A one-to-four polarization-maintaining fiber optical isolator

Abstract

This application provides a 1-to-4 polarization-maintaining fiber optic isolator, relating to the field of optical fiber communication technology. The 1-to-4 polarization-maintaining fiber optic isolator includes a housing and an optical component module disposed within the housing. The optical component module includes an input unit, a polarization beam splitter unit, a Faraday rotation unit, a half-wave plate unit, and an output unit. The input unit ensures that the light is input with a 45° polarization state through a polarization-maintaining fiber collimator. After being filtered to 0° or 90° polarization by a polarization beam splitter, it is corrected to a specific polarization state by a half-wave plate, then rotated counterclockwise by 45° by a black plate, and finally corrected to 0° polarization by a ±22.5° half-wave plate, outputting four horizontal signals. This invention achieves four-channel optical isolation integrated in a single housing, with a compact size and low loss.

Description

Technical Field

[0001] This application relates to the field of optical fiber communication technology, and in particular to a 1-to-4 polarization-maintaining fiber optic isolator. Background Technology

[0002] With the rapid development of optical fiber communication technology, polarization-maintaining fiber is widely used in high-precision optical systems because it can maintain the polarization state of optical signals. Optical isolators, as key components in optical fiber systems, are mainly used to prevent reflected light from interfering with the light source and improve system stability.

[0003] For related technologies, please refer to Chinese Utility Model Patent No. CN208188404U, which discloses a novel polarization-maintaining optical isolator structure. This device eliminates the need for direct contact between optical fibers through the intermediate conductor, reducing both the difficulty of fiber connection and the frequency of damage from repeated fiber connections. The ball bearings inside the connecting tube reduce the friction between the tube sleeve and the inner wall. The tube sleeve is fixed by symmetrically arranged screws, thereby achieving the fixation of the optical fiber connection to the conductor.

[0004] However, existing polarization-maintaining fiber optic isolators still have the following shortcomings: in scenarios such as high-precision fiber optic sensing systems, quantum communication systems, and lidar systems that require isolation of multiple polarization-maintaining optical signals, using multiple single-path polarization-maintaining fiber optic isolators in parallel results in a large size, which is difficult to meet the needs of compact optical systems. Utility Model Content

[0005] This application provides a 1-to-4 polarization-maintaining fiber optic isolator, which solves the problem that multiple single-path polarization-maintaining fiber optic isolators connected in parallel are bulky and difficult to meet the requirements of compact optical systems.

[0006] The technical solution adopted in the embodiments of this application is as follows:

[0007] In a first aspect, embodiments of this application provide a 1-to-4 polarization-maintaining fiber optic isolator. The housing contains an optical component module, which includes an input unit, a polarization beam-splitting unit, a Faraday rotation unit, a half-wave plate unit, and an output unit.

[0008] The input unit includes a polarization-maintaining fiber collimator, which is used to ensure that the input light is polarized at 45°.

[0009] The polarization beam splitting unit includes five polarization beam splitting cubes numbered 0-4. Each polarization beam splitting cube has a beam splitting surface at a 45° angle. The beam splitting surface transmits horizontal light and reflects vertical light. The polarization beam splitting cube is used to select the optical path of different polarization states. The incident light with a 45° polarization state is separated into light with a 0° polarization state and light with a 90° polarization state after being filtered by the polarization beam splitting cube. The 0° light is transmitted through the polarization beam splitting cube, and the 90° light is reflected.

[0010] The half-wave plate unit includes a +22.5° half-wave plate, a -22.5° half-wave plate, and a +45° half-wave plate. The +22.5° half-wave plate can correct the optical path of 0° polarization to 45° and also correct the optical path of 90° polarization to 45°. The -22.5° half-wave plate can correct the optical path of 0° polarization to -45°. The +45° half-wave plate can correct the optical path of 0° polarization to 90°. The above correction process is reversed. After the 0° and 90° optical paths are corrected by the +22.5° half-wave plate, they become optical paths of 45° polarization and reach the next polarization beam splitter cube for further filtering. After filtering, one of the 0° polarization optical paths is corrected to 90° by the +45° half-wave plate.

