Hollow core fiber connector

Abstract

This invention discloses a hollow-core fiber optic connector and an optical connection system. The connector includes a standard communication fiber optic connector shell and an internal coupling structure. The coupling structure includes a solid-core fiber unit, a hollow-core fiber unit, a first sleeve, a second sleeve, and a third sleeve. The coupling end face of the solid-core fiber unit is beveled; the coupling end face of the hollow-core fiber unit is either flat or beveled; the axes of the two units are coplanar and directly coupled at a certain angle. This invention uses a standard shell, and its external dimensions are completely consistent with existing standard connectors, achieving physical compatibility and plug-and-play functionality with existing solid-core fiber optic connectors. Through a specific bevel angle and angled coupling design, combined with thermal expansion core mode field matching and end face coating technology, a hollow-core fiber optic connector with low insertion loss and high return loss is achieved. The absence of lenses and bridging fibers, simple structure, and low cost facilitate the large-scale application of hollow-core fibers in existing communication networks.

Description

Technical Field

[0001] This invention relates to the field of optical fiber communication technology, and in particular to a hollow optical fiber connector, which is suitable for the large-scale application of hollow optical fibers in existing communication networks. Background Technology

[0002] Hollow-core optical fiber, with its excellent characteristics such as low loss, low nonlinearity, and low latency, has become a research hotspot in the field of next-generation optical communication. However, for hollow-core optical fiber to achieve large-scale application, the compatibility issue between it and existing large and mature optical communication systems based on solid-core optical fiber must be resolved.

[0003] In the prior art, various hollow fiber connection schemes have been proposed. For example, Chinese patent application CN120335088A discloses a fiber optic expander contact and a hollow fiber optic connector, which expands and collimates the light output from the hollow fiber by placing a light transmission medium (such as a lens) with focusing function in front of the hollow fiber before output. Although this scheme can achieve efficient coupling, it introduces an additional lens element, resulting in a complex structure and higher manufacturing difficulty and cost.

[0004] Chinese patent application CN202410587599 discloses a coupling method for mode field matching by fusion splicing "bridge fibers". Although this method can achieve low-loss coupling, it introduces additional bridge fiber structures and fusion splicing processes, which increases the process flow, manufacturing costs and assembly difficulty, and is not conducive to rapid and low-cost mass production.

[0005] In addition, most existing hollow fiber optic connectors add an extra coupling device to the rear end of the standard housing, which increases the size of the connector and makes it difficult to promote its application in high-density connector scenarios such as data center server rooms. Summary of the Invention

[0006] In view of this, the present invention addresses the shortcomings of the prior art by providing a highly compatible direct-coupled hollow fiber optic connector, which aims to simplify the structure, reduce costs, improve compatibility with existing systems, and ensure excellent optical performance.

[0007] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a hollow fiber optic connector, comprising: a connector housing and a coupling structure fixedly installed therein; the coupling structure includes a solid fiber unit and a hollow fiber unit. The outer end face of the solid fiber unit is a communication standard PC, UPC, or APC end face; the coupling end face of the solid fiber unit is an inclined plane with an angle of a first specific angle θ. aThe coupling end face of the hollow fiber unit is a plane or an inclined plane; the axis of the solid fiber unit is coplanar with the axis of the hollow fiber unit, and the angle between them is a second specific angle θ. b The coupling end face of the solid fiber unit is directly coupled to the coupling end face of the hollow fiber unit.

[0008] Furthermore, the solid fiber unit includes a metal tailstock, a solid fiber ferrule, and a solid fiber. The solid fiber ferrule is inserted into the metal tailstock and pressed and fixed as a single unit. The solid fiber is inserted into the solid fiber ferrule and glued to it. The end face of the solid fiber is flush with that of the solid fiber ferrule. The hollow fiber unit includes a hollow fiber ferrule and a hollow fiber. The hollow fiber is inserted into the hollow fiber ferrule and glued to it. The coupling end face of the hollow fiber is flush with or extends beyond the coupling end face of the hollow fiber ferrule.

