Hollow optical fiber connector and method of manufacturing the same

Abstract

The application belongs to the technical field of optical communication, and discloses a hollow optical fiber connector and a preparation method thereof. The hollow optical fiber connector comprises a mode field adapter, a hollow optical fiber, a first optical fiber and a plug body. The mode field adapter is a hollow structure, and the hollow structure is sequentially provided with a first accommodating part, a mode field matching part and a second accommodating part along an axis. The first accommodating part is used for inserting the first optical fiber, and the first optical fiber is used for plugging the air hole of the hollow optical fiber. The second accommodating part is used for inserting the hollow optical fiber. The mode field matching part is a conical hole structure, the inner wall of the conical hole structure is plated with a reflective film, and the mode field matching part is used for realizing mode field matching between the hollow optical fiber and a single-mode optical fiber to be connected. The hollow optical fiber and the first optical fiber are respectively inserted into the mode field adapter and solidified to obtain a combined body, and the combined body is assembled with the plug body to form the hollow optical fiber connector. The application can effectively reduce the loss of the hollow optical fiber during connection.

Description

Technical Field

[0001] This invention belongs to the field of optical communication technology, and more specifically, relates to a hollow optical fiber connector and its manufacturing method. Background Technology

[0002] Hollow fiber is a new type of optical fiber that has been developed in recent years. It utilizes the principle that light travels 50% faster in air than in glass. Inside, there is a central air-filled channel surrounded by a ring of glass capillaries. Its cross-section resembles a honeycomb with a central opening. This unique structural design confines light within the air core for transmission. Hollow fiber is generally considered to refer to hollow photonic bandgap fiber, hollow Bragg fiber, and coupling-suppressing hollow fiber, all of which share the common characteristics of an air-filled central core, an outer ring of glass for guiding the laser beam, and signal transmission speeds very close to the speed of light.

[0003] In fiber optic communication systems, it is frequently necessary to connect optical fibers to each other or to devices, often requiring detachable connections. During these connections, the two end faces of the fibers must be precisely aligned, with the most crucial aspect being ensuring the axes of the two fibers are aligned to maximize the coupling of light energy from the transmitting fiber to the receiving fiber. Because hollow optical fibers have air holes in their core, moisture or other impurities from the surrounding environment can enter these holes during connection adjustments, causing core blockage and affecting optical signal transmission.

[0004] Existing research on hollow fiber optic connectors, for example, involves heating the fiber to collapse the air core, sealing the air holes, followed by polishing to treat the fiber end face. However, the length of the collapsed portion is difficult to control and measure, easily leading to a significant increase in insertion loss. Furthermore, the collapsed fiber cladding diameter changes, affecting the matching between the fiber's outer diameter and the ferrule diameter, further increasing insertion loss. Some hollow fiber optic connectors require secondary processing of the ferrule, increasing technical difficulty and production costs, consuming more manpower and time, and severely impacting production efficiency. For example, a hollow fiber optic connector consists of an auxiliary fiber, an air-core photonic bandgap fiber, and a single-mode fiber. The refractive index of the core material in the auxiliary fiber is greater than that of the cladding material in the air-core photonic bandgap fiber. The auxiliary fiber is located inside the air core of the air-core photonic bandgap fiber and is tightly wrapped by the structure formed by the collapse of the air holes in the air-core photonic bandgap fiber to form a refractive index guided fiber. The refractive index guided fiber is connected to the single-mode fiber. In this scheme, the single-mode auxiliary fiber required needs to be etched to match the hollow fiber. The etching process is difficult to control, and the actual operation is difficult, making it difficult to mass-produce. Summary of the Invention

[0005] This invention provides a hollow optical fiber connector and its manufacturing method, thereby solving the problem of high insertion loss in existing hollow optical fiber connectors.

[0006] This invention provides a hollow fiber optic connector, comprising: a mode field adapter, a hollow fiber, a first fiber, and a ferrule; the mode field adapter is a hollow structure, and the hollow structure has a first receiving portion, a mode field matching portion, and a second receiving portion arranged sequentially along its central axis; the first receiving portion is used to insert the first fiber, and the first fiber is used to seal the air hole of the hollow fiber; the second receiving portion is used to insert the hollow fiber; the mode field matching portion is a tapered central hole structure, and the inner wall of the tapered central hole structure is coated with a reflective film; the mode field matching portion is used to achieve mode field matching between the hollow fiber and the single-mode fiber to be connected; the hollow fiber and the first fiber are respectively inserted into the mode field adapter and cured to obtain an assembly, and the assembly and the ferrule are assembled to form a hollow fiber optic connector.

