A fiber combiner and a method for manufacturing the same

Abstract

The application provides an optical fiber combiner and a preparation method thereof. The optical fiber combiner comprises an optical fiber bundle, a second polarization maintaining signal optical fiber and an encapsulating body. The optical fiber bundle comprises a polarization maintaining signal optical fiber assembly and a plurality of pump optical fibers. The polarization maintaining signal optical fiber assembly comprises a first polarization maintaining signal optical fiber and a transition optical fiber which are fused together. The pump optical fibers comprise a first part optical fiber and a second part optical fiber which are arranged in sequence. The plurality of pump optical fibers are uniformly distributed around the polarization maintaining signal optical fiber assembly. The second part optical fiber is spirally wound on the transition optical fiber to form a fusion cone. The second polarization maintaining signal optical fiber comprises a first section optical fiber and a second section optical fiber which are arranged in sequence. The first section optical fiber is fused with the fusion cone. The fusion cone is located in the encapsulating body. The transition optical fiber serves as an intermediate connecting section, which ensures low-loss transmission of the signal light and provides a fusion cone base for the spiral winding of the pump optical fibers. The plurality of pump optical fibers can be seamlessly and closely arranged around the transition optical fiber, the fusion loss is reduced, and the pump coupling efficiency and power carrying capacity are improved.

Description

Technical Field

[0001] This application belongs to the field of optical fiber combiner technology, and more specifically, relates to an optical fiber combiner and its fabrication method. Background Technology

[0002] After more than two decades of rapid development, fiber optic combiners are now being developed by many manufacturers focusing on higher pump power and competing to develop polarization-maintaining high-power fiber optic combiners. Polarization-maintaining high-power fiber optic combiners are key components of coherently synthesized single-mode fiber lasers.

[0003] Coherent combining technology can achieve a geometric increase in output power while ensuring high beam quality, thus it can be used to manufacture laser weapons to destroy aerial threats such as missiles, rockets, and drones.

[0004] Currently, polarization-maintaining (6+1)*1 fiber combiners manufactured using the sleeve process have performance limitations: IL=0.25dB; M2=1.20; PER=20dB; single-arm pump power ≤1000W; signal transmission power ≤1000W. Therefore, it is impossible to manufacture single-mode fiber lasers with good beam quality (M2) and PER, and the single-arm pump power and signal transmission power are both below 1000W, making them unsuitable for higher power input applications.

[0005] Formula for calculating fiber optic brightness: Fiber luminance = fiber cladding area * fiber NA; The law of conservation of luminance: (R1)^2*n*NA1=(R2)^2*NA2; Fabricating a fiber optic combiner requires initial brightness design and must meet the following basic conditions to avoid pump light leakage and produce a fiber optic combiner with high pump efficiency. These conditions can be expressed by the following formula:

[0006] in: R1: Cladding radius of the pump fiber; NA1: NA of the pump fiber; n: The number of pump fibers (strands). R2: Cladding radius of the output fiber; NA2: The cladding NA of the output fiber; In other words, to manufacture a fiber combiner with high pump efficiency, the basic condition must be met: "the brightness of the output fiber cladding must be greater than the sum of the brightness of the pump fibers." Conversely, if this condition is not met, pump light leakage will occur, causing the device and fiber temperature to rise or even burn out.

[0007] Based on the aforementioned law of conservation of light intensity, the polarization-maintaining (6+1)*1 fiber combiner fabricated using the existing sleeve process has a fundamental design flaw. It is prone to breakage and cannot meet the design requirements of small IL, high pump efficiency, and simple structure that is easy to manufacture. Summary of the Invention

[0008] The purpose of this application is to provide an optical fiber combiner and its fabrication method to solve the technical problems of existing polarization-maintaining optical fiber combiners, such as easy breakage, low pump efficiency, high insertion loss, complex structure, and high manufacturing difficulty.

[0009] To achieve the above objectives, the technical solution adopted in this application is as follows: An optical fiber combiner is provided, comprising an optical fiber bundle, a second polarization-maintaining signal fiber, and a package. The optical fiber bundle includes a polarization-maintaining signal fiber assembly and multiple pump fibers. The polarization-maintaining signal fiber assembly includes a first polarization-maintaining signal fiber and a transition fiber fused together. The pump fiber includes a first portion fiber and a second portion fiber arranged sequentially. The first portion fiber has a coating, while the transition fiber and the second portion fiber have no coating. The multiple pump fibers are uniformly distributed around the polarization-maintaining signal fiber assembly, and the second portion fiber is spirally wound around the transition fiber to form a fused taper. The second polarization-maintaining signal fiber includes a first segment fiber and a second segment fiber arranged sequentially. The first segment fiber is fused to the fused taper. The first segment fiber has no coating, while the second segment fiber has a coating. The fused taper is located within the package, with the first polarization-maintaining signal fiber and the first portion fiber extending from a first end of the package, and the second segment fiber extending from a second end of the package.

[0010] Furthermore, the first end of the package is provided with a first sealing adhesive, which is used to fix the first polarization-maintaining signal fiber and the first part of the fiber to the first end of the package; the second end of the package is provided with a second sealing adhesive, which is used to fix the second segment of the fiber to the second end of the package.

[0011] Furthermore, the package body is provided with a low-refractive-index encapsulating adhesive, which is used to fix the fused cone body within the package body.

