Optical connection structure

Abstract

The optical connection structure has a MCF, a first ferrule, a plurality of optical fibers, and a second ferrule. The MCF has a plurality of first cores and a first cladding. The first ferrule has a first inner hole that houses a front end portion of the MCF and a first ferrule end face. The plurality of optical fibers that are optically connected to the MCF each have a second core and a second cladding. The second ferrule has a second inner hole that houses each front end portion of the plurality of optical fibers and a second ferrule end face. The second ferrule fixes each front end portion of the optical fibers in the second inner hole by a wire bonding agent. The wire bonding agent is filled in a manner that the surface thereof is recessed further into the second inner hole than the second ferrule end face. A refractive index matching agent is enclosed in a space sealed by the first ferrule end face and the second ferrule end face.

Description

Technical Field

[0001] This invention relates to optical connection structures. This application claims priority to Japanese Application No. 2021-094989, filed on June 7, 2021, the entire contents of which are incorporated herein by reference. Background Technology

[0002] Japanese Patent Application Publication No. 2019-113597 discloses an optical connection structure for optically connecting multi-core optical fibers and multiple optical fibers. In this optical connection structure, two optical fibers are optically connected by aligning the front end face of the multi-core optical fiber housed in a ferrule with the front end faces of each of the multiple optical fibers housed in another ferrule. US Patent No. 9,599,776 discloses an example of an optical coupling component. Japanese Patent Application Publication No. Hei 01-262507 discloses an example of an optical fiber connector. Japanese Utility Model Application Publication No. Hei 01-136904 discloses a multi-core optical fiber connector. Summary of the Invention

[0003] This invention provides an optical connection structure. The optical connection structure includes a multi-core optical fiber, a first ferrule, multiple optical fibers, and a second ferrule. The multi-core optical fiber has multiple first cores extending in the length direction, a first cladding covering the multiple first cores, and a first fiber front end face including the front ends of each of the multiple first cores and the first cladding. The first ferrule has a first inner hole for receiving the front end portion of the multi-core optical fiber and a first ferrule end face exposing the front end face of the first optical fiber on its inner side. The first ferrule fixes the front end portion of the multi-core optical fiber within the first inner hole. Each of the multiple optical fibers optically connected to the multi-core optical fiber has a second core extending in the length direction, a second cladding covering the second core, and a second fiber front end face including the front ends of each of the second cores and the second cladding. The second ferrule has a second inner hole for receiving the front end portion of each of the multiple optical fibers and a second ferrule end face exposing the front end face of each of the multiple optical fibers on its inner side. The second ferrule secures the front ends of multiple optical fibers to the second inner hole using a connector adhesive. The connector adhesive is filled into the second inner hole such that the surface opposite the front end face of the first optical fiber is recessed further into the second inner hole than the end face of the second ferrule. A refractive index matching agent is sealed within the space sealed by the end faces of the first and second ferrules. Attached Figure Description

[0004] Figure 1 This is a perspective view showing an optical connection structure according to one embodiment.

[0005] Figure 2 It is Figure 1 The diagram shows a perspective view of the disassembled light-connected structure.

[0006] Figure 3 It is along Figure 1A cross-sectional view of the light connection structure along line III-III.

[0007] Figure 4 It is Figure 3 A magnified cross-sectional view of region T, which is a part of the light-connected structure shown.

[0008] Figure 5 This is a diagram showing the front end and the end face of the ferrule in a multi-core optical fiber.

[0009] Figure 6 It is a diagram showing the front end and end face of multiple optical fibers and ferrules.

[0010] Figure 7 This is a perspective view showing the initial state in which multiple optical fibers are fixed inside the ferrule by wiring adhesive, with the front end face of each optical fiber aligned with the end face of the ferrule.

[0011] Figure 8 It means Figure 7 A cross-sectional view of the initial state.

[0012] Figure 9 It means from Figure 7 and Figure 8 The image shown is a perspective view of the initial state in which a portion of the optical fiber is tucked inwards.

[0013] Figure 10 It means Figure 9 A cross-sectional view of the trapped state.

[0014] Figure 11 It means to Figure 1 The diagram shows a perspective view of the structure used to fix the light-connecting structure.

[0015] Figure 12 It means to Figure 1 The diagram shows a perspective view of another structure used to fix the light-connecting structure.

[0016] Figure 13 It means to Figure 1 The diagram shows a perspective view of other structures used to fix the light-connecting structure.

[0017] Figure 14 It is a cross-sectional view used to illustrate the state of fiber entrapment in an optical connection structure. Detailed Implementation

[0018] [The problem this invention aims to solve]

[0019] The optical connection structure disclosed in Japanese Patent Application Publication No. 2019-113597, etc., such as Figure 14As shown, multiple optical fibers 200 are housed within a ferrule 201 with their respective front ends 200a aligned with the end faces 201a of the ferrule 201, and are fixed to the ferrule 201 by an adhesive 202 filling around the optical fibers 200. At this time, the ferrule end faces 201a, including the front ends of the optical fibers 200 and the adhesive 202, are formed to be coplanar through grinding or the like. However, among the multiple optical fibers 200 fixed by the adhesive 202, there are (trapped) optical fibers 200A that have moved backward along the longitudinal direction due to thermal effects during continuous use. In this case, from the state where the multiple optical fibers 200 are mated with the multi-core optical fiber 210 held by the ferrule 211, a portion of the optical fiber 200A of the multiple optical fibers 200 is trapped backward, forming a gap V between the multi-core optical fiber 210 and the trapped optical fiber 200A. If gap V is formed, the reflection attenuation and insertion loss between the multi-core optical fiber 210 and the trapped optical fiber 200A will deteriorate. Therefore, it is desirable to construct an optical connection that can suppress the degradation of optical properties over time.

