Optical fiber connector

Abstract

The present invention provides a fiber connector that can suppress heat generation in the resin caused by light leaking into the cladding. [Solution] The optical fiber connector 1 comprises an optical fiber 2 having a decoating portion 25 from which the coating 23 has been removed, an optical fiber 3 having a decoating portion 35 from which the coating 33 has been removed, a fusion splice portion 50 from which the ends of the decoating portion 25 and the ends of the decoating portion 35 are fusion spliced ​​together in the longitudinal direction, a protective resin 81 covering the edge end 33A of the coating 33 of the optical fiber 3 and the decoating portion 35, and a relaxation resin portion 90 adjacent to the protective resin 81 in the longitudinal direction and covering the decoating portion 35. The relaxation resin portion 90 has a refractive index lower than that of the protective resin 81. The relaxation resin portion 90 includes a plurality of relaxation resins 91, 92 arranged along the longitudinal direction. The refractive index of the relaxation resins 91, 92 gradually decreases as they move away from the protective resin 81.

Description

Technical Field

[0001] The present invention relates to an optical fiber connector.

Background Art

[0002] Generally, in a connection structure in which optical fibers are fusion-connected to each other (hereinafter referred to as an optical fiber connector), the coating that covers the periphery of the cladding of each optical fiber is peeled off, and the optical fibers are abutted and fusion-connected. In such an optical fiber connector, there is a concern that moisture may enter from the edge part when the coating is peeled off, causing the coating to swell and deteriorating the optical characteristics of the optical fiber. Therefore, the edge part of the coating may be covered with resin (see, for example, Patent Document 1).

[0003] Since the refractive index of the resin that covers the edge part of such a coating is higher than the refractive index of air, when the light propagating in the core leaks into the cladding, this leaked light propagates in the cladding at the exposed part of the cladding, but is locally leaked into the resin and generates heat at the part covered with the resin. When such heat generation occurs, the resin undergoes thermal degradation, increasing the light absorption rate of the resin and further advancing the thermal degradation, resulting in a decrease in the reliability of the optical fiber connector.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In view of such problems of the prior art, the present invention is made, and an object thereof is to provide a fiber connector capable of suppressing heat generation of resin due to light leaking into the cladding.

Means for Solving the Problems

[0006] One aspect of the present invention is: A first optical fiber comprising a first core, a first cladding having a refractive index lower than that of the first core and covering the periphery of the first core, and a first covering covering the periphery of the first cladding, wherein the first optical fiber has a first uncovered portion where the first covering has been removed, A second optical fiber comprising a second core, a second cladding having a refractive index lower than that of the second core and covering the periphery of the second core, and a second covering covering the periphery of the second cladding, wherein the second optical fiber has a second uncovered portion where the second covering has been removed, A fusion joint is formed in which the end of the first coating removal portion and the end of the second coating removal portion are fused together in the longitudinal direction. A first protective resin covering the edge of the second coating and the second coating removal portion of at least one second optical fiber, A first relaxation resin portion adjacent to the first protective resin in the longitudinal direction and covering the second coating removal portion, wherein the first relaxation resin portion has a refractive index lower than that of the first protective resin. Equipped with, It is an optical fiber connector.

[0007] Aspect 2 of the present invention relates to the optical fiber connector of Aspect 1 described above, The first relaxation resin portion described above includes a plurality of first relaxation resins arranged along the longitudinal direction, The refractive index of the multiple first relaxation resins described above gradually decreases as they move away from the first protective resin.

[0008] A third aspect of the present invention is the optical fiber connector of the above aspect 2, The above-mentioned plurality of first relaxation resins contain first refractive index adjusting particles at different concentrations for adjusting the refractive index.

[0009] Aspect 4 of the present invention is the optical fiber connector of the above-described aspect 3, The first refractive index adjusting particle described above is a hollow particle with a cavity formed inside.

[0010] Aspect 5 of the present invention relates to an optical fiber connector according to any of the above aspects 1 to 4. The refractive index of the first protective resin is less than or equal to the refractive index of the first coating.

