Optical connector ferrule, optical connector, and optical coupling structure

Abstract

An optical connector ferrule (20) disclosed herein comprises: a front end face (21); a rear end face (22) arranged side by side with the front end face in a first direction (X); an inner wall surface (26) that is formed between the front end face and the rear end face, and that intersects in the first direction; an introduction hole (24) that extends in the first direction from the rear end face to the inner wall surface, and can introduce, from the rear end face, a holding member (13) for holding a plurality of optical fibers (10); and a plurality of insertion holes (25) which extend in the first direction from the inner wall surface toward the front end face and are arranged in a second direction (Y) intersecting the first direction, and in which leading ends (10a) of the plurality of optical fibers protruding from an end face (13a) of the holding member can be inserted. Each of the plurality of insertion holes includes at least a holding portion (27) that extends in the first direction between the inner wall surface and the front end face, and that has a constant inner diameter capable of holding the leading ends of the optical fibers. The length of the insertion holes in the first direction is 1.5 mm or less.

Description

Optical Connector Ferrule, Optical Connector, and Optical Coupling Structure

[0001] The present disclosure relates to an optical connector ferrule, an optical connector, and an optical coupling structure. This application claims priority based on Japanese Application No. 2023-000155 filed on January 4, 2023, and incorporates all the descriptions described in the above Japanese application.

[0002] Patent Document 1 discloses a ferrule that holds the connection end portion of an optical fiber ribbon core wire. At the connection end portion of the optical fiber ribbon core wire, the outer skin is removed and the connection end portions of a plurality of optical fiber core wires are exposed. Inside the ferrule, a fiber insertion space portion communicating with the fiber insertion port on the rear end face and a plurality of fiber insertion holes penetrating in the front-rear direction from the fiber insertion space portion to the connection face of the ferrule are formed. The connection end portion of each optical fiber core wire is inserted and fixed into each fiber insertion hole from the fiber insertion space portion.

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

[0004] The optical connector ferrule according to an embodiment of the present disclosure is an optical connector ferrule into which a holding member that holds a plurality of optical fibers each having a coated portion covered by a resin coating and a tip portion of a glass portion protruding from the coated end of the coated portion can be inserted. This optical connector ferrule includes a front end face, a rear end face aligned with the front end face in a first direction, an inner wall face formed between the front end face and the rear end face and intersecting the first direction, an introduction hole extending in the first direction from the rear end face to the inner wall face and through which the holding member can be introduced from the rear end face, and a plurality of insertion holes extending in the first direction from the inner wall face toward the front end face and aligned in a second direction intersecting the first direction and into which the tip portions of the plurality of optical fibers protruding from the end face of the holding member can be inserted respectively. Each of the plurality of insertion holes extends in the first direction between the inner wall face and the front end face and includes at least a holding portion having a constant inner diameter capable of holding the tip portion. The length of the insertion hole in the first direction is 1.5 mm or less.

[0005] FIG. 1 is a perspective view of an optical connector according to an embodiment. FIG. 2 is a cross-sectional view of the optical connector of FIG. 1. FIG. 3 is another cross-sectional view of the optical connector of FIG. 1. FIG. 4 is a cross-sectional view of a tape fiber along the IV-IV line of FIG. 2. FIG. 5 is a cross-sectional view of an optical connector ferrule included in the optical connector of FIG. 1. FIG. 6 is another cross-sectional view of the optical connector ferrule of FIG. 5. FIG. 7 is a side view of a tape fiber included in the optical connector of FIG. 1. FIG. 8 is a view showing a state where the tape fiber of FIG. 7 is mounted on an optical connector ferrule. FIG. 9 is a perspective view of an optical coupling structure including the optical connector of FIG. 1. FIG. 10 is a cross-sectional view of an optical connector according to a comparative example. FIG. 11 is a side view of a tape fiber included in the optical connector of FIG. 10. FIG. 12 is a view showing a state where the tape fiber of FIG. 11 is mounted on an optical connector ferrule. FIG. 13 is a cross-sectional view of an optical connector according to Modification 1. FIG. 14 is a cross-sectional view of an optical connector according to Modification 2. FIG. 15 is a cross-sectional view of an optical connector according to Modification 3. FIG. 16 is another cross-sectional view of the optical connector of FIG. 15. FIG. 17 is a cross-sectional view of an optical connector according to Modification 4. FIG. 18 is another cross-sectional view of the optical connector of FIG. 17. FIG. 19 is a cross-sectional view of the optical connector along the XIX-XIX line of FIG. 17. FIG. 20 is a cross-sectional view of an optical connector ferrule included in the optical connector of FIG. 17. FIG. 21 is another cross-sectional view of the optical connector ferrule of FIG. 20. FIG. 22 is a cross-sectional view of an optical connector according to Modification 5. FIG. 23 is another cross-sectional view of the optical connector of FIG. 22. FIG. 24 is a cross-sectional view of an optical connector ferrule included in the optical connector of FIG. 22. FIG. 25 is another cross-sectional view of the optical connector ferrule of FIG. 24. FIG. 26 is a cross-sectional view of an optical connector according to Modification 5. FIG. 27 is a perspective view of an optical fiber holding member included in the optical connector of FIG. 26. FIG. 28 is a perspective view of a modified example of an optical fiber holding component. FIG. 29 is a perspective view of another modified example of an optical fiber holding component.