[0007] Preferably, the mode field diameter at one end of the mode field matching part matches the mode field diameter of the hollow optical fiber, and the mode field diameter at the other end of the mode field matching part matches the mode field diameter of the single-mode optical fiber to be connected, wherein the mode field diameter of the hollow optical fiber is larger than the mode field diameter of the single-mode optical fiber to be connected.

[0008] Preferably, the mold field adapter is a glass capillary with a customized structure.

[0009] Preferably, the mode field adapter is a three-dimensional optical waveguide with a customized structure, and the material of the three-dimensional optical waveguide is quartz glass or silicon-based material.

[0010] Preferably, the first optical fiber is a coreless optical fiber, a multimode optical fiber, or a self-focusing optical fiber.

[0011] Preferably, the length of the first optical fiber is less than or equal to 200 μm.

[0012] Preferably, the mode field adapter is further provided with a collimation part, which is located between the first receiving part and the mode field matching part. The collimation part is a circular central hole structure, and the inner wall of the circular central hole structure is coated with a reflective film. The collimation part is used to collimate the optical signal.

[0013] Preferably, the end faces of both the mold field adapter and the insert are ground, polished, and coated with an anti-reflective film.

[0014] Preferably, the insert is a single-hole ceramic insert or a porous polymer insert.

[0015] On the other hand, the present invention provides a method for manufacturing a hollow optical fiber connector, comprising the following steps:

[0016] Step 1: Prepare the model field adapter;

[0017] The mold field adapter is a hollow structure, and the hollow structure is provided with a first receiving part, a mold field matching part and a second receiving part in sequence along the central axis; or, the hollow structure is provided with a first receiving part, a collimation part, a mold field matching part and a second receiving part in sequence along the central axis.

[0018] Step 2: Assemble the first optical fiber, the hollow optical fiber, the mode field adapter, and the ferrule to obtain the hollow optical fiber connector described above.

[0019] One or more technical solutions provided in this invention have at least the following technical effects or advantages:

[0020] (1) The present invention first prepares a mode field adapter with a specific special structure. The mode field adapter is a hollow structure. The hollow structure is provided with a first receiving part, a mode field matching part and a second receiving part along the central axis. The first receiving part is used to insert the first optical fiber, and the first optical fiber is used to block the air hole of the hollow optical fiber. The second receiving part is used to insert the hollow optical fiber. The mode field matching part is a conical hole structure. The inner wall of the conical hole structure is coated with a reflective film. The mode field matching part is used to realize the mode field matching between the hollow optical fiber and the single-mode optical fiber to be connected. Then, the first optical fiber, the hollow optical fiber, the mode field adapter and the ferrule are assembled to obtain the hollow optical fiber connector. This invention utilizes a first optical fiber to seal the air holes in a hollow optical fiber. This invention eliminates the need for heating or other treatments to seal the air holes in the hollow optical fiber, and also avoids direct polishing of the fiber's end face. This prevents air hole blockage caused by broken end face plates in the hollow optical fiber, and does not affect optical signal transmission. Furthermore, this invention uses a specially structured mode field adapter to achieve mode field matching between the hollow optical fiber and the single-mode fiber to be connected, reducing insertion loss and achieving better optical connection performance.

[0021] (2) By setting a collimation part between the first receiving part and the mode field matching part, the present invention can further optimize the transmission quality of optical signals and improve the optical connection performance.

[0022] (3) When the hollow fiber optic connector provided by the present invention is used for optical connection, the hollow fibers do not directly contact each other, which effectively improves the fiber docking coupling efficiency, and has good anti-pollution ability and excellent environmental performance.

[0023] (4) The present invention does not require secondary processing of the ferrule or complex operation process. Therefore, compared with the existing solution, the present invention can reduce the manufacturing difficulty and cost of hollow fiber optic connector and improve the manufacturing efficiency. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the mode field adapter in a hollow optical fiber connector provided by an embodiment of the present invention;

[0025] Figure 2 This is a schematic diagram showing the dimensions of a mode field adapter in a hollow optical fiber connector, provided by an embodiment of the present invention.

[0026] Figure 3 This is a schematic diagram showing the dimensions of a mode field adapter in a hollow optical fiber connector, provided by an embodiment of the present invention.