[0009] Furthermore, the connector also includes a first sleeve, a second sleeve, and a third sleeve; the first sleeve is fitted onto the coupling end of the solid fiber unit and glued to it as a whole; the second sleeve is fitted onto the coupling end of the hollow fiber unit and glued to it as a whole; the end faces of the first sleeve and the second sleeve are glued to each other as a whole; the third sleeve is fitted onto the outside of both the first sleeve and the second sleeve and glued to them as a whole.

[0010] Furthermore, the connector housing is a standard fiber optic connector housing in the communications industry, which has standard structural dimensions and includes LC, FC, SC or ST types.

[0011] Furthermore, according to Snell's law: n1sinθ1= n2sinθ2 (θ1 is the refractive index of the incident medium, θ2 is the refractive index of the refracting medium, θ1 is the angle of incidence, and θ2 is the angle of refraction.) The first specific angle θ is derived. a With the second specific angle θ b Satisfying the relation: n core sinθ a =sin(θ a +θ b ), where n core The refractive index of the solid fiber core is given; and the first specific angle θ is given. a The value range is from 3° to 10°, and the second specific angle θ b The value ranges from 1.35° to 4.6°.

[0012] Furthermore, the solid fiber ferrule is a one-piece long ferrule, or is composed of at least two ferrule segments coaxially combined.

[0013] Furthermore, one side of the coupling end of the solid fiber undergoes thermal expansion treatment, and its mode field diameter matches that of the hollow fiber.

[0014] Furthermore, the coupling end face of the solid optical fiber, after thermal expansion treatment, is coated with an antireflection film.

[0015] Furthermore, the solid fiber ferrule has the same outer diameter as the hollow fiber ferrule; the solid fiber ferrule and the hollow fiber ferrule are fiber ceramic ferrules or fiber metal ferrules.

[0016] Furthermore, the first sleeve and the second sleeve have the same outer diameter; the first sleeve, the second sleeve, and the third sleeve are ceramic tubes, glass tubes, or metal tubes.

[0017] In addition, the present invention also provides a variety of optical connection systems based on the hollow fiber connector.

[0018] An optical connection system includes a first optical fiber connector, an adapter, and a second optical fiber connector; at least one of the first and second optical fiber connectors is a hollow optical fiber connector as described in any of the above technical solutions; the adapter includes a sleeve for fixing the solid optical fiber ferrule of the first optical fiber connector and the ferrule of the second optical fiber connector, so that the solid optical fiber in the first optical fiber connector and the solid optical fiber in the second optical fiber connector are coaxially aligned.

[0019] An optical connection system includes an optical module, an adapter, and a third fiber optic connector; the third fiber optic connector is a hollow fiber optic connector as described in any of the above technical solutions; the optical module includes a module ferrule and a module fiber, the module fiber being at least partially disposed in the inner hole of the module ferrule, and the module fiber being a solid fiber; the adapter includes a sleeve for fixing the module ferrule and the solid fiber ferrule of the third fiber optic connector, so that the module fiber and the solid fiber in the third fiber optic connector are coaxially aligned.

[0020] An optical connection system includes a first optical module, a second optical module, and an optical fiber cable; the two ends of the optical fiber cable are a fourth optical fiber connector and a fifth optical fiber connector, respectively; the fourth optical fiber connector and the fifth optical fiber connector are both hollow-core optical fiber connectors as described in any of the above technical solutions; one end of the optical fiber cable is optically connected to the fourth optical module, and the other end of the optical fiber cable is optically connected to the fifth optical module; the optical fiber cable includes at least one hollow-core optical fiber.

[0021] An optical connection system includes an optical module and a sixth optical fiber connector, wherein the sixth optical fiber connector is a hollow optical fiber connector as described in any of the above technical solutions; the sixth optical fiber connector is connected to the optical interface of the optical module, the optical module has an optical chip disposed inside, and the optical chip is optically coupled to the optical fiber connector. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of a hollow fiber optic connector provided by the present invention.

