Hollow core fiber coupler

Abstract

The application belongs to the technical field of optical fiber communication, and discloses a hollow-core fiber coupler. The hollow-core fiber coupler comprises a shell, a first plug, a first sleeve, a second plug, a second sleeve, a lens and a mounting seat. The first plug is used for connecting a solid-core optical fiber, the first sleeve is sleeved on the first plug, the first sleeve is fixedly installed in the shell, the second plug is used for connecting a hollow-core optical fiber, the diameters of the first plug and the second plug are different, the second sleeve is sleeved on the second plug, the second sleeve is fixedly installed in the shell, the lens is arranged between the first plug and the second plug, the mounting seat is installed in the shell, the lens is connected in the mounting seat, the first sleeve is inserted in one side of the mounting seat, and the second sleeve is inserted in the other side of the mounting seat. The hollow-core fiber coupler can realize efficient coupling of the solid-core optical fiber to the hollow-core optical fiber, has a compact structure, a simple assembly mode, can accurately control the position of the plug, improve the coupling precision, and can take into account the universality of standardized parts.

Description

Technical Field

[0001] This invention relates to the field of optical fiber communication technology, and in particular to a hollow optical fiber coupler. Background Technology

[0002] Hollow-core fiber (HCF) is a novel type of optical fiber that uses air or vacuum as the light transmission medium. Its core is hollow, and the optical signal is primarily transmitted within the air core. Compared to traditional solid-core silica fiber, HCF exhibits significant advantages in low delay, low nonlinearity, low dispersion, high power transmission, and transmission in specific wavelength bands. With continuous advancements in HCF manufacturing processes, it shows broad application prospects in fields such as optical fiber communication, high-energy laser transmission, and optical fiber sensing.

[0003] However, hollow-core and solid-core optical fibers differ fundamentally in mode field diameter, transmission medium, and refractive index distribution. The mode field diameter of hollow-core fibers is typically much larger than that of solid-core fibers, and the core is air. This leads to technical challenges such as severe mode field mismatch when directly splicing the two. Currently, coupling between solid-core and hollow-core optical fibers mainly employs direct fiber fusion splicing and ferrule-mounted lens coupling. Direct fiber fusion splicing involves directly fusing solid-core and hollow-core fibers together using a fusion splicer. However, due to the hollow structure of hollow-core fibers, the fiber end face is prone to collapse during splicing, resulting in a complex splicing process with high requirements for equipment and operating environment, poor reliability, and difficulty in large-scale production. Ferrule-mounted lens coupling uses a ferrule to fix the fiber, and the lens collimates and focuses the light emitted from the solid-core fiber before coupling it into the hollow-core fiber. However, the assembly accuracy of lens coupling is difficult to guarantee, the position adjustment of the ferrule is difficult, and it is difficult to accurately control the position between the fiber and the lens, resulting in low coupling accuracy and inconvenient assembly.

[0004] Therefore, there is an urgent need for a hollow fiber coupler to solve the above-mentioned technical problems. Summary of the Invention

[0005] The purpose of this invention is to provide a hollow fiber optic coupler. The hollow fiber optic coupler has a compact overall structure, simple assembly method, can accurately control the position of the first and second ferrules, improve coupling accuracy, and can also take into account the versatility of standardized parts.

[0006] To achieve this objective, the present invention adopts the following technical solution: A hollow fiber coupler is provided, comprising: shell; The first ferrule is used to connect a solid optical fiber; A first sleeve is fitted onto the first insert and is fixedly installed inside the outer casing. The second ferrule is used to connect hollow optical fibers, and the diameters of the first ferrule and the second ferrule are different. The second sleeve is fitted onto the second insert and is fixedly installed inside the outer casing; A lens is disposed between the first ferrule and the second ferrule; Mounting base, the mounting base is installed inside the housing, the lens is connected inside the mounting base, the first sleeve is inserted into one side of the mounting base, and the second sleeve is inserted into the other side of the mounting base.

[0007] Optionally, the lens is a double aspherical lens, with a first convex surface on the side of the lens facing the first ferrule and a second convex surface on the side of the lens facing the second ferrule, the curvatures of the first convex surface and the second convex surface being different.

