A polarization beam combining air gap structure for high power pump source

Abstract

The present invention discloses a polarization beam combining air gap structure for a high-power pump source, which comprises: a first optical plate, both end faces of which are coated with anti-reflection films; a second optical plate, one end face of which is coated with a beam splitting film, and the other end face of which is coated with an anti-reflection film; a connecting bracket, which is respectively connected to the first optical plate and the second optical plate and makes the planes where the first optical plate and the second optical plate are located located on the side of a virtual 45° right-angle triangle, the plane corresponding to the first optical plate is located on one of the right-angled faces of the virtual 45° right-angle triangle, and the plane corresponding to the second optical plate is located on the inclined face of the virtual 45° right-angle triangle, and the connecting bracket is provided with an open structure for optical signal transmission corresponding to the first optical plate and the second optical plate. The scheme has low cost, short entire processing cycle, is easy to operate, and effectively guarantees quality, and can be applied to mass production.

Description

Technical Field

[0001] The invention belongs to the field of optical communication devices and optical fiber laser applications, and in particular relates to a polarization beam combining air gap structure for a high-power pump source. Background Art

[0002] The schematic diagram of the structure of a conventional fiber laser application PBC is as follows: Figure 1 The disadvantage of this structure is that the flat sheet is first coated with PBS film, and then bonded with another flat sheet by glue, optical glue, or deepening optical glue, and then the optical glue is used to turn the two sides of the body at 45 degrees, and then the optical glue is used twice or more to process the plate to shape the PBC CUBE, and then the thick quartz crystal sheet is bonded to the PBC CUBE by glue, optical glue, or deepening optical glue, and then the optical glue is used again to polish the wave plate delay, and finally coated with anti-reflection film and cut into suitable sizes to form a solid polarization beam combiner. The disadvantage of this structure is that the process is very cumbersome, the processing cycle is long, the cost is low, and it cannot be mass-produced. Summary of the invention

[0003] In view of the prior art, the purpose of the present invention is to provide a polarization beam combining air gap structure for high-power pump sources which has low cost, short entire processing cycle, is easy to operate, and effectively guarantees quality and can be applied to mass production.

[0004] In order to achieve the above technical objectives, the technical solution adopted by the present invention is:

[0005] A polarization beam combining air gap structure for a high power pump source, comprising:

[0006] The first optical flat plate has both end surfaces coated with anti-reflection films;

[0007] A second optical flat plate, one end surface of which is coated with a beam splitting film, and the other end surface of which is coated with an anti-reflection film;

[0008] A connecting bracket is connected to the first optical plate and the second optical plate respectively, and the planes where the first optical plate and the second optical plate are located are located on the side of a virtual 45° right-angle triangle, the plane corresponding to the first optical plate is located on one of the right-angled faces of the virtual 45° right-angle triangle, and the plane corresponding to the second optical plate is located on the inclined face of the virtual 45° right-angle triangle, and the connecting bracket is provided with an open structure for optical signal transmission corresponding to the first optical plate and the second optical plate, and the structure is a two-piece structure.

[0009] As a possible implementation manner, when the signal light output by the combined beam meets the specified or preset wavelength requirement, the present solution further includes: a third optical plate, one end surface of which is coated with an anti-reflection film, and the other end surface of which is coated with a dichroic film; the connecting bracket is respectively connected to the first optical plate, the second optical plate and the third optical plate, and the planes where the first optical plate, the second optical plate and the third optical plate are located are surrounded to form a virtual 45° right-angled triangle, the plane corresponding to the first optical plate is located on one of the right-angled faces of the virtual 45° right-angled triangle, the plane corresponding to the second optical plate is located on the inclined face of the virtual 45° right-angled triangle, and the plane corresponding to the third optical plate is located on the other right-angled face of the virtual 45° right-angled triangle, and the connecting bracket is provided with an open structure for optical signal transmission corresponding to the first optical plate, the second optical plate and the third optical plate, and the structure is a three-piece structure.

[0010] On the basis of the three-piece structure, the solution of the present invention can also have the following implementation forms:

[0011] To prevent the laser from being reflected back to the laser and damaging it, all anti-reflection films use an incident angle of 0 to 10 degrees; the incident angle on the BS surface (i.e. the surface where the beam splitter film is coated) is 45 to 55 degrees.

