Optical connector, ferrule, and optical coupling structure

Abstract

An optical connector according to one embodiment of the present disclosure comprises: a plurality of optical fibers each having a coated part and a coating-removed part, and each having a core and / or a stress applying part at a position displaced from the central axis thereof; and a ferrule having a front end surface and a back end surface that are arranged in a first direction in which the central axis extends, and a plurality of fiber holding parts extending in the first direction between the front end surface and the back end surface and respectively holding the plurality of optical fibers while being arranged in a second direction crossing the first direction. Each of the plurality of fiber holding parts includes a holding hole into which the coating-removed part is inserted in the first direction to maintain the position of the coating-removed part within a plane perpendicular to the first direction, and an introduction part located between the holding hole and the back end surface and having an inner wall surface in which a virtual circle having a diameter larger than the inner diameter of the holding hole is inscribed. The length of the holding hole in the first direction is shorter than the length of the introduction part in the first direction.

Description

Optical connector, ferrule, and optical coupling structure

[0001] This application claims priority to Japanese Patent Application No. 2022-123796, filed on August 3, 2022, and incorporates by reference the entire contents of that application.

[0002] Patent Document 1 discloses a ferrule for an optical connector. The ferrule has a plurality of fiber insertion holes formed therein for inserting a plurality of optical fibers. Each of the fiber insertion holes has a small diameter portion opening at its distal end and an introduction portion communicating with the small diameter portion and having an inner diameter larger than that of the small diameter portion. When installing a plurality of optical fibers in the ferrule, each optical fiber is inserted from the introduction portion into the small diameter portion and fixed.

[0003] Japanese Patent Application Laid-Open No. 2002-333549

[0004] An optical connector according to one embodiment of the present disclosure includes a plurality of optical fibers, each of which has a coating-removing portion where a predetermined length of resin coating has been removed from its tip face and a coating portion where the resin coating remains, and each of which has at least one of a core and a stress-applying portion positioned offset from a central axis; and a ferrule having a front end face and a rear end face aligned in a first direction along which the central axis extends, and a plurality of fiber holding portions extending in the first direction between the front end face and the rear end face and holding the plurality of optical fibers aligned in a second direction intersecting the first direction. Each of the plurality of fiber holding portions includes a holding hole into which the coating-removing portion is inserted in the first direction and which holds the coating-removing portion so as to maintain its position in a plane perpendicular to the first direction, and an introduction portion located between the holding hole and the rear end face and having an inner wall surface inscribed with an imaginary circle having a diameter larger than the inner diameter of the holding hole. The length of the holding hole in the first direction is shorter than the length of the introduction portion in the first direction.

[0005] FIG. 1 is a perspective view of an optical connector according to a first embodiment. FIG. 2 is a cross-sectional view of the optical connector of FIG. 1. FIG. 3 is a front view of an optical fiber provided in the optical connector of FIG. 1. FIG. 4 is a cross-sectional view of a ferrule provided in the optical connector of FIG. 1. FIG. 5 is another cross-sectional view of the ferrule of FIG. 4. FIG. 6 is a cross-sectional view showing how an optical fiber is mounted in the ferrule of FIG. 4. FIG. 7 is a perspective view of an optical coupling structure provided with the optical connector of FIG. 1. FIG. 8 is a diagram for explaining the problem of the optical connector according to Comparative Example 1. FIG. 9 is a diagram for explaining the problem of the optical connector according to Comparative Example 2. FIG. 10 is a cross-sectional view showing a modified example of the ferrule. FIG. 11 is a cross-sectional view showing a fiber holding part provided in the ferrule of FIG. 10. FIG. 12 is a cross-sectional view showing another modified example of the fiber holding part of FIG. 11. FIG. 13 is a cross-sectional view of an optical connector according to a second embodiment. FIG. 14 is a cross-sectional view of a ferrule provided in the optical connector of FIG. 13. FIG. 15 is a perspective view of holding equipment for optical fiber provided in the optical connector of FIG. 13. Fig. 16 is a cross-sectional view showing how holding equipment for optical fiber is mounted on the ferrule of Fig. 14. Fig. 17 is a cross-sectional view showing a modified example of the optical connector of Fig. 13. Fig. 18 is a perspective view of holding equipment for optical fiber provided in the optical connector of Fig. 17. Fig. 19 is a cross-sectional view showing another modified example of the optical connector of Fig. 13. Fig. 20 is a perspective view of holding equipment for optical fiber provided in the optical connector of Fig. 19. Fig. 21 is a cross-sectional view showing a modified example of holding equipment for optical fiber.

[0006] [Problem to be Solved by the Present Disclosure] The ferrule described in Patent Document 1 may be mounted with multiple optical fibers that require rotational alignment. However, because there is only a small clearance between the small-diameter portion of the fiber insertion hole of the ferrule and the optical fibers, when the optical fibers are inserted into this small-diameter portion, friction between the small-diameter portion and the optical fibers tends to cause twisting of the optical fibers. Such twisting can cause angular misalignment in the rotational direction of the optical fibers. Therefore, it is difficult to hold such optical fibers with precision using such a ferrule.

[0007] Effect of the Present Disclosure The optical connector, ferrule, and optical coupling structure according to the present disclosure can hold a plurality of optical fibers with high precision.

[0008] [Description of Embodiments of the Present Disclosure] First, the contents of the embodiments of the present disclosure will be listed and described.

[0009] (1) An optical connector according to one embodiment of the present disclosure includes a plurality of optical fibers, each of which has a coating-removing portion where a predetermined length of resin coating has been removed from a tip face and a coating portion where the resin coating remains, and each of which has at least one of a core and a stress-applying portion positioned offset from a central axis; and a ferrule having a front end face and a rear end face aligned in a first direction along which the central axis extends, and a plurality of fiber holding portions extending in the first direction between the front end face and the rear end face and holding the plurality of optical fibers aligned in a second direction intersecting the first direction. Each of the plurality of fiber holding portions includes a holding hole into which the coating-removing portion is inserted in the first direction and which holds the coating-removing portion so as to maintain its position in a plane perpendicular to the first direction, and an introduction portion located between the holding hole and the rear end face and having an inner wall surface inscribed with an imaginary circle having a diameter larger than the inner diameter of the holding hole. The length of the holding hole in the first direction is shorter than the length of the introduction portion in the first direction.

[0010] In the above-described optical connector, when multiple optical fibers are mounted in a ferrule, rotationally aligned optical fibers are inserted from the introduction portion of the fiber holding portion into the holding hole in a first direction. In the holding hole, the position of the coating removal portion is maintained in a plane perpendicular to the first direction, so the clearance between the holding hole and the coating removal portion is set small. Therefore, when the optical fiber is inserted into the holding hole, friction is likely to occur between the holding hole and the coating removal portion. Meanwhile, the introduction portion has an inner wall surface inscribed with an imaginary circle having a diameter larger than the inner diameter of the holding hole. Therefore, when the optical fiber is inserted into the holding hole, friction between the introduction portion and the coating removal portion is relatively unlikely to occur. Therefore, in the above-described optical connector, the length of the holding hole in the first direction is set shorter than the length of the introduction portion in the first direction. By shortening the length of the holding hole in this way, the possibility of friction occurring between the holding hole and the coating removal portion can be reduced. Furthermore, even if friction occurs between the holding hole and the coating removal portion, frictional resistance between the holding hole and the coating removal portion can be reduced. As a result, torsional rotation of the optical fiber due to friction between the holding hole and the coating removal portion can be suppressed. This makes it possible to suppress angular deviation (rotational deviation) in the rotational position of the optical fiber. Therefore, the optical connector described above makes it possible to hold a plurality of optical fibers with high precision.