[0008] Optionally, the lens is provided with an anti-reflective layer on both the side facing the first ferrule and the side facing the second ferrule.

[0009] Optionally, the outer casing includes an upper casing and a lower casing, which are bonded and fixed together.

[0010] Optionally, one of the upper housing and the lower housing is provided with a positioning post, and the other is provided with a positioning hole, with the positioning post inserted into the positioning hole.

[0011] Optionally, the housing is filled with potting compound, which completely fills the internal space of the housing.

[0012] Optionally, the hollow fiber coupler further includes a first crimping ring and a second crimping ring. The solid fiber is provided with a first cladding layer at the end away from the lens, and the hollow fiber is provided with a second cladding layer at the end away from the lens. The first crimping ring and the second crimping ring are both installed inside the housing. The first crimping ring is sleeved on the first cladding layer, and the second crimping ring is sleeved on the second cladding layer.

[0013] Optionally, the inner walls of both the first crimping ring and the second crimping ring are provided with anti-slip serrations.

[0014] Optionally, the hollow fiber coupler further includes a first support member and a second support member, wherein the first support member is sleeved on the solid fiber and attached to the inner wall of the first cladding layer, and the second support member is sleeved on the hollow fiber and attached to the inner wall of the second cladding layer.

[0015] Optionally, the hollow fiber coupler further includes a first tail sleeve and a second tail sleeve, wherein the first tail sleeve is fitted onto the first cladding layer and is sealed to the first cladding layer and the outer shell, and the second tail sleeve is fitted onto the second cladding layer and is sealed to the second cladding layer and the outer shell.

[0016] The beneficial effects of this invention are: This invention provides a hollow-core fiber coupler, comprising a housing, a first ferrule, a first sleeve, a second ferrule, a second sleeve, a lens, and a mounting base. The first ferrule connects to a solid-core fiber. The first sleeve is fitted onto the first ferrule and fixedly installed within the housing. The second ferrule connects to a hollow-core fiber. The first and second ferrules have different diameters. The second sleeve is fitted onto the second ferrule and fixedly installed within the housing. The lens is positioned between the first and second ferrules. The mounting base is installed within the housing, and the lens is connected to the mounting base. The first sleeve is inserted into one side of the mounting base, and the second sleeve is inserted into the other side. This invention secures the solid-core fiber with the first ferrule and the hollow-core fiber with the second ferrule. The lens positioned between the first and second ferrules enables efficient beam collimation and focusing from the solid-core fiber to the hollow-core fiber. The different diameters of the first and second ferrules allow for a compact overall design while ensuring sufficient space for lens installation. By providing a first and second sleeve, the installation and fixation of the first and second ferrules are facilitated. The radial position of the first and second ferrules along the outer shell is limited, and the first and second sleeves support multiple insertions and removals of the ferrules, facilitating adjustment of their axial position along the outer shell. This results in high positioning accuracy, stable coupling performance, and ease of installation and debugging, thereby precisely controlling the position between the hollow-core fiber, the solid-core fiber, and the lens. The mounting base facilitates lens installation. The first sleeve is inserted into one side of the mounting base, and the second sleeve into the other side, facilitating the installation of both sleeves and improving their positioning accuracy. This invention's hollow-core fiber coupler achieves efficient coupling from solid-core fiber to hollow-core fiber, and features a compact structure, easy assembly, and high coupling accuracy. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the hollow fiber coupler, the first cladding layer, and the second cladding layer provided in the embodiment of the present invention; Figure 2 This is a cross-sectional view of the hollow fiber coupler, the first cladding layer, and the second cladding layer provided in the embodiments of the present invention; Figure 3 This is a cross-sectional view of the hollow fiber coupler provided in an embodiment of the present invention; Figure 4 This is a cross-sectional view of the hollow fiber coupler (without a shell) provided in an embodiment of the present invention; Figure 5 This is a schematic diagram of the upper shell structure involved in the embodiment of the present invention; Figure 6 This is a schematic diagram of the mounting base involved in the embodiments of the present invention.