[0020]

Effects of the Invention

[0021] According to the present invention, the degradation of optical properties over time can be suppressed.

[0022] [Description of Embodiments of the Invention]

[0023] First, embodiments of the present invention will be described. One embodiment of the optical connection structure includes a multi-core optical fiber, a first ferrule, multiple optical fibers, and a second ferrule. The multi-core optical fiber has multiple first cores extending in the length direction, a first cladding covering the multiple first cores, and a first optical fiber front end face including the front ends of each of the multiple first cores and the first cladding. The first ferrule has a first inner hole for receiving the front end portion of the multi-core optical fiber and a first ferrule end face exposing the front end face of the first optical fiber inside. The first ferrule fixes the front end portion of the multi-core optical fiber within the first inner hole. Each of the multiple optical fibers optically connected to the multi-core optical fiber has a second core extending in the length direction, a second cladding covering the second core, and a second optical fiber front end face including the front ends of each of the second core and the second cladding. The second ferrule has a second inner hole for receiving the front end portion of each of the multiple optical fibers and a second ferrule end face exposing the front end face of each of the multiple optical fibers inside. The second ferrule secures the front ends of multiple optical fibers to the second inner hole using a connector adhesive. The connector adhesive is filled into the second inner hole such that the surface opposite the front end face of the first optical fiber is recessed further into the second inner hole than the end face of the second ferrule. A refractive index matching agent is sealed within the space sealed by the end faces of the first and second ferrules.

[0024] In this optical connection structure, the surface of the bonding adhesive filling the second ferrule, which holds multiple optical fibers, is recessed further into the second inner hole than the end face of the second ferrule. Furthermore, a refractive index matching agent is sealed within the space enclosed by the end faces of the first and second ferrules. According to this method, even if a portion of the multiple optical fibers becomes trapped due to thermal effects on the optical connection structure, the refractive index matching agent will move to and fill the gap. Therefore, according to this optical connection structure, even with thermal effects, the reflection attenuation and insertion loss between the multi-core optical fibers and the trapped fiber will not deteriorate, and the degradation of optical properties over time can be suppressed.

[0025] In one embodiment, the maximum depth along the length direction from the end face of the second ferrule to the surface of the bonding adhesive can be 0.1 μm to 5 μm or less. According to this method, the space where the refractive index matching agent is sealed becomes extremely small, so even if a portion of multiple optical fibers is trapped due to thermal effects, the refractive index matching agent will immediately move to the gap and fill it through capillary action. Therefore, according to this optical connection structure, the degradation of reflection attenuation and insertion loss between multi-core optical fibers and trapped optical fibers can be easily prevented, and the degradation of optical properties over time can be easily suppressed. Alternatively, the maximum depth along the length direction from the end face of the second ferrule to the surface of the bonding adhesive can be 3 μm or less.

[0026] In one implementation, the refractive index matching agent can be sealed within the space defined by the front end face of the first fiber, the second inner hole, the recessed surface of the connector adhesive, and the exposed front end portion of the front end face of the second fiber containing multiple fibers. According to this method, even if a portion of the multiple fibers becomes trapped due to thermal effects on the optical connection structure, the refractive index matching agent positioned near the gap will immediately move and fill the gap. Therefore, according to this optical connection structure, it is possible to easily prevent the degradation of reflection attenuation and insertion loss between the multi-core fiber and the trapped fiber, and it is possible to easily suppress the degradation of optical properties over time. Alternatively, a portion of the refractive index matching agent can be sealed between the first ferrule end face of the first ferrule and the second ferrule end face of the second ferrule.

[0027] As one implementation, the refractive index matching agent can have a refractive index that deviates from the refractive index of the second fiber core by less than 3%. According to this method, it is possible to more reliably prevent the degradation of reflection attenuation and insertion loss between the multi-core fiber and the trapped fiber, and to more reliably suppress the degradation of optical properties over time.

[0028] In one implementation, the arrangement of the plurality of first fiber cores along the planar direction of the front end face of the first fiber can be consistent with the arrangement of each second fiber core along the planar direction of the front end face of the second fiber. According to this method, the optical connection of multi-core optical fibers and multiple optical fibers can be further optimized. Furthermore, the arrangement can be such that all the fiber cores of the multi-core optical fiber and the fiber cores of the multiple optical fibers correspond to each other, or some may not have corresponding configurations. Additionally, the fiber cores of the multi-core optical fiber and the fiber cores of the multiple optical fibers can be rotated and adjusted in a manner that ensures their corresponding configurations.

[0029] In one implementation, the first and second ferrules can be pressed against each other by a pressing member to seal the end faces of the first and second ferrules. According to this method, a refractive index matching agent can be maintained within the space defined by the end faces of the first and second ferrules using a simple structure.

[0030] In one implementation, the first and second ferrules can be bonded together to maintain a close contact between the end faces of the first and second ferrules. According to this method, a refractive index matching agent can be sealed within the space defined by the end faces of the first and second ferrules using a simple structure.