[0012] In order to achieve a high reflection extinction ratio, the Rs reflectivity of the splitter film is required to be greater than 99.5% or higher.

[0013] The first optical plate, the second optical plate and the third optical plate can be fixed by glue or a slot structure.

[0014] As a possible implementation manner, further, the connecting bracket is a 45° right-angled triangle frame structure, and the first optical plate, the second optical plate and the third optical plate are respectively fixed on three sides of the 45° right-angled triangle frame structure.

[0015] As an optional implementation manner, preferably, the first optical plate, the second optical plate and the third optical plate are respectively embedded and fixed on three side surfaces of the 45° right-angle triangle frame structure.

[0016] As a possible implementation manner, further, the connecting bracket is a U-shaped frame structure, and slots are respectively provided on both sides of the U-shaped structure for the first optical plate, the second optical plate and the third optical plate to be inserted and connected to the U-shaped frame structure and so that the planes on which they are located form a virtual 45° right-angled triangle, and the slot on at least one side of the two sides of the U-shaped structure is a through slot.

[0017] As a possible implementation manner, further, the connecting bracket is a U-shaped frame structure, and the diagonal position from the upper part to the lower part of the U-shaped frame structure and the opening side of the U-shaped structure are respectively provided with connecting slide grooves for sliding insertion of the second optical plate and the first optical plate, at least one end of the connecting slide groove extends out of the side surface of the connecting bracket and forms a mounting port for sliding insertion of the second optical plate or the first optical plate, and the third optical plate is fixedly connected to the upper part or the lower part of the connecting bracket, and the plane where the third optical plate is located and the plane where the third optical plate is located form a virtual 45° right triangle.

[0018] As an optional implementation, preferably, one end of the connecting slide groove extends out of the side surface of the connecting bracket and forms a mounting opening for slidingly inserting the second optical plate or the first optical plate.

[0019] As an optional implementation, preferably, both ends of the connecting slide groove extend out of the side surface of the connecting bracket and form a mounting opening for the second optical plate or the first optical plate to be slidably inserted.

[0020] As an optional implementation, preferably, the upper or lower part of the connecting bracket is also provided with a connecting groove for slidingly inserting the third optical plate, and the plane where the third optical plate is located and the plane where the third optical plate is located form a virtual 45° right triangle; or, the third optical plate is directly fixed on the upper end face or the lower end face of the connecting bracket.

[0021] As a possible implementation manner, further, the connecting bracket is formed by a pair of relatively arranged fixing plates, the first optical plate, the second optical plate and the third optical plate are arranged between the pair of fixing plates, and a virtual 45° right-angled triangle is formed between the planes where the first optical plate, the second optical plate and the third optical plate are located, and slots corresponding to the two sides of the first optical plate, the second optical plate and the third optical plate are respectively provided on the opposite side surfaces of the pair of fixing plates.

[0022] As a possible implementation manner, further, the first optical plate is located at the U-shaped structure opening side of the U-shaped frame structure of the connecting bracket; in this case, when one of the signal lights is set on the second optical plate from the side of the second optical plate away from the third optical plate, it is divided into P light and S light with different polarization states, the P light passes through the second optical plate and is combined with another signal light input from the first optical plate setting position, and the S light is reflected by the second optical plate and transmitted along the side of the connecting bracket away from the U-shaped structure opening side; it should be noted that the reflected S light may be reflected again by the connecting bracket away from the U-shaped structure opening side, so that when the three-piece structure of this scheme combines and outputs light beams, an interference light signal appears. Therefore, in the case where the connecting bracket is a U-shaped frame structure, a through hole for the S light to escape is provided on the side of the connecting bracket away from the U-shaped structure opening side.

[0023] It should be further explained that, based on the three-piece structure, when the requirements for the signal light of the combined output are not high or no specific wavelength output is required, the third optical plate can be removed from the above three-piece structure, that is, directly pulled out, to produce a corresponding two-piece structure, and its function is achieved by the first optical plate and the second optical plate.