[0018] In the picture: 1. Outer shell; 101. Upper shell; 102. Lower shell; 103. Positioning pin; 104. Mounting groove; 2. First insert; 3. First sleeve; 4. Second insert; 5. Second sleeve; 6. Lens; 7. Mounting base; 71. Stepped hole; 8. First crimping ring; 9. Second crimping ring; 10. First support member; 11. Second support member; 12. First tail sleeve; 13. Second tail sleeve; 100, First coating layer; 200, Second coating layer. Detailed Implementation

[0019] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar components or components having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0020] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection or a detachable connection; a mechanical connection or an electrical connection; a direct connection or an indirect connection through an intermediate medium; or the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0021] In the description of this invention, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0022] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0023] like Figures 1 to 6As shown, this embodiment provides a hollow fiber coupler, which includes a housing 1, a first ferrule 2, a first sleeve 3, a second ferrule 4, a second sleeve 5, a lens 6, and a mounting base 7. The first ferrule 2 is used to connect solid fiber. The first sleeve 3 is fitted onto the first ferrule 2 and fixedly installed inside the housing 1. The second ferrule 4 is used to connect hollow fiber. The diameters of the first ferrule 2 and the second ferrule 4 are different. The second sleeve 5 is fitted onto the second ferrule 4 and fixedly installed inside the housing 1. The lens 6 is disposed between the first ferrule 2 and the second ferrule 4. The mounting base 7 is installed inside the housing 1, and the lens 6 is connected to the mounting base 7. The first sleeve 3 is inserted into one side of the mounting base 7, and the second sleeve 5 is inserted into the other side of the mounting base 7. In this embodiment, the solid fiber is fixed by the first ferrule 2, and the hollow fiber is fixed by the second ferrule 4. The lens 6, placed between the first ferrule 2 and the second ferrule 4, enables efficient beam collimation and focusing from the solid fiber to the hollow fiber. The first ferrule 2 and the second ferrule 4 have different diameters, achieving a compact overall structure while ensuring sufficient installation space for the lens 6. The first sleeve 3 and the second sleeve 5 facilitate the installation and fixation of the first ferrule 2 and the second ferrule 4, restricting their radial position along the outer shell 1. The first sleeve 3 and the second sleeve 5 support multiple insertions and removals of the first ferrule 2 and the second ferrule 4, facilitating adjustment of their axial position along the outer shell 1. This results in high positioning accuracy, stable coupling performance, and ease of installation and debugging, thereby precisely controlling the position of the hollow fiber and solid fiber relative to the lens 6. The mounting base 7 facilitates the installation of the lens 6. The first sleeve 3 is inserted into one side of the mounting base 7, and the second sleeve 5 is inserted into the other side, facilitating the installation of both sleeves and improving positioning accuracy. This embodiment of the hollow fiber coupler achieves efficient coupling from solid fiber to hollow fiber, with a compact structure, easy assembly, and high coupling accuracy.

[0024] Specifically, the first insert 2 is a 2.5mm ceramic insert. The second insert 4 is a 1.25mm ceramic insert. The first sleeve 3 is a 2.5mm ceramic sleeve, and the second sleeve 5 is a 1.25mm ceramic sleeve. With this configuration, the first insert 2, the second insert 4, the first sleeve 3, and the second sleeve 5 are all standard parts, eliminating the need for custom-made parts of special dimensions, significantly reducing procurement costs and production cycles, and facilitating mass production. The elastic contact between the ceramic insert and the ceramic sleeve avoids alignment deviations caused by adhesive curing stress and temperature expansion mismatch, improving assembly accuracy and reliability. The mounting base 7 is provided with a stepped hole 71 extending axially along the outer shell 1. The lens 6 is bonded to the inner wall of the stepped hole 71 by dispensing adhesive. The diameter of the stepped hole 71 matches the outer diameter of the first sleeve 3 and the second sleeve 5, and both the first sleeve 3 and the second sleeve 5 are inserted into the stepped hole 71.

[0025] Optionally, lens 6 is a double aspherical lens, meaning that both the side of lens 6 facing the first ferrule 2 and the side facing the second ferrule 4 are aspherical. The side of lens 6 facing the first ferrule 2 is a first convex surface, whose main function is to collimate the diverging beam emitted from the solid fiber into parallel light; the side of lens 6 facing the second ferrule 4 is a second convex surface. The curvatures of the first and second convex surfaces are different, and the main function of the second convex surface is to focus the parallel light into the hollow fiber. The double aspherical lens has a mature optical design and controllable surface accuracy, which can effectively reduce wavefront aberrations, substantially improve coupling efficiency, and achieve high-efficiency, low-aberration mode-field conversion between hollow and solid fibers.

