A photonic crystal fiber connector and its fabrication method

Abstract

This invention belongs to the field of fiber optic connector technology and discloses a photonic crystal fiber connector and its fabrication method. The photonic crystal fiber connector provided by this invention includes a photonic crystal fiber, a bridge fiber, and a connector assembly. A light-transmitting positioning plate is embedded in the ferrule of the connector assembly. The photonic crystal fiber and the bridge fiber are respectively fixed on both sides of the light-transmitting positioning plate. The mode field diameter of the end of the bridge fiber closest to the light-transmitting positioning plate is the same as the mode field diameter of the photonic crystal fiber. The end of the bridge fiber furthest from the light-transmitting positioning plate serves as the mating end face with other fiber optic connectors, and the mode field diameter of this end is the same as the mode field diameter of the other fiber optic connectors to be mated with. In fabricating the photonic crystal fiber connector, this invention only grinds the end of the bridge fiber furthest from the light-transmitting positioning plate. This invention can effectively avoid the blockage, damage, or contamination of the micropore structure of the photonic crystal fiber.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of optical fiber connectors, and more particularly relates to a photonic crystal fiber connector and a preparation method thereof. BACKGROUND

[0002] A photonic crystal fiber (PCF) is a microstructure fiber formed based on a two-dimensional periodic arrangement of a low refractive index material (air) in a high refractive index background material (quartz glass), and is divided into a solid-core photonic crystal fiber and a hollow-core photonic crystal fiber. The hollow-core photonic crystal fiber (HC-PCF) has a special hollow structure, and light transmission in the fiber is no longer completely limited by the material, and the light can be transmitted in air or even vacuum. The hollow-core photonic crystal fiber has outstanding advantages such as low nonlinearity, low dispersion, single-mode transmission with a super-large core diameter, and accommodation of various gases or liquids in the core, and has a wide range of applications in the fields of high-power laser transmission, pulse compression, high-sensitivity sensing, fiber amplifiers, etc. At present, there are mainly two types of hollow-core photonic crystal fibers, namely, a hollow-core photonic bandgap fiber (HC-PBGF) and a hollow-core anti-resonant fiber (HC-ARF).

[0003] Future photonic crystal fibers have important application prospects in the fields of fiber communication, high-power laser sensing, and lasers, and it is also an urgent need to realize low-loss and convenient interconnection between the photonic crystal fiber and the traditional single-mode solid-core fiber. An optical connector is indispensable for building an optical fiber network, and a physical contact (PC) connector is usually used in the optical network at present, and the principle is to polish the end face of the fiber protruding from the ferrule into a convex spherical shape, and to press the end faces against each other through butt joint to maintain complete physical contact of the end faces of the fibers. Due to the fragility of the air hole microstructure in the photonic crystal fiber, the butt joint process usually needs to be controlled finely. In addition, mode field mismatch is inevitable in direct butt joint, especially for the hollow-core anti-resonant fiber which usually has a large core diameter, and a large difference in the mode field diameters of the fibers at the two ends of the butt joint will result in high butt joint loss. Due to the special micro-pore structure of the photonic crystal fiber, if the conventional grinding process of the connector is used, the air holes (i.e., the micro-pore structure) of the photonic crystal fiber will be inevitably blocked, the glass fiber around the holes will be broken and enter the holes, the structure will be changed, and the light transmission efficiency will be reduced. In addition, if the micro-pore structure of the photonic crystal fiber is exposed to air for a long time, the entry of dust and water vapor will also affect the transmission performance of the fiber. SUMMARY

[0004] The present application provides a photonic crystal fiber connector and a preparation method thereof, and solves the problems of easy blockage, damage or pollution of the micro-pore structure of the photonic crystal fiber in the photonic crystal fiber connector in the prior art.