[0011] Aspect 6 of the present invention relates to an optical fiber connector according to any of the above aspects 1 to 5, The second coating removal portion is exposed between the first relaxation resin portion and the fusion connection portion.

[0012] Aspect 7 of the present invention relates to an optical fiber connector according to any of the above aspects 1 to 6. A second protective resin covering the edge of the first coating and the portion where the first coating has been removed from the at least one first optical fiber, A second relaxation resin portion adjacent to the second protective resin in the longitudinal direction and covering the first coating removal portion, the second relaxation resin portion having a refractive index lower than that of the second protective resin. To further prepare.

[0013] Aspect 8 of the present invention is the optical fiber connector of the above aspect 7, The above-mentioned second relaxation resin portion includes a plurality of second relaxation resins arranged along the longitudinal direction, The refractive index of the multiple second relaxation resins described above gradually decreases as they move away from the second protective resin.

[0014] Aspect 9 of the present invention is the optical fiber connector of the above-described aspect 8, The above-mentioned multiple second relaxation resins contain second refractive index adjusting particles at different concentrations to adjust the refractive index.

[0015] Aspect 10 of the present invention relates to the optical fiber connector of aspect 9 described above, The second refractive index adjusting particle described above is a hollow particle with a cavity formed inside.

[0016] Aspect 11 of the present invention is in the optical fiber connector according to any one of Aspects 7 to 10 above, The refractive index of the second protective resin is equal to or less than the refractive index of the second coating.

[0017] Aspect 12 of the present invention is in the optical fiber connector according to any one of Aspects 7 to 11 above, The first coating removal portion is exposed between the second relaxation resin portion and the fusion connection portion.

[0018] Aspect 13 of the present invention is in the optical fiber connector according to any one of Aspects 1 to 12 above, A base member in which a fiber groove for accommodating the first coating removal portion of the at least one first optical fiber and the second coating removal portion of the at least one second optical fiber is formed along the longitudinal direction, A first fixing resin that surrounds the first coating of the at least one first optical fiber and fixes the at least one first optical fiber to the fiber groove, A second fixing resin that surrounds the second coating of the at least one second optical fiber and fixes the at least one second optical fiber to the fiber groove and further includes.

Brief Description of Drawings

[0019] [Figure 1] FIG. 1 is a plan view schematically showing an optical fiber connector in a first embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view taken along line A-A of FIG. 1. [Figure 3] FIG. 3 is a cross-sectional view taken along line B-B of FIG. 1. [Figure 4] FIG. 4 is a plan view schematically showing an optical fiber connector in a second embodiment of the present invention. [Figure 5] FIG. 5 is a cross-sectional view taken along line C-C of FIG. 4. [Figure 6] FIG. 6 is a plan view schematically showing a modified example of the optical fiber connector shown in FIG. 4. [Figure 7]Figure 7 is a schematic plan view showing a modified example of the optical fiber connector shown in Figure 1. [Modes for carrying out the invention]

[0020] Hereinafter, embodiments of the optical fiber connection according to the present invention will be described in detail with reference to Figures 1 to 7. In Figures 1 to 7, the same or corresponding components are denoted by the same reference numerals, and redundant descriptions are omitted. Also, in Figures 1 to 7, the scale and dimensions of each component may be exaggerated, or some components may be omitted. In the following description, unless otherwise specified, terms such as "first" and "second" are used only to distinguish components from one another and do not represent a specific rank or order.

[0021] Figure 1 is a schematic plan view of the optical fiber connector 1 in the first embodiment of the present invention, Figure 2 is a cross-sectional view along line AA in Figure 1, and Figure 3 is a cross-sectional view along line BB in Figure 1. As shown in Figures 1 to 3, the optical fiber connector 1 includes a plurality of bundled optical fibers 2 (first optical fibers), a single optical fiber 3 (second optical fiber), and a base member 4 that protects the optical fibers 2 and 3 from external forces, shocks, and vibrations. The base member 4 can be formed from a glass material such as Neoceram® or quartz.