[0023] Figure 2 A schematic diagram of a coupling structure provided by the present invention; Figure 3 This is a schematic diagram of a first optical connection combination of an optical connection system provided in Embodiment 2 of the present invention; Figure 4 This is a schematic diagram of a second optical connection combination of an optical connection system provided in Embodiment 3 of the present invention; Figure 5 This is a schematic diagram of a third optical connection combination of an optical connection system provided in Embodiment 4 of the present invention; Figure 6 This is a schematic diagram of the fourth optical connection combination of an optical connection system provided in Embodiment 5 of the present invention; Explanation of reference numerals in the attached diagram: To make the differences between the present invention and the prior art clearer, the reference numerals in the accompanying drawings of the present invention will be described below: Figure 1-2 The attached figures are labeled as follows: 100, connector housing; 200, coupling structure; 210, solid fiber unit; 220, hollow fiber unit; 211, solid fiber ferrule; 212, solid fiber; 213, metal tailstock; 221, hollow fiber ferrule; 222, hollow fiber; 231, first sleeve; 232, second sleeve; 233, third sleeve; θ a θ is the angle of the bevel at the coupling end of the solid fiber unit. b The angle between the axis of the solid fiber unit and the axis of the hollow fiber unit.

[0024] Figure 3 The attached figures are labeled as follows: 301, first fiber optic connector; 302, adapter; 303, second fiber optic connector.

[0025] Figure 4 The attached diagram is labeled as follows: 401, optical module; 402, module ferrule; 403, adapter; 404, third fiber optic connector.

[0026] Figure 5The attached diagram is labeled as follows: 501, first optical module; 502, fourth optical fiber connector; 503, optical fiber cable; 504, fifth optical fiber connector; 505, second optical module.

[0027] Figure 6 The attached diagram is labeled as follows: 601, optical module; 602, sixth fiber optic connector; 603, optical chip. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it.

[0029] It should be noted that the "connector housing" mentioned in this invention refers to a conventional fiber optic connector housing assembly in the art, which typically includes standard components such as the housing body, springs, stoppers, and tail sleeves. The specific structure, connection method, and function of these components are common knowledge in the art, and for the sake of brevity, they are collectively referred to as "connector housing". The core improvement of this invention lies in the coupling structure, which can be assembled into any fiber optic connector housing assembly that conforms to communication industry standards.

[0030] A type of hollow fiber optic connector, such as Figure 1 As shown: The hollow fiber optic connector includes a connector housing 100 and a coupling structure 200 fixedly installed within it. The coupling structure 200 mainly includes a solid fiber unit 210 and a hollow fiber unit 220. The solid fiber unit 210 is used to mate with an external standard fiber optic connector or optical module, and the hollow fiber unit 220 is used to connect with a hollow fiber optic cable. The two are directly coupled inside the connector to achieve optical signal transmission.

[0031] Specifically, the solid fiber unit 210 includes a metal tailstock 213, a solid fiber ferrule 211, and a solid fiber 212. The solid fiber ferrule 211 is cylindrical and inserts into the central hole of the metal tailstock 213, and is fixed together by compression. The solid fiber 212 inserts into the central micro-hole of the solid fiber ferrule 211 and is fixed with adhesive. The outer end of the solid fiber ferrule 211 and the corresponding end face of the solid fiber ferrule 212 are polished, making their end faces flush and forming a PC, UPC, or APC end face according to communication standards.

[0032] The hollow fiber unit 220 includes a hollow fiber ferrule 221 and a hollow fiber 222. The coupling end of the hollow fiber 222 is cut flat and inserted into the central micro-hole of the hollow fiber ferrule 221, and then fixed with adhesive. The coupling end face of the hollow fiber 222 can be inserted until it is flush with the end face of the hollow fiber ferrule 221, or slightly protrude from the end face of the hollow fiber ferrule 221.