[0005] This invention provides a photonic crystal fiber connector, comprising: a photonic crystal fiber, a bridge fiber, and a connector assembly; the connector assembly includes a ferrule and a housing, wherein a light-transmitting positioning plate is embedded in the ferrule; the photonic crystal fiber and the bridge fiber are respectively fixed on both sides of the light-transmitting positioning plate; the mode field diameter of the end of the bridge fiber near the light-transmitting positioning plate is the same as the mode field diameter of the photonic crystal fiber, and the end of the bridge fiber away from the light-transmitting positioning plate serves as the end face for mating with other fiber optic connectors, wherein the mode field diameter of the end of the bridge fiber away from the light-transmitting positioning plate is the same as the mode field diameter of the other fiber optic connectors to be mated.

[0006] Preferably, the end of the bridge fiber away from the light-transmitting positioning plate is ground into a UPC plane or an APC 8° angle, and is flush with the end face of the ferrule.

[0007] Preferably, the photonic crystal fiber is inserted from the tail end of the ferrule until one end of the photonic crystal fiber abuts against one side of the light-transmitting positioning plate, and the photonic crystal fiber is fixed to the tail end of the ferrule by adhesive application; the bridge fiber is inserted from the end face of the ferrule until one end of the bridge fiber abuts against one side of the light-transmitting positioning plate, and the bridge fiber is fixed to the inner wall of the ferrule by adhesive application.

[0008] Preferably, both sides of the light-transmitting positioning plate are coated with an anti-reflective coating.

[0009] Preferably, the thickness of the light-transmitting positioning plate is 30-100 μm.

[0010] Preferably, the vertical tilt angle of the light-transmitting positioning plate is 0-8°.

[0011] Preferably, the bridging fiber is an optical fiber with a graded refractive index, or the bridging fiber is a combination of several optical fibers with different refractive index distributions.

[0012] Preferably, the end face cutting angle of the photonic crystal fiber is within the range of ±0.1°.

[0013] Preferably, when the operating wavelength is greater than 1600nm, the insertion loss of the photonic crystal fiber connector is ≤1dB, the return loss is ≤-40dB, and the insertion loss variation is ≤0.3dB.

[0014] On the other hand, the present invention provides a method for fabricating a photonic crystal fiber connector, comprising the following steps:

[0015] Step 1: Cut the photonic crystal fiber and the bridge fiber respectively;

[0016] Step 2: Insert one cleaved end of the photonic crystal fiber into the tail end of the ferrule until the photonic crystal fiber abuts against one side of the light-transmitting positioning plate embedded in the ferrule. The photonic crystal fiber is fixed to the tail end of the ferrule by applying adhesive. Insert one cleaved end of the bridge fiber into the end face of the ferrule until the bridge fiber abuts against one side of the light-transmitting positioning plate. The bridge fiber is fixed to the inner wall of the ferrule by applying adhesive.

[0017] Step 3: Cut and grind the end of the bridge fiber away from the light-transmitting positioning plate to obtain the above-mentioned photonic crystal fiber connector.

[0018] One or more technical solutions provided in this invention have at least the following technical effects or advantages:

[0019] The photonic crystal fiber connector provided by this invention includes a photonic crystal fiber, a bridge fiber, and a connector assembly. A light-transmitting positioning plate is embedded in the ferrule of the connector assembly. The photonic crystal fiber and the bridge fiber are respectively fixed on both sides of the light-transmitting positioning plate. The mode field diameter of the end of the bridge fiber closest to the light-transmitting positioning plate is the same as the mode field diameter of the photonic crystal fiber. The end of the bridge fiber furthest from the light-transmitting positioning plate serves as the mating end face with other fiber optic connectors, and the mode field diameter of this end is the same as the mode field diameter of the other fiber optic connectors to be mated. In manufacturing the photonic crystal fiber connector, this invention only grinds the end of the bridge fiber furthest from the light-transmitting positioning plate. In other words, the end face of the photonic crystal fiber in this invention does not need to be directly polished, which can effectively avoid the blockage of the micropore structure caused by the breakage of the end face of the photonic crystal fiber. When the photonic crystal fiber connector is mated, the end face of the photonic crystal fiber does not directly contact the mating end face, which can effectively avoid damage or contamination of the micropore structure of the photonic crystal fiber, and can greatly increase the number of mating cycles. By controlling the mode field at both ends of the bridge fiber in this invention (for example, by changing the type of bridge fiber), efficient and low-loss mating of photonic crystal fiber with fibers of different mode field diameters can be achieved, and the application range of photonic crystal fiber connectors can be expanded. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of a photonic crystal fiber connector provided in Embodiment 1 of the present invention;