[0012] This application also provides a method for fabricating an optical fiber combiner, the method comprising: fusing two first polarization-maintaining signal fibers to both ends of a transition fiber; cleaning the transition fiber after removing the coating layer and performing pretreatment; removing part of the coating layer of the pump fiber to form the second part of the fiber and cleaning the pump fiber; fixing the pump fiber and the transition fiber with a pair of fiber clamping fixtures and performing pre-stretching treatment; spirally winding multiple pump fibers onto the transition fiber using the fiber clamping fixtures; simultaneously tapering the transition fiber and multiple pump fibers to form the fused taper; breaking the fused taper at its thinnest point, including a longer pigtail portion as an optical fiber bundle; fusing the optical fiber bundle with the second polarization-maintaining signal fiber; and encapsulating the optical fiber bundle and the second polarization-maintaining signal fiber with an encapsulation body.

[0013] Furthermore, the fiber clamping fixture includes a base, a clamping stage, a sliding seat, a hollow shaft, a positioning sleeve, and a clamping plate; the clamping stage is fixed on the base and is used to clamp the first polarization-maintaining signal fiber; the sliding seat is slidably connected to the base; one end of the hollow shaft is rotatably connected to the sliding seat; the hollow shaft is used for the transition fiber to pass through; the positioning sleeve is connected to the other end of the hollow shaft, and has a first positioning hole for the transition fiber to pass through and a plurality of second positioning holes for the pump fiber to pass through; the clamping plate is fixedly connected to the hollow shaft and is used to clamp the pump fiber.

[0014] Furthermore, the positioning sleeve includes a positioning block and a positioning cylinder sleeved on the positioning block; the first positioning hole is provided on the positioning block; a positioning groove is provided on the outer wall of the positioning block, and the positioning groove and the positioning cylinder surround to form the second positioning hole.

[0015] Furthermore, the sliding seat is provided with a slider, which is slidably connected to the base; the fiber optic clamping fixture also includes an elastic element and a locking element, one end of the elastic element abuts against the limiting part on the base, and the other end of the elastic element abuts against the slider; the locking element is detachably connected to the sliding seat and the base.

[0016] Furthermore, the pretreatment of the transition fiber includes etching it with a solution containing hydrogen fluoride on a special etching fixture to etch the diameter of the transition fiber to a set size.

[0017] Furthermore, the pre-stretching of the pump fiber and the transition fiber includes: setting the intensity of the oxyhydrogen flame; setting the taper length of the pump fiber by adjusting the initial compression of the elastic element; fixing the sliding seat and the base with the locking element; fixing the pump fiber and the transition fiber; while heating the pump fiber with the oxyhydrogen flame, releasing the locking element, and the sliding seat sliding under the elastic force of the elastic element, thereby realizing the tapering of the pump fiber and the transition fiber.

[0018] Furthermore, the drawing of the fiber bundle includes: passing the transition fiber through the hollow shaft and then fixing it again; rotating the clamping plate to spirally wind multiple pump fibers around the transition fiber and then fixing the hollow shaft; setting the hydrogen-oxygen flame intensity and the tapered length of the fiber bundle; and synchronously tapering the transition fiber and multiple pump fibers.

[0019] The beneficial effects of the fiber optic combiner provided in this application are as follows: Compared with the prior art, this application effectively solves the problem of easy breakage of the polarization-maintaining signal fiber during the tapering process by adopting a structural design of fusion splicing the transition fiber and the first polarization-maintaining signal fiber to form a polarization-maintaining signal fiber assembly, thereby improving the product qualification rate. The transition fiber, as an intermediate connecting segment, not only ensures low-loss transmission of the signal light but also provides an ideal fusion tapering substrate for the helical winding of the pump fiber, enabling multiple pump fibers to be uniformly, seamlessly, and tightly arranged around the transition fiber, reducing splicing loss and significantly improving the coupling efficiency and power carrying capacity of the pump light.

[0020] The beneficial effects of the fiber optic combiner fabrication method provided in this application are as follows: Compared with the prior art, this application achieves pre-fusion splicing of two first polarization-maintaining signal fibers by using a transition fiber as an intermediate connection medium, effectively reducing the alignment difficulty during subsequent fusion splicing with the fiber bundle and significantly improving the fusion quality and efficiency; the pre-stretching treatment of the pump fiber and transition fiber by the fiber clamping fixture enables multiple pump fibers to be uniformly and tightly spirally wound on the surface of the transition fiber, forming a stable structural arrangement, which lays the foundation for the uniform forming of the fused cone during the subsequent synchronous tapering process; the synchronous tapering process ensures that the transition fiber and multiple pump fibers shrink and fuse synchronously at high temperature, forming a fused cone. The dense, tapered structure and gentle taper effectively reduce scattering loss and mode mismatch during optical transmission. Breaking the fiber at its thinnest point and selecting the longer portion of the pigtail as the fiber bundle ensures both the flatness and optical performance of the fiber bundle end face, and facilitates precise docking with the second polarization-maintaining signal fiber. The overall fabrication process organically integrates signal fiber preprocessing, pump fiber arrangement, synchronous tapering, fusion splicing, and packaging, enabling efficient and mass production of fiber combiners. The fabricated fiber combiners feature high pump coupling efficiency, excellent signal light polarization extinction ratio, and a compact and stable structure, meeting the dual requirements of high-power fiber lasers for pump injection and polarization maintenance. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the fiber optic combiner provided in the embodiments of this application; Figure 2 This is a schematic diagram of the structure of the fusion cone in the fiber optic combiner provided in the embodiments of this application; Figure 3 for Figure 2 Sectional view of AA; Figure 4 for Figure 2 BB section view; Figure 5 for Figure 2 CC section view; Figure 6 A process flow diagram of the method for fabricating an optical fiber combiner provided in the embodiments of this application; Figure 7 A three-dimensional structural schematic diagram of the fiber optic clamping fixture provided in the embodiments of this application; Figure 8 This is a schematic diagram of the main structure of the fiber optic clamping fixture provided in the embodiments of this application; Figure 9 A three-dimensional structural diagram of the positioning block in the optical fiber clamping fixture provided in the embodiments of this application; Figure 10 A cross-sectional view of the positioning block in the fiber optic clamping fixture provided in this application embodiment; The following are the labeling elements in the figure: 100 - Fused taper; 110 - First polarization-maintaining signal fiber; 120 - Pump fiber; 130 - Transition fiber; 200 - Second polarization-maintaining signal fiber; 210 - First fiber segment; 220 - Second fiber segment; 300 - Encapsulation body; 301 - First sealing and fixing adhesive; 302 - Second sealing and fixing adhesive; 303 - Encapsulation adhesive; 410-Base; 420-Clamping table; 430-Sliding seat; 431-Locking element; 432-Slider; 440-Hollow shaft; 441-Positioning screw; 450-Positioning sleeve; 451-Positioning block; 452-First positioning hole; 453-Positioning groove; 460-Clamping plate; 470-Elastic element; 480-Bearing. Detailed Implementation