[0031] As one implementation, the optical connection structure described above may further include a sleeve that holds the first and second ferrules from the outside in a manner that aligns the optical axes of the plurality of first fiber cores and the respective optical axes of the second fiber cores. The first and second ferrules and the sleeve may be bonded and fixed to maintain a close contact between the end faces of the first and second ferrules. According to this method, a refractive index matching agent can be sealed within the space defined by the end faces of the first and second ferrules using a simple structure.

[0032] As one implementation, the first ferrule end face and the second ferrule end face may have a spherical shape with a radius of curvature of 1 mm to 50 mm in at least a portion. According to this method, when the first ferrule and the second ferrule are mated, the front ends of the two ferrules can be easily brought into close contact, thus enabling easy direct joining of the front ends of multi-core optical fibers with the front ends of multiple optical fibers, such as PC (Physical Contact) connections.

[0033] Furthermore, as another aspect, the present invention relates to a method for manufacturing an optical connection structure having any of the above-described configurations. This manufacturing method includes the following steps: inserting the front ends of a plurality of optical fibers into the second inner hole of a second ferrule, and fixing the plurality of optical fibers to the second ferrule using a bonding agent; grinding the end face of the second ferrule to which the plurality of optical fibers are fixed; and, after the grinding step, subjecting the component containing the bonding agent to an additional heat treatment. In this method for manufacturing the optical connection structure, the surface of the bonding agent is recessed further into the second inner hole than the end face of the second ferrule. According to this manufacturing method, spaces for configuring the multi-core optical fibers and the refractive index matching agent injected between the plurality of optical fibers can be easily formed.

[0034] [Detailed Description of Embodiments of the Invention]

[0035] Hereinafter, specific examples of embodiments of the present invention will be described with reference to the accompanying drawings. The present invention is not limited to these examples, but is illustrated by the claims, which are intended to include all modifications equivalent to and within the scope of the claims. In the description of the drawings, the same reference numerals are used to denote the same elements, and repeated descriptions are omitted.

[0036] Figure 1 This is a perspective view showing an optical connection structure according to one embodiment. Figure 2 It is Figure 1 The diagram shows a perspective view of the disassembled light-connected structure. Figure 3 It is along Figure 1 A cross-sectional view along line III-III of the light-connecting structure shown. (See image.) Figures 1 to 3 As shown, the optical connector 1 includes a first optical connector 10, a second optical connector 20, and a slotted sleeve 30. The first optical connector 10 includes a multi-core fiber 12 (hereinafter also referred to as "MCF 12"), a ferrule 14 (first ferrule), and a flange 16. The second optical connector 20 includes multiple optical fibers 22, a ferrule 24 (second ferrule), and a flange 26. The slotted sleeve 30 (sleeve) is a component used for alignment by holding the ferrule 14 and ferrule 24 from the outside, aligning the optical axes of the MCF 12 cores of the first optical connector 10 with the optical axes of the multiple optical fibers 22. (See also...) Figure 4 ).

[0037] MCF 12 Figures 3 to 5 As shown, it has a plurality of fiber cores 12a (first fiber cores) extending in the length direction A, a cladding 12b (first cladding) extending in the length direction A and covering the plurality of fiber cores 12a, and a front end face 12c (first fiber front end face). Figure 4 It is a cross-sectional view showing a portion T of the light-connecting structure 1 magnified. Figure 5This diagram shows the front end of the MCF 12 and the end face of the ferrule 14. The front end face 12c is composed of the front ends of multiple fiber cores 12a and the front end of the cladding 12b. The fiber cores 12a can be made of, for example, silicon glass with an increased refractive index due to the addition of dopants such as germanium, and the cladding 12b can be made of, for example, silicon glass with a decreased refractive index due to the addition of dopants such as fluorine. The combination of materials and dopants can be appropriately selected. In the MCF 12 described above, optical signals of a specified wavelength can be transmitted through each fiber core 12a.

[0038] In MCF 12, for example, each core 12a is configured in a two-dimensional shape. MCF 12, as... Figure 5 As shown, for example, it can have 4 fiber cores 12a, 7 fiber cores 12a, 8 fiber cores 12a, or 19 fiber cores 12a, without limitation. Figure 5 In the example shown, four fiber cores 12a are arranged in a square configuration. The diameter of each fiber core 12a can be, for example, less than 10 μm, less than 5 μm, or more than 1 μm. The spacing between the cores of each fiber core 12a can be, for example, more than 10 μm and less than 50 μm. The diameter of the cladding 12b can be, for example, less than 200 μm, less than 125 μm, less than 100 μm, less than 80 μm, or more than 50 μm.

[0039] The insert 14 is a cylindrical component that holds the front end portion 12d of the MCF 12. It has a through hole, i.e., an inner hole 14a (first inner hole), that accommodates the front end portion 12d of the MCF 12, and an end face 14b of the insert 14. The insert 14 fixes the front end portion 12d of the MCF 12 to the inner hole 14a such that the front end face 12c of the MCF 12 is exposed inside the end face 14b. The inner diameter of the inner hole 14a is the same as or slightly larger than the outer diameter of the MCF 12, and the front end portion 12d of the MCF 12 is fitted into the inner hole 14a. The insert 14 is, for example, 6 mm or more but less than 8 mm in length and is made of a ceramic material such as zirconium oxide.

[0040] Flange 16 Figure 3 As shown, this is a cylindrical component that holds the rear end portion of the insert 14 and houses the MCF 12 inside. The portion of the MCF 12 housed within the flange 16 can be fixed to the flange 16 using an adhesive or the like. The flange 16 is made of, for example, metal or resin.