[0026] Specifically, lens 6 is circular. Lens 6 is made of K-VC80 optical glass with a refractive index n=1.6708@1550nm and an Abbe number Vd=53.1. Lens 6 has a diameter of 2.5mm, a center thickness of 1.0mm, and an edge thickness of 0.6mm. In this embodiment, the distance between the ends of the first ferrule 2 and the second ferrule 4 that are furthest from each other is 4.77mm. The distance between the curved surface of lens 6 facing the first ferrule 2 and the end face of the solid fiber is 2.706mm. The distance between the curved surface of lens 6 facing the second ferrule 4 and the end face of the hollow fiber is 1.065mm.

[0027] Optionally, the lens 6 has a first radius of curvature on the side facing the first ferrule 2 and a second radius of curvature on the side facing the second ferrule 4, and the first and second radii of curvature are not equal. This configuration optimizes the two end faces of the aspherical lens for the different mode field characteristics of hollow and solid optical fibers, respectively. It achieves sufficient beam collimation on the solid fiber side and precise beam focusing on the hollow fiber side, effectively suppressing higher-order modes excited by mode field mismatch, improving the fundamental mode coupling ratio, and enhancing the quality of the transmitted beam.

[0028] Specifically, the first radius of curvature R1 = 1.272 mm, and the second radius of curvature R2 = 0.972 mm. The ratio of the first radius of curvature R1 to the second radius of curvature R2 is approximately 1:3.34. Through optimized design, lens 6 achieves the best aberration correction effect within a limited center thickness. The side of lens 6 facing the first ferrule 2 is ellipsoidal with an aspherical coefficient K1 = -0.52, mainly used to correct spherical aberration, ensuring that light rays from different incident heights can be focused to the same position. The side of lens 6 facing the second ferrule 4 is curved with an aspherical coefficient K2 = -1.18, mainly used to correct coma and astigmatism, ensuring the uniformity of the focused spot throughout the mode field of the hollow fiber. Through the synergistic effect of the aspherical surfaces on both sides of lens 6, near-diffraction-limited imaging quality is achieved.

[0029] Lens 6 in this embodiment has the following properties across the entire 1525-1565nm wavelength range: Wavefront RMS error: less than 0.02λ (λ=1550nm), much smaller than that of a spherical lens, and close to the diffraction limit; Peak coupling efficiency: greater than 95.5% (insertion loss <0.2dB); average coupling efficiency: greater than 94% (insertion loss <0.27dB), with relatively low loss; Focused spot diameter: 28μm, with high uniformity of focused spot; The working distance, which is the distance between the curved surface of lens 6 facing the second ferrule 4 and the end face of the hollow fiber, is 1.065mm, and the alignment tolerance is relatively high.

[0030] Optionally, anti-reflection layers are provided on both the side of lens 6 facing the first insert 2 and the side facing the second insert 4. The anti-reflection layers effectively reduce Fresnel reflection loss and improve return loss of lens 6. Specifically, the anti-reflection layer is a broadband anti-reflection film of SiO2 or TiO2, with a reflectivity of <0.2% in the 1525-1565nm wavelength range. The anti-reflection film is deposited on the surface of lens 6 using ion beam assisted deposition (IAD). Ion beam assisted deposition results in better film density, stronger adhesion, and excellent environmental stability.

[0031] Optionally, such as Figures 2 to 5 As shown, the outer casing 1 includes an upper casing 101 and a lower casing 102, which are bonded together. This arrangement facilitates the installation of the first insert 2, the first sleeve 3, the second insert 4, the second sleeve 5, the lens 6, and the mounting base 7, enabling semi-automated or fully automated production, improving assembly efficiency, and reducing production costs. Specifically, mounting grooves 104 are provided at corresponding positions on the inner walls of the upper casing 101 and the lower casing 102, and the mounting base 7 is installed in the mounting grooves 104 for easy positioning. The upper casing 101 and the lower casing 102 are bonded together.