[0024] By adopting the above technical scheme, the present invention has the following beneficial effects compared with the prior art: the present scheme intends to process the Cube-type PBC with a flat-plate BS, firstly polish the BS substrate in a large piece, then coat one side with a BS film and the other side with an AR film, and then cut the large piece into finished product specifications and sizes; at the same time, the quartz wave plate is polished in a large piece, then coated with an AR film on both sides, and then cut the large piece into finished product specifications and sizes; the dichroic film window at the outlet can also be polished in a large piece, then coated with an anti-reflection film on one side and a dichroic film on the other side, and then cut the large piece into finished product specifications and sizes; finally, the BS flat plate, the dichroic window and the wave plate are fixed on a triangular metal frame by glue or fixed on a base by a slot method, and finally a polarization-appropriate (PBC) air gap structure of a high-power pump source is formed, which can be widely used in light combining and light splitting components such as PBC and PBS, and has the advantages of low cost, short entire processing cycle, easy operation, and effective quality assurance, and can be applied to mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments:

[0026] Figure 1 It is a schematic diagram of a brief implementation structure of the prior art;

[0027] Figure 2 A brief optical path schematic diagram of the solution of the present invention;

[0028] Figure 3 This is one of the schematic diagrams of the simplified implementation structure of Example 1 of the present invention;

[0029] Figure 4 This is a second schematic diagram of a simplified implementation structure of Example 1 of the present invention;

[0030] Figure 5 This is a third schematic diagram of a simplified implementation structure of Example 1 of the present invention;

[0031] Figure 6 This is one of the schematic diagrams of the simplified implementation structure of Example 2 of the present invention;

[0032] Figure 7 This is a second schematic diagram of a simplified implementation structure of Embodiment 2 of the present invention;

[0033] Figure 8 for Figure 7 Schematic diagram of the section at AA in the middle;

[0034] Fig. 9 This is one of the schematic diagrams of the simplified implementation structure of Example 3 of the present invention;

[0035] Fig.10 This is the second schematic diagram of the simplified implementation structure of Example 3 of the present invention;

[0036] Fig.11 This is one of the schematic diagrams of the simplified implementation structure of Example 4 of the present invention;

[0037] Fig.12 This is the second schematic diagram of the simplified implementation structure of Example 4 of the present invention;

[0038] Fig.13 for Fig.12 Schematic diagram of the section at AA in the middle;

[0039] Fig.14 This is one of the schematic diagrams of the simplified implementation structure of Example 5 of the present invention;

[0040] Fig.15 This is a second schematic diagram of a simplified implementation structure of Embodiment 5 of the present invention;

[0041] Fig.16 for Fig.15 Schematic diagram of the section at AA in the middle;

[0042] Fig.17 This is one of the schematic diagrams of the implementation structure of Example 6 of the present invention;

[0043] Fig.18 This is a second schematic diagram of a simplified implementation structure of Example 6 of the present invention;

[0044] Fig.19 for Fig.18Schematic diagram of the section at AA in the middle;

[0045] Fig. 20 This is one of the schematic diagrams of the simplified implementation structure of Example 7 of the present invention;

[0046] Fig.21 This is a second schematic diagram of a simplified implementation structure of Example 7 of the present invention;

[0047] Fig. 22 for Fig.21 Schematic diagram of the section at AA in the middle;

[0048] Fig.23 This is another schematic diagram of an implementation structure when the connecting bracket is a U-shaped frame structure in the solution of the present invention. DETAILED DESCRIPTION

[0049] Example 1

[0050] like Figures 2 to 5 As shown in one of the embodiments, a polarization beam combining air gap structure for a high power pump source is provided in the present embodiment, which comprises:

[0051] The first optical plate 1 has anti-reflection films coated on both end surfaces, that is, it serves as a wave plate;

[0052] The second optical flat plate 2 has one end surface coated with a beam splitter film and the other end surface coated with an anti-reflection film, that is, it serves as a polarization beam splitter;

[0053] The third optical flat plate 3 has an anti-reflection film coated on one end surface and a dichroic film coated on the other end surface, that is, it serves as a dichroic filter;

[0054] The connecting bracket 4 is respectively connected to the first optical plate 1, the second optical plate 2 and the third optical plate 3 so that the planes where the first optical plate 1, the second optical plate 2 and the third optical plate 3 are located form a virtual 45° right triangle, the plane corresponding to the second optical plate 2 is located on the inclined surface side of the virtual 45° right triangle, and the connecting bracket is provided with an open structure for optical signal transmission corresponding to the first optical plate 1, the second optical plate 2 and the third optical plate 3.