[0041] Multiple optical fibers 22 are optical fibers that are optically connected to the MCF 12. Each optical fiber 22 is as follows: Figure 3 , Figure 4 and Figure 6As shown, it has a fiber core 22a (second fiber core) extending in the length direction A, a cladding 22b (second cladding) extending in the length direction A and covering the fiber core 22a, and a front end face 22c (second fiber front end face). Figure 6 This diagram shows the front ends of multiple optical fibers 22 and the end faces of the ferrules 24. The front end face 22c is composed of the front ends of the fiber cores 22a and the cladding 22b. The fiber cores 22a can be made of, for example, silicon glass with an increased refractive index due to the addition of dopants such as germanium, and the cladding 22b can be made of, for example, silicon glass with a decreased refractive index due to the addition of dopants such as fluorine. The combination of materials and dopants can be appropriately selected. In the optical fibers 22 described above, optical signals of a specified wavelength are transmitted through each fiber core 22a. The multiple optical fibers 22 can be, for example, a bundle of optical fibers or individual optical fibers.

[0042] In the second optical connector 20, each optical fiber 22 is configured in a two-dimensional shape. The second optical connector 20 is as follows... Figure 6 As shown, the second optical connector 20 can have, for example, 4, 7, 8, or 19 optical fibers 22, without limitation. The number and configuration of the optical fibers 22 of the second optical connector 20 correspond to the number and configuration of the multiple fiber cores 12a of the MCF 12 of the first optical connector 10. In other words, the configuration of the multiple optical fibers 22 is similar to (consistent with) the configuration of the multiple fiber cores 12a of the MCF 12. However, the number and configuration of the multiple optical fibers 22 need not be completely consistent with the number and configuration of the MCF 12; it can be a structure in which some fibers are not optically connected. The multiple optical fibers 22 of the second optical connector 20 are configured to be optically coupled to each fiber core 12a of the MCF 12 of the first optical connector 10 by rotating and adjusting them around the central axis of the ferrule 24.

[0043] The diameter of each fiber core 22a can be, for example, less than 10 μm, less than 5 μm, or more than 1 μm. The spacing between the cores of each fiber core 22a can be, for example, more than 10 μm and less than 50 μm. The diameter of the cladding 22b outside the ferrule 24 (described later) can be more than 80 μm and more than 125 μm, and can be reduced in diameter within the ferrule 24 in a manner corresponding to MCF 12. The outer tangent circle of the reduced fiber 22 (corresponding to the inner diameter of the inner hole 24a of the ferrule 24) corresponds to the cladding diameter of MCF 12, and can be, for example, less than 200 μm, less than 125 μm, less than 100 μm, less than 80 μm, or more than 50 μm. The cladding 22b inside the ferrule 24 can be changed from a typical outer diameter of 125 μm or 80 μm to a smaller diameter. The optical fiber described above can be achieved by etching the front end portion with hydrofluoric acid or the like. In this case, the inner diameter of the ferrule 24 that houses multiple optical fibers 22 may differ between the portion housing the thinner optical fiber and the portion housing the normally outer diameter optical fiber.

[0044] The ferrule 24 is a cylindrical component that holds the front end portions 22d of multiple optical fibers 22 together. It has a through-hole, i.e., an inner hole 24a (second inner hole), and an end face 24b (second ferrule end face), for accommodating the front end portions of the multiple optical fibers 22. The ferrule 24 fixes the front end portions 22d of the multiple optical fibers 22 within the inner hole 24a with the front end faces 22c of the multiple optical fibers 22 exposed inside the end face 24b of the ferrule 24, using a bonding adhesive 28. The inner diameter of the inner hole 24a is the same as or slightly smaller than the outer diameter of the bundled optical fibers 22. The front end portions 22d of the multiple optical fibers 22 are inserted into the inner hole 24a and bonded by bonding adhesive 28 injected into their gaps. The bonding adhesive 28 is, for example, a thermosetting adhesive, which is cured by heating after being injected into a designated area. Like the ferrule 14, the insert 24 is made of ceramic materials such as zirconium oxide, for example, with a length of 6 mm or more but less than 8 mm.

[0045] Flange 26 Figure 3 As shown, this is a cylindrical component that holds the rear end portion of the ferrule 24 and houses multiple optical fibers 22 inside. The portion of the multiple optical fibers 22 housed within the flange 26 can be fixed within the flange 26 by means of adhesive or the like. The flange 26 is made of, for example, metal or resin.

[0046] Here, the relationship between the end face 24b of the ferrule 24 of the second optical connector 20 of the optical connection structure 1, the front end face 22c of the optical fiber 22, the exposed front end portion 22e including the front end face 22c, and the surface 28a of the wiring adhesive 28 is described with reference to... Figures 7 to 10 Please provide an explanation. Figure 7 This is an oblique view showing the initial state in which multiple optical fibers are fixed inside the ferrule by wiring adhesive, with the front end face of each optical fiber aligned with the end face of the ferrule. Figure 8 It means Figure 7 A cross-sectional view of the initial state. Figure 9 It means from Figure 7 and Figure 8 The image shown is a perspective view of the initial state, where a portion of the optical fiber is recessed inwards. Figure 10 It means Figure 9 A cross-sectional view of a state where something is trapped.