[0011] The Faraday rotation unit includes a black plate and a magnetic ring. The black plate and the magnetic ring are connected by a tenon and mortise joint. The Faraday rotation unit is used to rotate the polarization state of the light path counterclockwise by 45°. Four paths of light with 0° or 90° polarization state reach the black plate and are rotated 45° in the opposite direction, becoming light with 45° or -45° polarization state. The light with 45° polarization state is corrected to 0° by a +22.5° half-wave plate, and the light with -45° polarization state is corrected to 0° polarization state by a -22.5° half-wave plate before being output horizontally.

[0012] The output unit includes four polarization-maintaining optical fibers, and the output unit outputs horizontally polarized light.

[0013] By adopting the above technical solution, each optical component is housed inside the casing. Incident light with a 45° polarization state is filtered by a PBSCube and split into 0° and 90° polarization states. The 0° light passes through the PBSCube, while the 90° light is reflected. These two paths, 0° and 90°, are then corrected by a +22.5° half-wave plate to become 45° polarized light and reach the next PBSCube for further filtering. After filtering, one of the 0° polarized light paths is corrected to 90° by a 45° half-wave plate. At this point, there are four paths of 0° or 90° polarized light reaching the black plate and being reverse-rotated to 45° or -45° polarization. The rotated light is then corrected to 0° polarization by a ±22.5° half-wave plate before being output horizontally. This multi-path isolation, using a single optical path subdivided into four, reduces the overall system size, achieving a compact device with convenient operation.

[0014] In one optional implementation, the polarization-maintaining fiber collimator includes an inner lens, an inner fiber optic head, and an outermost glass tube. The lens, fiber optic head, and outermost glass tube are all millimeter-sized. The lens is located above the fiber optic head, and the lens, fiber optic head, and glass tube are all directly connected with bare fibers.

[0015] By adopting the above technical solution, the components of the fiber collimator are all millimeter-sized, making them small in size and achieving the effects of compact size, easy operation, and reduced loss.

[0016] In one alternative implementation, the half-wave plate is millimeter-scale.

[0017] By adopting the above technical solution, the half-wave plate is made in millimeters, achieving a compact size that meets the requirements of compact optical systems.

[0018] In one alternative implementation, the magnetic ring is millimeter-sized and made of samarium cobalt.

[0019] By adopting the above technical solution, the magnetic ring is made of samarium cobalt material, which has stable performance and achieves the effect of reducing space occupation and durability.

[0020] In one alternative implementation, the magnetic ring has four grooves located in the inner cavity, the grooves are matched with the black sheet, and after the black sheet is connected to the magnetic ring, the surface of the black sheet is flush with the end face of the magnetic ring.

[0021] By adopting the above technical solution, the magnetic ring has 4 grooves inside, and the black sheet is connected to the magnetic ring by tenon and tenon joints, which reduces the space occupation. The grooves match the black sheet, so that the black sheet can fit completely into the grooves. The surface of the black sheet is flush with the end face of the magnetic ring, which achieves the effect of high stability and long service life.

[0022] In one alternative implementation, the black plate is millimeter-sized and has the characteristic that any light entering the black plate from either side will rotate it 45° counterclockwise.

[0023] By adopting the above technical solution, the black film is millimeter-sized and has the characteristic that it will rotate 45° counterclockwise no matter which side of the black film the light path enters from, thus achieving the effect of small size and rotating light path.

[0024] In one alternative implementation, the polarization-maintaining fiber collimator can be connected to a polarization-maintaining fiber, which has a fiber core in the middle and cylindrical slow shafts on both sides.

[0025] By adopting the above technical solution, slow axes are provided on both sides of the polarization-maintaining fiber, which achieves the effect of ensuring that the polarization state of light is located on the slow axis of the polarization-maintaining fiber and is in a linear state.