[0011] (2) In the optical connector described in (1) above, the introduction portion may be an introduction hole communicating with the holding hole in the first direction. The inner diameter of the introduction hole, defined by the diameter of an imaginary circle, may be equal to or greater than the outer diameter of the coating portion. The coating portion may be inserted into the introduction hole. In this case, inserting the coating portion into the introduction hole can regulate the orientation of the optical fiber to be aligned with the first direction. This allows the coating removal portion to be inserted into the holding hole in the first direction while minimizing friction between the coating removal portion and the holding hole. As a result, rotational misalignment of the optical fiber can be more reliably suppressed. Furthermore, if the introduction portion is configured to have a hole shape in this way, it becomes easier to introduce the coating removal portion from the introduction hole into the holding hole.

[0012] (3) In the optical connector described in (1) above, the introduction portion may be an introduction hole communicating with the holding hole in the first direction. The inner diameter of the introduction hole, defined by the diameter of an imaginary circle, may be equal to or greater than the outer diameter of the coating removal portion. Of the coating removal portion and the coating portion, only the coating removal portion may be inserted into the introduction hole. In this case, inserting the coating removal portion into the introduction hole can regulate the orientation of the optical fiber to be aligned with the first direction. This allows the coating removal portion to be inserted into the holding hole in the first direction while minimizing friction between the coating removal portion and the holding hole. As a result, rotational misalignment of the optical fiber can be more reliably suppressed. Furthermore, if the introduction portion has a hole-shaped configuration, the coating removal portion can be easily introduced from the introduction hole into the holding hole.

[0013] (4) In the optical connector described in (1) above, the introduction portion may be an introduction groove communicating with the holding hole in the first direction. The diameter of an imaginary circle inscribed in the introduction groove may be equal to or greater than the outer diameter of the coating removal portion. The introduction groove may accommodate only the coating removal portion of the coating removal portion and the coating portion. In this case, by accommodating the coating removal portion in the introduction groove, the orientation of the optical fiber can be regulated to be along the first direction. This allows the coating removal portion to be inserted into the holding hole in the first direction while minimizing friction between the coating removal portion and the holding hole. As a result, rotational misalignment of the optical fiber can be more reliably suppressed. Furthermore, if the introduction portion has a groove shape in this way, the optical fiber can be positioned accurately relative to the introduction portion.

[0014] (5) In the optical connector described in (1) above, the introduction portion may be an introduction groove communicating with the holding hole in the first direction. The diameter of an imaginary circle inscribed in the introduction groove may be equal to or greater than the outer diameter of the coating portion. The introduction groove may accommodate the coating portion. In this case, accommodating the coating portion in the introduction groove can restrict the orientation of the optical fiber to a state along the first direction. This allows the coating removal portion to be inserted into the holding hole in the first direction while reducing friction between the coating removal portion and the holding hole. As a result, rotational misalignment of the optical fiber can be more reliably suppressed. Furthermore, if the introduction portion is configured to have a groove shape in this way, the optical fiber can be positioned with high precision relative to the introduction portion.

[0015] (6) The optical connector according to any one of (1) to (5) above may further include an optical fiber holding component arranged inside the ferrule at a position facing the plurality of fiber holding parts in the first direction, and holding the plurality of optical fibers. In this case, by arranging the optical fiber holding component inside the ferrule with the plurality of rotationally aligned optical fibers held in the optical fiber holding component, the coating-removed portions of the plurality of rotationally aligned optical fibers can be inserted collectively into the plurality of holding holes. This facilitates the installation of the plurality of optical fibers in the ferrule.

[0016] (7) In the optical connector described in (6) above, the holding equipment for optical fiber may be a resin layer that covers the coatings of the optical fibers collectively. In this case, the holding equipment for optical fiber can be realized with a simple structure.

[0017] (8) In the optical connector described in (6) above, the holding equipment for optical fiber may have a plurality of V-grooves extending in a first direction and accommodating a plurality of optical fibers aligned in a second direction. In this case, by accommodating and fixing a plurality of rotationally aligned optical fibers in the plurality of V-grooves of the holding equipment for optical fiber, the holding equipment for optical fiber is placed inside the ferrule, whereby the coating removal portions of the plurality of optical fibers can be inserted together into the plurality of holding holes with the orientation of the plurality of optical fibers aligned in the first direction. This more reliably reduces the possibility of friction occurring between the holding holes and the coating removal portions, and also makes it easier to mount a plurality of optical fibers in the ferrule.

[0018] (9) In the optical connector described in (6) above, the holding equipment for optical fiber may have a plurality of through holes that penetrate in a first direction and through which a plurality of optical fibers are inserted side by side in a second direction. In this case, by placing the holding equipment for optical fiber inside the ferrule with a plurality of rotationally aligned optical fibers inserted and fixed in the plurality of through holes of the holding equipment for optical fiber, the coating removal portions of the plurality of optical fibers can be inserted together into the plurality of holding holes with the orientation of the plurality of optical fibers aligned in the first direction. This more reliably reduces the possibility of friction occurring between the holding holes and the coating removal portions and makes it easier to mount the plurality of optical fibers in the ferrule.

[0019] (10) In the optical connector according to any one of (1) to (9), the optical fiber may be any one of a multicore fiber, a polarization-maintaining fiber, and a bundle fiber. When such an optical fiber is used, rotational alignment of the optical fiber is required, and rotational misalignment of the optical fiber due to friction between the holding hole and the coating removal portion becomes a problem. In contrast, the above-mentioned optical connector can suppress the occurrence of rotational misalignment of the optical fiber, thereby preferably achieving the above-mentioned effects.

[0020] (11) A ferrule according to an embodiment of the present disclosure is a ferrule for holding multiple optical fibers, each of which has a coating-removing portion where a predetermined length of resin coating has been removed from a tip end face and a coating portion where the resin coating remains, and each of which has at least one of a core and a stress-applying portion positioned offset from a central axis. The ferrule includes a front end face, a rear end face aligned with the front end face in a first direction, and multiple fiber holding portions extending in the first direction between the front end face and the rear end face and configured to hold the multiple optical fibers aligned in a second direction intersecting the first direction. Each of the multiple fiber holding portions includes a holding hole into which the coating-removing portion is inserted in the first direction and configured to maintain the position of the coating-removing portion in a plane perpendicular to the first direction, and an introduction portion located between the holding hole and the rear end face and having an inner wall surface inscribed with an imaginary circle having a diameter larger than the inner diameter of the holding hole. The length of the holding hole in the first direction is shorter than the length of the introduction portion in the first direction. In this ferrule, as described above, shortening the length of the holding hole can suppress rotational misalignment of the optical fiber. Therefore, the above ferrule makes it possible to hold a plurality of optical fibers with high precision.

[0021] (12) An optical coupling structure according to an embodiment of the present disclosure includes a first optical connector and a second optical connector as the optical connectors described in any one of (1) to (10) above. The first optical connector is arranged to face the second optical connector in a first direction and is optically coupled to the second optical connector. Because this optical coupling structure includes the first optical connector and the second optical connector as the optical connectors described above, it is possible to hold multiple optical fibers with high precision, as described above.

[0022] [Details of the Embodiments of the Present Disclosure] Specific examples of optical connectors, ferrules, and optical coupling structures according to the embodiments of the present disclosure will be described below with reference to the drawings. The present disclosure is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims. In the following description, the same elements in the drawings will be given the same reference numerals, and duplicate descriptions will be omitted as appropriate.