[0033] To achieve precise alignment and fixation between the solid fiber 212 and the hollow fiber 222, this invention also incorporates a multi-stage sleeve structure. Specifically, it includes a first sleeve 231, a second sleeve 232, and a third sleeve 233. The first sleeve 231 is fitted onto the outside of the coupling end of the solid fiber unit 210 and fixed together with adhesive. The second sleeve 232 is fitted onto the outside of the coupling end of the hollow fiber unit 220 and fixed together with adhesive. The end faces of the first sleeve 231 and the second sleeve 232 are mated together and fixed with adhesive, achieving an initial connection between the solid fiber unit 210 and the hollow fiber unit 220. Then, the third sleeve 233 is fitted onto the outside of both the first sleeve 231 and the second sleeve 232, covering their mating area and fixed with adhesive, further enhancing the connection strength and alignment stability.

[0034] like Figure 2 As shown: The coupling end face of the solid fiber 212 is ground into a bevel, with a tilt angle of a first specific angle θ. a The coupling end face of the hollow fiber 222 is planar and perpendicular to its axis. The axis of the solid fiber 212 is coplanar with the axis of the hollow fiber 222, and the two are at a second specific angle θ. b That is, the axis of the solid fiber 212 is tilted by θ relative to the axis of the hollow fiber 222. b Angle. The two end faces are directly coupled, with an air gap in between. The first specific angle θ. a The value range is from 3° to 10°, and the second specific angle θ b The value ranges from 1.35° to 4.6°.

[0035] To reduce coupling loss, the first specific angle θ a With the second specific angle θ b Certain relationships need to be satisfied. According to the law of refraction of light beams in inclined planes and air gaps, when the following relationship is satisfied, the principal ray of the light beam emitted from the solid fiber 212, after being refracted by the inclined plane, can enter the core (i.e., the air core) of the hollow fiber 222 in a direction parallel to the axis of the hollow fiber 222: n core sinθ a = sin(θ a +θ b ), n core is the refractive index of the solid fiber core.

[0036] To reduce coupling loss, the coupling end of the solid fiber 212 can be thermally expanded to match the mode field diameter of the hollow fiber 222. To further reduce coupling loss, an antireflection coating can be deposited on the beveled surface of the coupling end of the solid fiber 212.

[0037] Example 1: Example 1 provides a standard LC-type hollow fiber optic connector for communication, see [link / reference]. Figure 1 , Figure 2 The connector housing 100 adopts a communication standard LC connector housing; the solid fiber ferrule 211 and the metal tail shank 213 are attenuator ferrules of a communication standard LC attenuator, which are composed of a standard LC metal tail shank and two sections of standard LC ceramic ferrules; the solid fiber 212 is a communication standard G657.A2 single-mode fiber; the hollow fiber 222 is an anti-resonant hollow fiber with a cladding diameter of 125μm and a mode field diameter of 11.5μm at 1310nm; the hollow fiber ferrule 221 is a standard LC ceramic ferrule with an outer diameter of 1.25mm; the first sleeve 231 and the second sleeve 232 are the same quartz capillary tubes with an inner diameter slightly larger than the outer diameter of the LC ceramic ferrule; the third sleeve 233 is a stainless steel capillary tube with an inner diameter slightly larger than the outer diameter of the quartz capillary tube and an outer diameter less than 2mm.

[0038] One end of the solid fiber 212 is heated at approximately 1300℃ using an oxyhydrogen flame to thermally expand its core, increasing its 1310nm mode field diameter to 11.5μm. The thermally expanded solid fiber 212 is then inserted into a solid fiber ferrule 211, ensuring that the inner part of the ferrule's outer end is unexpanded and the inner part of the coupling end is expanded. These parts are then bonded together using thermosetting epoxy adhesive. The bonded solid fiber ferrule 211 is then polished, with both the outer and coupling ends polished to a standard 8° APC end face. Finally, an antireflective coating with a 1310nm transmittance of 99.5% is deposited on the coupling end of the polished solid fiber ferrule 211, resulting in the desired solid fiber unit 210. The end face of the hollow fiber 222 is flattened and inserted into the hollow fiber ferrule 221 until it protrudes 100μm from the ferrule end face. This is then bonded together using thermosetting epoxy adhesive, resulting in the desired hollow fiber unit 220.