[0032] Optionally, one of the upper housing 101 and the lower housing 102 is provided with a positioning post 103, and the other is provided with a positioning hole, with the positioning post 103 inserted into the positioning hole. By providing the positioning post 103 and the positioning hole, the assembly of the upper housing 101 and the lower housing 102 is facilitated, ensuring the assembly accuracy of the upper housing 101 and the lower housing 102. Specifically, the upper housing 101 is provided with a positioning post 103, and the lower housing 102 is provided with a positioning hole; at least two positioning posts 103 and positioning holes are provided, and they correspond one-to-one. The diameter of the positioning post 103 is 2mm, and the positioning post 103 and the positioning hole adopt an H7 / g6 fit, ensuring that the coaxiality of the positioning post 103 and the positioning hole is <1μm. The outer shell 1 is made of stainless steel and precision ground, with a surface roughness Ra <0.4μm. The positioning post 103 and the upper housing 101 can be fixed by welding or insertion. In other embodiments, the outer shell 1 can also be manufactured using 3D printing technology. In other embodiments, the outer shell 1 may also be made of plastic by injection molding or 3D printing.

[0033] Optionally, the housing 1 is filled with potting compound, which completely fills the internal space of the housing 1. Filling with potting compound improves the sealing performance of the housing 1, effectively preventing moisture intrusion. It is suitable for various harsh environments. Furthermore, the encapsulation effect of the potting compound enhances the vibration and shock resistance of the optical components inside the housing 1. Specifically, a vacuum potting process is used inside the housing 1, injecting low-stress epoxy resin in a vacuum environment to ensure that the resin completely fills all gaps without air bubbles. The hollow fiber optic coupler of this embodiment achieves an IP protection rating of IP67. It exhibits stable and reliable performance within a wide temperature range of -40℃ to +85℃. Optionally, the hollow fiber coupler further includes a first crimp ring 8 and a second crimp ring 9. A first cladding layer 100 is provided at the end of the solid fiber furthest from the lens 6, and a second cladding layer 200 is provided at the end of the hollow fiber furthest from the lens 6. Both the first crimp ring 8 and the second crimp ring 9 are installed inside the housing 1, with the first crimp ring 8 fitted onto the first cladding layer 100 and the second crimp ring 9 fitted onto the second cladding layer 200. The first crimp ring 8 and the second crimp ring 9 can fix the first cladding layer 100 and the second cladding layer 200, thereby improving the tensile strength and service life of the solid and hollow fibers.

[0034] Specifically, the first cladding layer 100 and the second cladding layer 200 are the outer sheaths of solid-core optical fiber and hollow-core optical fiber, respectively. Both the first crimping ring 8 and the second crimping ring 9 are cylindrical structures. The length of both the first crimping ring 8 and the second crimping ring 9 is 6 mm. Both the first crimping ring 8 and the second crimping ring 9 are made of metal. In this embodiment, the first crimping ring 8 and the second crimping ring 9 are made of copper alloy, and their surfaces are nickel-plated. The inner diameters of the first crimping ring 8 and the second crimping ring 9 are slightly larger than the outer diameters of the first cladding layer 100 and the second cladding layer 200, respectively; that is, the first crimping ring 8 and the first cladding layer 100 are in a clearance fit, and the second crimping ring 9 and the second cladding layer 200 are also in a clearance fit. The first crimping ring 8 and the second crimping ring 9 are then pressed and fixed together using a crimping device. The crimping device is a mature technology in this field and will not be described in detail here.

[0035] Optionally, the inner walls of both the first crimping ring 8 and the second crimping ring 9 are provided with anti-slip serrations. The anti-slip serrations can increase the friction between the first and second crimping rings 8 and 9 and the first and second covering layers 100 and 200, thereby increasing the fixing strength of the first and second covering layers 100 and 200. Specifically, the anti-slip serrations are diamond-shaped knurled textures with a depth of 0.1 mm. After crimping, the knurled teeth are embedded in the first and second covering layers 100 and 200, increasing friction. Compared to smooth first and second crimping rings 8 and 9, the pull-out force can be increased by more than 20%. In other embodiments, the shape and depth of the anti-slip serrations are set according to specific circumstances and are not limited to this embodiment.