[0023] [First embodiment] Fig. 1 is a perspective view of an optical connector 1 according to a first embodiment. Fig. 2 is a cross-sectional view of the optical connector 1. In the following description, for convenience of explanation, the longitudinal direction of the optical connector 1 is referred to as the X direction (an example of a "first direction"), the short side direction of the optical connector 1 is referred to as the Y direction (an example of a "second direction"), and the height direction of the optical connector 1 is referred to as the Z direction. The X direction, Y direction, and Z direction intersect with each other (in one example, are orthogonal). In the following description, one side in the Z direction may be referred to as the "top," the other side in the Z direction as the "bottom," one side in the X direction as the "front," and the other side in the X direction as the "rear."

[0024] As shown in Fig. 1, the optical connector 1 includes, for example, a plurality of optical fibers 10 and a ferrule 20 that holds the plurality of optical fibers 10. The plurality of optical fibers 10 are cables that transmit optical signals. The plurality of optical fibers 10 extend in the X direction and are arranged side by side in the Y direction. Fig. 1 shows an example in which 12 optical fibers 10 are arranged in a row in the Y direction. However, the number of the plurality of optical fibers 10 is not limited to 12, and may be other numbers such as 4, 8, or 24. The plurality of optical fibers 10 may also be arranged in two or more rows.

[0025] As shown in FIG. 2 , each optical fiber 10 has, for example, a tip end face 11, a coating-removed portion 12, and a coating portion 13. In FIG. 2 and subsequent figures, the optical fiber 10 may be depicted in light gray for ease of understanding. The tip end face 11 is the end face located at the tip of the optical fiber 10 in the X direction. The coating-removed portion 12 is a portion of the optical fiber 10 from which a predetermined length of the resin coating 15 (see FIG. 3 ) has been removed from the tip end face 11. The coating portion 13 is a portion of the optical fiber 10 where the resin coating 15 remains. The coating portion 13 is located on the opposite side of the coating-removed portion 12 from the tip end face 11. In the coating-removed portion 12, the cladding 16 (see FIG. 3 ) of the optical fiber 10 is exposed. The outer diameter of the coating-removed portion 12 (i.e., the diameter of the cladding 16) is, for example, 30 μm or more and 300 μm or less. In the coating portion 13, the cladding 16 of the optical fiber 10 is covered with the resin coating 15. The outer diameter of the covering portion 13 is, for example, not less than 50 μm and not more than 500 μm.

[0026] FIG. 3 is a front view of the optical fiber 10. The optical fiber 10 is an optical fiber that requires rotational alignment with respect to the central axis L. In this embodiment, a multi-core fiber (MCF) is exemplified as the optical fiber 10 that requires rotational alignment. In this case, the optical fiber 10 has multiple cores 17 covered with a cladding 16. In the example shown in FIG. 3 , the multiple cores 17 include a central core 17a arranged on the central axis L and multiple (e.g., six) peripheral cores 17b arranged at positions offset from the central axis L. The state in which the peripheral cores 17b are offset from the central axis L may be defined as a state in which the centers of the peripheral cores 17b do not coincide with the central axis L when viewed in the X direction.

[0027] The number and arrangement of the multiple cores 17 are not limited to the example shown in FIG. 3 and can be changed as appropriate. For example, the number of the multiple cores 17 is not limited to six, and may be two, four, eight, or more. The multiple cores 17 do not have to have a central core 17a arranged on the central axis L. In addition to multicore fibers, examples of the optical fiber 10 that require rotational alignment include bundle fibers and polarization-maintaining fibers (PMFs). When the optical fiber 10 is a polarization-maintaining fiber, the optical fiber 10 has a stress-applying portion at a position offset from the central axis L. In this case, for example, the optical fiber 10 has a central core arranged on the central axis L, and a pair of stress-applying portions are arranged on both sides of the central core.

[0028] FIG. 4 is a cross-sectional view of the ferrule 20. FIG. 5 is another cross-sectional view of the ferrule 20. FIGS. 4 and 5 show the optical connector 1 of FIG. 2 with the optical fibers 10 removed. The ferrule 20 is a component that holds the ends of the optical fibers 10, and is, for example, an MT ferrule. The ferrule 20 has a substantially rectangular parallelepiped shape. The ferrule 20 is made of a resin such as PPS (Polyphenylene Sulfide). The ferrule 20 has, for example, a front end face 21, a rear end face 22, a pair of guide holes 23, 23 (see FIG. 1), a fiber accommodating portion 24, and a plurality of fiber holding portions 25.

[0029] The front end face 21 is an end face located at the front end of the ferrule 20 in the X direction. The rear end face 22 is an end face located at the rear end of the ferrule 20 in the X direction. The front end face 21 and the rear end face 22 extend along the Y and Z directions and are aligned in the X direction. A pair of guide holes 23, 23 open at both ends of the front end face 21 in the Y direction and extend in the X direction from the front end face 21 toward the rear end face 22 (see FIG. 1 ). The rear end face 22 has an opening 22a formed therein that can collectively receive multiple optical fibers 10.

[0030] The fiber accommodating section 24 is formed in the rear portion of the ferrule 20 between the front end face 21 and the rear end face 22 and closer to the rear end face 22. The rear portion of the ferrule 20 is the portion of the ferrule 20 from a wall surface 26 formed inside the ferrule 20 to the rear end face 22. The wall surface 26 is a flat surface extending along the Y and Z directions and is disposed between the front end face 21 and the rear end face 22 in the X direction. The fiber accommodating section 24 is an internal space formed between the wall surface 26 and the rear end face 22 inside the rear portion of the ferrule 20. The fiber accommodating section 24 extends forward from an opening 22a in the rear end face 22 and is connected to multiple fiber holding sections 25. The fiber accommodating section 24 can collectively accommodate multiple optical fibers 10 received through the opening 22a.

[0031] The plurality of fiber holding portions 25 are formed in the front portion of the ferrule 20 between the front end face 21 and the rear end face 22, closer to the front end face 21. The front portion of the ferrule 20 is the portion of the ferrule 20 from the front end face 21 to the wall surface 26. The plurality of fiber holding portions 25 extend in the X direction and are aligned in the Y direction in the front portion of the ferrule 20 corresponding to the plurality of optical fibers 10. The plurality of fiber holding portions 25 respectively hold the plurality of optical fibers 10 introduced into the fiber accommodating portion 24.

[0032] Each fiber holding portion 25 has, for example, a holding hole 27 that holds the optical fiber 10 and an introduction hole 28 (an example of an "introduction portion") for introducing the optical fiber 10 into the holding portion. The holding hole 27 is a small-diameter circular hole extending from the front end face 21 in the X direction. The inner wall surface S1 that constitutes the holding hole 27 has a constant inner diameter D1 at each position along the X direction. As shown in FIG. 2 , the coating removal portion 12 of the optical fiber 10 is inserted into the holding hole 27. The holding hole 27 opens at the front end face 21, and the tip face 11 of the optical fiber 10 is exposed from the opening of the front end face 21. The holding hole 27 maintains the position of the coating removal portion 12 in the YZ plane perpendicular to the X direction. To this end, the clearance between the holding hole 27 and the coating removal portion 12 in the YZ plane is set to be extremely small so that the position of the coating removal portion 12 relative to the holding hole 27 in the YZ plane is determined.