[0022] As shown in Figure 2, the optical fiber connector 1 in this embodiment includes seven optical fibers 2, each optical fiber 2 including a core 21 (first core), a cladding 22 (first cladding) surrounding the core 21, and a covering 23 (first covering) surrounding the cladding 22. The refractive index of the cladding 22 is lower than that of the core 21, allowing light to propagate inside the core 21. The covering 23 is formed from, for example, resin. At the end of each optical fiber 2, a portion of the covering 23 is removed over a certain length in the longitudinal direction (X direction), forming a covered portion 25 (first covered portion) where the cladding 22 is exposed (see Figure 1).

[0023] As shown in Figure 3, the optical fiber 3 includes a core 31 (second core), a cladding 32 (second cladding) surrounding the core 31, and a covering 33 (second covering) surrounding the cladding 32. The refractive index of the cladding 32 is lower than that of the core 31, allowing light to propagate inside the core 31. The covering 33 is formed from, for example, resin. At the end of the optical fiber 3, a portion of the covering 33 is removed over a certain length in the longitudinal direction (X direction), forming a covered portion 35 (second covered portion) where the cladding 32 is exposed (see Figure 1).

[0024] The ends of the stripped portions 25 of optical fiber 2 and 35 of optical fiber 3 are fusion-spliced ​​to each other at the fusion splice 50. That is, the stripped portions 25 and 35 are fusion-spliced ​​to each other so that the cores 21 of multiple optical fibers 2 and the cores 31 of optical fibers 3 are optically coupled. This allows light to be introduced from the cores 21 of multiple optical fibers 2 into the cores 31 of optical fibers 3. In this embodiment, the case where light propagates from the cores 21 of optical fiber 2 to the cores 31 of optical fiber 3 is described, but the direction of light propagation may be reversed. In this embodiment, the direction in which light propagates, i.e., the direction from optical fiber 2 to optical fiber 3, is called the "downstream side," and the opposite direction is called the "upstream side." For example, an excitation light source may be connected to the upstream side of optical fiber 2 and an optical amplifier may be connected to the downstream side of optical fiber 3, or an optical amplifier may be connected to the upstream side of optical fiber 2 and a laser emitter may be connected to the downstream side of optical fiber 3.

[0025] A fiber groove 60 extending along the longitudinal direction (X direction) is formed on the upper surface 41 of the base member 4, and optical fibers 2 and 3 are housed inside this fiber groove 60, fused together at a fusion splice 50. In this way, the coating removal portions 25, 35 and the fusion splice 50 of the optical fibers 2 and 3, which are particularly susceptible to external forces, are housed within the fiber groove 60 of the base member 4, thus protecting these parts from external forces, shocks, and vibrations. A cover may be placed on the upper surface 41 of the base member 4 to protect the fiber groove 60 from dust.

[0026] As shown in Figures 1 and 2, the optical fiber 2 is fixed within the fiber groove 60 by a fixing resin 71 (first fixing resin) placed in the fiber groove 60. As shown in Figure 2, this fixing resin 71 surrounds the entire outer circumference of the sheath 23 of each optical fiber 2. Also, as shown in Figures 1 and 3, the optical fiber 3 is fixed within the fiber groove 60 by a fixing resin 72 (second fixing resin) placed in the fiber groove 60. As shown in Figure 3, this fixing resin 72 surrounds the entire outer circumference of the sheath 33 of the optical fiber 3. For example, UV-curing resins can be used as these fixing resins 71 and 72.

[0027] As shown in Figures 1 and 2, the stripped edge (end portion) 33A of the coating 33 of the optical fiber 3 is covered with a protective resin 81 (first protective resin), and this protective resin 81 protects the coating 33 from moisture. The protective resin 81 covers the edge portion 33A of the coating 33 of the optical fiber 3 and a part of the coating removal portion 35. Preferably, the refractive index of this protective resin 81 is less than or equal to the refractive index of the coating 33 of the optical fiber 3. For example, the refractive index of the protective resin 81 is 1.33. In Figure 1, the protective resin 81 is shown to be in contact with the fixing resin 72, but the protective resin 81 does not have to be in contact with the fixing resin 72. Also, the protective resin 81 does not have to be in contact with the bottom or side surface of the fiber groove 60.