[0023] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0024] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0025] It should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0026] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0027] Please refer to the following: Figure 1 and Figure 2 The fiber optic combiner provided in the embodiments of this application will now be described. The fiber optic combiner includes a fiber bundle, a second polarization-maintaining signal fiber 200, and a package 300. The fiber bundle includes a polarization-maintaining signal fiber assembly and multiple pump fibers 120. The polarization-maintaining signal fiber assembly includes a first polarization-maintaining signal fiber 110 and a transition fiber 130 fused together. The pump fiber 120 includes a first part fiber and a second part fiber arranged sequentially. The first part fiber has a coating, while the transition fiber 130 and the second part fiber have no coating. The multiple pump fibers 120 are evenly distributed around the polarization-maintaining signal fiber assembly, and the second part fiber is spirally wound around the transition fiber 130 to form a fused cone. The second polarization-maintaining signal fiber 200 includes a first segment fiber 210 and a second segment fiber 220 arranged sequentially. The first segment fiber 210 is fused to the fused cone 100. The first segment fiber 210 has no coating, while the second segment fiber 220 has a coating. The fused cone 100 is located inside the package 300. The first polarization-maintaining signal fiber 110 and the first part fiber extend from the first end of the package 300, and the second segment fiber 220 extends from the second end of the package 300.

[0028] Compared with the prior art, the fiber optic combiner provided in this application effectively solves the problem of easy breakage of the polarization-maintaining signal fiber during the tapering process by adopting a structural design of fusion splicing the transition fiber 130 and the first polarization-maintaining signal fiber 110 to form a polarization-maintaining signal fiber assembly, thereby improving the product qualification rate. The transition fiber 130, as an intermediate connecting segment, not only ensures low-loss transmission of the signal light but also provides an ideal fusion tapering substrate for the helical winding of the pump fiber 120. This allows multiple pump fibers 120 to be uniformly and seamlessly arranged around the transition fiber 130, reducing splicing loss and significantly improving the coupling efficiency and power carrying capacity of the pump light.

[0029] In one embodiment of this application, please refer to Figure 1 The first end of the package 300 is provided with a first sealing adhesive 301, which is used to fix the first polarization-maintaining signal fiber 110 and the first part of the fiber to the first end of the package 300; the second end of the package 300 is provided with a second sealing adhesive 302, which is used to fix the second section of the fiber 220 to the second end of the package 300.

[0030] In this embodiment, by setting a first sealing adhesive 301 and a second sealing adhesive 302 at the first and second ends respectively, reliable fixation and sealing protection of the fiber ends are achieved. The first sealing adhesive 301 fixes the first polarization-maintaining signal fiber 110 and the first part of the fiber together to the first end of the encapsulation body 300, which not only enhances the overall stability of the structure, but also effectively prevents external water vapor, dust and other contaminants from entering the interior of the encapsulation body 300, avoiding the degradation of the optical performance of the fused taper 100 area. The second sealing adhesive 302 fixes the second fiber 220, ensuring that when the output fiber is subjected to external tensile or bending stress, the stress will not be directly transmitted to the fused taper 100 area, thereby protecting the structural integrity of the fused taper 100. This double-end sealing and fixing design significantly improves the environmental adaptability and long-term operational reliability of the fiber combiner, enabling it to maintain a stable polarization extinction ratio and optical power transmission characteristics under harsh conditions such as high humidity and high vibration, and extending the service life of the device.

[0031] Specifically, both the first sealing and fixing adhesive 301 and the second sealing and fixing adhesive 302 can be UVJ69 sealing and fixing adhesive. This material has excellent ultraviolet curing characteristics, low shrinkage rate and good fiber cladding adhesion. After curing, it forms a dense polymer protective layer, which can effectively block water vapor penetration and buffer mechanical stress.

[0032] In one embodiment of this application, please refer to Figure 1 The encapsulation body 300 contains a low-refractive-index encapsulating adhesive 303, which is used to fix the fusion cone 100 inside the encapsulation body 300.