[0033] As shown in FIGS. 4 and 5 , the introduction hole 28 is a circular, large-diameter hole extending in the X direction from the holding hole 27 to the wall surface 26. The introduction hole 28 communicates with the holding hole 27 in the X direction and is formed larger than the holding hole 27 as viewed in the X direction. The introduction hole 28 communicating with the holding hole 27 in the X direction means that the internal space of the introduction hole 28 and the internal space of the holding hole 27 are connected in the X direction. As viewed in the X direction, the center of the introduction hole 28 coincides with the center of the holding hole 27, for example. The center of the introduction hole 28 does not have to coincide strictly with the center of the holding hole 27. The deviation between the center of the introduction hole 28 and the center of the holding hole 27 as viewed in the X direction may be, for example, 3 μm or less. The introduction hole 28 opens in the wall surface 26 and receives the optical fiber 10 through the opening in the wall surface 26. The introduction hole 28 includes, for example, a tapered portion 28 a and a constant diameter portion 28 b.

[0034] The constant diameter portion 28b is a portion of the introduction hole 28 closer to the rear end face 22 in the X direction. The constant diameter portion 28b extends forward in the X direction from the rear end face 22. The inner wall surface S2 constituting the constant diameter portion 28b has a constant inner diameter D2 at each position along the X direction. The inner diameter D2 of the inner wall surface S2 is larger than the inner diameter D1 of the inner wall surface S1. As shown in FIG. 3 , the inner diameter D2 of the inner wall surface S2 can be expressed as the diameter D2 of an imaginary circle C2 inscribed in the inner wall surface S2. The inner diameter D2 of the inner wall surface S2 is set to be, for example, the same as the outer diameter d2 of the coating 13 or slightly larger than the outer diameter d2 of the coating 13. On the other hand, the inner diameter D1 of the inner wall surface S1 is set to be, for example, the same as the outer diameter d1 of the coating removal portion 12 of the optical fiber 10 or slightly larger than the outer diameter d1 of the coating removal portion 12. 2, the coating portion 13 is inserted into the constant diameter portion 28b. By inserting the coating portion 13 into the constant diameter portion 28b, movement of the optical fiber 10 in the YZ plane is restricted, and the orientation of the optical fiber 10 is restricted to be along the X direction.

[0035] 4 and 5 , the tapered portion 28a is provided between the constant diameter portion 28b and the holding hole 27. The tapered portion 28a is formed so that the inner diameter of the tapered portion 28a decreases in the X direction from the constant diameter portion 28b toward the holding hole 27. The coating removal portion 12 of the optical fiber 10 inserted into the constant diameter portion 28b is guided into the holding hole 27 by the tapered portion 28a. In this way, the introduction hole 28 serves to assist the introduction of the coating removal portion 12 into the holding hole 27.

[0036] In this embodiment, the length L1 of the holding hole 27 in the X direction is set shorter than the length L2 of the introduction hole 28 in the X direction. The length L1 of the holding hole 27 is the distance in the X direction from the front end face 21 to a connection point P1 between the holding hole 27 and the introduction hole 28. The length L2 of the introduction hole 28 is the distance in the X direction from the connection point P1 to the wall surface 26. The sum of the length L1 of the holding hole 27 and the length L2 of the introduction hole 28 (L1 + L2) corresponds to the length of the fiber holding portion 25 in the X direction, i.e., the distance in the X direction from the front end face 21 to the rear end face 22. Therefore, the statement that the length L1 of the holding hole 27 is shorter than the length L2 of the introduction hole 28 can be rephrased as the length L1 of the holding hole 27 being shorter than half the length (L1 + L2) of the fiber holding portion 25. For example, if the length of the fiber holding portion 25 is 4 mm, the length L1 of the holding hole 27 is set to be 0.5 mm or more but shorter than 2 mm. In one example, the length L2 of the introduction hole 28 is set to 3 mm, and the length L1 of the holding hole 27 is set to 1 mm. When the ratio of the length L2 of the introduction hole 28 to the length (L1 + L2) of the fiber holding part 25 is defined, the ratio may be set to, for example, 12% or more and less than 50%.

[0037] 6 is a cross-sectional view showing how the optical fiber 10 is mounted in the ferrule 20. When mounting the optical fiber 10 in the ferrule 20, for example, the rotationally aligned optical fiber 10 is introduced into the fiber accommodating section 24 through the opening 22a of the rear end face 22, and then inserted in the X direction from the fiber accommodating section 24 into the introduction hole 28 of the fiber holding section 25. Here, the length L12 of the coating removal section 12 is typically set to approximately 2 mm, which is half the length (L1 + L2) of the fiber holding section 25. Therefore, the length L1 of the holding hole 27 is shorter than the length L12 of the coating removal section 12, and the length L2 of the introduction hole 28 is longer than the length L12 of the coating removal section 12. In this case, the coating 13 enters the introduction hole 28 before the tip surface 11 of the optical fiber 10 that has entered the introduction hole 28 reaches the holding hole 27.

[0038] When the coating portion 13 is inserted into the introduction hole 28 in the X direction, the movement of the coating portion 13 in the YZ plane is restricted in the introduction hole 28, thereby restricting the orientation of the optical fiber 10 to be aligned in the X direction. In this state, the coating removal portion 12 is inserted into the holding hole 27 in the X direction. The optical fiber 10 is then fixed to the fiber holding portion 25 with an adhesive. This results in the optical connector 1 shown in FIG. 2 . After inserting the coating removal portion 12 into the holding hole 27, rotational alignment of the optical fiber 10 may be performed. However, in this case, the clearance between the coating removal portion 12 and the holding hole 27 is extremely small, which may make rotational alignment of the optical fiber 10 difficult.

[0039] 7 is a perspective view of an optical coupling structure 100 according to this embodiment. The optical coupling structure 100 includes, for example, a first optical connector 1a, a second optical connector 1b, a pair of guide pins 40, 40, and a spacer 50. The first optical connector 1a and the second optical connector 1b have the same configuration as the optical connector 1 described above. In the optical coupling structure 100, the front end face 21 of the first optical connector 1a and the front end face 21 of the second optical connector 1b face each other in the X direction with a gap therebetween. The pair of guide pins 40, 40 fit into a pair of guide holes 23, 23 of the first optical connector 1a and a pair of guide holes 23, 23 of the second optical connector 1b. This defines the positions of the first optical connector 1a and the second optical connector 1b in the YZ plane.

[0040] The spacer 50 is a plate-like member having an opening 50a. The spacer 50 is disposed between the front end face 21 of the first optical connector 1a and the front end face 21 of the second optical connector 1b. The opening 50a allows a plurality of optical paths extending between the first optical connector 1a and the second optical connector 1b to pass through. This optically couples the first optical connector 1a and the second optical connector 1b. The spacer 50 abuts against the front end face 21 of the first optical connector 1a and the front end face 21 of the second optical connector 1b. This defines a gap between the first optical connector 1a and the second optical connector 1b in the X direction.

[0041] The effects obtained by the optical connector 1, the ferrule 20, and the optical coupling structure 100 according to the present embodiment described above will be described together with the problems of the comparative example.