[0028] Similarly, the stripped edge (end portion) 23A of the coating 23 of the optical fiber 2 is covered with a protective resin 82 (second protective resin), and this protective resin 82 protects the coating 23 from moisture. The protective resin 82 covers the edge portion 23A of the coating 23 of the optical fiber 2 and a part of the coating removal portion 25. Preferably, the refractive index of this protective resin 82 is less than or equal to the refractive index of the coating 23 of the optical fiber 2. For example, the refractive index of the protective resin 82 is 1.33. In Figure 1, the protective resin 82 is shown to be in contact with the fixing resin 71, but the protective resin 82 does not have to be in contact with the fixing resin 71. Also, the protective resin 82 does not have to be in contact with the bottom or sides of the fiber groove 60.

[0029] In this embodiment, a relaxation resin portion 90 (first relaxation resin portion) that covers a part of the removed coating portion 35 of the optical fiber 3 is positioned on the -X direction side of the protective resin 81. This relaxation resin portion 90 is in contact with the protective resin 81 in the longitudinal direction and has a refractive index lower than that of the protective resin 81. A part of the removed coating portion 35 of the optical fiber 3 is exposed between the relaxation resin portion 90 and the fusion splice portion 50. In the illustrated example, the relaxation resin portion 90 is in contact with the protective resin 81 in the longitudinal direction, but this relaxation resin portion 90 does not need to be in contact with the protective resin 81 in the longitudinal direction; the relaxation resin portion 90 and the protective resin 81 may be adjacent to each other while being spaced apart in the longitudinal direction.

[0030] In this embodiment, the relaxation resin portion 90 is composed of a relaxation resin 91 (first relaxation resin) in contact with the protective resin 81 and a relaxation resin 92 (first relaxation resin) in contact with the relaxation resin 91. The relaxation resin 91 has a refractive index (e.g., 1.28) lower than the refractive index of the protective resin 81 (e.g., 1.33), and the relaxation resin 92 has a refractive index (e.g., 1.25) lower than the refractive index of the relaxation resin 91. That is, the refractive indices of the relaxation resins 91 and 92 of the relaxation resin portion 90 gradually decrease as they move away from the protective resin 81. In the illustrated example, the relaxation resin 92 is in contact with the relaxation resin 91, but the relaxation resin 92 does not need to be in contact with the relaxation resin 91 in the longitudinal direction; the relaxation resin 91 and the relaxation resin 92 may be adjacent to each other while being spaced apart in the longitudinal direction.

[0031] To change the refractive index in the relaxation resin portion 90 in this way, for example, particles capable of adjusting the refractive index (first refractive index adjusting particles) can be used. For example, by including more particles that have the effect of lowering the refractive index in the relaxation resin 92 than in the relaxation resin 91, the refractive index of the relaxation resin 92 can be made lower than that of the relaxation resin 91. Alternatively, when using particles that have the effect of raising the refractive index, by including more particles that have the effect of raising the refractive index in the relaxation resin 91 than in the relaxation resin 92, the refractive index of the relaxation resin 92 can be made lower than that of the relaxation resin 91. Examples of such refractive index adjusting particles include hollow particles formed from silica, polymer, metal, etc. Since a cavity is formed inside the hollow particle, the hollow particle can be used as a particle that has the effect of lowering the refractive index.

[0032] In the optical fiber connector 1 of this embodiment, since the relaxation resin portion 90 (relaxation resin 91 and relaxation resin 92), which has a refractive index lower than that of the protective resin 81, is adjacent to the protective resin 81, when light with a large diffusion angle leaks into the cladding 32 of the optical fiber 3, this leaked light is confined within the cladding 32 in the portion of the removal-from-covering section 35 surrounded by air with a low refractive index (refractive index 1) and propagates within the cladding 32. However, in the portion of the removal-from-covering section 35 covered by the relaxation resin 92, which has a refractive index higher than that of air, a portion of the light leaks into the relaxation resin 92 (see P in Figure 1). The light that did not leak into the relaxation resin 92 leaks into the relaxation resin 91 in the portion of the removal-from-covering section 35 covered by the relaxation resin 91, which has a refractive index higher than that of the relaxation resin 92 (see Q in Figure 1). The light that did not leak into the relaxation resin 91 leaks into the protective resin 81 in the portion of the removal-from-covering section 35 covered by the protective resin 81, which has a refractive index higher than that of the relaxation resin 91 (see R in Figure 1). Thus, according to this embodiment, the light propagating through the cladding 32 of the optical fiber 3 can be leaked in stages to the relaxation resin 92, relaxation resin 91, and protective resin 81. This suppresses heat generation in the resin caused by localized leakage of high-power light at one location, thereby increasing the reliability of the optical fiber connector 1.