[0026] In one optional implementation, the optical component module has a reverse isolation mechanism, which is as follows: the horizontally polarized light incident in the opposite direction is transmitted through the polarization beam splitter cube by the output unit, and the transmitted horizontally polarized light is corrected by a ±22.5° half-wave plate to become a 45° / -45° polarization state, and then rotated by a black plate to become a 0° / 90° polarization state. The 0° polarized light is transmitted and escaped after passing through the polarization beam splitter cube, and the 90° polarized light is blocked by reflection by the polarization beam splitter cube.

[0027] By adopting the above technical solution, the reverse-incident light is converted into two polarization states, 0° and 90°, after being corrected by a half-wave plate and rotated by a black plate. The 0° polarized light is transmitted and escaped after passing through a polarization beam splitter cube, while the 90° polarized light is blocked by reflection from the polarization beam splitter cube, thus achieving the effect of reverse isolation.

[0028] In summary, this application includes at least one of the following beneficial technical effects:

[0029] 1. The device is compact and easy to operate;

[0030] 2. It prevents incident light at the exit from interfering with the equipment;

[0031] 3. The materials used are rigorously selected, resulting in low waste. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the internal optical path and components of a 1-to-4 polarization-maintaining fiber optic isolator.

[0033] Figure 2 This is a diagram illustrating the operation of the reverse isolation mechanism.

[0034] Explanation of reference numerals in the attached diagram: 1. Polarization-maintaining fiber collimator; 2. PBS Cube 0; 3. PBS Cube 1; 4. PBS Cube 2; 5. PBS Cube 3; 6. PBS Cube 4; 7. Black plate a; 8. Black plate b; 9. Black plate c; 10. Black plate d; 11. Half-wave plate A; 12. Half-wave plate B; 13. Half-wave plate C; 14. Half-wave plate D; 15. Half-wave plate E; 16. Half-wave plate F; 17. Half-wave plate G; 18. Lens; 19. Fiber optic head; 20. Glass tube. Detailed Implementation

[0035] The present application will be further described in detail below with reference to all the accompanying drawings in the embodiments of the present application.

[0036] In the description of the embodiments of this application, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation" and "connection" should be interpreted broadly. For example, "connection" can be a detachable connection or a non-detachable connection; it can be a direct connection or an indirect connection through an intermediate medium. "Fixed connection" refers to a connection where the relative positional relationship remains unchanged after the connection. It should be understood that when component A is fixedly connected to component C via component B, changes in the relative positional relationship due to deformation of components A, B, and C are permissible. The integrated structure obtained by the two components through a one-piece molding process means that during the formation of one of the two components, that component is connected to the other component, without requiring further processing (such as bonding, welding, snap-fit ​​connections, or screw connections) to connect the two components.

[0037] The directional terms mentioned in the embodiments of this application, such as "upper", "lower", "side", etc., are only for reference to the direction of the accompanying drawings. Therefore, the directional terms used are for better and clearer explanation and understanding of the embodiments of this application, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0038] The term "multiple" refers to at least two. The term "more than" includes the stated number. The term "and / or" describes a relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone. The terms "first," "second," etc., are used for descriptive purposes only and should not be construed as implying or suggesting relative importance or implicitly indicating the number of technical features indicated. Therefore, a feature specified as "first" or "second" may explicitly or implicitly include one or more of that feature.

[0039] This application discloses a 1-to-4 polarization-maintaining fiber optic isolator.

[0040] Reference Figure 1 A one-to-four polarization-maintaining fiber optic isolator includes a housing.

[0041] The housing is cylindrical, and an optical element module is located inside the housing.

[0042] The optical element module includes an input unit, a polarization beam splitter unit, a Faraday rotation unit, a half-wave plate unit, and an output unit.

[0043] The input unit includes a polarization-maintaining fiber collimator 1, which includes a lens 18, a fiber optic head 19, and glass tubes 20 on both sides.

[0044] Lens 18, fiber optic head 19 and glass tube 20 are directly connected by bare fiber, lens 18 and fiber optic head 19 are spliced ​​at an angle, and glass tube 20 is located on both sides of lens 18 and fiber optic head 19 after the splicing.