[0033] In this embodiment, by using encapsulating adhesive 303, the fusion taper 100 is completely encapsulated and fixed inside the encapsulation body 300, forming a stable optical support structure. The low refractive index of the encapsulating adhesive 303 ensures that its refractive index is lower than that of the fiber cladding in the fusion taper 100, thereby ensuring that the optical signal in the region of the fusion taper 100 can still meet the total internal reflection condition, preventing light energy from leaking into the encapsulating adhesive 303 layer, and maintaining the high transmission efficiency of the combiner.

[0034] Specifically, the encapsulating adhesive 303 can be UVJ49 low refractive index adhesive, which can effectively ensure the total internal reflection conditions of the 100 region of the fused cone.

[0035] In this embodiment, the encapsulation body 300 includes a groove and a cover plate that closes to the opening of the groove. Both the groove and the cover plate can be made of quartz material. The fiber optic combiner encapsulated in quartz material can promptly transmit stray light to the outside, avoiding the risk of thermal damage caused by heat accumulation inside the device. Quartz material has excellent thermal conductivity and chemical stability, and its low coefficient of thermal expansion can effectively reduce the stress caused by the difference in thermal expansion and contraction of the material during temperature cycling, thereby protecting the integrity of the fused cone 100 structure.

[0036] This application also provides a method for fabricating an optical fiber combiner; please refer to [link to relevant documentation]. Figure 6 The preparation methods include: Two first polarization-maintaining signal fibers 110 are fused to both ends of the transition fiber 130. The transition fiber 130, after its coating has been removed, is cleaned and pre-treated. Part of the coating on the pump fiber 120 is removed to form the second fiber, and the pump fiber 120 is cleaned. The pump fiber 120 and the transition fiber 130 are fixed using a pair of fiber clamping fixtures and pre-stretched. Please refer to [further details omitted]. Figure 3 , Figure 4 and Figure 5 Multiple pump fibers 120 are spirally wound onto a transition fiber 130 using an optical fiber clamping fixture; the transition fiber 130 and multiple pump fibers 120 are simultaneously tapered to form a fused taper 100; the fused taper 100 is broken at its thinnest point, including the longer portion of the pigtail as an optical fiber bundle; the optical fiber bundle is fused with a second polarization-maintaining signal fiber 200; the optical fiber bundle and the second polarization-maintaining signal fiber 200 are encapsulated with a package 300.

[0037] Compared with existing technologies, the fiber optic combiner fabrication method provided in this application achieves pre-fusion splicing of two first polarization-maintaining signal fibers 110 by using a transition fiber 130 as an intermediate connecting medium. This effectively reduces the alignment difficulty during subsequent fusion splicing with the fiber bundle, significantly improving splicing quality and efficiency. The pump fiber 120 and transition fiber 130 are pre-stretched using a fiber clamping fixture, enabling multiple pump fibers 120 to be uniformly and tightly spirally wound on the surface of the transition fiber 130, forming a stable structural arrangement. This lays the foundation for the uniform forming of the fused taper 100 during the subsequent synchronous tapering process. The synchronous tapering process ensures that the transition fiber 130 and multiple pump fibers 120 shrink and fuse synchronously at high temperatures. The resulting fused taper 100 has a dense structure and a gently tapered shape, effectively reducing scattering loss and mode mismatch during optical transmission. The taper 100 is broken at its thinnest point, and a longer portion of the pigtail is selected as the fiber bundle. This ensures the flatness and optical performance of the fiber bundle end face and facilitates precise docking with the second polarization-maintaining signal fiber 200. The overall fabrication process organically integrates signal fiber preprocessing, pump fiber 120 arrangement, synchronous tapering, fusion splicing, and packaging, achieving efficient and mass production of the fiber combiner. The fabricated fiber combiner features high pump coupling efficiency, excellent signal light polarization extinction ratio, and a compact and stable structure, meeting the dual requirements of high-power fiber lasers for pump injection and polarization maintenance.

[0038] In this embodiment, the pump fiber 120 is model 200 / 220-0.22NA; its parameters are as follows: cladding radius R1: 110μm; NA1: 0.22; quantity n: 6; The first polarization-maintaining signal fiber 110 and the second polarization-maintaining fiber are of type PM GDF 20 / 400-0.065NA; their parameters are as follows: cladding radius R2: 200μm; core NA: 0.065; cladding NA2: 0.46; The transition fiber 130 is model LMA-GDF-20 / 400-M, and its parameters are as follows: cladding radius R2: 200μm; core NA: 0.065.

[0039] Based on the above parameters, the optical brightness of the two optical fibers can be calculated: (R2)2×(NA2) = (200)2×(0.46) = 18400; (R1)2×(NA1)2×(n) = (110)2×(0.22)×(6) = 15972; As described above, the selected pump fiber 120 and output fiber (second polarization-maintaining signal fiber 200) can satisfy the basic condition that "the brightness of the output fiber cladding is greater than the sum of the brightness of the pump fiber 120", that is: .

[0040] In one embodiment of this application, please refer to the following: Figure 7 and Figure 8 The fiber optic clamping fixture includes a base 410, a clamping stage 420, a sliding seat 430, a hollow shaft 440, a positioning sleeve 450, and a clamping plate 460. The clamping stage 420 is fixed on the base 410 and is used to clamp the first polarization-maintaining signal fiber 110. The sliding seat 430 is slidably connected to the base 410. One end of the hollow shaft 440 is rotatably connected to the sliding seat 430. The hollow shaft 440 is used for the passage of the fiber 130. For positioning at the other end connected to the hollow shaft 440, please refer to [reference needed]. Figure 10 The positioning sleeve 450 is provided with a first positioning hole 452 for the transition optical fiber 130 to pass through and a plurality of second positioning holes for the pump optical fiber 120 to pass through; the clamping plate 460 is fixedly connected to the hollow shaft 440 and is used to clamp the pump optical fiber 120.