[0042] FIG. 8 is a diagram illustrating a problem with the optical connector 200 according to Comparative Example 1. In the optical connector 200 according to Comparative Example 1, the length L1a of the holding hole 127 of the fiber holding portion 125 formed in the ferrule 120 is set to be the same as the length L2a of the introduction hole 128 of the fiber holding portion 125. When the optical fiber 10 is mounted in this ferrule 120, the coating removal portion 12 of the optical fiber 10 reaches the holding hole 127 before the coating portion 13 of the optical fiber 10 enters the introduction hole 128. In this case, the coating removal portion 12 enters the holding hole 127 with the orientation of the optical fiber 10 significantly tilted from the X direction. When the coating removal portion 12 enters the holding hole 127 at an angle in this manner, the coating removal portion 12 comes into contact with the holding hole 127, and friction between the coating removal portion 12 and the holding hole 127 causes the optical fiber 10 to twist and rotate. As a result, an angular misalignment (i.e., rotational misalignment) occurs in the rotational direction of the optical fiber 10. Furthermore, because the clearance between the holding hole 127 and the coating removal portion 12 is set to be extremely small, the coating removal portion 12 is likely to come into contact with the holding hole 127. Therefore, rotational misalignment of the optical fiber 10 is likely to occur even in the process of inserting the coating removal portion 12 into the holding hole 127. Such rotational misalignment can lead to misalignment of the core at the tip surface 11 of the optical fiber 10, which can cause deterioration of optical characteristics such as increased connection loss.

[0043] FIG. 9 is a diagram illustrating a problem with the optical connector 300 according to Comparative Example 2. In the optical connector 300 according to Comparative Example 2, the length L1b of the holding hole 227 of the fiber holding portion 225 formed in the ferrule 220 is set longer than the length L2b of the introduction hole 228 of the fiber holding portion 225. When the optical fiber 10 is mounted in this ferrule 220, the coating removal portion 12 enters the holding hole 227 with the optical fiber 10 tilted even more significantly from the X direction. In this case, the coating removal portion 12 is more likely to come into contact with the holding hole 227, making rotational misalignment of the optical fiber 10 more likely to occur. Furthermore, when the holding hole 227 is set longer in this manner, the coating removal portion 12 is more likely to come into contact with the holding hole 227, and the contact area of ​​the coating removal portion 12 with the holding hole 227 is larger. In this case, frictional resistance between the holding hole 227 and the coating removal portion 12 increases, making rotational misalignment of the optical fiber 10 more likely to occur. As a result, similar to the optical connector 200 according to the first comparative example, the core may be misaligned at the tip end face 11 of the optical fiber 10, which may result in deterioration of optical characteristics such as an increase in connection loss.

[0044] On the other hand, in this embodiment, as shown in FIG. 6 , the length L1 of the holding hole 27 of the fiber holding unit 25 is set shorter than the length L2 of the introduction hole 28. By shortening the length L1 of the holding hole 27 in this manner, the orientation of the optical fiber 10 in the introduction hole 28 can be restricted to a state along the X direction. As a result, the optical fiber 10 is centered by the introduction hole 28, and the center of the optical fiber 10 coincides with the center of the introduction hole 28 when viewed in the X direction. By centering the optical fiber 10 in this manner, the center of the holding hole 27 of the optical fiber 10 can also coincide with the center of the holding hole 27 when viewed in the X direction. This makes it possible to insert the coating removal portion 12 of the optical fiber 10 straight into the holding hole 27. If the coating removal portion 12 can be inserted straight into the holding hole 27, the coating removal portion 12 is less likely to come into contact with the holding hole 27. This reduces the possibility of friction occurring between the coating removal portion 12 and the holding hole 27. Furthermore, if the length L1 of the holding hole 27 is shorter than the length L2 of the introduction hole 28, even if friction occurs between the holding hole 27 and the coating removal portion 12, the frictional resistance between the holding hole 27 and the coating removal portion 12 can be reduced. As a result, it is possible to suppress the occurrence of torsional rotation of the optical fiber 10 due to friction between the holding hole 27 and the coating removal portion 12. This makes it possible to suppress the occurrence of rotational misalignment of the optical fiber 10. Therefore, according to this embodiment, it is possible to hold multiple optical fibers 10 with high precision. This makes it possible to suppress the occurrence of misalignment of the core 17 at the tip face 11 of the optical fiber 10. As a result, it is possible to suppress the occurrence of deterioration of optical characteristics, such as an increase in connection loss.

[0045] As in this embodiment, the inner diameter D2 of the introduction hole 28 may be larger than the outer diameter d2 of the coating portion 13, and the coating portion 13 may be inserted into the introduction hole 28. In this case, inserting the coating portion 13 into the introduction hole 28 can restrict the orientation of the optical fiber 10 to a state along the X direction. This allows the coating removal portion 12 to be inserted into the holding hole 27 in the X direction while reducing friction between the coating removal portion 12 and the holding hole 27. As a result, rotational misalignment of the optical fiber 10 can be more reliably suppressed. Furthermore, using an introduction hole 28 having a hole shape makes it possible to easily introduce the coating removal portion 12 from the introduction hole 28 into the holding hole 27.

[0046] As in the present embodiment, the optical fiber 10 may be any one of a multicore fiber, a polarization-maintaining fiber, and a bundle fiber. When such an optical fiber 10 is used, rotational alignment of the optical fiber 10 is required, and rotational misalignment of the optical fiber 10 due to friction between the holding hole 27 and the coating removal portion 12 becomes a problem. In contrast, in the present embodiment, the occurrence of rotational misalignment of the optical fiber 10 can be suppressed, and the above-mentioned effects can be preferably obtained.

[0047] FIG. 10 is a cross-sectional view of a ferrule 20A according to a modified example. FIG. 11 is a cross-sectional view of a fiber holding portion 25A included in the ferrule 20A. As shown in FIG. 10 , the ferrule 20A includes a fiber holding portion 25A instead of the fiber holding portion 25 described above. The fiber holding portion 25A has an introduction groove 28A (an example of an "introduction portion") instead of the introduction hole 28 described above. The introduction groove 28A is, for example, a V-shaped groove extending in the X direction and communicates with the holding hole 27 in the X direction. As shown in FIG. 11 , the inner wall surface of the introduction groove 28A includes a pair of inner surfaces S2A, S2A. When viewed in the X direction, the diameter D2 of an imaginary circle C2 inscribed in the pair of inner surfaces S2A, S2A is larger than the diameter D1 of an imaginary circle C1 representing the inner wall surface S1 of the holding hole 27 (i.e., the inner diameter D1 of the holding hole 27). When viewed in the X direction, the center of the imaginary circle C2 coincides with, for example, the center of the holding hole 27. The diameter D2 of the imaginary circle C2 is set to be, for example, the same as the outer diameter d2 (see FIG. 2) of the covering portion 13. In this case, the imaginary circle C2 coincides with the outer edge of the covering portion 13.

[0048] The introduction groove 28A accommodates the coating portion 13. By placing the coating portion 13 in the introduction groove 28A, the position of the coating portion 13 relative to the introduction groove 28A in the YZ plane is defined, and the orientation of the optical fiber 10 is restricted to be along the X direction. By restricting the position and orientation of the optical fiber 10 in this manner, the introduction groove 28A assists in guiding the coating removal portion 12 into the holding hole 27. Even in this configuration, the same effect as that of the optical connector 1 according to the first embodiment can be obtained. Furthermore, if the introduction groove 28A is configured to accommodate the coating portion 13, the position of the optical fiber 10 relative to the introduction groove 28A can be accurately positioned. "Accommodating the coating portion 13 in the introduction groove 28A" means that at least a portion of the coating portion 13 is disposed in the internal space of the introduction groove 28A.