[0021] Figure 2 This is a cross-sectional view of the photonic crystal fiber in a photonic crystal fiber connector provided in Embodiment 1 of the present invention;

[0022] Figure 3 This is a schematic diagram of the optical fiber structure located inside the ferrule in a photonic crystal fiber connector provided in Embodiment 1 of the present invention;

[0023] Figure 4This is a schematic diagram of the structure of two photonic crystal fiber connectors provided by this invention being connected;

[0024] Figure 5 This is a schematic diagram of the structure of the photonic crystal fiber connector and the single-mode fiber connector provided by the present invention. Detailed Implementation

[0025] 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.

[0026] Example 1:

[0027] See Figures 1 to 5 Example 1 provides a photonic crystal fiber connector 10, including: a photonic crystal fiber 110, a bridge fiber 120, and a connector assembly 130; the connector assembly 130 includes a ferrule and a housing, the ferrule having a light-transmitting positioning plate 131 embedded therein; the photonic crystal fiber 110 and the bridge fiber 120 are respectively fixed on both sides of the light-transmitting positioning plate 131; the mode field diameter of the end of the bridge fiber 120 near the light-transmitting positioning plate 131 is the same as the mode field diameter of the photonic crystal fiber 110, and the end of the bridge fiber 120 away from the light-transmitting positioning plate 131 serves as the end face for mating with other fiber optic connectors, and the mode field diameter of the end of the bridge fiber 120 away from the light-transmitting positioning plate 131 is the same as the mode field diameter of the other fiber optic connectors to be mated.

[0028] The photonic crystal fiber 110 is used to control the end face quality by laser cutting, and the end face cutting angle of the photonic crystal fiber 110 is within the range of ±0.1°.

[0029] The photonic crystal fiber 110 includes an air core 111, a microporous cladding 112, and a coating layer 113. The air core 111 is used to transmit optical signals. The diameter of the microporous cladding 112 is 80–150 μm, and the diameter of the coating layer 113 is 165–400 μm. The principle of optical transmission in the photonic crystal fiber 110 is as follows: light is coherently reflected back and forth between the microporous cladding 112 (i.e., the tubular glass film) within the fiber, confining the light to the vicinity of the air core 111 and transmitting it along the axis. This allows for the transmission of single-mode optical signals at operating wavelengths greater than 1600 nm.

[0030] The end of the bridge fiber 120 furthest from the light-transmitting positioning plate 131 is ground to a UPC plane or an APC 8° angle and is flush with the end face of the ferrule. The bridge fiber 120 serves as a mode field diameter converter, matching the mode field diameter of the photonic crystal fiber 110 with that of the fiber being connected, achieving efficient and low-loss connection. The bridge fiber 120 is a graded-index fiber, or it may be a combination of several fibers with different refractive index distributions.

[0031] Example 1 modifies the ferrule of an existing fiber optic connector by embedding an extremely thin light-transmitting positioning plate 131 at a fixed position inside the ferrule. For example, the light-transmitting positioning plate 131 can be a glass plate. Specifically, both sides of the light-transmitting positioning plate 131 are coated with an anti-reflection coating to give it anti-reflective properties. For example, Fresnel reflection is reduced by covering both sides of the light-transmitting positioning plate 131 with a metal anti-reflection coating. The thickness of the light-transmitting positioning plate 131 is 30-100 μm, and the vertical tilt angle of the light-transmitting positioning plate 131 is 0-8°. The light-transmitting positioning plate 131 serves to protect the end face of the photonic crystal fiber 110 and reduce return loss.