[0055] See also Figure 2The optical path includes a light beam incident on the wave plate surface at 2 to 5 degrees from the air, and then incident on the beam splitter surface at 47 to 50 degrees; another light beam is incident on the beam splitter from the air at 2 to 5 degrees, and the two light beams are combined to achieve the beam combining or beam splitting function of PBC. As a possible option, a beam splitter with an air incidence of 46 to 49 degrees and a wave plate with an air incidence of 2 to 5 degrees are bonded in the constructed air gap triangular structure (i.e., the connecting bracket 4) by gluing; and as a processing method, the beam splitter can be polished in large pieces, and then coated with an anti-reflection film on one side and a beam splitter film on the other side. The incident angles in the air corresponding to the two film systems are 46 to 49 degrees, in order to avoid the laser from being burned by the laser when the laser is incident on the beam splitter at 45 degrees and the light beam returns to the laser by the original path; therefore, all anti-reflection films are incident at an angle of 0 to 10 degrees; the incident angle on the BS surface (i.e., the surface where the beam splitter film is coated) is 45 to 55 degrees.

[0056] In order to achieve a high reflection extinction ratio, the Rs reflectivity of the splitter film is required to be greater than 99.5% or higher.

[0057] The specific implementation form of this embodiment is as follows: the connecting bracket 4 is a 45° right-angle triangle frame structure, and the first optical plate 1, the second optical plate 2 and the third optical plate 3 are respectively fixed on three sides of the 45° right-angle triangle frame structure.

[0058] In this embodiment, the first optical plate 1 , the second optical plate 2 and the third optical plate 3 can be fixed by glue.

[0059] Example 2

[0060] like Figures 6 to 8 As shown in one, this embodiment is substantially the same as the embodiment 1, and the first optical plate 1, the second optical plate 2 and the third optical plate 3 are the same as the embodiment 1, except that: the first optical plate 1, the second optical plate 2 and the third optical plate 3 are respectively embedded and fixed on the three sides of the 45° right-angle triangle frame structure (i.e., the connecting bracket 4).

[0061] Example 3

[0062] like Figures 9 and 10 As shown in one, this embodiment is substantially the same as the embodiment 1, and the first optical plate 1, the second optical plate 2 and the third optical plate 3 are the same as the embodiment 1, except that: the connecting bracket 4 is a U-shaped frame structure, and the U-shaped frame structure has two sides provided with slots for the first optical plate 1, the second optical plate 2 and the third optical plate 3 to be inserted and connected to the U-shaped frame structure and to form a virtual 45° right triangle between the planes where the first optical plate 1, the second optical plate 2 and the third optical plate 3 are located, and the slot on at least one side of the two sides of the U-shaped structure is a through slot.

[0063] In addition, in this embodiment, the first optical plate 1 is located at the U-shaped structure opening side of the U-shaped frame structure.

[0064] Example 4

[0065] like Figures 11 to 13 As shown in one, this embodiment is substantially the same as the embodiment 1, and the first optical plate 1, the second optical plate 2 and the third optical plate 3 are the same as the embodiment 1, except that: the connecting bracket 4 is a U-shaped frame structure, and the diagonal position from the upper part to the lower part of the U-shaped frame structure and the opening side of the U-shaped structure are respectively provided with connecting slide grooves for sliding insertion of the second optical plate 2 and the first optical plate 1, and at least one end of the connecting slide groove extends out of the side of the connecting bracket and forms a mounting port for sliding insertion of the second optical plate 2 or the first optical plate 1, and the third optical plate 3 is fixedly connected to the upper part or the lower part of the connecting bracket 4, and the plane where the third optical plate 3 is located and the plane where the third optical plate 3 is located and the plane where the first optical plate 1 and the second optical plate 2 are located form a virtual 45° right triangle. In this embodiment, both ends of the connecting slide groove extend out of the side of the connecting bracket 4 and form a mounting port for sliding insertion of the second optical plate 2 or the first optical plate 1.

[0066] Example 5

[0067] like Figures 14 to 16 As shown in one, this embodiment is substantially the same as the embodiment 4, and the first optical plate 1, the second optical plate 2 and the third optical plate 3 are the same as the embodiment 4, except that one end of the connecting slide groove extends out of the side of the connecting bracket 4 and forms a mounting opening for the second optical plate 2 or the first optical plate 1 to be slidably inserted.