[0047] like Figure 7 and Figure 8 As shown, in the second optical connector 20, the wiring adhesive 28 is filled in the inner hole 24a such that its surface 28a is recessed further into the inner hole 24a than the end face 24b of the ferrule 24. The surface 28a of the wiring adhesive 28 faces the front end face 12c of the MCF 12. The amount of recess along the length direction A from the imaginary surface along the end face 24b of the ferrule 24 to the surface 28a of the wiring adhesive 28 is not particularly limited; for example, the recess amount can be at most 0.1 μm to 5 μm, or it can be less than 3 μm. Furthermore, the surface 28a is as follows... Figure 7 The surface shown can be flat or uneven. In the case of an uneven surface, the depth can be the shortest distance from the imaginary surface along the end face 24b of the insert 24 to the most recessed area on the surface 28a. The distance described above can be measured, for example, using a surface height measuring instrument based on the principle of a white light interferometer or a laser microscope.

[0048] Furthermore, in the second optical connector 20 according to this embodiment, a refractive index matching agent 40 is injected into the space S formed by the recess of the surface 28a of the wiring adhesive 28 as described above. This space S is a region (gap) defined by the front end face 12c of the MCF 12, the inner hole 24a, the recessed surface 28a of the wiring adhesive 28, and the exposed front end portions 22e of each front end face 22c of the plurality of optical fibers 22. In addition, the refractive index matching agent 40 has a refractive index that is approximately the same as that of the core 12a of the MCF 12 and the core 22a of the optical fiber 22, for example, a refractive index that deviates from the refractive index of the core 12a or the core 22a by an amount of less than 3%, and is composed of a liquid that is transparent to the wavelength used in optical communication. The refractive index matching agent 40 can be, for example, silicone oil with a specified refractive index that allows light to pass through. The refractive index matching agent 40 can be in gel form, but considering the immediate flowability of the refractive index matching agent 40, an oil form is preferred. The viscosity of the refractive index matching agent 40 is, for example, 1 mPa·s or more and 10,000 mPa·s or less, preferably 3,000 mPa·s or less. The space S described above is formed by sealing the end face 14b of the insert 14 and the end face 24b of the insert 24, thereby sealing the wiring adhesive 28 injected into the space S. That is, the wiring adhesive 28 will not leak outward from the mating surfaces of the insert 14 and the insert 24.

[0049] Next, refer to Figure 9 and Figure 10 This explains the situation where, in the optical connector 1 having the above-described structure, a portion of the optical fiber 22 is recessed inward (rearward) in the second optical connector 20 due to the effects of heat, etc. Figure 9 and Figure 10 One optical fiber 22A is recessed inward, and the front end face 22c of the optical fiber 22A is roughly aligned with or slightly above the surface 28a of the connector adhesive 28.

[0050] In the optical connection structure 1 described in this embodiment, even assuming, as described above, that a portion of the optical fiber 22A is recessed inwards, the refractive index matching agent 40 injected into the space S will enter between the leading edge face 22c of the recessed optical fiber 22A and the corresponding core 12a of the MCF 12 through capillary action or the like. Therefore, optical communication between the core 22a of the optical fiber 22A and the core 12a of the MCF 12 can continue in the same state as before. Furthermore, when the refractive index matching agent 40 is oily, it is easier for the refractive index matching agent 40 to move to the required location earlier.

[0051] Next, regarding the retaining structure in the optical connection structure 1 described above for maintaining the mating state of the ferrule 14 and ferrule 24, refer to... Figures 11 to 13 Please provide an explanation. Figure 11 This is a perspective view showing the structure for fixing the light connection structure 1. Figure 12 This is a perspective view showing another structure that fixes the light connection structure 1. Figure 13 This is a perspective view showing other structures that fix the optical connection structure 1. In the optical connection structure 1, the refractive index matching agent 40 is kept from leaking from the mating surface of the ferrule 14 and ferrule 24 by the retaining structure described above.

[0052] exist Figure 11 The structure 100 shown includes a spring member 50 (pressing member) that presses the flange 16 of the first optical connector 10 inward along arrow A1 and a spring member 52 (pressing member) that presses the flange 26 of the second optical connector 20 inward along arrow A2. Furthermore, in Figure 11 The illustrations relating to the retaining structures at the base ends of each spring component 50, 52 are omitted. In this structure 100, each spring component 50, 52 is pressed against each other, thereby sealing the end face 14b of the insert 14 and the end face 24b of the insert 24. In this structure, the insert 14 and the insert 24 may also be bonded to each other with adhesive within the slotted sleeve 30 to maintain a tight seal between the end faces 14b and 24b. Alternatively, the insert 14 and the insert 24 may be bonded to the slotted sleeve 30 to maintain a tight seal between the end faces 14b and 24b. With the above configuration, in structure 100, the refractive index matching agent 40 injected into the space S is sealed in.

[0053] exist Figure 12 The structure 101 shown includes a leaf spring member 60 (pressing member) that presses the flange 16 of the first optical connector 10 and the flange 26 of the second optical connector 20 inward. The leaf spring member 60 has a support portion 62 that engages with the flange 16 and a support portion 64 that engages with the flange 26. In this structure 101, the end faces 14b of the ferrule 14 and 24b of the ferrule 24 are sealed by the pressing action of the leaf spring member 60. Similarly, in this structure, the ferrules 14 and 24 are bonded and fixed to maintain a tight seal between the end faces 14b and 24b. Through this configuration, the refractive index matching agent 40 injected into the space S is maintained sealed within the structure 101.