[0039] The external end of the solid fiber unit 210 is connected to a 1310nm light source, and the hollow fiber pigtail of the hollow fiber unit 220 is connected to a detector to monitor coupling insertion loss in real time; according to the coupling angle formula n core sinθ a = sin(θ a +θ b ), θ a =8°, n core =1.45, so θ b=3.6°. Place the solid-core hollow fiber unit 210 and the hollow fiber 220 on the coupling platform and adjust them until the axes of the solid-core fiber unit 210 and the hollow fiber 220 are coplanar and the included angle is 3.6°. The coupling end of the hollow fiber 222 is just in contact with the coupling end of the solid fiber 212. At this time, the insertion loss is the lowest. The first sleeve 231 is fitted onto the coupling end of the solid fiber unit 210 and bonded together with thermosetting epoxy. The second sleeve 232 is fitted onto the coupling end of the hollow fiber unit and bonded together with thermosetting epoxy. The end faces of the first sleeve 231 and the second sleeve 232 are bonded together with thermosetting epoxy. The third sleeve 233 is fitted onto the outside of both the first sleeve 231 and the second sleeve 232, covering their mating area, and bonded together with thermosetting epoxy, thus obtaining the desired coupling structure 200. Finally, the coupling structure 200 is assembled into the connector housing 100, thus obtaining the LC type hollow fiber connector of this embodiment.

[0040] Example 2: Example 2 provides an optical connection system, see [link to example]. Figure 3 (a) and (b) include: a first optical fiber connector 301, an adapter 302, and a second optical fiber connector 303. At least one of the first optical fiber connector 301 and the second optical fiber connector 303 is a hollow-core optical fiber connector as described in any of the foregoing technical solutions. Figure 3 (a) The first fiber optic connector 301 shown is a standard solid fiber optic connector, and the second fiber optic connector 303 is the aforementioned hollow fiber optic connector. Figure 3 (b) shows that both the first fiber optic connector 301 and the second fiber optic connector 303 are the aforementioned hollow fiber optic connectors. The adapter 302 is a standard fiber optic adapter (also known as a flange) in the communications industry, and it has an alignment sleeve inside. This sleeve is a high-precision open ceramic or metal sleeve, and its inner diameter is precisely matched with the outer diameter of the solid fiber ferrule of the first fiber optic connector 301 and the ferrule of the second fiber optic connector 303.

[0041] The optical connection system of this embodiment can realize the interconnection between connectors containing hollow optical fibers and existing standard optical fiber connectors, and is compatible with existing communication infrastructure.

[0042] Example 3: Example 3 provides an optical connection system, see [link to example]. Figure 4 It includes an optical module 401, an adapter 403, and a third fiber optic connector 404. The third fiber optic connector 404 is the hollow fiber optic connector described in any of the aforementioned technical solutions.

[0043] Optical module 401 is a standard communication optical module, containing a module ferrule 402 and a module optical fiber. The module optical fiber is a solid-core fiber, at least partially housed within the inner hole of the module ferrule 402 and secured with adhesive. The end face of the module ferrule 402 is polished to form a standard PC, UPC, or APC end face and extends from the optical interface of optical module 401. Adapter 403 is either an adapter installed at the optical interface of optical module 401 or a separately configured standard adapter.

[0044] When the third fiber optic connector 404 is inserted into the adapter 403, the solid fiber ferrule of the third fiber optic connector 404 and the module ferrule 402 of the optical module 401 simultaneously enter the sleeve inside the adapter 403. The sleeve precisely aligns the two ferrules, ensuring that the module fiber inside the module ferrule 402 and the solid fiber inside the third fiber optic connector 404 are coaxially aligned, achieving physical contact or gap coupling at the end faces.

[0045] The optical connection system in this embodiment enables direct interconnection between a connector containing hollow optical fiber and a standard optical module, providing a compatibility solution for hollow optical fiber in module-level applications.