[0006] [Problem to be Solved by the Present Disclosure] When an optical fiber is mounted in the above-described ferrule, there is only a small clearance between the fiber insertion hole and the splice end of the optical fiber. Therefore, in order to avoid contact of the splice end of the optical fiber with the fiber insertion hole, it is desirable to insert the splice end of the optical fiber as straight as possible into the fiber insertion hole. However, in reality, the splice end position of the optical fiber is likely to deviate from the ideal position depending on the length of the optical fiber from the outer jacket. Therefore, the splice end of the optical fiber may be inserted into the fiber insertion hole with a significantly tilted posture. In this case, the splice end may come into strong contact with the fiber insertion hole, causing fluctuations in the installation state, such as twisting and rotation, of the optical fiber. Such fluctuations in the installation state of the optical fiber may lead to deterioration of the optical characteristics, such as increased connection loss.

[0007] The present disclosure provides an optical connector ferrule, an optical connector, and an optical coupling structure that can reduce the occurrence of fluctuations in the installation state of an optical fiber.

[0008] [Advantages of the Present Disclosure] According to the optical connector ferrule, optical connector, and optical coupling structure of the present disclosure, it is possible to reduce the occurrence of fluctuations in the installation state of optical fibers.

[0009] [Description of Embodiments of the Present Disclosure] First, the contents of the embodiments of the present disclosure will be listed and described.

[0010] (1) An optical connector ferrule according to one embodiment of the present disclosure is an optical connector ferrule into which a holding member can be inserted, the holding member holding multiple optical fibers, each having a coating portion covered with a resin coating and a glass portion protruding from the coating end of the coating portion. The optical connector ferrule includes a front end face, a rear end face aligned with the front end face in a first direction, an inner wall surface formed between the front end face and the rear end face and intersecting the first direction, an introduction hole extending from the rear end face to the inner wall surface in the first direction and allowing the holding member to be introduced from the rear end face, and multiple insertion holes extending from the inner wall surface toward the front end face in the first direction and aligned in a second direction intersecting the first direction, allowing the insertion of the respective tips of the multiple optical fibers protruding from the end face of the holding member. Each of the multiple insertion holes extends in the first direction between the inner wall surface and the front end face and includes at least a holding portion having a constant inner diameter capable of holding the tip. The length of the insertion hole in the first direction is 1.5 mm or less.

[0011] When multiple optical fibers are mounted in the optical connector ferrule, the multiple optical fibers are introduced into the introduction hole of the optical connector ferrule while being held together by a holding member. The tip ends of the fibers protruding from the holding member are inserted into the insertion hole through the introduction hole. In this configuration, the longer the insertion hole, the longer the length of the optical fibers protruding from the holding member. The longer the length of the optical fibers protruding from the holding member, the more likely it is that the tip of the optical fiber will be significantly misaligned. If such a large misalignment occurs, the tip end of the optical fiber is inserted into the insertion hole with a significantly tilted attitude. In this case, the tip end may come into strong contact with the insertion hole or its surrounding area, which may cause fluctuations in the installation state, such as twisting and rotation of the optical fiber. In contrast, if the length of the insertion hole is set to be short, such as 1.5 mm or less, as in the above optical connector ferrule, the length of the optical fiber from the holding member can be shortened, and the positional misalignment of the tip of the optical fiber can be reduced. This makes it possible to insert the tip end of the optical fiber into the insertion hole while suppressing tilt in attitude and preventing the tip end from coming into strong contact with the insertion hole, etc. As a result, it is possible to reduce the occurrence of fluctuations in the installation state, such as twisting and rotation of the optical fiber, caused by friction between the insertion hole and the tip portion.