[0045] Lens 18 has an outer diameter of 1.8 mm, a length of 3.0 mm, and a radius of curvature of 1.419 mm. Fiber optic head 19 has an outer diameter of 1.8 mm, a length of 5.5 mm, and is made of PM1550 fiber. Glass tube 20 has an outer diameter of 2.4 mm, an inner diameter of 1.8 mm, and a length of 8.0 mm.

[0046] The lens 18, fiber optic head 19, and outermost glass tube 20 are all millimeter-sized, compact, and take up little space.

[0047] The glass tube 20 is made of high borosilicate glass, which has excellent extreme temperature adaptability and can withstand instantaneous temperature differences from -20℃ to 520℃, which is 3 times that of ordinary glass. The material has ultra-wide temperature range stability, with an operating temperature range covering -270℃ to 1600℃. The material has good optical properties, with a light transmittance of over 90%, compared to only 82% for ordinary glass. The surface smoothness of the material reaches the nanometer level, and the adhesion rate is low.

[0048] The polarization beam splitter unit consists of five polarization beam splitter cubes, numbered 0-4, also known as PBS Cubes.

[0049] The polarization beam splitter cube has a length, width, and height of 3mm. Inside the polarization beam splitter cube is a beam splitting surface at a 45° angle. The beam splitting surface of the PBSCube can be used to select the optical path of different polarization states. Horizontally polarized light will be transmitted in the optical path, while vertically polarized light will be reflected by the beam splitting surface of the PBSCube.

[0050] There are four optical elements inside the housing. The incident light is horizontally incident into PBS Cube2 (0). PBS Cube5 (3) is located directly below PBS Cube2 (0), PBS Cube6 (4) is located directly below PBS Cube5 (3), PBS Cube4 (2) is located horizontally to the right of PBS Cube2 (0), and PBS Cube3 (1) is located directly above PBS Cube4 (2). PBS Cube6 (0, 3, and 4) are arranged in the same direction, and PBS Cube3 (1) and PBS Cube4 (2) are arranged in the same direction. However, the arrangement directions of PBS Cube6 (0, 3, and 4) are opposite to those of PBS Cube3 (1) and PBS Cube4 (2).

[0051] The Faraday rotation unit consists of a magnetic ring and a black plate, the black plate being scientifically known as the Faraday rotation plate.

[0052] The magnetic ring is 2mm thick and has 4 grooves inside. It is 2mm long, 2mm wide, and 0.43mm thick. The units of the magnetic ring and the black plate are both in millimeters. It is small in size and easy to use.

[0053] The magnetic ring is made of samarium cobalt, which has good adaptability to extreme temperatures.

[0054] The black sheet has the characteristic that it will rotate 45° counterclockwise regardless of which side the light enters from. This characteristic is used for the reverse isolation mechanism. The size and shape of the black sheet are designed so that it can be embedded in the groove through a tenon and mortise structure without the influence of glue stress.

[0055] Among them, PBS Cube3 (No. 1), PBS Cube4 (No. 2), PBS Cube5 (No. 3), and PBS Cube6 (No. 4) have black films a7, b8, c9, and d10 respectively on their right sides.

[0056] The half-wave plate unit includes a ±22.5° half-wave plate and a +45° half-wave plate C13, with a length of 2mm, a width of 2mm, and a thickness of 0.09mm.

[0057] The half-wave plate has a light correction function, specifically as follows: the +22.5° half-wave plate corrects 0° and 90° to 45°, the -22.5° half-wave plate corrects 0° and 90° to -45°, and the 45° half-wave plate C13 corrects 0° to 90° and 90° to 0°. A +22.5° half-wave plate is located between PBS Cube2 (0) and PBS Cube4 (2) and between PBS Cube2 (0) and PBS Cube5 (3). A +45° half-wave plate C13 is located between PBS Cube5 (3) and PBS Cube6 (4). A +22.5° half-wave plate E15 is horizontally located to the right of black plate b8. A -22.5° half-wave plate D14, a -22.5° half-wave plate F16, and a -22.5° half-wave plate G17 are horizontally located to the right of black plates a7, c9, and d10, respectively.