[0033] In this embodiment, the relaxation resin portion 90 is composed of two resins 91 and 92, but the number of resins constituting the relaxation resin portion 90 is not limited to this. For example, the relaxation resin portion 90 may be composed of a single resin having a refractive index lower than that of the protective resin. Alternatively, the relaxation resin portion 90 may be composed of three or more resins with different refractive indices, in which case the light propagating through the cladding 32 can be further dispersed and leaked.

[0034] Figure 4 is a schematic plan view of the optical fiber connector 201 in the second embodiment of the present invention, and Figure 5 is a cross-sectional view taken along the CC line of Figure 4. In this embodiment, the optical fiber connector 201 includes a single optical fiber 202 (first optical fiber) instead of the plurality of optical fibers 2 in the first embodiment described above. This optical fiber 202 includes a core 221 (first core), a cladding 222 (first core) covering the core 221, and a covering 223 (first covering) covering the cladding 222. The refractive index of the cladding 222 is lower than that of the core 221, allowing light to propagate inside the core 221. The covering 223 is formed from, for example, resin. At the end of the optical fiber 202, a portion of the covering 223 is removed over a certain length in the longitudinal direction (X direction), forming a covered portion 225 (first covered portion) where the cladding 222 is exposed (see Figure 4).

[0035] The coating removal section 225 includes a large-diameter section 225A and a tapered section 225B whose outer diameter gradually decreases from the large-diameter section 225A, such that the outer diameter of the end of the tapered section 225B matches the outer diameter of the coating removal section 35 of the optical fiber 3. The end of the tapered section 225B of the coating removal section 225 and the end of the coating removal section 35 of the optical fiber 3 are fusion-spliced ​​to each other at the fusion splice section 250. In other words, the coating removal sections 225 and 35 are fusion-spliced ​​to each other so that the core 221 of the optical fiber 202 and the core 31 of the optical fiber 3 are optically coupled. This allows light to be introduced from the core 221 of the optical fiber 202 into the core 31 of the optical fiber 3. In this embodiment, the case where light propagates from the core 221 of the optical fiber 202 to the core 31 of the optical fiber 3 is described, but the direction of light propagation may be reversed.

[0036] In this embodiment as well, since the relaxation resin portion 90 (relaxation resin 91 and relaxation resin 92), which has a refractive index lower than that of the protective resin 81, is adjacent to the protective resin 81, the light leaked into the cladding 32 of the optical fiber 3 can be leaked in stages to the relaxation resin 92, relaxation resin 91, and protective resin 81. This suppresses heat generation of the resin due to localized leakage of high-power light in one place, thereby increasing the reliability of the optical fiber connector 1. In particular, in the tapered portion 225B of the optical fiber 202, the diffusion angle of the propagating light tends to be large, making it easier for light to leak into the cladding 32 of the optical fiber 3, and the relaxation resin portion 90, which is located downstream of the tapered portion 225B, functions effectively.

[0037] In the example shown in Figure 4, the stripped portion 225 of the optical fiber 202 has a tapered portion 225B. However, as shown in Figure 6, for example, a larger diameter portion 225A, which has a larger diameter than the stripped portion 35 of the optical fiber 3, may be directly fusion-spliced ​​to the stripped portion 35 of the optical fiber 3 without forming a tapered portion 225B.