[0012] (2) In the optical connector ferrule described in (1) above, the insertion hole may extend in a first direction from the holding portion to the inner wall surface and may further include a tapered portion whose diameter decreases as it approaches the holding portion from the inner wall surface. In this case, it is possible to facilitate insertion of the tip end of the optical fiber into the holding portion. Furthermore, with this configuration, the length of the insertion hole can be made shorter than in a configuration in which the insertion hole has another portion between the tapered portion and the inner wall surface, thereby further minimizing positional deviation of the tip end of the optical fiber. This more reliably reduces the occurrence of fluctuations in the installation state of the optical fiber.

[0013] (3) In the optical connector ferrule described in (1) or (2) above, the introduction hole may include an abutment surface configured so that the holding member abuts in a first direction, and the abutment surface may be formed at a position spaced apart from the inner wall surface in the first direction. If the distance from the holding member to the inner wall surface is too close, the optical fiber between the holding member and the inner wall surface is likely to be sharply bent due to axial alignment between the optical fiber protruding from the holding member and the insertion hole in the inner wall surface. On the other hand, if the abutment surface is formed at a position spaced apart from the inner wall surface as in the above configuration, the distance between the holding member and the inner wall surface can be maintained, thereby reducing sharp bending of the optical fiber between the holding member and the inner wall surface. This reduces excessive bending stress on the optical fiber.

[0014] (4) In the optical connector ferrule described in (3) above, the distance between the inner wall surface and the abutting surface in the first direction may be 0.5 mm or more and 2 mm or less. By making the distance between the inner wall surface and the abutting surface 0.5 mm or more, it is possible to more reliably reduce the occurrence of sudden bending of the optical fiber, thereby more reliably reducing the application of excessive bending stress to the optical fiber. Furthermore, by making the distance between the inner wall surface and the abutting surface 2 mm or less, it is possible to more reliably reduce the length of the tip of the optical fiber from the holding member from becoming excessively long, thereby more reliably reducing the occurrence of fluctuations in the installation state of the optical fiber when it is mounted in the optical connector ferrule.

[0015] (5) In the optical connector ferrule described in any one of (1) to (4) above, the introduction hole may include a lower surface extending in the first and second directions between the inner wall surface and the rear end face, and an upper surface facing the lower surface. The upper surface may be inclined relative to the lower surface so that the distance between the upper surface and the lower surface narrows as the distance from the rear end face approaches the inner wall surface. In this case, when inserting the holding member into the introduction hole, the holding member can be advanced along the upper and lower surfaces to easily guide the optical fiber held by the holding member into the insertion hole. At the same time, the position of the optical fiber relative to the insertion hole can be accurately determined. This more reliably reduces fluctuations in the installation state of the optical fiber.

[0016] (6) In the optical connector ferrule described in any one of (1) to (5), the introduction hole may include a first side surface and a second side surface facing each other in the second direction between the inner wall surface and the rear end face, and the first side surface and the second side surface may be inclined with respect to a plane perpendicular to the second direction so that the distance between the first side surface and the second side surface narrows from the rear end face toward the inner wall surface. In this case, when inserting the holding member into the introduction hole, the holding member can be advanced along the first side surface and the second side surface to easily guide the optical fiber held by the holding member into the insertion hole. At the same time, the position of the optical fiber relative to the insertion hole can be accurately determined. This more reliably reduces the occurrence of fluctuations in the installation state of the optical fiber.