[0068] Example 6

[0069] like Figures 17 to 19 As shown in one, this embodiment is substantially the same as the embodiment 4, and the first optical plate 1, the second optical plate 2 and the third optical plate 3 are the same as the embodiment 4, except that: the upper or lower part of the connecting bracket 4 is also provided with a connecting groove for the third optical plate 3 to slide into, and the plane where the third optical plate 3 is located and the plane where the third optical plate 3 is located are surrounded by a virtual 45° right triangle.

[0070] Example 7

[0071] like Figure 20 to Figure 22As shown in one, this embodiment is substantially the same as the embodiment 1, and the first optical plate 1, the second optical plate 2 and the third optical plate 3 are the same as the embodiment 1, except that: the connecting bracket 4 is formed by a pair of oppositely arranged fixing plates, the first optical plate 1, the second optical plate 2 and the third optical plate 3 are arranged between the pair of fixing plates, and the planes where the first optical plate 1, the second optical plate 2 and the third optical plate 3 are located form a virtual 45° right triangle, and the opposite side surfaces of the pair of fixing plates are respectively provided with slots corresponding to the two sides of the first optical plate 1, the second optical plate 2 and the third optical plate 3.

[0072] Example 8

[0073] like Fig.23 As shown, this embodiment is a derivative of one of the embodiments 3 to 6. On the basis of one of the embodiments 3 to 6, this embodiment further improves the structure of the U-shaped frame structure of the connecting bracket 4, wherein the first optical plate (not shown) is located at the U-shaped structure opening side of the U-shaped frame structure of the connecting bracket 4; in this case, when one of the signal lights is set on the second optical plate from the side of the second optical plate away from the third optical plate, it is divided into P light and S light with different polarization states, and the P light passes through the second optical plate and is combined with another light input from the first optical plate. A beam of signal light is combined, and the S light is reflected by the second optical plate and transmitted along the side of the connecting bracket 4 away from the opening side of its U-shaped structure; it should be noted that the reflected S light may be reflected again by the opening side of the connecting bracket away from the U-shaped structure, so that when the three-piece structure of one of Examples 3 to 6 combines the output light beams, an interference light signal will appear. Therefore, in the case where the connecting bracket 4 is a U-shaped frame structure, this embodiment provides a through hole 41 for the S light to escape on the side of the connecting bracket 4 away from the opening side of the U-shaped structure, so as to improve the interference of the optical signal.

[0074] Example 9

[0075] This embodiment is a further adjustment based on Embodiments 1 to 8. When the wavelength requirement of the combined output light beam is relatively wide (that is, the light signal of the combined output light beam is not limited to a few specified wavelengths), the third optical plate (that is, the dichroic filter) is removed on the basis of the three-plate structure to generate a corresponding two-plate structure solution, and its function is realized only by the first optical plate and the second optical plate. Since the three-plate structure solution has been specifically described in conjunction with the drawings, it will not be repeated here.

[0076] It should be noted that the embodiments disclosed herein are subject to modification and change, and replacement and equivalent components of the embodiments are well known to those skilled in the art. It should be clear to those skilled in the art that various changes made to the present invention in form and detail without departing from the spirit and scope of the present invention as defined in the appended claims are within the scope of protection of the present invention.

Claims

1. A polarization beam combining air gap structure for a high power pump source, characterized in that: It includes: The first optical flat plate has both end surfaces coated with anti-reflection films; A second optical flat plate, one end surface of which is coated with a beam splitting film, and the other end surface of which is coated with an anti-reflection film; A connecting bracket is connected to the first optical plate and the second optical plate respectively, and the planes where the first optical plate and the second optical plate are located are located on the side of a virtual 45° right-angled triangle, the plane corresponding to the first optical plate is located on one of the right-angled faces of the virtual 45° right-angled triangle, and the plane corresponding to the second optical plate is located on the inclined face of the virtual 45° right-angled triangle, and the connecting bracket is provided with an open structure for optical signal transmission corresponding to the first optical plate and the second optical plate.

2. The polarization beam combining air gap structure for a high power pump source according to claim 1, characterized in that: It also includes: a third optical plate, one end surface of which is coated with an anti-reflection film, and the other end surface is coated with a dichroic film; the connecting bracket is respectively connected to the first optical plate, the second optical plate and the third optical plate, and the planes where the first optical plate, the second optical plate and the third optical plate are located are surrounded to form a virtual 45° right-angled triangle, the plane corresponding to the first optical plate is located on one of the right-angled faces of the virtual 45° right-angled triangle, the plane corresponding to the second optical plate is located on the inclined face of the virtual 45° right-angled triangle, and the plane corresponding to the third optical plate is located on the other right-angled face of the virtual 45° right-angled triangle, and the connecting bracket is provided with an open structure for optical signal transmission corresponding to the first optical plate, the second optical plate and the third optical plate.