[0058] The output unit consists of four polarization-maintaining optical fibers that output horizontally polarized light. The polarization-maintaining optical fibers have a core in the middle and cylindrical slow axes on both sides to ensure that the polarization state of the light is located on the slow axis of the polarization-maintaining optical fiber and is linear.

[0059] The implementation principle of one embodiment of this application is as follows: The polarization-maintaining fiber collimator 1 inputs an optical path with a polarization state of 45° into PBS Cube 2 (No. 0). The PBS Cube filters the optical path into light with polarization states of 0° and 90°. The light with a polarization state of 0° passes through PBS Cube 2 and is corrected to a light path with a polarization state of 45° by the +22.5° half-wave plate 11. This optical path reaches PBS Cube 4 (No. 2) and is further filtered into light with polarization states of 0° and 90°. The light with a polarization state of 0° passes through PBS Cube 4 (No. 2) and is rotated to a light with a polarization state of 45° by the black plate b8. This light with a polarization state of 45° is corrected to 0° by the +22.5° half-wave plate E15 and then output horizontally. This is the complete optical path No. 2.

[0060] The light with a 90° polarization state selected at PBS Cube 2 is reflected to PBS Cube 3 directly above it. At this point, the polarization state of the light path remains unchanged at 90°. It is then reflected by PBS Cube 3 to the black plate a7. After being rotated by the black plate a7, the polarization state of the light path becomes 135°, or -45°. This -45° polarization light is corrected to 0° by the -22.5° half-wave plate D14 and then output horizontally. This is the complete first light path.

[0061] The light with a 90° polarization state selected at PBS Cube2 (0) is reflected to PBS Cube5 (3). It is then corrected to 45° by the +22.5° half-wave plate B12. At this point, the light with a 45° polarization state is selected by PBS Cube5 (3), and the light with a 90° polarization state is reflected to the black plate c9. The subsequent steps are the same as those of optical path 1. This is the complete optical path 3.

[0062] The 0° polarized light filtered at PBS Cube5 is transmitted to PBS Cube6 at PBS Cube6 and is corrected to 90° polarization by the +45° half-wave plate 13. This 90° light is reflected by PBS Cube6 at PBS Cube6 to the black plate d10. The subsequent steps are the same as optical path 4, which is the complete optical path 4.

[0063] A 1-to-4 polarization-maintaining fiber optic isolator also has a reverse isolation mechanism, which is naturally formed by the pre-order arrangement. The reverse isolation mechanism works as follows: When light is incident from the output device in the reverse direction, the 90° polarized light will be directly reflected, and the 0° polarized light will pass through the ±22.5° half-wave plate. The light passing through the 22.5° half-wave plate is corrected to 45°, and the light passing through the -22.5° half-wave plate is corrected to -45°. The corrected light will reach the black plate and rotate counterclockwise by 45°. After rotation, the 45° light becomes 90°, and the -45° light becomes 0°. When the rotated light reaches the PBS Cube, the 0° light will be directly transmitted and escape, and the 90° light will be reflected. Neither of the polarization states of the light will return along the original path, thus achieving the effect of reverse isolation.

[0064] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of this application can be combined with each other, and any combination of features in different embodiments is also within the protection scope of this application. That is to say, the multiple embodiments described above can also be arbitrarily combined according to actual needs.

[0065] It should be noted that all the above-mentioned figures are exemplary illustrations of this application and do not represent the actual size of the product. Furthermore, the dimensional proportions between the components in the figures are not intended to limit the actual product of this application.