[0041] In this embodiment, the base 410 serves as the supporting foundation for the entire fixture, providing a stable installation platform for subsequent functional modules. The clamping stage 420 is fixed to one end of the base 410, and its interior is provided with a V-groove or precision slot structure that matches the outer diameter of the first polarization-maintaining signal fiber 110. The radial positioning and axial fixation of the fiber are achieved by fine-tuning screws, ensuring that the polarization axis direction of the core of the first polarization-maintaining signal fiber 110 can be precisely adjusted and locked.

[0042] The sliding seat 430 forms a sliding pair with the base 410 via a precision guide rail. The direction of the guide rail is parallel to the axis of the first polarization-maintaining signal fiber 110, allowing the sliding seat 430 to drive subsequent components to move smoothly along the axial direction. This sliding design facilitates the adjustment of the relative distance between the fibers during assembly, enabling a gradual approach alignment operation. The hollow shaft 440 adopts a hollow tubular structure, with its inner diameter slightly larger than the cladding diameter of the transition fiber 130. This ensures that the transition fiber 130 can pass through smoothly while avoiding excessive gaps that could cause fiber wobbling. One end of the hollow shaft 440 is connected to the sliding seat 430 via a bearing 480 assembly, allowing the hollow shaft 440 to rotate freely around its axis.

[0043] The positioning sleeve 450, as the core component for the spatial arrangement of optical fibers, is detachably connected to the other end of the hollow shaft 440, facilitating the replacement of the positioning sleeve 450 with the appropriate specification for different types of combiners. The first positioning hole 452 on the positioning sleeve 450 is located at the center, and its diameter precisely matches the cladding of the transition fiber 130, ensuring the accurate axial position of the transition fiber 130. Multiple second positioning holes are arranged in a circular array around the first positioning hole 452, with their diameters matching the cladding of the pump fiber 120. The number and distribution radius of the holes are designed according to the number of pump fibers 120 and the cladding diameter of the target combiner. For example, for a typical (6+1)×1 combiner structure, there are six second positioning holes, and the distribution radius ensures that the six pump fibers 120 tightly surround the transition fiber 130. The clamping plate 460 is fixedly connected to the outer wall of the hollow shaft 440 and rotates synchronously with the hollow shaft 440.

[0044] In one embodiment of this application, please refer to Figure 9 The positioning sleeve 450 includes a positioning block 451 and a positioning cylinder sleeved on the positioning block 451; a first positioning hole 452 is provided on the positioning block 451; a positioning groove 453 is provided on the outer wall of the positioning block 451, and the positioning groove 453 and the positioning cylinder form a second positioning hole.

[0045] In this embodiment, by directly setting the first positioning hole 452 on the positioning block 451 and designing the second positioning hole as a structure formed by the positioning groove 453 and the positioning cylinder, the precise positioning and isolation of the transition fiber 130 and multiple pump fibers 120 are achieved. Simultaneously, the design of the positioning groove 453 reduces processing difficulty, and the sleeve structure between the positioning cylinder and the positioning block 451 facilitates assembly and replacement. Positioning blocks 451 with positioning grooves 453 of various sizes can be designed, and the appropriate size positioning block 451 can be selected according to different specifications of pump fibers 120, improving the versatility and adaptability of the fixture.

[0046] Specifically, the positioning slot 453 can be a U-shaped slot. According to the dimensions of the pump fiber 120 and the transition fiber 130 used in this embodiment, the slot width of the U-shaped slot is 370μm, which is just enough to fit one pump fiber 120; the aperture of the first positioning hole 452 is 570μm, which is just enough to fit one transition fiber 130.

[0047] In one embodiment of this application, the sliding seat 430 is provided with a slider 432, which is slidably connected to the base 410; the fiber optic clamping fixture also includes an elastic element 470 and a locking element 431, one end of the elastic element 470 abuts against the limiting portion on the base 410, and the other end of the elastic element 470 abuts against the slider 432; the locking element 431 is detachably connected to the sliding seat 430 and the base 410.

[0048] In this embodiment, the elastic element 470 provides a continuous preload to the sliding seat 430, ensuring a stable sliding fit between the slider 432 and the base 410. Simultaneously, it provides damping feedback during adjustment, facilitating precise control of the sliding seat 430's displacement by the operator. Once the sliding seat 430 is adjusted to the target position, the locking element 431 secures it to the base 410, effectively preventing displacement deviations caused by vibration or external interference during processing. This ensures the fiber optic clamping fixture maintains stable and reliable positioning accuracy throughout the entire manufacturing process. This design, combining elastic preload and rigid locking, guarantees both the flexibility and convenience of adjustment while meeting the rigid requirements of high-precision positioning, significantly improving the manufacturing efficiency and finished product consistency of the fiber optic combiner.

[0049] In one embodiment of this application, the pretreatment of the transition fiber 130 includes etching it with a solution containing hydrogen fluoride on a dedicated etching fixture to etch the diameter of the transition fiber 130 to a set size.