[0027] Figure 4 This invention provides a schematic diagram of the structure and dimensions of the ferrule in a hollow optical fiber connector, as shown in the embodiment of the invention.

[0028] Figure 5 This is a schematic diagram illustrating the assembly of a mode field adapter and a ferrule in a hollow optical fiber connector, as provided in an embodiment of the present invention.

[0029] Figure 6 This is a schematic diagram of the overall structure of a hollow optical fiber connector provided in an embodiment of the present invention. Detailed Implementation

[0030] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods.

[0031] Example 1:

[0032] See Figure 6 Example 1 provides a hollow fiber optic connector, comprising: a mode field adapter 100, a ferrule 200, a first optical fiber 300, and a hollow optical fiber 400. See also... Figure 1 , Figure 2 and Figure 6 The mode field adapter 100 has a hollow structure, and the hollow structure has a first receiving part 130, a mode field matching part 110, and a second receiving part 120 arranged sequentially along its central axis. The first receiving part 130 is used to insert the first optical fiber 300, and the first optical fiber 300 is used to block the air hole of the hollow optical fiber 400. The second receiving part 120 is used to insert the hollow optical fiber 400. The mode field matching part 110 has a conical central hole structure, and the inner wall of the conical central hole structure is coated with a reflective film. The mode field matching part 110 is used to achieve mode field matching between the hollow optical fiber 400 and the single-mode optical fiber to be connected. After the hollow optical fiber 400 and the first optical fiber 130 are respectively inserted into the mode field adapter 100 and cured, an assembly is obtained. The assembly and the ferrule 200 are assembled to form a hollow optical fiber connector.

[0033] Wherein, the mode field diameter at one end of the mode field matching part 110 is matched with the mode field diameter of the hollow optical fiber 400, and the mode field diameter at the other end of the mode field matching part 110 is matched with the mode field diameter of the single-mode optical fiber to be connected, wherein the mode field diameter of the hollow optical fiber 400 is larger than the mode field diameter of the single-mode optical fiber to be connected.

[0034] The mode field adapter 100 is a glass capillary with the above-described customized structure. Alternatively, the mode field adapter 100 is a three-dimensional optical waveguide with the above-described customized structure, wherein the material of the three-dimensional optical waveguide is quartz glass or silicon-based material.

[0035] In Example 1, a glass capillary tube or three-dimensional optical waveguide with a special structural size is used as the mode field adapter 100 to achieve mode field matching between the hollow optical fiber 400 and the single-mode optical fiber. The tapered central hole structure inside the mode field adapter 100 plays the role of mode field conversion. The inner wall of the tapered central hole structure is coated with a reflective film (covered with one or more layers of metal thin film, which has high reflectivity). Light undergoes total internal reflection at the interface of the reflective film, which can confine the light to the tapered air region for transmission with almost no loss.

[0036] The first optical fiber 300 enters from one side of the mode field adapter 100, is located in the first receiving portion 130, and is close to the tapered end of the central hole of the mode field matching portion 110. The first optical fiber 300 is a coreless optical fiber, multimode optical fiber, self-focusing optical fiber, or other light-transmitting material with the same function (the function of sealing the air holes of hollow optical fibers). The length of the first optical fiber 300 is less than or equal to 200 μm, and the first optical fiber 300 is suitable for polishing and coating.

[0037] The insert body 200 is a single-hole ceramic insert or a porous polymer insert.

[0038] Furthermore, the end faces of both the mode field adapter 100 and the ferrule 200 are ground, polished, and coated with an anti-reflective film. This coating process reduces Fresnel reflection, thereby improving insertion loss and return loss. For example, after grinding and polishing, one or more layers of a metallic anti-reflective film are coated in a vacuum coating cavity, resulting in high anti-reflective properties. The coating method can be physical vapor deposition by electron beam evaporation.

[0039] The hollow optical fiber 400 has an air core and a cladding of multiple glass capillary rings. These hollow glass capillary rings can be single, double, or multiple rings, arranged regularly or irregularly, and can be single-layered or multi-layered. The hollow optical fiber 400 has a glass ring cladding diameter of 100-400 μm and an optical fiber coating diameter of 200-700 μm. The core layer of the hollow optical fiber 400 can transmit single-mode signals.