[0046] Example 4: Example 4 provides an optical connection system, see [link to example]. Figure 5 The system includes a first optical module 501, a second optical module 505, and an optical fiber cable 503. A fourth optical fiber connector 502 and a fifth optical fiber connector 504 are respectively provided at both ends of the optical fiber cable 503. Both the fourth optical fiber connector 502 and the fifth optical fiber connector 504 are hollow-core optical fiber connectors as described in any of the aforementioned technical solutions.

[0047] The first optical module 501 and the second optical module 505 are transceiver devices in an optical communication system, and can be standard optical modules or circuit boards containing optical modules. Each optical module has a standard optical interface for connecting fiber optic connectors. The optical fiber cable 503 contains at least one hollow-core optical fiber for transmitting optical signals. Both ends of the optical cable are connected to the fourth optical fiber connector 502 and the fifth optical fiber connector 504, respectively. Specifically, the hollow-core optical fiber in the optical fiber cable 503 is connected to the hollow-core optical fiber unit within the fourth optical fiber connector 502, and similarly, to the hollow-core optical fiber unit within the fifth optical fiber connector 504. The fourth optical fiber connector 502 is connected to the optical interface of the first optical module 501, and the fifth optical fiber connector 504 is connected to the optical interface of the second optical module 505.

[0048] The optical connection system in this embodiment constructs an end-to-end hollow fiber transmission link, which can fully leverage the low latency and low nonlinearity transmission advantages of hollow fiber.

[0049] Example 5: Example 5 provides an optical connection system, see [link to example]. Figure 6 The system includes an optical module 601 and a sixth fiber optic connector 602. The sixth fiber optic connector 602 is a hollow-core fiber optic connector as described in any of the aforementioned technical solutions. The optical module 601 is an optoelectronic device package, internally housing an optical chip 603. The optical chip 603 can be a laser chip (such as a VCSEL or DFB laser) or a detector chip (such as a PIN or APD). The optical interface of the optical module 601 has a socket or guiding structure for connecting to the sixth fiber optic connector 602.

[0050] When the sixth fiber optic connector 602 is inserted into the optical interface of the optical module 601, the solid fiber ferrule of the sixth fiber optic connector 602 enters the interior of the optical module 601, and its end face aligns with the optical components (such as lenses) inside the optical module 601, thereby forming optical coupling with the optical chip 603. Since the end face of the solid fiber of the sixth fiber optic connector 602 is a standard end face, the optical design inside the optical module 601 can adopt a mature solution that matches the standard connector.

[0051] The optical connection system in this embodiment couples the hollow fiber connector directly to the optical module with the internally integrated optical chip, realizing a direct optical path connection from the optical chip to the hollow fiber.

[0052] The above description is merely a few preferred embodiments of the present invention and does not constitute any limitation on the technical scope of the present invention. Therefore, any minor modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A hollow fiber optic connector, characterized in that, include: Connector housing and coupling structure fixedly mounted therein; The coupling structure includes solid fiber units and hollow fiber units; The external end face of the solid fiber unit is a communication standard PC, UPC, or APC end face; the coupling end face of the solid fiber unit is an inclined plane with an angle of a first specific angle θ. a The coupling end face of the hollow fiber unit is a plane or an inclined plane; the axis of the solid fiber unit is coplanar with the axis of the hollow fiber unit, and the angle between them is a second specific angle θ. b The coupling end face of the solid fiber unit is directly coupled to the coupling end face of the hollow fiber unit.

2. The hollow fiber optic connector according to claim 1, characterized in that, The solid fiber unit includes a metal tailstock, a solid fiber ferrule, and a solid fiber. The solid fiber ferrule is inserted into the metal tailstock and pressed and fixed together. The solid fiber is inserted into the solid fiber ferrule and glued to it. The end face of the solid fiber is flush with that of the solid fiber ferrule. The hollow fiber unit includes a hollow fiber ferrule and a hollow fiber. The hollow fiber is inserted into the hollow fiber ferrule and glued to it. The coupling end face of the hollow fiber is flush with or extends out of the coupling end face of the hollow fiber ferrule.