[0017] (7) In the optical connector ferrule described in any one of (1) to (4), the introduction hole may include a lower surface configured to face the bottom surface of the holding member introduced into the introduction hole. The lower surface may extend in the first and second directions between the inner wall surface and the rear end surface. The lower surface or the bottom surface may have a convex portion extending in the first direction. The lower surface or the bottom surface may have a concave portion that can fit into the convex portion. If the convex portion is formed on the lower surface, a concave portion may be formed on the bottom surface. If the convex portion is formed on the bottom surface, a concave portion may be formed on the lower surface. In this case, when inserting the holding member into the introduction hole, the holding member can be advanced along the convex portion and the concave portion to easily guide the optical fiber held by the holding member into the insertion hole. At the same time, the position of the optical fiber relative to the insertion hole can be accurately determined. This more reliably reduces the occurrence of fluctuations in the installation state of the optical fiber.

[0018] (8) An optical connector according to an embodiment of the present disclosure includes the optical connector ferrule according to any one of (1) to (7), a plurality of optical fibers, and a holding member inserted into the optical connector ferrule while holding the plurality of optical fibers. Because this optical connector includes any one of the optical connector ferrules described above, as described above, it is possible to reduce the occurrence of fluctuations in the installation state of the optical fibers.

[0019] (9) In the optical connector described in (8), the holding member may be a resin layer that surrounds only the coatings of the optical fibers. In this case, by holding the coatings of the optical fibers, which have a relatively high strength, with the holding member, it is possible to reduce the occurrence of damage to the optical fibers due to stress concentration at the boundary between the holding member and the optical fibers.

[0020] (10) In the optical connector described in (8) above, the holding member may be a resin layer that surrounds only the tip ends of the optical fibers. In this case, the clearance between the tip ends and the holding member can be reduced, thereby further reducing the positional deviation of the tip ends of the optical fibers. This more reliably reduces the occurrence of fluctuations in the installation state of the optical fibers.

[0021] (11) In the optical connector described in (8) above, the holding member may extend in a first direction and be aligned in a second direction, and may have a plurality of V-grooves for accommodating a plurality of optical fibers. In this case, the tip ends of the optical fibers can be inserted into the holding portions of the insertion holes while the orientation of the optical fibers is adjusted by the V-grooves. This reduces the occurrence of fluctuations in the installation state, such as twisting and rotation of the optical fibers, due to friction between the insertion holes and the tip ends.

[0022] (12) In the optical connector described in (8) above, the holding member may penetrate in a first direction and be arranged in a second direction, and may have a plurality of through holes into which a plurality of optical fibers are respectively inserted. In this case, the tip ends of the optical fibers can be inserted into the holding portions of the insertion holes while the orientation of the optical fibers is adjusted by the through holes. This reduces the occurrence of fluctuations in the installation state, such as twisting and rotation of the optical fibers, due to friction between the insertion holes and the tip ends.

[0023] (13) In the optical connector according to any one of (8) to (12), each of the multiple optical fibers may be a multicore fiber, a polarization-maintaining fiber, or a bundle fiber. When such optical fibers are used, rotational alignment of the optical fibers is required. Therefore, fluctuations in the installation state, such as twisting and rotation of the optical fibers due to friction between the insertion hole or the like and the tip, are likely to become a problem. In contrast, the optical connector described above can reduce such fluctuations in the installation state of the optical fibers, thereby more effectively achieving the above-mentioned effects.

[0024] (14) 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 (8) to (13), the first optical connector being arranged to face the second optical connector in a first direction and being 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, as described above, it is possible to reduce the occurrence of fluctuations in the installation state of the optical fiber.

[0025] [Details of Embodiments of the Present Disclosure] Specific examples of optical connector ferrules, optical connectors, and optical coupling structures according to 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, identical elements in the drawings will be designated by the same reference numerals, and duplicate descriptions will be omitted as appropriate.

[0026] FIG. 1 is a perspective view of an optical connector 1 according to this embodiment. In the following description, for convenience of explanation, the longitudinal direction of the optical connector 1 is defined as the X direction (first direction), the short direction of the optical connector 1 as the Y direction (second direction), and the height direction of the optical connector 1 as the Z direction. The X direction, Y direction, and Z direction intersect with each other (in one example, are perpendicular). In the following description, "up and down" may be defined by the relative position of the Z coordinate, "front and back" by the relative position of the X coordinate, and "left and right" by the relative position of the Y coordinate. A larger Z coordinate is "up." A larger X coordinate is "front." A larger Y coordinate is "right."