[0054] exist Figure 13 The structure 102 shown can... Figure 11The structure 101 shown is further encapsulated with a sealing resin or the like to provide a sealing portion 70. According to this structure 102, the refractive index matching agent 40 injected into the space S can be more reliably maintained in a sealed state. In structure 102, a protective cover 72 covering the flange 16 and MCF 12 and a protective cover 74 covering the flange 26 and optical fiber 22 can also be provided. This can suppress or protect the MCF 12 and optical fiber 22 from movement along their length. Furthermore, it is also possible to... Figure 12 The structure 101 shown is constructed by means of, as Figure 13 Encapsulated with sealing resins as shown.

[0055] Next, the method for fabricating the aforementioned optical connection structure 1 will be described. First, prepare an MCF 12, a ferrule 14, a flange 16, multiple optical fibers 22, a ferrule 24, a flange 26, a splice adhesive 28, a slotted sleeve 30, and a refractive index matching agent 40. The MCF 12 is obtained by setting each fiber core 12a to a specified configuration (e.g., a square configuration with 4 fiber cores), for example, preparing an optical fiber with a cladding diameter of 125 μm and a core spacing of 40 μm. Ferrules 14 and 24 are, for example, ferrules for LC (Liquid Crystal Laminate) applications.

[0056] Next, the MCF 12 is inserted into the inner hole of the flange 16 and the inner hole 14a of the ferrule 14, so that the front end portion 12d of the MCF 12 fits into the inner hole 14a of the ferrule 14. At this time, the front end face 12c of the MCF 12 can be made to match the end face 14b of the ferrule 14, or the end face 14b of the ferrule 14 can be PC (Physical Contact) polished after fitting to make the front end face 12c of the MCF 12 match the end face 14b of the ferrule 14. When PC polishing is performed, the radius of curvature of the ferrule diameter is, for example, 1 mm or more and 50 mm or less. Thus, the first optical connector 10 is prepared.

[0057] Furthermore, multiple optical fibers 22 are inserted into the inner hole of the flange 26 and the inner hole 24a of the ferrule 24, with the front end portion 22d of the optical fiber 22 positioned in the inner hole 24a of the ferrule 24. The optical fiber 22 is either finely machined with the front end portion 22d corresponding to the MCF 12, or drawn into a single fiber with the aforementioned diameter (e.g., an optical fiber with a cladding diameter of 40 μm). The optical fibers 22 are arranged in the ferrule 24 in a two-dimensional configuration, corresponding to the MCF configuration as described above. At this time, each optical fiber 22 is configured such that its cladding 22b is connected to each other and also connected to the inner hole 24a of the ferrule 24. Subsequently, a bonding agent 28 is injected into the gap between the inner hole 24a of the ferrule 24 and the multiple optical fibers 22. The bonding agent 28 is injected sufficiently to cover the front end face 22c of the optical fiber 22 and the end face 24b of the ferrule 24. Then, the bonding agent 28 is heat-cured, for example, by heating. This fixes multiple optical fibers 22 to the ferrule 24. Next, the end face 24b of the ferrule 24 and the front face 22c of the optical fiber 22 are PC-polished together until the front face 22c of the optical fiber 22 aligns with the end face 24b of the ferrule 24. Through PC polishing, the adhesive on the front face 22c and end face 24b is removed, exposing the front face 22c and end face 24b. When performing PC polishing, the radius of curvature of the diameter of the ferrule 24 is, for example, 1 mm to 50 mm. This prepares the initial form of the second optical connector 20.

[0058] Next, if the PC grinding is completed, the second optical connector 20 in its initial form undergoes additional heat treatment. This additional heat treatment can be performed at a higher temperature or for a longer duration than the temperature at which the wiring adhesive 28 is cured. Through this additional heat treatment as described above, the wiring adhesive 28 shrinks, causing its surface 28a to recess further into the inner hole 24a than the end face 24b of the ferrule 24, for example, by a maximum depth of 0.5 μm to 5 μm or 3 μm. Thus, the second optical connector with a space S is prepared such that the surface 28a of the wiring adhesive 28 recesses further into the inner hole 24a than the end face 24b of the ferrule 24.

[0059] Next, a refractive index matching agent 40 is applied to the end face 24b of the ferrule 24 containing the space S of the second optical connector 20. Furthermore, the first optical connector 10 and the second optical connector 20 are connected within the slotted sleeve 30 by mating the end face 14b of the ferrule 14 with the end face 24b of the ferrule 24.

[0060] Next, within the slotted sleeve 30, the optical fiber is rotated to perform core alignment, so that each fiber core 12a of the MCF 12 and the corresponding fiber core 22a of the plurality of optical fibers 22 are optically coupled.

[0061] Next, after the fiber core is aligned, it is then... Figures 11 to 13 The pressing component shown secures the first optical connector 10 and the second optical connector 20 in a pressed-against-each-other state. Alternatively, the pressing component can be omitted, and the ferrules 14 and 24 can be pressed down by friction with the slotted sleeve 30. Furthermore, the ferrules 14 and 24 can be bonded together using adhesive. With these configurations, optical connection structures 1, 100, 101, and 102 can be obtained.

[0062] In the optical connection structure 1 described in this embodiment, the surface 28a of the bonding agent 28 filling the ferrule 24 holding the plurality of optical fibers 22 is recessed further into the inner hole 24a than the end face 24b of the ferrule 24. Furthermore, a refractive index matching agent 40 is sealed within the space S sealed by the end face 14b of the ferrule 14 and the end face 24b of the ferrule 24. According to this structure, even if a portion of the optical fiber 22 is recessed inward due to thermal effects on the optical connection structure 1, the refractive index matching agent 40 will move into the gap and fill it. Therefore, according to the optical connection structure 1, even with thermal effects, the reflection attenuation and insertion loss between the MCF 12 and the recessed optical fiber 22 will not deteriorate, and the degradation of optical characteristics over time can be suppressed.