[0049] 12 is a cross-sectional view of a fiber holding unit 25B according to another modification. The fiber holding unit 25B has an introduction groove 28B (an example of an "introduction portion") that houses the coating removal unit 12. In this case, the diameter D3 of an imaginary circle C3 inscribed in the pair of inner surfaces S2B, S2B of the introduction groove 28B is larger than the diameter D1 of the imaginary circle C1 (i.e., the inner diameter D1 of the holding hole 27) and smaller than the diameter D2 of the imaginary circle C2. The diameter D2 of the imaginary circle C2 coincides with the outer diameter d2 of the coating unit 13.

[0050] By accommodating the coating removal portion 12 in the introduction groove 28B, the position of the coating removal portion 12 relative to the introduction groove 28B in the YZ plane is defined, and the orientation of the optical fiber 10 is restricted to a state along the X direction. By restricting the position and orientation of the optical fiber 10 in this manner, the introduction groove 28B assists in guiding the coating removal portion 12 into the holding hole 27. Even in this configuration, the same effect as that of the optical connector 1 according to the first embodiment can be obtained. Furthermore, if the coating removal portion 12 is configured to be accommodated in the introduction groove 28B, the position of the optical fiber 10 relative to the introduction groove 28B can be accurately positioned. Accommodating the coating removal portion 12 in the introduction groove 28B means that at least a portion of the coating removal portion 12 is disposed in the internal space of the introduction groove 28B.

[0051] Second Embodiment Next, an optical connector 1A according to a second embodiment will be described. In the following description of the second embodiment, descriptions of parts that overlap with the first embodiment will be omitted as appropriate, and differences from the first embodiment will be mainly described.

[0052] FIG. 13 is a cross-sectional view of an optical connector 1A according to the second embodiment. FIG. 14 is a cross-sectional view of a ferrule 20B included in the optical connector 1A. In the optical connector 1A, only the coating removal portion 12, out of the coating portion 13 and the sheath removal portion 12, is inserted into an introduction hole 28C (an example of an "introduction portion") of a fiber holding portion 25C of the ferrule 20B. The sheath removal portion 13 is not inserted into the introduction hole 28C, but is disposed behind the introduction hole 28C (i.e., outside the fiber holding portion 25C). The introduction hole 28C includes a tapered portion 28c and a constant diameter portion 28d instead of the tapered portion 28a and the constant diameter portion 28b. The inner diameter D4 of the constant diameter portion 28d is larger than the inner diameter D1 of the holding hole 27. The inner diameter D4 of the constant diameter portion 28d is larger than the outer diameter d1 of the sheath removal portion 12 and smaller than the outer diameter d2 of the sheath removal portion 12. The clearance between introduction hole 28C and coating removal portion 12 as viewed in the X direction is set to, for example, 3 μm or more. As shown in Fig. 14, length L2 of introduction hole 28C in the X direction is longer than length L1 of holding hole 27 in the X direction. The relationship between length L2 of introduction hole 28C and length L1 of holding hole 27 may be the same as the relationship between length L2 of introduction hole 28 and length L1 of holding hole 27 described in the first embodiment.

[0053] The fiber accommodating part 24 of the ferrule 20B is provided with a fiber support part 29. The fiber support part 29 extends rearward from a position lower than the fiber holding part 25C on the wall surface 26 of the ferrule 20B. The upper surface of the fiber support part 29 functions as a support surface 29a that supports holding equipment for optical fiber 30. The support surface 29a is a plane that extends along the X and Y directions, for example, and is formed perpendicular to the wall surface 26.

[0054] 15 is a perspective view of holding equipment for optical fiber 30. Holding equipment for optical fiber 30 is a part that holds a plurality of optical fibers 10. Holding equipment for optical fiber 30 is constructed as a separate body from the ferrule 20B, and is placed inside the ferrule 20B. Holding equipment for optical fiber 30 is made of materials such as resin or metal. Holding equipment for optical fiber 30 has, for example, a front surface 30a, a rear surface 30b, an upper surface 30c, a lower surface 30d, a side surface 30e, and a side surface 30f.

[0055] 3. The front surface 30a is an end surface located at the front end of holding equipment for optical fiber 30 in the X direction. The rear surface 30b is an end surface located at the rear end of holding equipment for optical fiber 30 in the X direction. The front surface 30a and the rear surface 30b are, for example, planes along the YZ plane, and are arranged side by side along the X direction. The top surface 30c is an end surface located at the top end of holding equipment for optical fiber 30 in the Z direction. The bottom surface 30d is an end surface located at the bottom end of holding equipment for optical fiber 30 in the Z direction. The top surface 30c and the bottom surface 30d are, for example, planes along the XY plane, and are arranged side by side along the Z direction. The side surface 30e is an end surface located at one end of holding equipment for optical fiber 30 in the Y direction. The side surface 30f is an end surface located at the other end of holding equipment for optical fiber 30 in the Y direction. The side surface 30e and the side surface 30f are, for example, planes along the XZ plane, and are arranged side by side along the Y direction.

[0056] 3. The holding equipment for optical fiber 30 has a fixing surface 30g for fixing the coating parts 13 of multiple optical fibers 10 together in a part closer to the rear surface 30b in the X direction. The fixing surface 30g is, for example, a plane along the XY plane, and forms a step with respect to the upper surface 30c. The fixing surface 30g and the upper surface 30c are connected via a step surface 30s. The step surface 30s is, for example, a plane along the YZ plane, and is formed perpendicular to the fixing surface 30g and the upper surface 30c. The fixing surface 30g extends from the step surface 30s to the rear surface 30b in the X direction. The holding equipment for optical fiber 30 has a plurality of V-grooves 30h for holding the coating removal parts 12 of multiple optical fibers 10 respectively in a part closer to the rear surface 30b in the X direction. The plurality of V-grooves 30h are formed on the upper surface 30c. The plurality of V-shaped grooves 30h extend in the X direction from the front surface 30a to the step surface 30s on the upper surface 30c and are arranged side by side along the Y direction.

[0057] 13, the coating removal portions 12 of the optical fibers 10 are placed in the plurality of V-grooves 30h, respectively, and the coating portions 13 of the optical fibers 10 are placed on the fixing surface 30g. By placing the coating removal portions 12 in each V-groove 30h, the position of the optical fiber 10 in the YZ plane relative to the holding equipment for optical fiber 30 is defined. With the coating removal portions 12 placed in the V-grooves 30h, rotational alignment of the optical fibers 10 is performed. Each V-groove 30h is configured to hold the coating removal portions 12 rotatably around the central axis L. With all the rotationally aligned optical fibers 10 placed in their respective V-grooves 30h, adhesive is applied onto the optical fibers 10, and the coating removal portions 12 are pressed against the V-grooves 30h by a rectangular plate-shaped cover 31 provided on the coating removal portions 12. When the adhesive hardens in this state, the coating removal portions 12 are fixed to the V-grooves 30h via the adhesive. Similarly, the coating 13 is fixed to the fixing surface 30g via adhesive. In this way, holding equipment for optical fiber 30 for holding a plurality of optical fibers 10 is obtained.

[0058] Fig. 16 is a cross-sectional view showing how to mount holding equipment for optical fiber 30 on a ferrule 20B. As shown in Fig. 16, holding equipment for optical fiber 30 holding a plurality of optical fibers 10 is arranged inside the ferrule 20B at a position facing a plurality of fiber holding parts 25C in the X direction. At this time, the lower surface 30d of holding equipment for optical fiber 30 is placed on the support surface 29a of the ferrule 20B, and the side surface 30e of holding equipment for optical fiber 30 is abutted against the inner surface 24a of the ferrule 20B. By matching the lower surface 30d and the side surface 30e with the support surface 29a and the inner surface 24a respectively in this way, the position of holding equipment for optical fiber 30 in the YZ plane with respect to the ferrule 20B is defined, and the arrangement of a plurality of optical fibers 10 held by holding equipment for optical fiber 30 corresponds to the arrangement of a plurality of fiber holding parts 25C.