[0027] As shown in FIG. 1 , the optical connector 1 includes a ribbon fiber T and an optical connector ferrule (hereinafter simply referred to as a "ferrule") 20. The ribbon fiber T includes a plurality of optical fibers 10 extending in the X direction and aligned in the Y direction. Each of the plurality of optical fibers 10 is a cable that transmits an optical signal. FIG. 1 shows an example in which 12 optical fibers 10 are aligned in a row in the Y direction. However, the number of the plurality of optical fibers 10 is not limited to 12. For example, other numbers such as 4, 8, or 24 may also be used. The plurality of optical fibers 10 may also be aligned in two or more rows.

[0028] FIG. 2 is a cross-sectional view showing the XZ cross section of the optical connector 1. FIG. 3 is a cross-sectional view showing the XY cross section of the optical connector 1. FIG. 4 is a cross-sectional view of the ribbon fiber T taken along line IV-IV in FIG. 2. As shown in FIGS. 2 and 3, each optical fiber 10 has a tip portion 14 and a coating portion 15. The tip portion 14 is the portion of the glass portion 11 of the optical fiber 10 that protrudes forward from the coating end 15a of the coating portion 15. In other words, the tip portion 14 is the glass portion 11 from the coating end 15a to the tip 10a. The coating end 15a is the front edge of the coating portion 15 and is located at the boundary between the coating portion 15 and the tip portion 14.

[0029] At the tip portion 14, the glass portion 11 is exposed and not covered by the coating portion 15. The tip portion 14 is formed by removing a predetermined length of the resin coating 12 from the tip 10a. Therefore, the tip portion 14 can also be said to be a coating-removed portion from which the resin coating 12 has been removed. The outer diameter of the tip portion 14 (i.e., the diameter of the glass portion 11) may be, for example, 30 μm or more and 300 μm or less. The coating portion 15 is the portion of the optical fiber 10 where the glass portion 11 is covered with the resin coating 12. In other words, the coating portion 15 is the portion of the optical fiber 10 behind the coating end 15a. The outer diameter of the coating portion 15 may be, for example, 50 μm or more and 500 μm or less.

[0030] The optical fiber 10 is, for example, an optical fiber that requires rotational alignment with respect to the central axis C. In this embodiment, a multi-core fiber (MCF) is exemplified as the optical fiber 10 that requires rotational alignment. In this case, as shown in Fig. 4 , the glass portion 11 of the optical fiber 10 includes a plurality of cores 11 a and a cladding 11 b that covers the plurality of cores 11 a. In the example shown in Fig. 4 , at least one of the plurality of cores 11 a is disposed at a position shifted from the central axis C.

[0031] The number and arrangement of the multiple cores 11a are not limited to the example shown in FIG. 4 and can be changed as appropriate. For example, the number of the multiple cores 11a is not limited to six, and may be two, four, eight, or more. The multiple cores 11a do not have to include a central core arranged on the central axis C. 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 C. In this case, for example, the optical fiber 10 has a core arranged on the central axis C, and a pair of stress-applying portions are arranged on both sides of the core.

[0032] As shown in FIG. 4 , the optical fibers 10 are arranged in a row in the Y direction and held by a resin tape 13 (holding member). The resin tape 13 is a resin layer that holds the optical fibers 10 together in a bundle to reduce positional fluctuations among the optical fibers 10. The resin tape 13 is, for example, provided behind the coated ends 15 a of the coatings 15 of the optical fibers 10. In this case, the resin tape 13 collectively covers only the coatings 15 of the optical fibers 10. As shown in FIG. 2 , the position of the end face 13 a of the resin tape 13 in the X direction is aligned with the position of the coated ends 15 a of the coatings 15 of the optical fibers 10 in the X direction. The tip ends 14 of the optical fibers 10 protrude forward from the end face 13 a of the resin tape 13.

[0033] FIG. 5 is a cross-sectional view of the ferrule 20. FIG. 6 is another cross-sectional view showing the ferrule 20. The ferrule 20 is a component that holds the ends of multiple 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, for example, 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), an introduction hole 24 (fiber introduction hole), and multiple insertion holes 25 (fiber insertion holes).

