating, and a control chip; wherein the fiber array is used to input an optical signal to the concave grating; the concave grating is used to realize spot transformation of the optical signal, and then the optical signal after spot transformation is incident to the control chip; and the control chip is used to control the optical signal to perform optical signal operation. The scheme adopts a single concave grating to replace the shaping lens, the diffraction grating, and the converging lens in the prior art, thereby optimizing the problem of excessive number of optical elements of the existing wavelength selective switch. However, the scheme does not consider the occupied space, position, and angle of the switch lens in the actual application process, thereby not having strong practicality and wide applicability. SUMMARY

[0005] 1. Technical problem to be solved

[0006] In view of the problems in the prior art that the switch lens is close to the optical elements or the optical path of the wavelength selective switch (WSS) optical system structure, the switch lens occupies a large space, and the position and angle of the switch lens need to be adjusted in combination with other optical elements, the present application provides a wavelength selective switch. In the WSS optical system structure, a self-focusing dispersion prism grating is used to separate the wavelength of the light beam, without using a switch lens or combining other optical elements for optical path adjustment, so that the WSS optical system structure is simpler.

[0007] 2. Technical scheme

[0008] The object of the present application is achieved by the following technical scheme.

[0009] A wavelength selective switch comprises a polarized light beam, and the wavelength selective switch comprises a self-focusing dispersion prism grating. The self-focusing dispersion prism grating comprises a prism and a second lens. The second lens is connected to one side of the prism to form a self-focusing dispersion prism grating, and the prism and the second lens are arranged in sequence along the incident direction of the polarized light beam. The self-focusing dispersion prism grating is used to separate the wavelength of the polarized light beam.

[0010] Further, the second lens comprises a diffraction grating and a self-focusing lens. The diffraction grating is covered on one side of the self-focusing lens to form the second lens, and the self-focusing lens and the diffraction grating are arranged in sequence along the incident direction of the polarized light beam.

[0011] Further, the self-focusing lens is a graded refractive index lens.

[0012] Further, the refractive index of the self-focusing lens along the switch direction is:

[0013]

[0014] Wherein, x represents the distance from the center, n represents the refractive index, n(x) represents the refractive index of the corresponding position of the switch direction, and A represents the refractive index distribution constant.

[0015] Further, the focal length of the self-focusing lens is represented as:

[0016]

[0017] Wherein, f represents the focal length of the self-focusing lens, and L represents the thickness of the self-focusing lens.

[0018] Further, the polarization beam passes through the diffraction grating and is reflected again into the self-focusing lens to form a combined focal length, and the combined focal length of the self-focusing lens is represented as:

[0019]

[0020] Wherein, F represents the combined focal length of the self-focusing lens.

[0021] Further, the wavelength selective switch further comprises a reflective imaging mirror and a silicon-based liquid crystal device; the reflective imaging mirror reflects the polarization beam into the self-focusing dispersion prism grating, the self-focusing dispersion prism grating separates the polarization beam by wavelength, the self-focusing dispersion prism grating reflects the polarization beam separated by wavelength to the reflective imaging mirror, and the reflective imaging mirror reflects the polarization beam separated by wavelength into the silicon-based liquid crystal device to form a circular light spot.

[0022] 3. Advantages

[0023] Compared with the prior art, the advantages of the present application are:

[0024] The wavelength selective switch provided by the present application uses a self-focusing dispersion prism grating to separate the light beam by wavelength in the WSS optical system structure, without the need for using a switch lens, thereby avoiding the problem of spatial interference between the switch lens and other optical elements or light paths, effectively simplifying the WSS optical system structure; at the same time, using the self-focusing dispersion prism grating does not require combining other optical elements for light path adjustment, simplifying the process development difficulty and greatly reducing the development cost. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 is a schematic diagram of the overall structure of the present application;

[0026] Figure 2 is a schematic diagram of the self-focusing dispersion prism grating structure of the embodiment;

[0027] Figure 3 is a schematic diagram of the diffraction grating structure of the embodiment;

[0028] Figure 4 This is a schematic diagram of a diffraction grating covering a self-focusing lens structure, as shown in the embodiment.

[0029] Figure 5 This is a diagram illustrating the trajectory of the light beam in the switching direction of the self-focusing lens, as shown in the example.

[0030] Figure 6 This is a diagram showing the trajectory of the light beam in the dispersion direction of the self-focusing lens, as shown in the example.

[0031] The following are the labels in the diagram: 1. Optical fiber; 2. First lens; 3. Polarization separation component; 4. Birefringent crystal; 5. Waveplate; 6. Reflecting imaging mirror; 7. Self-focusing dispersive prism grating; 71. Prism; 72. Second lens; 721. Diffraction grating; 722. Self-focusing lens; 8. Silicon-based liquid crystal device; 9. Polarized beam. Detailed Implementation

[0032] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0033] Example

[0034] In traditional WSS optical system structures, wavelength separation of the beam is achieved through the combined action of a dispersive prism and a switching lens. The switching lens is located relatively close to the dispersive prism and other optical components or the optical path. However, in practical applications, a certain safety margin in the aperture must be maintained between each optical component. The close proximity of the switching lens to the dispersive prism and other optical components or the optical path results in a large space occupation for the switching lens. As the overall size requirements of WSS optical system structures become increasingly smaller, this problem becomes more prominent, hindering the miniaturization of WSS optical system structures. Furthermore, in existing WSS optical system structures, the position and angle of the switching lens need to be adjusted in conjunction with other optical components to achieve optical path adjustment, which also increases the development difficulty and cost of WSS optical system structure fabrication.