[0038] The optical fiber connector 1,201 in the above-described embodiment has a structure that takes into account the case when light propagating from optical fiber 2 or 202 toward optical fiber 3 leaks into the cladding 32 of optical fiber 3. However, if it is also necessary to consider the leakage of light propagating from optical fiber 3 toward optical fiber 2 or 202 (e.g., reflected light) into the cladding 22,222 of optical fiber 2,202, then, as shown in the optical fiber connector 301 in Figure 7, a relaxation resin portion 390 (second relaxation resin portion) covering the uncoated portion 25 of optical fiber 2 may be placed on the +X direction side of the protective resin 82. This relaxation resin portion 390 is in contact with the protective resin 82 in the longitudinal direction and has a refractive index lower than that of the protective resin 82. A part of the uncoated portion 25 of optical fiber 2 is exposed between the relaxation resin portion 390 and the fusion splice 50. In the illustrated example, the relaxation resin portion 390 is in contact with the protective resin 82 in the longitudinal direction. However, the relaxation resin portion 390 does not need to be in contact with the protective resin 82 in the longitudinal direction; the relaxation resin portion 390 and the protective resin 82 may be adjacent to each other while being spaced apart in the longitudinal direction.

[0039] In the example shown in Figure 7, the relaxation resin portion 390 is composed of a relaxation resin 391 (second relaxation resin) in contact with the protective resin 82 and a relaxation resin 392 (second relaxation resin) in contact with the relaxation resin 391. The relaxation resin 391 has a refractive index (e.g., 1.28) lower than the refractive index of the protective resin 82 (e.g., 1.33), and the relaxation resin 392 has a refractive index (e.g., 1.25) lower than that of the relaxation resin 391. That is, the refractive indices of the relaxation resins 391 and 392 in the relaxation resin portion 390 gradually decrease as they move away from the protective resin 82. In order to change the refractive index in the relaxation resin portion 390 in this way, as with the relaxation resin portion 90, particles (second refractive index adjusting particles) that can adjust the refractive index, such as hollow particles, can be used. In the illustrated example, the relaxation resin 392 is in contact with the relaxation resin 391, but the relaxation resin 392 does not need to be in contact with the relaxation resin 391 in the longitudinal direction; the relaxation resin 391 and the relaxation resin 392 may be adjacent to each other while being spaced apart in the longitudinal direction.

[0040] According to the optical fiber connector 301 shown in Figure 7, since the relaxation resin portion 390 (relaxation resin 391 and relaxation resin 392), which has a refractive index lower than that of the protective resin 82, is adjacent to the protective resin 82, when light with a large diffusion angle (e.g., reflected light) leaks into the cladding 22 of the optical fiber 2, a portion of this leaked light leaks into the relaxation resin 392 in the area where the removal portion 25 is covered by the relaxation resin 392, which has a refractive index higher than that of air. A portion of the light that did not leak into the relaxation resin 392 leaks into the relaxation resin 391 in the area where the removal portion 25 is covered by the relaxation resin 391, which has a refractive index higher than that of the relaxation resin 392. A portion of the light that did not leak into the relaxation resin 391 leaks into the protective resin 82 in the area where the removal portion 25 is covered by the protective resin 82, which has a refractive index higher than that of the relaxation resin 391. Thus, according to this embodiment, the light propagating through the cladding 22 of the optical fiber 2 can be leaked in stages to the relaxation resin 392, relaxation resin 391, and protective resin 82. This suppresses heat generation in the resin caused by localized leakage of high-power light at one location, thereby increasing the reliability of the optical fiber connector 301.

[0041] Furthermore, in the example shown in Figure 7, if the relaxation resin portion 90 is not necessary, only the relaxation resin portion 390 may be provided without the relaxation resin portion 90. In this case, the optical fiber 3 corresponds to the first optical fiber, the optical fiber 2 to the second optical fiber, the protective resin 82 to the first protective resin, and the relaxation resin portion 390 to the first relaxation resin portion.