3. The hollow fiber optic connector according to claim 1, characterized in that, It also includes the first sleeve, the second sleeve, and the third sleeve; The first sleeve is fitted onto the coupling end of the solid fiber unit and glued to it as a whole; the second sleeve is fitted onto the coupling end of the hollow fiber unit and glued to it as a whole; the end faces of the first sleeve and the second sleeve are glued to each other as a whole; the third sleeve is fitted onto the outside of both the first sleeve and the second sleeve and glued to them as a whole.

4. The hollow fiber optic connector according to claim 1, characterized in that, The connector housing is a standard fiber optic connector housing in the communications industry, with standard structural dimensions, and its types include LC, FC, SC or ST.

5. The hollow fiber optic connector according to claim 1, characterized in that, The first specific angle θ a With the second specific angle θ b Satisfying the relation: n core sinθ a = sin(θ a +θ b ), n core The refractive index of the solid fiber core is given; and the first specific angle θ is given. a The value of θ ranges from 3° to 10°, and the value of the second specific angle θ ranges from 1.35° to 4.6°.

6. The hollow fiber optic connector according to claim 2, characterized in that, The solid fiber ferrule is a one-piece long ferrule, or is composed of at least two ferrule segments coaxially combined.

7. The hollow fiber optic connector according to claim 2, characterized in that, The solid fiber coupling end undergoes thermal expansion treatment to enlarge its mode field diameter to match that of the hollow fiber; the thermal expansion process includes flame heating, laser heating, or resistance furnace heating.

8. The hollow fiber optic connector according to claim 2, characterized in that, The coupling end face of the solid fiber that has undergone thermal expansion is coated with an antireflection film.

9. The hollow fiber optic connector according to claim 2, characterized in that, The solid fiber ferrule has the same outer diameter as the hollow fiber ferrule; the solid fiber ferrule and the hollow fiber ferrule are either fiber ceramic ferrules or fiber metal ferrules.

10. The hollow fiber optic connector according to claim 3, wherein the outer diameter of the first sleeve and the second sleeve are the same; the first sleeve, the second sleeve and the third sleeve may be ceramic tubes, glass tubes or metal tubes.

11. An optical connection system, characterized in that, It includes a first optical connection assembly, which includes a first optical fiber connector, an adapter, and a second optical fiber connector. At least one of the first and second fiber optic connectors is a hollow fiber optic connector as described in any one of claims 1 to 10; the adapter includes a sleeve for fixing the solid fiber ferrule of the first fiber optic connector and the ferrule of the second fiber optic connector, so that the solid fiber in the first fiber optic connector is coaxially aligned with the solid fiber in the second fiber optic connector.

12. An optical connection system according to claim 11, characterized in that, It includes a second optical connection assembly, which includes an optical module, an adapter, and a third fiber optic connector; The third fiber optic connector is a hollow fiber optic connector as described in any one of claims 1 to 10; the optical module includes a module ferrule and a module fiber, the module fiber being at least partially disposed in the inner hole of the module ferrule, and the module fiber being a solid fiber; the adapter includes a sleeve for fixing the module ferrule and the solid fiber ferrule of the third fiber optic connector, so that the module fiber is coaxially aligned with the solid fiber in the third fiber optic connector.

13. An optical connection system according to claim 11, characterized in that, It includes a third optical connection assembly, which includes a first optical module, a second optical module, and an optical fiber cable; The optical fiber cable has a fourth optical fiber connector and a fifth optical fiber connector at each end; the fourth optical fiber connector and the fifth optical fiber connector are both hollow optical fiber connectors as described in any one of claims 1 to 10; one end of the optical fiber cable is connected to the fourth optical module, and the other end of the optical fiber cable is connected to the fifth optical module; the optical fiber cable includes at least one hollow optical fiber.

14. An optical connection system according to claim 11, characterized in that, It includes a fourth optical connection assembly, which includes an optical module and a sixth fiber optic connector; The sixth fiber optic connector is a hollow fiber optic connector as described in any one of claims 1 to 10; the sixth fiber optic connector is connected to the optical interface of the optical module, the optical module is provided with an optical chip, and the optical chip is optically coupled to the fiber optic connector.

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