[0035] like Figures 1-6 The image shows a wavelength selective switch provided in this embodiment. The wavelength selective switch includes a polarized beam 9 and a self-focusing dispersive prism grating 7. The self-focusing dispersive prism grating 7 includes a prism 71 and a second lens 72. The second lens 72 is connected to one side of the prism 71 to form the self-focusing dispersive prism grating 7. The prism 71 and the second lens 72 are arranged sequentially along the incident direction of the polarized beam 9. The self-focusing dispersive prism grating 7 is used to achieve wavelength separation of the polarized beam 9.

[0036] Specifically, in this embodiment, such as Figure 2As shown in the figure, the self-focusing dispersion prism grating 7 comprises a prism 71 and a second lens 72, and the second lens 72 is connected to one side of the prism 71 to form the self-focusing dispersion prism grating 7. In this embodiment, the second lens 72 can be connected to one side of the prism 71 by adhesion or other similar means, and the prism 71 and the second lens 72 are sequentially arranged along the incident direction of the polarized light beam 9. Further, as shown in the figure, Figure 4 As shown in the figure, the second lens 72 comprises a diffraction grating 721 and a self-focusing lens 722, and the diffraction grating 721 is covered on one side of the self-focusing lens 722 to form the second lens 72, and the self-focusing lens 722 and the diffraction grating 721 are sequentially arranged along the incident direction of the polarized light beam 9. As shown in the figure, Figure 3 As shown in the figure, the diffraction grating 721 is provided with a plurality of equidistant lines, and the diffraction grating 721 is covered on one side of the self-focusing lens 722 along the line direction. It should be noted that in the structure of the WSS optical system, the switching direction and the dispersion direction are included. Further, the prism 71 is used for dispersing the polarized light beam 9; in this embodiment, the prism 71 comprises a triangular prism, a right-angle prism, a pentagonal prism, etc., and more preferably, an equilateral triangular prism is selected in this embodiment. The diffraction grating 721 is used for dispersing the polarized light beam 9, and the self-focusing lens 722 is used for changing the refractive index of the polarized light beam 9 in the switching direction. It is worth noting that the self-focusing lens 722 is a graded refractive index lens, that is, the self-focusing lens 722 can realize the gradual change of the refractive index in the switching direction, while keeping the refractive index fixed in the dispersion direction. As shown in the figure, Figure 4 As shown in the figure, n1 is the refractive index of the polarized light beam 9 passing through the second lens 72 in the switching direction, and n2 is the refractive index of the polarized light beam 9 passing through the second lens 72 in the dispersion direction. As shown in the figure, Figure 5 As shown in the figure, it is the trajectory diagram of the polarized light beam 9 in the switching direction of the self-focusing lens 722, from which it can be known that the refractive index of the polarized light beam 9 in the switching direction of the self-focusing lens 722 is gradually changed; as shown in the figure, Figure 6 As shown in the figure, it is the trajectory diagram of the polarized light beam 9 in the dispersion direction of the self-focusing lens 722, from which it can be known that the refractive index of the polarized light beam 9 in the dispersion direction of the self-focusing lens 722 is fixed.

[0037] Further, the refractive index of the self-focusing lens 722 in the switching direction is:

[0038]

[0039] wherein x represents the distance from the center, n represents the refractive index, n(x) represents the refractive index of the corresponding position in the switching direction, and A represents the refractive index distribution constant.

[0040] The focal length of the self-focusing lens 722 is:

[0041]

[0042] Wherein, f represents the focal length of the self-focusing lens 722, and L represents the thickness of the self-focusing lens 722.

[0043] It should be noted that the polarized light beam 9 is reflected by the diffraction grating 721 and then enters the self-focusing lens 722 again to generate a focal length, which forms a combined focal length with the focal length f of the self-focusing lens 722. The combined focal length of the self-focusing lens 722 is:

[0044]

[0045] Wherein, F represents the combined focal length of the self-focusing lens 722.

[0046] In this embodiment, the wavelength selective switch further comprises a reflective imaging mirror 6 and a silicon-based liquid crystal device 8. The reflective imaging mirror 6 is used to collimate the polarized light beam 9. The reflective imaging mirror 6 reflects the polarized light beam 9 into the self-focusing dispersion prism grating 7, which separates the polarized light beam 9 by wavelength. The self-focusing dispersion prism grating 7 reflects the polarized light beam 9 after wavelength separation to the reflective imaging mirror 6, and the reflective imaging mirror 6 reflects the polarized light beam 9 after wavelength separation into the silicon-based liquid crystal device 8 to form a circular light spot.