[0059] In this state, by advancing the holding equipment for optical fiber 30 in the X direction, the coating removal part 12 of each optical fiber 10 is inserted into the introduction hole 28C of the fiber holding part 25C. At this time, the posture of the optical fiber 10 is regulated to be along the X direction by the holding equipment for optical fiber 30, so the optical fiber 10 can be inserted straight into the introduction hole 28C. Then, the holding equipment for optical fiber 30 is advanced in the X direction until the front surface 30a of the holding equipment for optical fiber 30 abuts against the wall surface 26. As a result, as shown in Fig. 13, the coating removal part 12 is inserted into the holding hole 27 while the posture of the optical fiber 10 remains along the X direction. After that, the holding equipment for optical fiber 30 holding the plurality of optical fibers 10 is fixed to the ferrule 20B via adhesive, and the optical connector 1A shown in Fig. 13 is obtained.

[0060] Even with this configuration, the same effect as that of the optical connector 1 according to the first embodiment can be obtained. That is, since the coating removal portion 12 can be inserted into the holding hole 27 in the X direction in a state where friction between the coating removal portion 12 and the holding hole 27 is unlikely to occur, rotational deviation of the optical fiber 10 can be suppressed. This makes it possible to hold multiple optical fibers 10 with high precision. As a result, positional deviation of the core 17 at the tip surface 11 of the optical fiber 10 can be suppressed, and deterioration of optical characteristics such as increased connection loss can be suppressed. Furthermore, in this embodiment, the holding equipment for optical fiber 30 is placed inside the ferrule 20B in a state where multiple rotationally aligned optical fibers 10 are placed and fixed in the multiple V-grooves 30h of the holding equipment for optical fiber 30. As a result, the coating removal portions 12 of the multiple optical fibers 10 can be inserted collectively into the multiple holding holes 27 in a state where the orientation of the multiple optical fibers 10 is aligned in the X direction. This more reliably reduces the possibility of friction occurring between the holding hole 27 and the coating removal portion 12, and also makes it easier to mount the multiple optical fibers 10 in the ferrule 20B. Furthermore, by placing holding equipment for optical fiber 30 on the support surface 29a and keeping the posture of holding equipment for optical fiber 30 stable, stress can be prevented from being applied to the optical fiber 10. Furthermore, by holding equipment for optical fiber 30 holding both the coating removal part 12 and the coating part 13, the posture of the optical fiber 10 can be made more stable.

[0061] Fig. 17 is a cross-sectional view of an optical connector 1B according to a modified example of the second embodiment. Fig. 18 is a perspective view of holding equipment for optical fiber 30A included in the optical connector 1B. The optical connector 1B is provided with holding equipment for optical fiber 30A of Fig. 18 instead of holding equipment for optical fiber 30 of Fig. 15. Unlike holding equipment for optical fiber 30, holding equipment for optical fiber 30A does not have a fixing surface 30g, and an upper surface 30c extends from a front surface 30a to a rear surface 30b, and a plurality of V-grooves 30i formed on the upper surface 30c extend from the front surface 30a to the rear surface 30b. Coatings 13 of a plurality of optical fibers 10 are placed in the plurality of V-grooves 30i. Then, a plurality of rotationally aligned optical fibers 10 are accommodated and fixed in the plurality of V-grooves 30i, respectively. A rectangular plate-shaped cover 31 that covers the coatings 13 of the plurality of optical fibers 10 is provided on the plurality of V-grooves 30i.

[0062] The ferrule 20C of the optical connector 1B has the same fiber holding part 25 as in the first embodiment. Holding equipment for optical fiber 30A is arranged in a position facing the fiber holding part 25 in the X direction inside the ferrule 20C, while holding the coating parts 13 of a plurality of optical fibers 10. As shown in Fig. 17 , the coating parts 13 protruding forward from holding equipment for optical fiber 30A are inserted into the introduction hole 28 of the fiber holding part 25, and the coating removal part 12 protruding further forward from the coating part 13 is inserted into the holding hole 27 of the fiber holding part 25.

[0063] In this modification, similarly to the optical connector 1A according to the second embodiment, by advancing the holding equipment 30A for optical fiber on the support surface 29a, the coating part 13 is inserted into the introduction hole 28 and the coating removal part 12 is inserted into the holding hole 27 while the posture of the optical fiber 10 is kept along the X direction. After that, the holding equipment 30A for optical fiber holding a plurality of optical fibers 10 is fixed to the ferrule 20C via adhesive, and the optical connector 1B shown in Fig. 17 is obtained. Even in this form, the same effect as the optical connector 1A according to the second embodiment can be obtained.

[0064] Fig. 19 is a cross-sectional view of an optical connector 1C according to another modified example of the second embodiment. Fig. 20 is a perspective view showing holding equipment for optical fiber 30B included in the optical connector 1C. The optical connector 1C is equipped with holding equipment for optical fiber 30B of Fig. 20 instead of holding equipment for optical fiber 30 of Fig. 15. Unlike holding equipment for optical fiber 30, holding equipment for optical fiber 30B does not have a fixing surface 30g, and an upper surface 30c extends from a front surface 30a to a rear surface 30b. And holding equipment for optical fiber 30B is equipped with a plurality of through holes 32 instead of a plurality of V-grooves 30h. The plurality of through holes 32 penetrate in the X direction from the front surface 30a to the rear surface 30b, and are lined up along the Y direction. A plurality of optical fibers 10 are inserted into the plurality of through holes 32, respectively.

[0065] As shown in Figure 19, each through hole 32 has a small diameter portion 32a and a large diameter portion 32b. The coating removal portion 12 of the optical fiber 10 is inserted into the small diameter portion 32a. The inner diameter of the small diameter portion 32a is set to be the same as the outer diameter d1 of the coating removal portion 12 or slightly larger than the outer diameter d1 of the coating removal portion 12. The large diameter portion 32b has an inner diameter larger than the inner diameter of the small diameter portion 32a. The coating portion 13 of the optical fiber 10 is inserted into the large diameter portion 32b. The inner diameter of the large diameter portion 32b is set to be the same as the outer diameter d2 of the coating portion 13 or slightly larger than the outer diameter d2 of the coating portion 13. With the coating removal portion 12 and the coating portion 13 inserted into the small diameter portion 32a and the large diameter portion 32b, respectively, rotational alignment of the optical fiber 10 is performed, and the optical fiber 10 is fixed to the through hole 32 by an adhesive injected into the through hole 32.

[0066] The optical connector 1C includes the same ferrule 20B as in the second embodiment. Holding equipment for optical fiber 30B is arranged in the ferrule 20B at a position facing the fiber holding part 25C in the X direction while holding a plurality of optical fibers 10. As shown in Fig. 19, the coating part 13 protruding forward from the holding equipment for optical fiber 30B is inserted into the introduction hole 28C of the fiber holding part 25C, and the coating removal part 12 protruding further forward from the coating part 13 is inserted into the holding hole 27 of the fiber holding part 25C.