[0042] Although preferred embodiments of the present invention have been described above, it goes without saying that the present invention is not limited to the embodiments described above and may be implemented in various different forms within the scope of its technical concept. [Explanation of Symbols]

[0043] 1,201,301 Optical fiber connectors 2,202 Optical Fibers (First Optical Fiber) 3. Optical fiber (second optical fiber) 4 Base member 21,221 cores (the first core) 22,222 clad (first clad) 23,223 Covering (First covering) 23A Edge 25,225 Coating removal section (first coating removal section) 31 cores (second core) 32. Clad (Second Clad) 33. Covering (second cladding) 33A Edge 35 Coating removal section (second coating removal section) 50,250 Fusion splice 60 fiber grooves 71 Fixing resin (first fixing resin) 72 Fixing resin (second fixing resin) 81 Protective resin (first protective resin) 82 Protective resin (second protective resin) 90 Relaxation resin part (first relaxation resin part) 91,92 Relaxation resin (first relaxation resin) 390 Relaxation resin part (second relaxation resin part) 391,392 Relaxation resin (second relaxation resin)

Claims

1. A first optical fiber comprising a first core, a first cladding having a refractive index lower than that of the first core and covering the periphery of the first core, and a first covering covering the periphery of the first cladding, wherein the first optical fiber has a first uncovered portion from which the first covering has been removed, A second optical fiber comprising a second core, a second cladding having a refractive index lower than that of the second core and covering the periphery of the second core, and a second coating covering the periphery of the second cladding, wherein the second optical fiber has a second coating removal portion where the second coating has been removed, A fusion joint is formed in which the end of the first coating removal portion and the end of the second coating removal portion are fused together in the longitudinal direction. A first protective resin covering the edge of the second coating and the second coating removal portion of the at least one second optical fiber, A first relaxation resin portion adjacent to the first protective resin in the longitudinal direction and covering the second coating removal portion, the first relaxation resin portion having a refractive index lower than that of the first protective resin. Equipped with, Optical fiber connector.

2. The first relaxation resin portion includes a plurality of first relaxation resins arranged along the longitudinal direction, The refractive index of the plurality of first relaxation resins gradually decreases as they move away from the first protective resin. The optical fiber connector according to claim 1.

3. The optical fiber connector according to claim 2, wherein the plurality of first relaxation resins contain first refractive index adjusting particles for adjusting the refractive index at different concentrations.

4. The optical fiber connector according to claim 3, wherein the first refractive index adjusting particle is a hollow particle with a cavity formed inside.

5. The optical fiber connector according to claim 1, wherein the refractive index of the first protective resin is less than or equal to the refractive index of the first coating.

6. The optical fiber connector according to claim 1, wherein the second coating removal portion is exposed between the first relaxation resin portion and the fusion splice portion.

7. A second protective resin covering the edge of the first coating and the first coating removal portion of the at least one first optical fiber, A second relaxation resin portion adjacent to the second protective resin in the longitudinal direction and covering the first coating removal portion, the second relaxation resin portion having a refractive index lower than that of the second protective resin. The optical fiber connector according to claim 1, further comprising:

8. The second relaxation resin portion includes a plurality of second relaxation resins arranged along the longitudinal direction, The refractive index of the plurality of second relaxation resins gradually decreases as it moves away from the second protective resin. The optical fiber connector according to claim 7.

9. The optical fiber connector according to claim 8, wherein the plurality of second relaxation resins contain second refractive index adjusting particles for adjusting the refractive index at different concentrations.

10. The optical fiber connector according to claim 9, wherein the second refractive index adjusting particle is a hollow particle with a cavity formed inside.

11. The optical fiber connector according to claim 7, wherein the refractive index of the second protective resin is less than or equal to the refractive index of the second coating.

12. The optical fiber connector according to claim 7, wherein the first coating removal portion is exposed between the second relaxation resin portion and the fusion splice portion.

13. A base member having a fiber groove formed along the longitudinal direction for accommodating the first coating removal portion of the at least one first optical fiber and the second coating removal portion of the at least one second optical fiber, A first fixing resin that surrounds the first covering of the at least one first optical fiber and fixes the at least one first optical fiber in the fiber groove, A second fixing resin surrounds the second covering of the at least one second optical fiber and fixes the at least one second optical fiber in the fiber groove. The optical fiber connector according to any one of claims 1 to 12, further comprising the above.

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