[0040] The dimensions of each component structure are crucial in this invention; see [link / reference]. Figure 2 , Figure 4 , Figure 5 The lengths of the first receiving portion 130, the mode field matching portion 110, and the second receiving portion 120 are denoted as L1, L2, and L3, respectively, where L1 is less than 200 μm and L3 is 2–3 mm. The total length of the mode field adapter 100 along its central axis is denoted as L4, for example, 10 mm. The diameter of the first receiving portion 130 is denoted as d1, which matches the diameter of the first optical fiber 300, for example, 10 μm. The diameter of the mode field matching portion 110 on the side closest to the second receiving portion 120 is denoted as d. 2. d2 matches the cladding diameter of the hollow optical fiber 400, for example, 125 μm; the diameter of the second receiving portion 120 is denoted as d3, which matches the coating diameter of the hollow optical fiber 400, for example, 250 μm; the outer diameter of the mode field adapter 100 is denoted as d4, which matches the inner diameter d5 of the ferrule 200, for example, 1 mm; the outer diameter of the ferrule 200 is denoted as d6, for example, 2.5 mm; the total length of the ferrule 200 is denoted as L5, for example, 10.5 mm. The optical fiber (including the first optical fiber 300 and the hollow optical fiber 400) and the mode field adapter 100, and both the mode field adapter 100 and the ferrule 200, have a high degree of concentricity, controlled within 1 μm, which can avoid core misalignment increasing docking loss.

[0041] This invention enables the transmission of optical signals from single-mode fiber to hollow fiber, or from hollow fiber to single-mode fiber, while ensuring low loss.

[0042] When the hollow fiber optic connector provided in Example 1 is used as an optical connector through an adapter, the hollow fibers 400 in the two hollow fiber optic connectors are not in contact with each other, while the end faces of the two ferrules 200 and the end faces of the two glass capillaries (or three-dimensional optical waveguides) that serve as the mode field adapter 100 are in physical contact.

[0043] Assemble the fiber optic connectors according to the manufacturing process to form the required fiber optic connectors, such as FC, SC, LC, etc., and then test their optical performance, such as insertion loss and return loss. The hollow fiber optic connector provided by this invention can provide an insertion loss of no more than 0.5dB at wavelengths of 1310nm and 1550nm, and a return loss of no more than -40dB at wavelengths of 1310nm and 1550nm.

[0044] Example 2:

[0045] The difference from Embodiment 1 is that the mode field adapter in the hollow fiber connector provided in Embodiment 2 is further provided with a collimation part 132. The collimation part 132 is located between the first receiving part 131 and the mode field matching part. The collimation part 132 is a circular central hole structure, and the inner wall of the circular central hole structure is coated with a reflective film. The collimation part is used to collimate the optical signal. See [link to documentation]. Figure 3 .

[0046] The hollow structure of the mode field adapter in the hollow fiber optic connector provided in Embodiment 2 is provided with a first receiving part 131, a collimation part 132, a mode field matching part, and a second receiving part in sequence along the central axis.

[0047] See Figure 3 Let L be the length of the first receiving portion in the hollow optical fiber connector provided in Embodiment 2. 11 Let the length of the collimation section be denoted as L. 12 For example, L 11 Take 0.1mm, L 12 Take 2mm. The mold field matching part and the second receiving part in Example 2 are similar to those in Example 1, so they will not be described again.

[0048] Example 2 can further optimize the transmission quality of optical signals and improve optical connection performance.

[0049] Example 3:

[0050] Example 3 provides a method for fabricating a hollow optical fiber connector as described in Example 1 or Example 2, mainly including the following steps:

[0051] Step 1: Prepare the model field adapter;

[0052] The mold field adapter is a hollow structure, and the hollow structure is provided with a first receiving part, a mold field matching part and a second receiving part in sequence along the central axis, which corresponds to the mold field adapter designed as in Embodiment 1; or, the hollow structure is provided with a first receiving part, a collimation part, a mold field matching part and a second receiving part in sequence along the central axis, which corresponds to the mold field adapter designed as in Embodiment 2.

[0053] Step 2: Assemble the first optical fiber, the hollow optical fiber, the mode field adapter, and the ferrule to obtain the hollow optical fiber connector.

[0054] The following example illustrates the fabrication method of hollow fiber optic connectors using parameters.