[0050] It is understandable that the cladding of the polarization-maintaining signal fiber has two stress axes, and the fiber cannot be directly etched, otherwise it would be extremely easy to break. Therefore, this embodiment uses transition fiber 130 as an intermediate medium, which avoids the structural damage risk caused by direct etching of the polarization-maintaining signal fiber, and also enables precise control of the fiber diameter.

[0051] Specifically, using specialized wire strippers, 60-68 mm of the coating layer on the transition fiber 130 is stripped from the side closest to the first polarization-maintaining signal fiber 110, and then cleaned with a lint-free cloth dampened with analytical grade alcohol. During the etching process, the hydrogen fluoride solution concentration is controlled at 40%, and the etching time is controlled between 230 and 235 minutes, reducing the diameter of the transition fiber 130 from 400 μm to 165-170 μm. It is crucial to avoid etching the fusion splice and the first polarization-maintaining signal fiber 110.

[0052] In one embodiment of this application, the pre-tensioning of the pump fiber 120 and the transition fiber 130 includes: setting the intensity of the oxyhydrogen flame; setting the tapered length of the pump fiber 120 by adjusting the initial compression of the elastic element 470; fixing the sliding seat 430 and the base 410 with the locking element 431; fixing the pump fiber 120 and the transition fiber 130; while heating the pump fiber 120 with the oxyhydrogen flame, releasing the locking element 431, and the sliding seat 430 sliding under the elastic force of the elastic element 470, thereby realizing the tapering of the pump fiber 120 and the transition fiber 130.

[0053] In this embodiment, there is a definite correspondence between the initial compression of the elastic element 470 and the length of the tapered section. By precisely controlling the pre-compression of the elastic element 470, the length of the tapered section can be quantitatively controlled. The locking element 431 adopts a quick-release mechanism design, which can quickly release the constraint on the sliding seat 430 during the heating process, ensuring that the starting moment of the tapered section's movement is precisely synchronized with the heating position of the oxyhydrogen flame.

[0054] Specifically, first, position the two fiber clamping fixtures. Set the intensity and gas flow rate of the oxyhydrogen flame as follows: hydrogen: 120-150 SCCM; oxygen: 18-38 SCCM. Use special wire strippers to strip the 46-52 mm coating layer from the transition fiber 130 and the six pump fibers 120 at a distance of 10 cm from the port, and clean them with a lint-free cloth soaked in alcohol (analytical grade). Then, pass the transition fiber 130 through the center hole of the hollow shaft 440 of the two fiber clamping fixtures in sequence. The transition fiber 130 with the 46-52 mm coating layer removed is positioned in the center of the two fiber clamping fixtures.

[0055] Loosen the positioning screws 441 that restrict the rotation of the hollow shaft 440 and the locking pieces 431 that restrict the movement of the sliding seat 430 in the two fiber optic clamping fixtures. Press the sliders 432 of the two fiber optic clamping fixtures against the corresponding elastic pieces 470 (springs may be used). Place the six pump fibers 120 into the positioning slots 453 of the cleaned positioning block 451, and then fit the positioning block 451 into the positioning cylinder. Each fiber must be placed in its corresponding positioning slot in the two fiber optic clamping fixtures to ensure that each pump fiber 120 is horizontal. The pump fiber 120 with the 46-52mm coating stripped should be positioned in the center of the two fiber optic clamping fixtures.

[0056] Lock the positioning screws 441 and locking parts 431 of the two fiber optic clamping fixtures. Fix the first polarization-maintaining signal lines at both ends of the transition fiber 130 to the clamping platforms 420 of the two fiber optic clamping fixtures respectively. Fix the six pump fibers 120 to the clamping plates 460 of the two fiber optic clamping fixtures respectively.

[0057] Check the 46-52mm transition fiber 130 and pump fiber 120 for cleanliness. If there is dust or other dirt, clean them with high-pressure nitrogen or analytical grade alcohol. Set the taper length to 14-16mm and simultaneously taper the six pump fibers 120 and transition fibers 130, uniformly reducing the diameter of the pump fiber 120 from 220μm to 170-175μm.

[0058] In one embodiment of this application, the fiber bundle drawing includes: passing the transition fiber 130 through the hollow shaft 440 and then fixing it again; rotating the clamping plate 460 to spirally wind multiple pump fibers 120 onto the transition fiber 130 and then fixing the hollow shaft 440; setting the oxyhydrogen flame intensity and the tapered length of the fiber bundle; and synchronously tapering the transition fiber 130 and the multiple pump fibers 120.

[0059] In this embodiment, the helical winding arrangement enables the pump fiber 120 to form a stable and tightly bonded structure in the conical region, increasing the coupling contact area between the pump light and the signal light, while avoiding relative slippage between the fibers. Precise control of the oxyhydrogen flame heating ensures a smooth transition in the conical region, reducing micro-bending losses caused by temperature gradients.

[0060] Specifically, the two clamping platforms 420 that hold the fixed transition fiber 130 are loosened. The pre-stretched transition fiber 130 is pulled through the center hole of the two hollow shafts 440, so that the pre-treated 60-68mm transition fiber 130 is positioned in the center of the two fiber clamping fixtures.

[0061] Keep the transition fiber 130 straight: Secure the two clamping platforms 420 that hold the transition fiber 130 in place again. Loosen the positioning screws 441 that hold the hollow shaft 440 in place, and rotate the two clamping plates 460 so that the pump fiber 120 forms the first knot in the middle position. Continue to rotate the right clamp of the tapered machine and the pump fiber 120 clamping platform 420 to form the 6th to 8th knots, so that multiple pump fibers 120 are spirally wound around the transition fiber 130.