[0066] The above are all preferred embodiments of this application and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A one-to-four polarization maintaining fiber optical isolator comprising a housing, characterized by: The housing houses an optical component module, which includes an input unit, a polarization beam splitter unit, a Faraday rotation unit, a half-wave plate unit, and an output unit. The input unit includes a polarization-maintaining fiber collimator (1), which is used to ensure that the input light is polarized at 45°. The polarization beam splitting unit includes five polarization beam splitting cubes numbered 0-4. Each polarization beam splitting cube has a beam splitting surface at a 45° angle. The beam splitting surface transmits horizontal light and reflects vertical light. The polarization beam splitting cube is used to select the optical path of different polarization states. The incident light with a 45° polarization state is separated into light with a 0° polarization state and light with a 90° polarization state after being filtered by the polarization beam splitting cube. The 0° light is transmitted through the polarization beam splitting cube, and the 90° light is reflected. The half-wave plate unit includes a +22.5° half-wave plate, a -22.5° half-wave plate, and a +45° half-wave plate. The +22.5° half-wave plate can correct the optical path of 0° polarization to 45° and also correct the optical path of 90° polarization to 45°. The -22.5° half-wave plate can correct the optical path of 0° polarization to -45°. The +45° half-wave plate can correct the optical path of 0° polarization to 90°. The above correction process is reversed. After the 0° and 90° optical paths are corrected by the +22.5° half-wave plate, they become optical paths of 45° polarization and reach the next polarization beam splitter cube for further filtering. After filtering, one of the 0° polarization optical paths is corrected to 90° by the +45° half-wave plate. The Faraday rotation unit includes a black plate and a magnetic ring. The black plate and the magnetic ring are connected by a tenon and mortise joint. The Faraday rotation unit is used to rotate the polarization state of the light path counterclockwise by 45°. Four paths of light with 0° or 90° polarization state reach the black plate and are rotated 45° in the opposite direction, becoming light with 45° or -45° polarization state. The light with 45° polarization state is corrected to 0° by a +22.5° half-wave plate, and the light with -45° polarization state is corrected to 0° polarization state by a -22.5° half-wave plate before being output horizontally. The output unit includes four polarization-maintaining optical fibers, and the output unit outputs horizontally polarized light.

2. A one-to-four polarization maintaining fiber optical isolator as set forth in claim 1, wherein: The polarization-maintaining fiber collimator (1) includes an inner lens (18), an inner fiber head (19), and an outermost glass tube (20). The lens (18), fiber head (19), and outermost glass tube (20) are all millimeter-sized. The lens (18) is located above the fiber head (19). The lens (18), fiber head (19), and glass tube (20) are all directly connected with bare fibers.

3. The one-to-four polarization-maintaining fiber optic isolator as described in claim 1, characterized in that: The half-wave plate is millimeter-sized.

4. The one-to-four polarization-maintaining fiber optic isolator as described in claim 1, characterized in that: The magnetic ring is millimeter-sized and made of samarium cobalt.

5. A one-to-four polarization-maintaining fiber optic isolator as described in claim 4, characterized in that: The magnetic ring has four grooves located in the inner cavity. The grooves are matched with the black sheet. After the black sheet is connected to the magnetic ring, the surface of the black sheet is flush with the end face of the magnetic ring.

6. The one-to-four polarization-maintaining fiber optic isolator as described in claim 1, characterized in that: The black sheet is millimeter-sized, and it has the characteristic that when light enters the black sheet from either side, it will rotate 45° counterclockwise.

7. The one-to-four polarization-maintaining fiber optic isolator as described in claim 1, characterized in that: The polarization-maintaining fiber collimator (1) can be connected to a polarization-maintaining fiber, which has a fiber core in the middle and cylindrical slow shafts on both sides.

8. The one-to-four polarization-maintaining fiber optic isolator as described in claim 1, characterized in that: The optical component module has a reverse isolation mechanism, which is as follows: the horizontally polarized light incident in the opposite direction is transmitted through the polarization beam splitter cube by the output unit. The transmitted horizontally polarized light is corrected by a ±22.5° half-wave plate and then converted into a 45° or -45° polarization state. It is then rotated by a black plate and converted into a 0° or 90° polarization state. The 0° polarized light is transmitted and escaped after passing through the polarization beam splitter cube, while the 90° polarized light is blocked by reflection from the polarization beam splitter cube.

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