[0032] The photonic crystal fiber 110 is inserted from the tail end of the ferrule until one end of the photonic crystal fiber 110 abuts against one side of the light-transmitting positioning plate 131, and the photonic crystal fiber 110 is fixed to the tail end of the ferrule by adhesive application; the bridge fiber 120 is inserted from the end face of the ferrule until one end of the bridge fiber 120 abuts against one side of the light-transmitting positioning plate 131, and the bridge fiber 120 is fixed to the inner wall of the ferrule by adhesive application.

[0033] When the operating wavelength is greater than 1600nm, the insertion loss of the photonic crystal fiber connector is ≤1dB, the return loss is ≤-40dB, and the insertion loss variation is ≤0.3dB.

[0034] The photonic crystal fiber connector 10 can be an LC connector or an SC connector.

[0035] In applications, two photonic crystal fiber connectors 10 provided by this invention can be physically connected via the sleeve inside the adapter 20, such as... Figure 4 As shown; alternatively, the photonic crystal fiber connector 10 provided by this invention can be physically connected to a common single-mode fiber connector 30 through the sleeve inside the adapter 20 to achieve good transmission of optical signals, such as... Figure 5 As shown. The key to low-loss connection lies in the mode field matching of the two optical fibers. This invention controls the mode field diameter by controlling the mode field at both ends of the bridge fiber 120. When the optical fiber connector is connected, the ferrule end faces make direct physical contact, which can realize low-loss optical fiber connection.

[0036] The following provides a fabrication method corresponding to the photonic crystal fiber connector provided in Example 1.

[0037] Example 2:

[0038] Example 2 provides a method for fabricating a photonic crystal fiber connector, comprising the following steps:

[0039] Step 1: Cut the photonic crystal fiber and the bridge fiber respectively.

[0040] Step 1 is the laser cutting operation of the end face. Specifically, a fiber stripper is used to strip one end of the bridge fiber (the end closest to the light-transmitting positioning plate) and a certain length of the coating layer on the surface of the photonic crystal fiber. The fiber is then fixed on the corresponding tooling fixture, and the end face is laser-cut to obtain a flat end face. Afterward, the end face is inspected under a microscope to ensure that the micropores on the end face of the photonic crystal fiber are not damaged.

[0041] Step 2: Insert one cleaved end of the photonic crystal fiber into the tail end of the ferrule until the photonic crystal fiber abuts against one side of the light-transmitting positioning plate embedded in the ferrule. The photonic crystal fiber is fixed to the tail end of the ferrule by applying adhesive. Insert one cleaved end of the bridge fiber into the end face of the ferrule until the bridge fiber abuts against one side of the light-transmitting positioning plate. The bridge fiber is fixed to the inner wall of the ferrule by applying adhesive.

[0042] Step 2 includes the following operations: fixing the built-in bridge fiber, threading the photonic crystal fiber, and applying adhesive for curing. Specifically, the ferrule in this invention is specially customized and has a built-in light-transmitting positioning plate with an inclination angle of 0-8°. The light-transmitting positioning plate is used to position the subsequent fiber insertion. The mode field diameter of the end of the bridge fiber away from the light-transmitting positioning plate is consistent with the mode field diameter of the fiber to be connected, and the mode field diameter of the bridge fiber near the light-transmitting positioning plate is consistent with the mode field diameter of the photonic crystal fiber. Under a high-powered microscope, one end of the bridge fiber (the end near the light-transmitting positioning plate) is inserted from the end face of the ferrule until that end reaches the light-transmitting positioning plate. The bridge fiber and the inner wall of the ferrule are fixed with ultraviolet adhesive. One end of the photonic crystal fiber, after being laser-cut, is inserted into the tail end of the ferrule until the end face reaches the light-transmitting positioning plate. The tail end of the photonic crystal fiber is first pre-fixed with UV glue, then injected with polymer curing adhesive, such as 353ND glue, and then heat-cured in a curing oven.