[0034] 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, into which multiple optical fibers 10 held in the tape resin 13 can be inserted.

[0035] The introduction hole 24 is formed in the rear portion of the ferrule 20, which is a portion between the front end face 21 and the rear end face 22 and close to the rear end face 22. The rear portion of the ferrule 20 is a portion of the ferrule 20 from an inner wall surface 26 formed inside the ferrule 20 to the rear end face 22. The inner wall surface 26 is a flat surface along the Y and Z directions, and is formed between the front end face 21 and the rear end face 22 in the X direction. The introduction hole 24 extends in the X direction from an opening 22a in the rear end face 22 to the inner wall surface 26. The introduction hole 24 has an internal space into which the multiple optical fibers 10 held in the tape-formed resin 13 can be introduced.

[0036] The introduction hole 24 has a bottom surface 31, a top surface 32, a side surface 33 (first side surface), and a side surface 34 (second side surface) that surround the multiple optical fibers 10. The bottom surface 31, the top surface 32, the side surface 33, and the side surface 34 extend in the X direction from the inner wall surface 26 to the rear end face 22. The bottom surface 31, the top surface 32, the side surface 33, the side surface 34, and the inner wall surface 26 define the internal space of the introduction hole 24. As shown in FIG. 5 , the bottom surface 31 extends along the X direction and the Y direction between the inner wall surface 26 and the rear end face 22. The bottom surface 31 is, for example, a flat surface parallel to the XY plane and is formed perpendicular to the inner wall surface 26 and the rear end face 22.

[0037] The upper surface 32 faces the lower surface 31 in the Z direction and is spaced upward from the lower surface 31. The upper surface 32 is, for example, a flat surface inclined relative to the lower surface 31 along the XY plane. The upper surface 32 is inclined relative to the lower surface 31 so that the distance between the upper surface 32 and the lower surface 31 in the Z direction becomes narrower as the upper surface 32 approaches the inner wall surface 26 from the rear end surface 22 in the X direction. The minimum value of the distance between the upper surface 32 and the lower surface 31 in the Z direction is set to be greater than the width of the tape resin 13 in the Z direction. A window 35 for injecting adhesive is connected to the upper surface 32. The window 35 penetrates in the Z direction from the upper surface 32 to the outer surface of the ferrule 20 above. The window 35 is formed at a position closer to the inner wall surface 26 in the X direction than the rear end surface 22. This allows the adhesive to flow reliably from the window 35 into the insertion hole 25 formed in the inner wall surface 26 , so that the optical fiber 10 can be reliably bonded to the insertion hole 25 .

[0038] 6 , the side surfaces 33 and 34 face each other in the Y direction and are spaced apart in the Y direction. The side surfaces 33 and 34 are, for example, flat surfaces inclined from an XZ plane perpendicular to the Y direction. The side surfaces 33 and 34 are inclined with respect to the XZ plane so that the distance between the side surfaces 33 and 34 in the Y direction becomes narrower as they approach the inner wall surface 26 from the rear end surface 22 in the X direction. The minimum value of the distance between the side surfaces 33 and 34 in the Y direction is set to be larger than the width of the resin tape 13 in the Y direction.

[0039] The lower surface 31, the upper surface 32, the side surface 33, and the side surface 34 are configured as a positioning mechanism for guiding the optical fibers 10 into the insertion holes 25. Because the lower surface 31 is a flat surface parallel to the XY plane, the Z-direction positions of the optical fibers 10 relative to the insertion holes 25 are defined. At the same time, the arrangement direction of the optical fibers 10 is restricted to be along the arrangement direction of the insertion holes 25 (i.e., the Y-direction) (see FIGS. 2 and 3 ). Furthermore, because the upper surface 32 is inclined so that the distance between the upper surface 32 and the lower surface 31 gradually narrows, the Z-direction positions of the optical fibers 10 held in the tape-formed resin 13 are determined with greater precision as the tape-formed resin 13 advances in the introduction hole 24. Furthermore, because the side surfaces 33 and 34 are inclined so that the distance between the side surfaces 33 and 34 gradually narrows, the Y-direction positions of the optical fibers 10 held in the tape-formed resin 13 are determined with greater precision as the tape-formed resin 13 advances in the introduction hole 24.