[0047] Specifically, as shown in Figure 1 The first lens 2 collimates the light beam emitted by the optical fiber 1, the polarization separation component 3 performs polarization spatial separation on the light beam, and then two polarized light beams 9 are obtained. Further, the two polarized light beams 9 pass through the birefringent crystal 4 and the wave plate 5 to unify the polarization direction. The two polarized light beams 9 are collimated by the reflective imaging mirror 6 and then enter the self-focusing dispersion prism grating 7 for wavelength separation. Specifically, the two polarized light beams 9 pass through the prism 71, the self-focusing lens 722, and the diffraction grating 721 in sequence along the direction of incidence. The self-focusing dispersion prism grating 7 reflects the polarized light beam 9 after wavelength separation to the reflective imaging mirror 6. Specifically, the two polarized light beams 9 after wavelength separation pass through the diffraction grating 721, the self-focusing lens 722, and the prism 71 in sequence and then are emitted into the reflective imaging mirror 6. The reflective imaging mirror 6 reflects the polarized light beam 9 after wavelength separation into the silicon-based liquid crystal device 8 to form a circular light spot. Thus, the wavelength selective switch of the present embodiment uses the self-focusing dispersion prism grating 7 to replace the dispersion prism and the switch lens in the traditional WSS optical system structure, which simplifies the WSS optical system structure and avoids the problem of spatial interference between the switch lens and the optical path or other optical elements, further reducing the volume of the WSS optical system structure. At the same time, since the diffraction grating 721 is covered on one side of the self-focusing lens 722, the optical axis of the self-focusing lens 722 is perpendicular to the grating surface, and there is no need for optical path adjustment, which greatly simplifies the process development.

[0048] The above description of the application and its embodiments is illustrative and not restrictive, and the application can be practiced in other specific forms without departing from the spirit or essential character thereof. The drawings are intended to be illustrative, and not limiting, and the appended claims should not be limited to the drawings. Thus, if a person of ordinary skill in the art is inspired to design a similar structure and embodiment to the technical solution without departing from the spirit of the invention, it should be within the scope of protection of the patent. In addition, the word "comprising" does not exclude other elements or steps, and the word "one" before an element does not exclude the inclusion of "multiple" such elements. Multiple elements stated in a product claim can also be implemented by one element through software or hardware. The words "first", "second", etc. are used to indicate names, not any specific order.

Claims

1. A wavelength selective switch comprising a polarized light beam (9), characterized in that, The wavelength selective switch comprises a self-focusing dispersive prism grating (7); the self-focusing dispersive prism grating (7) comprises a prism (71) and a second lens (72), the second lens (72) is connected on one side of the prism (71) to form the self-focusing dispersive prism grating (7), and the prism (71) and the second lens (72) are sequentially arranged along the incident direction of the polarized light beam (9); the self-focusing dispersive prism grating (7) is used for realizing wavelength separation of the polarized light beam (9), wherein The second lens (72) comprises a diffraction grating (721) and a self-focusing lens (722), the diffraction grating (721) is covered on one side of the self-focusing lens (722) to form the second lens (72), and the self-focusing lens (722) and the diffraction grating (721) are sequentially arranged along the incident direction of the polarized light beam (9), wherein The self-focusing lens (722) is a graded refractive index lens, and the self-focusing lens (722) can realize refractive index variation in the switching direction and refractive index fixing in the dispersion direction.

2. A wavelength selective switch according to claim 1, wherein, The refractive index of the self-focusing lens (722) in the switching direction is: Wherein, x represents the distance from the center, n represents the refractive index, n(x) represents the refractive index of the corresponding position in the switching direction, n2 is the refractive index of the polarized light beam (9) in the dispersion direction through the second lens (72), and A represents the refractive index distribution constant.

3. A wavelength selective switch according to claim 2, wherein, The focal length of the self-focusing lens (722) is represented as: Wherein, f represents the focal length of the self-focusing lens (722), and L represents the thickness of the self-focusing lens (722).

4. A wavelength selective switch according to claim 3, wherein, The polarized light beam (9) enters the self-focusing lens (722) again after being reflected by the diffraction grating (721) to form a combined focal length, and the combined focal length of the self-focusing lens (722) is represented as: Wherein, F represents the combined focal length of the self-focusing lens (722).

5. A wavelength selective switch according to any of claims 1-4, characterized in that, The wavelength selective switch further comprises a reflective imaging mirror (6) and a silicon-based liquid crystal device (8); the reflective imaging mirror (6) reflects the polarized light beam (9) into the self-focusing dispersive prism grating (7), the self-focusing dispersive prism grating (7) separates the polarized light beam (9) by wavelength, the self-focusing dispersive prism grating (7) reflects the polarized light beam (9) separated by wavelength to the reflective imaging mirror (6), and the reflective imaging mirror (6) reflects the polarized light beam (9) separated by wavelength into the silicon-based liquid crystal device (8) to form a circular light spot.

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