[0062] Secure the two positioning screws 441 and the locking piece 431. Set the intensity and gas flow rate of the hydrogen-oxygen flame for pulling the optical fiber bundle as follows: hydrogen: 100-130 SCCM; oxygen: 15-30 SCCM.

[0063] The fiber bundle tapering length is set to 16-18 mm, and the six pump fibers 120 and transition fibers 130 are simultaneously tapered and uniformly thinned to 390-400 μm to form a compact fused taper 100.

[0064] As described above, apply 18-22 mm of UVJ49 low-refractive-index adhesive to the bare fiber near the fiber stripping step to prevent the fiber from spreading, and irradiate with UV light for 60-90 seconds. Simultaneously, nitrogen gas must be blown to ensure the UVJ49 adhesive cures effectively. Do not apply adhesive within 15 mm on either side of the narrowest point of the fusion cone 100, otherwise it may burn out.

[0065] As described above, use a fiber optic cleaver to make a cut at the thinnest point of the fusion taper 100, then move the fiber optic clamping fixture to break the fusion taper 100 at its thinnest point. Release the two clamping plates 460 and the clamping stage 420. Carefully remove the longer fusion taper 100, which is the finished fiber bundle.

[0066] The method for fabricating the fiber optic combiner provided in this application also includes fiber optic bundle fusion splicing. The fabricated fiber optic bundle is fused with the second polarization-maintaining signal fiber 200 using an LSP (Laser Spinning Processing) CO2 laser welding machine under online monitoring. Before fusion splicing, the clamp holding the second polarization-maintaining signal fiber 200 on the LSP CO2 laser welding machine needs to be rotated to the optimal angle to maximize the PER (Percentage Error Rate). After fusion splicing, the following parameters must be met: IL ≤ 0.10 dB; PER ≥ 22.5 dB. If the fusion splicing parameters are not met, the end faces of the fiber optic bundle and the second polarization-maintaining signal fiber 200 need to be recut using the LSP CO2 laser welding machine and re-fused.

[0067] The method for fabricating the fiber optic combiner provided in this application also includes semi-finished product packaging and high-power pumping testing of the semi-finished product. The aforementioned packaging body 300 is used to package the fused fiber bundle and the second polarization-maintaining signal fiber 200. Then, six pump fibers 120 are connected to the output fibers of a 2000W laser with a working wavelength of 916nm, and the lasers are turned on one by one. Simultaneously, an infrared thermal imager is used to observe and record the bare fiber temperature in the taper region of the fiber bundle, the fiber stripping step temperature, the temperatures of the external pump fibers 120 and the polarization-maintaining signal fiber, and the temperature of the housing. Requirement: Temperature ≤ 60℃.

[0068] The method for preparing the fiber optic combiner provided in this application also includes high-temperature baking, cycling, and low-temperature storage tests. High-temperature baking: baking at 85℃ for 2 hours; cycling: cycling at -40℃ to +85℃ for 48 hours; low-temperature storage: storing at -40±3℃ for 24 hours.

[0069] The method for manufacturing the fiber optic combiner provided in this application also includes finished product inspection, which requires that the product appearance be normal after high-temperature baking, cycling, and low-temperature storage tests.

[0070] The method for fabricating the fiber optic combiner provided in this application also includes finished product packaging, wherein the groove of the packaging body 300 (such as...) Figure 6 Apply UVJ16 sealant to both sides of the edge, and then apply UVJ16 sealant to both sides of the matching quartz plate cover. After applying evenly, put the top cover on the tank and irradiate it back and forth with a UV gun for 50-60 seconds.

[0071] Apply an appropriate amount of UVJ47 adhesive to the root of the optical fiber at both ends of the quartz groove to make a protective cap for the optical fiber. Irradiate each cap with a UV gun for 15-20 seconds.

[0072] The method for fabricating the fiber combiner provided in this application also includes a high-power pump test of the finished product. Six finished pump fibers 120 are connected one by one to the output fiber of a 100W laser with a working wavelength of 916nm, and the pump efficiency of each pump fiber 120 is tested individually. Requirement: Pump efficiency ≥ 99%.

[0073] Connect the six finished pump fibers 120 to the output fibers of a 2000W laser with a working wavelength of 916nm, and turn on the lasers one by one. At the same time, use an infrared thermal imager to observe and record the bare fiber temperature in the fiber bundle taper area, the fiber stripping step temperature, the temperature of the pump fiber 120 and polarization-maintaining signal fiber outside the box, and the box temperature. Requirement: Temperature ≤ 60℃.

[0074] The method for fabricating the fiber optic combiner provided in this application also includes finished product performance testing. The IL, PER, and M2 of the finished product are tested using a 1μW light source with a working wavelength of 1064nm. The requirements are: IL≤0.10dB; PER≥22.5dB; M2≤1.10. Connect the polarization-maintaining signal fiber of the finished product to the output fiber of a 6000W light source with a working wavelength of 1080nm. Turn on the light source and use an infrared thermal imager to observe and record the bare fiber temperature in the fiber bundle taper area, the fiber stripping step temperature, the temperature of the external pump fiber 120 and the polarization-maintaining signal fiber, and the temperature of the housing. Requirement: Temperature ≤ 60℃. After passing the test, package the product.

[0075] In this embodiment, 10 fiber optic combiners were fabricated using the above-described preparation method, and the measured performance data are shown in Table 1.