[0036] Optionally, the hollow fiber coupler further includes a first support member 10 and a second support member 11. The first support member 10 is sleeved on the solid fiber and adheres to the inner wall of the first cladding layer 100, and the second support member 11 is sleeved on the hollow fiber and adheres to the inner wall of the second cladding layer 200. By providing the first support member 10 and the second support member 11, the solid fiber and the hollow fiber can be fixed. Furthermore, when the first crimping ring 8 and the second crimping ring 9 are tightened, the first support member 10 and the second support member 11 can support the solid fiber and the hollow fiber, and protect them from damage when the first cladding layer 100 and the second cladding layer 200 are bent.

[0037] Specifically, both the first support member 10 and the second support member 11 are made of stainless steel. The first support member 10 is interference-fitted with the inner wall of the first cladding layer 100, meaning the outer diameter of the first support member 10 is slightly larger than the inner diameter of the first cladding layer 100, and the first support member 10 abuts the first cladding layer 100 against the inner wall of the first crimping ring 8. The second support member 11 is interference-fitted with the inner wall of the second cladding layer 200, meaning the outer diameter of the second support member 11 is slightly larger than the inner diameter of the second cladding layer 200, and the second support member 11 abuts the second cladding layer 200 against the inner wall of the second crimping ring 9, thereby improving the fixing strength of the first cladding layer 100, the second cladding layer 200, the solid optical fiber, and the hollow optical fiber. The first support member 10 and the second support member 11 are covered with a nitrile rubber layer. The thickness of the nitrile rubber layer is 0.2 mm. The nitrile rubber layer increases the friction between the first support member 10 and the second support member 11 and the first covering layer 100 and the second covering layer 200, thereby improving the fixing strength. Limiting edges are provided at the ends of the first support member 10 and the second support member 11 away from the second pressing ring 9, respectively. These limiting edges abut against the ends of the first pressing ring 8 and the second pressing ring 9, thereby restricting the axial position of the first support member 10 and the second support member 11.

[0038] Optionally, the hollow fiber coupler further includes a first tail sleeve 12 and a second tail sleeve 13. The first tail sleeve 12 is fitted onto the first cladding layer 100 and is sealed to the first cladding layer 100 and the outer shell 1. The second tail sleeve 13 is fitted onto the second cladding layer 200 and is sealed to the second cladding layer 200 and the outer shell 1. By providing the first tail sleeve 12 and the second tail sleeve 13, the sealing performance of the outer shell 1 can be further improved. The multiple fixing structure of the first crimping ring 8, the second crimping ring 9, the first support member 10, the second support member 11, the first tail sleeve 12, and the second tail sleeve 13 enables the pull-out force of the first cladding layer 100 and the second cladding layer 200 to reach more than 100N, effectively preventing the first cladding layer 100 and the second cladding layer 200 from loosening or falling off during construction and use.

[0039] Specifically, both the first tail sleeve 12 and the second tail sleeve 13 are made of rubber material, which can release stress. The first tail sleeve 12 is bonded and fixed to the first covering layer 100 and the shell, and the second tail sleeve 13 is bonded and fixed to the second covering layer 200 and the outer shell 1.

[0040] like Figures 1 to 6 As shown, the assembly steps of the hollow fiber coupler in this embodiment are as follows: The first step is to insert the solid optical fiber into the first ferrule 2, fix it with glue, and grind the end face of the solid optical fiber; then insert the cut hollow optical fiber into the second ferrule 4 and fix it with glue. The second step is to install the lens 6 into the stepped hole 71 and fix it with glue; insert the first sleeve 3 and the second sleeve 5 into the stepped hole 71 from both sides of the mounting base 7 respectively. The third step is to place the mounting base 7 into the mounting groove 104 of the lower housing 102; Fourth step, insert the first ferrule 2 and the second ferrule 4 into the first sleeve 3 and the second sleeve 5 respectively, and adjust the first ferrule 2 and the second ferrule 4 along the axial direction to a suitable position to maximize the coupling efficiency; Fifth step, install the first support member 10 and the second support member 11, and then install the first crimping ring 8 and the second crimping ring 9; Step 6: Insert the positioning pin 103 of the upper housing 101 into the corresponding positioning hole, cover the upper housing 101, and fix the upper housing 101 and the lower housing 102 by dispensing glue. Step 7: Vacuum potting adhesive into the inside of the outer casing 1 and allow it to cure; Step 8: Assemble the first tail sleeve 12 and the second tail sleeve 13 to complete the overall assembly.