[0040] In this way, the positions of the optical fibers 10 relative to the insertion holes 25 in the YZ plane are determined with high precision by the lower surface 31 , the upper surface 32 , the side surface 33 , and the side surface 34 .

[0041] The introduction hole 24 further includes a protrusion 37 protruding from the lower surface 31. The top surface of the protrusion 37 protrudes upward from the lower surface 31 to a height that does not reach the opening of the insertion hole 25 in the inner wall surface 26. The protrusion 37 extends linearly in the Y direction at a position adjacent to the inner wall surface 26 in the X direction. The protrusion 37 is formed, for example, integrally with the ferrule 20 and connected to the inner wall surface 26 in the X direction. The protrusion 37 may also be formed separately from the ferrule 20. The protrusion 37 includes a butting surface 37a located on the opposite side of the inner wall surface 26 in the X direction.

[0042] The abutting surface 37a is spaced apart (separated) from the inner wall surface 26 of the introduction hole 24 in the X direction. That is, the abutting surface 37a is located inside the introduction hole 24 at a predetermined distance in the X direction from the inner wall surface 26. Therefore, the abutting surface 37a is located between the inner wall surface 26 and the rear end surface 22 in the X direction. The abutting surface 37a is, for example, a flat surface along the Y direction and the Z direction. The abutting surface 37a is, for example, formed perpendicular to the lower surface 31 and parallel to the inner wall surface 26. When the resin tape 13 is introduced into the introduction hole 24, the end surface 13a of the resin tape 13 abuts against the abutting surface 37a in the X direction (see FIGS. 2 and 3 ). This determines the position of the optical fiber 10 in the X direction relative to the insertion hole 25.

[0043] 5 and 6 , the multiple insertion holes 25 are formed in the front portion of the ferrule 20, which is the portion close to the front end face 21, between the front end face 21 and the rear end face 22. The front portion of the ferrule 20 is the portion of the ferrule 20 from the front end face 21 to the inner wall surface 26. The multiple insertion holes 25 penetrate in the X direction from the front end face 21 to the inner wall surface 26. The multiple insertion holes 25 are lined up in the Y direction between the front end face 21 and the inner wall surface 26 to correspond to the multiple optical fibers 10. The multiple insertion holes 25 open at the front end face 21 and the inner wall surface 26 and are connected to the introduction hole 24 in the X direction. The multiple insertion holes 25 receive the multiple optical fibers 10 to be introduced into the introduction hole 24, respectively.

[0044] Each insertion hole 25 has a holding portion 27 that holds the tip end 14 of the optical fiber 10 and a tapered portion 28 (introduction portion) for guiding the tip end 14 of the optical fiber 10 into the holding portion 27. The holding portion 27 is a small-diameter circular hole extending in the X direction from the front end face 21. The holding portion 27 has a constant inner diameter at each position along the X direction. The inner diameter of the holding portion 27 is large enough to hold the tip end 14. The inner diameter of the holding portion 27 is set so that the clearance between the holding portion 27 and the tip end 14 in the YZ plane is sufficiently small. The holding portion 27 is open at the front end face 21. The tip end 10a of the optical fiber 10 inserted into the holding portion 27 is exposed from the opening in the front end face 21 (see FIGS. 2 and 3 ).

[0045] The tapered portion 28 is disposed between the holding portion 27 and the inner wall surface 26. The tapered portion 28 extends in the X direction from the holding portion 27 to the inner wall surface 26. The tapered portion 28 connects the holding portion 27 and the inner wall surface 26 in the X direction. The tapered portion 28 has an inner diameter larger than the inner diameter of the holding portion 27. The inner diameter of the tapered portion 28 becomes smaller as it approaches the holding portion 27 from the inner wall surface 26 in the X direction. In other words, the diameter of the tapered portion 28 gradually decreases as it approaches the holding portion 27. The tapered portion 28 opens at the inner wall surface 26. The optical fiber 10 is inserted through the opening in the inner wall surface 26. When the optical fiber 10 is inserted into the insertion hole 25, the tip end 14 of the optical fiber 10 is guided to the holding portion 27 by the tapered portion 28 and inserted into the holding portion 27.