[0067] In this modification, similarly to the optical connector 1A according to the second embodiment, by advancing the holding equipment 30B on the support surface 29a, the coating part 13 is inserted into the introduction hole 28C and the coating removal part 12 is inserted into the holding hole 27 while the orientation of the optical fiber 10 remains along the X direction. After that, the holding equipment 30B holding the plurality of optical fibers 10 is fixed to the ferrule 20B via adhesive, and the optical connector 1C shown in FIG. 19 is obtained. Even in this form, the same effect as the optical connector 1A according to the second embodiment can be obtained. The through hole 32 may have only the thin diameter part 32a, and only the coating removal part 12 may be held by the thin diameter part 32a. Alternatively, the through hole 32 may have only the thick diameter part 32b, and only the coating part 13 may be held by the thick diameter part 32b.

[0068] 21 is a cross-sectional view showing a modified example of holding equipment for optical fiber 30. As shown in FIG. 21, holding equipment for optical fiber 30C is a resin layer that collectively covers the coatings 13 of multiple optical fibers 10. Holding equipment for optical fiber 30C constitutes a ribbon fiber including multiple optical fibers 10. Holding equipment for optical fiber 30C is used to suppress position changes between multiple optical fibers 10. Holding equipment for optical fiber 30C integrally holds the coatings 13 of multiple optical fibers 10 in a state where the multiple optical fibers 10 are arranged in the Y direction and rotationally aligned. Holding equipment for optical fiber 30C is, for example, arranged in a position facing the fiber holding part 25 in the X direction inside the ferrule 20C in a state where it holds multiple optical fibers 10. Even in this form, the same effect as that of the optical connector 1A according to the second embodiment can be obtained.

[0069] The present disclosure is not limited to the above-described embodiments and modifications, and various other modifications are possible. For example, the above-described embodiments and modifications may be combined with each other to the extent that there is no contradiction, depending on the required purpose and effect. The configuration of the optical connector is not limited to the above-described embodiments and modifications. For example, the fiber holding portion of the ferrule may not have a tapered portion, and may have only a holding hole and an introduction portion. The introduction groove of the fiber holding portion is not limited to a V-groove, and may be a groove with another shape, such as a U-groove or a rectangular groove.

[0070] DESCRIPTION OF SYMBOLS 1, 1A, 1B, 1C...Optical connector 1a...First optical connector 1b...Second optical connector 10...Optical fiber 11...Tip surface 12...Coating removal portion 13...Coating portion 15...Resin coating 16...Cladding 17...Core 17a...Central core 17b...Peripheral core 20, 20A, 20B, 20C...Ferrule 21...Front end surface 22...Rear end surface 22a...Opening 23...Guide hole 24...Fiber accommodating portion 24a...Inner surface 25, 25A, 25B, 25C...Fiber holding portion 26...Wall surface 27...Holding hole 28, 28C...Introduction hole (an example of an "introduction portion") 28A, 28B...Introduction groove (an example of an "introduction portion") 28a...Tapered portion 28b...Constant diameter portion 29...Fiber support portion 29a...Support surface 30, 30A, 30B, 30C...Optical fiber holding parts 30a...Front surface 30b...Back surface 30c...Top surface 30d...Bottom surface 30e, 30f...Side surface 30g...Fixing surface 30h, 30i...V groove 30s...Step surface 31...Lid 32...Through hole 32a...Small diameter part 32b...Large diameter part 40...Guide pin 50...Spacer 50a...Aperture 100...Optical coupling structure C1, C2, C3...Virtual circle D1, D2, D4...Inner diameter D1, D2, D3...Diameter d1, d2...Outer diameter L...Central axis P1...Connection portion S1, S2...Inner wall surface S2A, S2B...Inner surface

Claims

1. a plurality of optical fibers each having a coating removal portion where a predetermined length of resin coating is removed from a tip face and a coating portion where the resin coating remains, and each having at least one of a core and a stress applying portion at a position shifted from a central axis; a ferrule including a front end face and a rear end face aligned in a first direction in which the central axis extends, and a plurality of fiber holding portions extending in the first direction between the front end face and the rear end face and aligned in a second direction intersecting the first direction, the fiber holding portions holding the plurality of optical fibers, Equipped with Each of the plurality of fiber holding units is a holding hole into which the coating removal portion is inserted in the first direction and which holds the coating removal portion so as to maintain a position of the coating removal portion in a plane perpendicular to the first direction; an introduction portion located between the retaining hole and the rear end surface, the introduction portion having an inner wall surface inscribed in a virtual circle having a diameter larger than an inner diameter of the retaining hole; Including, The length of the retaining hole in the first direction is shorter than the length of the introduction portion in the first direction. Optical connector.

2. the introduction portion is an introduction hole communicating with the holding hole in the first direction, an inner diameter of the introduction hole defined by the diameter of the imaginary circle is equal to or larger than an outer diameter of the covering portion, The covering portion is inserted into the introduction hole.

2. The optical connector according to claim 1.

3. the introduction portion is an introduction hole communicating with the holding hole in the first direction, an inner diameter of the introduction hole defined by the diameter of the imaginary circle is equal to or larger than an outer diameter of the coating removal portion, Only the coating removal portion of the coating portion and the coating removal portion is inserted into the introduction hole.

2. The optical connector according to claim 1.

4. the introduction portion is an introduction groove communicating with the retaining hole in the first direction, a diameter of the imaginary circle inscribed in the introduction groove is equal to or larger than an outer diameter of the coating removal portion, the introduction groove accommodates only the coating removal portion of the coating portion and the coating removal portion; 2. The optical connector according to claim 1.

5. the introduction portion is an introduction groove communicating with the retaining hole in the first direction, a diameter of the imaginary circle inscribed in the introduction groove is equal to or greater than an outer diameter of the covering portion, The covering portion is accommodated in the introduction groove.

2. The optical connector according to claim 1.

6. The optical fiber holding parts are arranged inside the ferrule at positions opposite to the plurality of fiber holding parts in the first direction, and hold the plurality of optical fibers. The optical connector according to any one of claims 1 to 5.

7. The holding equipment for optical fiber is a resin layer which collectively covers the coating parts of the plurality of optical fibers.

7. The optical connector according to claim 6.

8. The holding equipment for optical fiber has a plurality of V-grooves extending in the first direction and arranged in the second direction, each of which accommodates the plurality of optical fibers.

7. The optical connector according to claim 6.

9. The holding equipment for optical fiber has a plurality of through holes penetrating in the first direction and arranged in the second direction through which the plurality of optical fibers are inserted, 7. The optical connector according to claim 6.

10. 6. The optical connector according to claim 1, wherein the optical fiber is any one of a multicore fiber, a polarization maintaining fiber, and a bundle fiber.

11. A ferrule for holding a plurality of optical fibers, each of which has a coating removal portion in which a predetermined length of resin coating has been removed from a tip face, and a coating portion in which the resin coating remains, and each of which has at least one of a core and a stress applying portion at a position offset from a central axis, A front end surface, a rear end surface aligned with the front end surface in a first direction; a plurality of fiber holding portions extending in the first direction between the front end surface and the rear end surface and configured to hold the plurality of optical fibers side by side in a second direction intersecting the first direction, Each of the plurality of fiber holding units is a retaining hole configured to receive the coating removal portion in the first direction and to maintain a position of the coating removal portion in a plane perpendicular to the first direction; an introduction portion located between the retaining hole and the rear end surface, the introduction portion having an inner wall surface inscribed in a virtual circle having a diameter larger than an inner diameter of the retaining hole; Including, The length of the retaining hole in the first direction is shorter than the length of the introduction portion in the first direction. Ferrule.

12. The optical connector according to any one of claims 1 to 5 includes a first optical connector and a second optical connector, The first optical connector is disposed opposite the second optical connector in the first direction and is optically coupled to the second optical connector.