[0041] The working principle of the hollow-core fiber coupler in this embodiment is as follows: A diverging beam emitted from a solid-core fiber is collimated into parallel light by the incident surface of lens 6, and then focused by the exit surface of lens 6 to form a focused spot matching the mode field diameter of the hollow-core fiber, which is then coupled into the hollow-core fiber. Conversely, a large-mode-field beam emitted from a hollow-core fiber is focused by lens 6 and then coupled into the solid-core fiber. Through the synergistic optimization of lens 6, low-loss, high-reliability coupling between the solid-core and hollow-core fibers is achieved.

[0042] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A hollow-core optical fiber coupler, characterized in that, include: Outer shell (1); The first ferrule (2) is used to connect a solid optical fiber; The first sleeve (3) is sleeved on the first insert (2) and the first sleeve (3) is fixedly installed inside the outer shell (1); The second ferrule (4) is used to connect hollow optical fibers. The diameters of the first ferrule (2) and the second ferrule (4) are different. The second sleeve (5) is fitted onto the second insert (4) and is fixedly installed inside the outer shell (1); Lens (6), the lens (6) being disposed between the first insert (2) and the second insert (4); Mounting base (7), which is installed inside the housing (1), and the lens (6) is connected inside the mounting base (7). The first sleeve (3) is inserted into one side of the mounting base (7), and the second sleeve (5) is inserted into the other side of the mounting base (7).

2. The hollow-core fiber coupler according to claim 1, characterized in that, The lens (6) is a double aspherical lens. The side of the lens (6) facing the first insert (2) is a first convex surface, and the side of the lens (6) facing the second insert (4) is a second convex surface. The curvatures of the first convex surface and the second convex surface are different.

3. The hollow-core fiber coupler according to claim 1, characterized in that, The lens (6) is provided with an anti-reflective layer on both the side facing the first ferrule (2) and the side facing the second ferrule (4).

4. The hollow-core fiber coupler according to claim 1, characterized in that, The outer shell (1) includes an upper shell (101) and a lower shell (102), which are bonded and fixed together.

5. The hollow fiber coupler according to claim 4, characterized in that, The upper housing (101) and the lower housing (102) are provided with a positioning post (103) in one and a positioning hole in the other, with the positioning post (103) inserted into the positioning hole.

6. The hollow-core fiber coupler according to claim 4, characterized in that, The outer shell (1) is filled with potting compound, which completely fills the internal space of the outer shell (1).

7. The hollow-core fiber coupler according to claim 1, characterized in that, The hollow fiber coupler further includes a first crimping ring (8) and a second crimping ring (9). The solid fiber is provided with a first cladding layer (100) at the end away from the lens (6), and the hollow fiber is provided with a second cladding layer (200) at the end away from the lens (6). The first crimping ring (8) and the second crimping ring (9) are both installed inside the housing (1). The first crimping ring (8) is sleeved on the first cladding layer (100), and the second crimping ring (9) is sleeved on the second cladding layer (200).

8. The hollow fiber coupler according to claim 7, characterized in that, The inner walls of the first crimping ring (8) and the second crimping ring (9) are provided with anti-slip teeth.

9. The hollow-core fiber coupler according to claim 7, characterized in that, The hollow fiber coupler further includes a first support member (10) and a second support member (11). The first support member (10) is sleeved on the solid fiber and attached to the inner wall of the first cladding layer (100). The second support member (11) is sleeved on the hollow fiber and attached to the inner wall of the second cladding layer (200).

10. The hollow-core fiber coupler according to claim 9, characterized in that, The hollow fiber coupler further includes a first tail sleeve (12) and a second tail sleeve (13). The first tail sleeve (12) is fitted onto the first cladding layer (100) and is sealed to the first cladding layer (100) and the outer shell (1). The second tail sleeve (13) is fitted onto the second cladding layer (200) and is sealed to the second cladding layer (200) and the outer shell (1).

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