[0043] Step 3: Cut and grind the end of the bridge fiber away from the light-transmitting positioning plate to obtain the photonic crystal fiber connector as described in Example 1.

[0044] Step 3 involves the polishing process. Specifically, the end of the bridge fiber furthest from the light-transmitting positioning plate is cut with a fiber cutter to remove excess fiber from the ferrule end face, and then the end face is polished using a conventional polishing process.

[0045] 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 photonic crystal fiber connector, characterized by, The application relates to a photonic crystal fiber, a bridge fiber and a connector assembly; the connector assembly comprises a ferrule and a shell, a light-transmitting positioning plate is embedded in the ferrule, the photonic crystal fiber and the bridge fiber are fixed on two sides of the light-transmitting positioning plate respectively, the mode field diameter of one end of the bridge fiber close to the light-transmitting positioning plate is consistent with the mode field diameter of the photonic crystal fiber, the other end of the bridge fiber away from the light-transmitting positioning plate serves as an end face for connecting with other fiber connectors, the mode field diameter of the other end of the bridge fiber away from the light-transmitting positioning plate is consistent with the mode field diameter of the other fiber connector for connection. The end face of the photonic crystal fiber is not directly polished, the photonic crystal fiber is inserted from the tail end of the ferrule until one end of the photonic crystal fiber abuts one side of the light-transmitting positioning plate, the photonic crystal fiber is fixed with the tail end of the ferrule through point gluing, the bridge fiber is inserted from the end face of the ferrule until one end of the bridge fiber abuts one side of the light-transmitting positioning plate, the bridge fiber is fixed with the inner wall of the ferrule through point gluing, and the other end of the bridge fiber away from the light-transmitting positioning plate is polished. The other end of the bridge fiber away from the light-transmitting positioning plate is polished into a UPC plane or an APC 8-degree angle and is flush with the end face of the ferrule.

2. The photonic crystal fiber connector of claim 1, wherein, The two sides of the light-transmitting positioning plate are coated with anti-reflection films.

3. The photonic crystal fiber connector of claim 1, wherein, The thickness of the light-transmitting positioning plate is 30-100 um.

4. The photonic crystal fiber connector of claim 1, wherein, The vertical inclination angle of the light-transmitting positioning plate is 0-8 degrees.

5. The photonic crystal fiber connector of claim 1, wherein, The bridge fiber is a fiber with a gradually changed refractive index, or the bridge fiber is a combination of several fibers with different refractive index distributions.

6. The photonic crystal fiber connector of claim 1, wherein, The cutting angle of the end face of the photonic crystal fiber is within the range of +0.1 degrees.

7. The photonic crystal fiber connector of claim 1, wherein, In the case that the working wavelength is greater than 1600 nm, the insertion loss of the photonic crystal fiber connector is less than or equal to 1 dB, the return loss is less than or equal to -40 dB, and the insertion loss variation is less than or equal to 0.3 dB.

8. The photonic crystal fiber connector of claim 1, wherein, The application further discloses a preparation method of the photonic crystal fiber connector.

9. A method of making a photonic crystal fiber connector, comprising: Step 1: cutting the photonic crystal fiber and the bridge fiber respectively; Step 2: inserting one end of the photonic crystal fiber after cutting into the tail end of the ferrule until the photonic crystal fiber abuts one side of the light-transmitting positioning plate embedded in the ferrule, and fixing the photonic crystal fiber with the tail end of the ferrule through point gluing; inserting one end of the bridge fiber after cutting into the end face of the ferrule until the bridge fiber abuts one side of the light-transmitting positioning plate, and fixing the bridge fiber with the inner wall of the ferrule through point gluing; Step 3: cutting and polishing the other end of the bridge fiber away from the light-transmitting positioning plate to obtain the photonic crystal fiber connector according to any one of claims 1-8. ​

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