[0076] Table 1: Measured Data of Fiber Optic Combiner

[0077] As shown in the table above, the fiber combiner fabricated using the method described in this application meets all the expected technical specifications: pump efficiency ≥ 99%; IL ≤ 0.10 dB; PER ≥ 22.5 dB; M² ≤ 1.10; signal transmission power ≥ 6000 W; single-arm pump power ≥ 2000 W. These test results fully verify the technical advantages of the fabrication method described in this application.

[0078] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. An optical fiber combiner, characterized in that, include: An optical fiber bundle includes a polarization-maintaining signal fiber assembly and multiple pump fibers; the polarization-maintaining signal fiber assembly includes a first polarization-maintaining signal fiber and a transition fiber fused together; the pump fiber includes a first portion fiber and a second portion fiber arranged sequentially, the first portion fiber having a coating layer, and the transition fiber and the second portion fiber having no coating layer; the multiple pump fibers are uniformly distributed around the polarization-maintaining signal fiber assembly, and the second portion fiber is spirally wound around the transition fiber to form a fused cone. The second polarization-maintaining signal fiber includes a first fiber segment and a second fiber segment arranged sequentially, wherein the first fiber segment is fused to the fusion taper; wherein the first fiber segment has no coating, and the second fiber segment has a coating. The package contains a fused cone located within it, with the first polarization-maintaining signal fiber and the first portion of the fiber extending from the first end of the package, and the second segment of the fiber extending from the second end of the package.

2. The fiber optic combiner as described in claim 1, characterized in that, The first end of the package is provided with a first sealing adhesive, which is used to fix the first polarization-maintaining signal fiber and the first part of the fiber to the first end of the package. The second end of the package is provided with a second sealing adhesive, which is used to fix the second optical fiber segment to the second end of the package.

3. The fiber optic combiner as described in claim 1, characterized in that, The encapsulation body contains a low-refractive-index encapsulating adhesive, which is used to fix the fused cone within the encapsulation body.

4. A method for fabricating an optical fiber combiner as described in any one of claims 1-3, characterized in that, The preparation method includes: Two first polarization-maintaining signal fibers are fused to both ends of the transition fiber. The transition fiber after the coating layer is removed is cleaned and pretreated. Part of the coating layer of the pump fiber is stripped to form the second part of the fiber, and the pump fiber is cleaned; the pump fiber and the transition fiber are fixed with a pair of fiber clamping fixtures and pre-stretched. The multiple pump fibers are spirally wound onto the transition fiber using the fiber clamping fixture. The transition fiber and the plurality of pump fibers are simultaneously tapered to form the fused taper; The fused cone breaks at its thinnest point, including the longer portion of the pigtail as an optical fiber bundle; The fiber bundle is fused to the second polarization-maintaining signal fiber; The fiber bundle and the second polarization-maintaining signal fiber are encapsulated in a package.

5. The method for fabricating an optical fiber combiner as described in claim 4, characterized in that, The fiber optic clamping fixture includes: Base A clamping stage, fixed on the base, is used to clamp the first polarization-maintaining signal fiber; A sliding seat, which is slidably connected to the base; A hollow shaft, one end of which is rotatably connected to the sliding seat; the hollow shaft is used for the passage of the transition optical fiber; A positioning sleeve is provided on the other end of the hollow shaft, and the positioning sleeve is provided with a first positioning hole for the passage of the transition optical fiber and a plurality of second positioning holes for the passage of the pump optical fiber. A clamping plate is fixedly connected to the hollow shaft and is used to clamp the pump optical fiber.

6. The method for fabricating an optical fiber combiner as described in claim 5, characterized in that, The positioning sleeve includes a positioning block and a positioning cylinder sleeved on the positioning block; the first positioning hole is provided on the positioning block; a positioning groove is provided on the outer wall of the positioning block, and the positioning groove and the positioning cylinder surround to form the second positioning hole.

7. The method for fabricating an optical fiber combiner as described in claim 5, characterized in that, The sliding seat is provided with a slider, which is slidably connected to the base; the fiber optic clamping fixture also includes an elastic element and a locking element, one end of the elastic element abuts against the limiting part on the base, and the other end of the elastic element abuts against the slider; the locking element is detachably connected to the sliding seat and the base.

8. The method for fabricating an optical fiber combiner as described in claim 5, characterized in that, The pretreatment of the transition fiber includes etching it on a special etching fixture with a solution containing hydrogen fluoride to etch the diameter of the transition fiber to a set size.

9. The method for fabricating an optical fiber combiner as described in claim 7, characterized in that, The pre-tensioning of the pump fiber and the transition fiber includes: The set intensity of the oxyhydrogen flame; The taper length of the pump fiber is set by adjusting the initial compression of the elastic element; and the sliding seat and the base are fixed by the locking element. Fix the pump fiber and the transition fiber; While the pump fiber is heated by the oxyhydrogen flame, the locking member is released, and the sliding seat slides under the elastic force of the elastic member, thereby tapering the pump fiber and the transition fiber.

10. The method for fabricating an optical fiber combiner according to any one of claims 5-9, characterized in that, The pulling of the optical fiber bundle includes: After passing the transition fiber through the hollow shaft, it is re-secured. Rotate the clamping plate to spirally wind multiple pump fibers onto the transition fiber and then fix the hollow shaft. The set oxyhydrogen flame intensity and the taper length of the fiber bundle; synchronously taper the transition fiber and the plurality of pump fibers.

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