3. The polarization beam combining air gap structure for a high power pump source according to claim 2, characterized in that: The connecting bracket is a 45° right-angled triangle frame structure, and the first optical plate, the second optical plate and the third optical plate are respectively fixed on the three sides of the 45° right-angled triangle frame structure; or, the first optical plate, the second optical plate and the third optical plate are respectively embedded and fixed on the three sides of the 45° right-angled triangle frame structure.

4. The polarization beam combining air gap structure for a high power pump source according to claim 2, characterized in that: The connecting bracket is formed by a pair of fixed plates arranged opposite to each other, the first optical plate, the second optical plate and the third optical plate are arranged between the pair of fixed plates, and a virtual 45° right triangle is formed between the planes where the first optical plate, the second optical plate and the third optical plate are located, and slots corresponding to the two sides of the first optical plate, the second optical plate and the third optical plate are respectively arranged on the opposite side surfaces of the pair of fixed plates.

5. The polarization beam combining air gap structure for a high power pump source according to claim 2, characterized in that: The connecting bracket is a U-shaped frame structure, and slots are respectively provided on both sides of the U-shaped structure for the first optical plate, the second optical plate and the third optical plate to be inserted and connected to the U-shaped frame structure so that the planes where they are located form a virtual 45° right-angled triangle, and at least one side of the slots on the two sides of the U-shaped structure is a through slot.

6. The polarization beam combining air gap structure for a high power pump source according to claim 2, characterized in that: The connecting bracket is a U-shaped frame structure, and the diagonal position from the upper part to the lower part of the U-shaped frame structure and the opening side of the U-shaped structure are respectively provided with connecting slide grooves for sliding insertion of the second optical plate and the first optical plate, at least one end of the connecting slide groove extends out of the side surface of the connecting bracket and forms a mounting port for sliding insertion of the second optical plate or the first optical plate, and the third optical plate is fixedly connected to the upper part or the lower part of the connecting bracket, and the plane where the third optical plate is located and the plane where the third optical plate is located form a virtual 45° right triangle.

7. The polarization beam combining air gap structure for a high power pump source according to claim 6, characterized in that: One end of the connecting slide extends out of the side of the connecting bracket and forms an installation opening for slidingly inserting the second optical plate or the first optical plate; or both ends of the connecting slide extend out of the side of the connecting bracket and form an installation opening for slidingly inserting the second optical plate or the first optical plate.

8. The polarization beam combining air gap structure for a high power pump source according to claim 7, characterized in that: The upper or lower part of the connecting bracket is also provided with a connecting slot for slidingly inserting the third optical plate, and the plane where the third optical plate is located and the plane where the third optical plate is located form a virtual 45° right triangle; or, the third optical plate is directly fixed on the upper end face or the lower end face of the connecting bracket.

9. A polarization beam combining air gap structure for a high power pump source according to any one of claims 5 to 8, characterized in that: The first optical plate is located at the U-shaped structure opening side of the U-shaped frame structure of the connecting bracket; when one of the signal lights is set on the second optical plate from the side of the second optical plate away from the third optical plate, it is divided into P light and S light with different polarization states, the P light passes through the second optical plate and is combined with another signal light input from the location where the first optical plate is set, while the S light is reflected by the second optical plate and transmitted along the side of the connecting bracket away from the U-shaped structure opening side; a through hole for the S light to escape is provided on the side of the connecting bracket away from the U-shaped structure opening side.

10. A polarization beam combining air gap structure for a high power pump source according to any one of claims 3 to 8, characterized in that: The third optical plate is removed, and when the connecting bracket is a U-shaped frame structure, the first optical plate is located at the U-shaped structure opening side of the U-shaped frame structure of the connecting bracket; when one of the signal lights is set on the second optical plate, it is divided into P light and S light with different polarization states, the P light passes through the second optical plate and is combined with another signal light input from the first optical plate setting position, and the S light is reflected by the second optical plate and transmitted along the side of the connecting bracket away from the U-shaped structure opening side; a through hole for the S light to escape is provided on the side of the connecting bracket away from the U-shaped structure opening side.

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