[0063] Furthermore, in this embodiment, the maximum embedment depth along the length direction A from the end face 24b of the ferrule 24 to the surface 28a of the bonding agent 28 can be 0.1 μm or more and 5 μm or less. According to this structure, the space S in which the refractive index matching agent 40 is enclosed becomes extremely small. Therefore, even if a portion of the multiple optical fibers 22 embeds due to thermal effects, the refractive index matching agent 40 will immediately move to the gap and fill it through capillary action. Thus, according to the optical connection structure 1, the degradation of reflection attenuation and insertion loss between the MCF 12 and the embedded optical fiber 22 can be easily prevented, and the degradation of optical properties over time can be easily suppressed.

[0064] Furthermore, in this embodiment, the refractive index matching agent 40 is sealed within the space S defined by the front end face 12c of the MCF 12, the inner hole 24a, the surface 28a of the wiring adhesive 28, and the exposed front end portion 22e of the front end face 22c containing the plurality of optical fibers 22. According to this structure, even if a portion of the plurality of optical fibers 22 becomes trapped due to thermal effects on the optical connection structure 1, the refractive index matching agent 40 disposed near the gap will immediately move and fill the gap. Thus, according to the optical connection structure 1, the degradation of reflection attenuation and insertion loss between the MCF 12 and the trapped optical fibers 22 can be easily prevented, and the degradation of optical properties over time can be easily suppressed. Furthermore, a portion of the refractive index matching agent 40 is located between the end face 14b of the ferrule 14 and the end face 24b of the ferrule 24.

[0065] Furthermore, in this embodiment, the refractive index matching agent 40 may have a refractive index of up to 3% relative to the refractive index of the fiber core 12a or the fiber core 22a. According to this structure, the degradation of reflection attenuation and insertion loss between the MCF 12 and the trapped fiber 22 can be prevented more reliably, and the degradation of time-dependent optical properties can be suppressed more reliably.

[0066] Furthermore, in this embodiment, the arrangement of the plurality of fiber cores 12a of the MCF 12 along the planar direction of the front end face 12c can be consistent with the arrangement of each fiber core 22a of the optical fiber 22 along the planar direction of the front end face 22c. According to this structure, the optical connection between the MCF 12 and the plurality of optical fibers 22 can be further optimized. Moreover, the fiber cores 12a of the MCF 12 and the fiber cores 22a of the plurality of optical fibers 22 can be configured to correspond entirely to each other, or some may not correspond.

[0067] In this embodiment, insert 14 and insert 24 can be pressed against each other by spring members 50, 51 or leaf spring member 60 to seal end faces 14b and 24b. According to this structure, the refractive index matching agent 40 can be reliably maintained within the space S defined by the end face 14b of insert 14 and the end face 24b of insert 24 through a simple structure.

[0068] Furthermore, in this embodiment, insert 14 and insert 24 can be bonded together to maintain a close contact between end faces 14b and 24b. According to this structure, a refractive index matching agent 40 can be sealed within the space S defined by end faces 14b and 24b using a simple structure.

[0069] In addition, in this embodiment, the optical connection structure 1 also includes a slotted sleeve 30, which holds the ferrule 14 and ferrule 24 from the outside in a manner that aligns the optical axes of the fiber core 12a and the fiber core 22a. The ferrule 14 and ferrule 24 and the slotted sleeve 30 can be bonded and fixed to maintain the end faces 14b and 24b in close contact with each other. According to this structure, it is possible to maintain the state in which the refractive index matching agent 40 is sealed in the space S defined by the end faces 14b of the ferrule 14 and 24b of the ferrule 24 with a simple structure.

[0070] Furthermore, in this embodiment, the end face 14b of ferrule 14 and the end face 24b of ferrule 24 may have a spherical shape with a radius of curvature of 1 mm to 50 mm in at least a portion. According to this structure, when ferrules 14 and ferrules 24 are mated, the front ends of the two ferrules are easily brought into close contact, thus enabling easy direct bonding, for example, PC (Physical Contact) connection, of the front end face 12c of MCF 12 and the front end faces 22c of the plurality of optical fibers 22.

[0071] Furthermore, the optical connection structure manufacturing method according to this embodiment includes the following steps: inserting the front end portions 22d of a plurality of optical fibers 22 into the inner hole 24a of the ferrule 24, and fixing the plurality of optical fibers 22 to the ferrule 24 using a wiring adhesive 28; grinding the end face of the ferrule 24 to which the plurality of optical fibers 22 are fixed; and after the grinding step, subjecting the component containing the wiring adhesive 28 to an additional heat treatment. In this method of manufacturing the optical connection structure, through this additional heat treatment, the surface 28a of the wiring adhesive 28 is recessed further into the inner hole 24a than the end face 24b of the ferrule 24. According to this manufacturing method, a space S in which the refractive index matching agent 40 injected between the MCF 12 and the plurality of optical fibers 22 can be easily formed.

[0072] The embodiments of the present invention have been described in detail above, but the present invention is not limited to the above embodiments and can be applied to various embodiments.