[0055] After stripping the coating from a short section of coreless optical fiber, the end face is flattened using a fiber optic cleaver. It is then inserted into the hollow structure (central hole) of a custom-designed mode field adapter, ensuring the length of the coreless fiber within the adapter is less than 200µm. 353ND epoxy adhesive is applied around the outer end face of the coreless fiber and cured. After curing, excess fiber is removed using a diamond cutter, and the end face is polished. A ring of 353ND epoxy adhesive is applied to the outer cylindrical surface of the polished mode field adapter, which is then inserted into the ferrule. The end face of the mode field adapter is flush with the end face of the ferrule. The adapter is then heated in a curing oven to cure, forming an assembly of the coreless fiber, mode field adapter, and ferrule. The end face of the resulting assembly is then polished, and one or more layers of high anti-reflective coating are deposited on the polished end face. The coating is then stripped from the hollow fiber, and the end face is flattened using a fiber optic cleaver, leaving a cladding portion of 2–3 mm in length. A layer of 353ND epoxy adhesive is applied to the coating layer of the hollow optical fiber, which is then inserted into the assembly obtained above and cured in a curing oven to obtain a hollow optical fiber connector.

[0056] It should be noted that the order in which the first optical fiber, the hollow optical fiber, the mode field adapter, and the ferrule are assembled can be adjusted as needed. For example, the first optical fiber, the hollow optical fiber, and the mode field adapter can be obtained first, and then this assembly can be inserted into the ferrule to obtain a hollow optical fiber connector.

[0057] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A hollow optical fiber connector, characterized by, include: The device comprises a mode field adapter, a hollow optical fiber, a first optical fiber, and a ferrule. The mode field adapter is a hollow structure, and the hollow structure has a first receiving part, a mode field matching part, and a second receiving part arranged sequentially along its central axis. The first receiving part is used to insert the first optical fiber, and the first optical fiber is used to seal the air hole of the hollow optical fiber. The second receiving part is used to insert the hollow optical fiber. The mode field matching part is a tapered central hole structure, and the inner wall of the tapered central hole structure is coated with a reflective film. The mode field matching part is used to achieve mode field matching between the hollow optical fiber and the single-mode optical fiber to be connected. The hollow optical fiber and the first optical fiber are respectively inserted into the mode field adapter and cured to obtain an assembly. The assembly and the ferrule are assembled to form a hollow optical fiber connector.

2. The hollow optical fiber connector of claim 1, wherein, The mode field diameter at one end of the mode field matching part matches the mode field diameter of the hollow optical fiber, and the mode field diameter at the other end of the mode field matching part matches the mode field diameter of the single-mode optical fiber to be connected. The mode field diameter of the hollow optical fiber is larger than the mode field diameter of the single-mode optical fiber to be connected.

3. The hollow optical fiber connector of claim 1, wherein, The mold field adapter is a glass capillary with a custom structure.

4. The hollow optical fiber connector of claim 1, wherein, The mode field adapter is a three-dimensional optical waveguide with a customized structure, and the material of the three-dimensional optical waveguide is quartz glass or silicon-based material.

5. The hollow optical fiber connector according to claim 1, characterized in that, The first optical fiber is a coreless optical fiber, a multimode optical fiber, or a self-focusing optical fiber.

6. The hollow optical fiber connector according to claim 1, characterized in that, The length of the first optical fiber is less than or equal to 200 μm.

7. The hollow optical fiber connector according to claim 1, characterized in that, The mode field adapter is further provided with a collimation part, which is located between the first receiving part and the mode field matching part. The collimation part is a circular central hole structure, and the inner wall of the circular central hole structure is coated with a reflective film. The collimation part is used to collimate the optical signal.

8. The hollow optical fiber connector of claim 1, wherein, The end faces of both the mold field adapter and the ferrule have been ground, polished, and coated with an anti-reflective film.

9. The hollow optical fiber connector of claim 1, wherein, The insert body is a single-hole ceramic insert or a porous polymer insert.

10. A method for manufacturing a hollow optical fiber connector, characterized in that, Includes the following steps: Step 1: Prepare the model field adapter; The mold field adapter is a hollow structure, and the hollow structure is provided with a first receiving part, a mold field matching part and a second receiving part in sequence along the central axis; or, the hollow structure is provided with a first receiving part, a collimation part, a mold field matching part and a second receiving part in sequence along the central axis. Step 2: Assemble the first optical fiber, the hollow optical fiber, the mode field adapter, and the ferrule to obtain the hollow optical fiber connector as described in any one of claims 1-9.

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