[0073] Explanation of the label

[0074] 1…Light Connection Structure

[0075] 10…First optical connector

[0076] 12… multi-core optical fiber

[0077] 12a… Core (First Core)

[0078] 12b…cladding (first cladding)

[0079] 12c…Front-end face (first fiber front-end face)

[0080] 12d…front end

[0081] 14… Plug (First Plug)

[0082] 14a…Inner hole (1st inner hole)

[0083] 14b… End face (first ferrule end face)

[0084] 16…Flange

[0085] 20…Second optical connector

[0086] 22… optical fibers (multiple optical fibers)

[0087] 22a…core (second core)

[0088] 22b…cladding (second cladding)

[0089] 22c… Front end face (second fiber front end face)

[0090] 22d…Front-end section

[0091] 22e…Exposed front portion

[0092] 24… Socket (Second Socket)

[0093] 24a…Inner hole (2nd inner hole)

[0094] 24b… End face (second ferrule end face)

[0095] 26…Flange

[0096] 28… Wiring adhesive

[0097] 28a… Surface

[0098] 30…slit sleeve

[0099] 40…Refractive index matching agent

[0100] 50, 52… Spring components (pressing components)

[0101] 60…Leaf spring assembly (pressing assembly)

[0102] 62, 64… Support sections

[0103] 70…Sealing part

[0104] 72, 74… protective shield

[0105] 100, 101, 102… structure

[0106] 200, 200A… fiber optic

[0107] 200a…Frontend

[0108] 201… ferrule

[0109] 201a…end face

[0110] 202… Adhesive

[0111] 210… multi-core optical fiber

[0112] 211…ferrule

[0113] A…length direction

[0114] A1, A2... arrows

[0115] S…space

[0116] T… area

[0117] V…gap

Claims

1. An optical connection structure having: A multi-core optical fiber has a plurality of first cores extending in the length direction, a first cladding covering the plurality of first cores, and a first optical fiber front end face including the front ends of the plurality of first cores and the first cladding. The first ferrule has a first inner hole for receiving the front end portion of the multi-core optical fiber and a first ferrule end face for exposing the front end face of the first optical fiber on the inner side, wherein the front end portion of the multi-core optical fiber is fixed in the first inner hole by the first ferrule. Multiple optical fibers are optically connected to the multi-core optical fiber. Each optical fiber has a second fiber core extending along the length direction, a second cladding covering the second fiber core, and a second fiber front end face including the second fiber core and the second cladding. as well as The second ferrule has a second inner hole for receiving the front ends of each of the plurality of optical fibers and a second ferrule end face on the inner side of each of the plurality of optical fibers, wherein the front ends of each of the plurality of optical fibers are fixed in the second inner hole by means of a connector adhesive. The bonding agent is filled into the second inner hole in such a way that the surface opposite the front end face of the first optical fiber is recessed further into the second inner hole than the end face of the second ferrule. A refractive index matching agent is sealed within the space enclosed by the first ferrule end face and the second ferrule end face. The maximum indentation along the length direction from the end face of the second ferrule to the surface of the wiring adhesive is 0.1 μm or more and 5 μm or less. The refractive index matching agent is sealed into the space defined by the first fiber front end face, the second inner hole, the surface into which the wiring adhesive is embedded, and the exposed front end portion of the second fiber front end face containing the plurality of fibers.

2. The optical connection structure according to claim 1, wherein, The refractive index matching agent has a refractive index that deviates from the refractive index of the second fiber core by less than 3%.

3. The optical connection structure according to claim 1 or 2, wherein, The viscosity of the refractive index matching agent is above 1 mPa•s and below 10000 mPa•s.

4. The optical connection structure according to claim 3, wherein, The viscosity of the refractive index matching agent is below 3000 mPa•s.

5. The optical connection structure according to claim 1 or 2, wherein, The arrangement of the plurality of first fiber cores along the planar direction of the front end face of the first fiber is consistent with the arrangement of the respective second fiber cores along the planar direction of the front end face of the second fiber.

6. The optical connection structure according to claim 1 or 2, wherein, The first insert and the second insert are pressed against each other by a pressing member to seal the end faces of the first insert and the second insert.

7. The optical connection structure according to claim 1 or 2, wherein, The first ferrule and the second ferrule are glued and fixed to maintain a close contact between the end faces of the first ferrule and the end faces of the second ferrule.

8. The optical connection structure according to claim 1 or 2, wherein, It also includes a sleeve that holds the first ferrule and the second ferrule from the outside in a manner that aligns the optical axes of the plurality of first fiber cores and the optical axes of the respective second fiber cores. The first insert, the second insert, and the sleeve are bonded and fixed together to maintain a close contact between the end faces of the first insert and the second insert.

9. The optical connection structure according to claim 1 or 2, wherein, The first ferrule end face and the second ferrule end face have at least a portion of a spherical shape with a radius of curvature of more than 1 mm and less than 50 mm.

10. A method for manufacturing an optical connection structure, wherein the optical connection structure according to any one of claims 1 to 9 is manufactured. The method for manufacturing this optical connection structure includes the following steps: The front ends of the plurality of optical fibers are respectively inserted into the second inner hole of the second ferrule, and the plurality of optical fibers are fixed to the second ferrule by the wiring adhesive; The end face of the second ferrule to which the plurality of optical fibers are fixed is ground together with the front end face of the second optical fiber; and After the grinding process, the component containing the wiring adhesive is subjected to an additional heat treatment. Through the additional heat treatment, the surface of the wiring adhesive is recessed further into the second inner hole than the end face of the second ferrule.

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