[0046] In this embodiment, the length L of the insertion hole 25 in the X direction is set to 1.5 mm or less. The length L of the insertion hole 25 corresponds to the distance in the X direction from the front end surface 21, where the front end of the insertion hole 25 is located, to the inner wall surface 26, where the rear end of the insertion hole 25 is located. The length L of the insertion hole 25 is the sum of the length L1 of the holding portion 27 in the X direction and the length L2 of the tapered portion 28 in the X direction. The length L1 of the holding portion 27 is set to be longer than the length L2 of the tapered portion 28, for example. By setting the length L of the insertion hole 25 to 1.5 mm or less, the length L10 (see FIG. 7 ) of the optical fiber 10 protruding from the end face 13 a can be shortened to a maximum of 1.5 mm. A shorter length L of the insertion hole 25 can shorten the length L10 of the optical fiber 10, as described below. Therefore, this is effective in reducing misalignment of the tip 10 a of the optical fiber 10. The length L of the insertion hole 25 can be measured by cutting the ferrule 20 in the X direction at a cross section including the insertion hole 25 and observing the cross section under a microscope.

[0047] However, if the end face 13a of the tape-formed resin 13 holding the optical fiber 10 is too close to the inner wall surface 26 where the insertion hole 25 is formed, it may be necessary to sharply bend the optical fiber 10 between the end face 13a and the inner wall surface 26 in order to axially align the optical fiber 10 extending from the end face 13a with the insertion hole 25. In this case, a large bending stress may be applied to the optical fiber 10, which may cause damage to the optical fiber 10. Therefore, in order to reduce the bending stress on the optical fiber 10, it is necessary to maintain a certain distance between the end face 13a and the inner wall surface 26, i.e., the length of the optical fiber 10 between the end face 13a and the inner wall surface 26.

[0048] The abutting surface 37a formed in the introduction hole 24 is used to adjust the distance between the end face 13a and the inner wall surface 26. When the resin tape 13 is inserted into the introduction hole 24, the end face 13a abuts against the abutting surface 37a. The distance between the end face 13a and the inner wall surface 26 corresponds to the distance D between the abutting surface 37a and the inner wall surface 26. Therefore, by adjusting the distance D in accordance with the position of the abutting surface 37a in the X direction, the length of the optical fiber 10 between the end face 13a and the inner wall surface 26 can be adjusted. In this way, the abutting surface 37a has the function of adjusting the distance between the end face 13a and the inner wall surface 26.

[0049] The distance D between the abutting surface 37a and the inner wall surface 26 is set to, for example, 0.5 mm or more and 2 mm or less. Setting the distance D to 0.5 mm or more effectively reduces the bending stress on the optical fiber 10. To more effectively reduce the bending stress on the optical fiber 10, the distance D may be set to, for example, 1 mm or more. On the other hand, if the end face 13a is too far from the inner wall surface 26, the length L10 of the optical fiber 10 becomes long, which raises concerns about increased positional deviation of the tip 10a of the optical fiber 10 due to factors such as manufacturing tolerances between the optical fiber 10 and the tape-formed resin 13. Therefore, to reduce the positional deviation of the tip 10a of the optical fiber 10, the distance D is set to 2 mm or less. To more effectively reduce the positional deviation of the tip 10a, the distance D may be set to 1.5 mm or less. The distance D can be measured by cutting the ferrule 20 in the X direction at a cross section including the abutting surface 37a and the inner wall surface 26 and observing the cross section under a microscope.

[0050] The total length L+D of the length L of the insertion hole 25 and the distance D from the inner wall surface 26 to the abutting surface 37a corresponds to the length L10 of the optical fiber 10 protruding from the end surface 13a of the tape-formed resin 13. In this embodiment, the total length L+D including the distance D is a maximum of 3.5 mm, so the length L10 of the optical fiber 10 can also be kept to 3.5 mm or less. If the optical fiber 10 can be shortened in this way, the positional deviation of the tip 10a of the optical fiber 10 can be sufficiently reduced. The reason for this will be explained below with reference to FIGS. 7 and 8.

[0051] FIG. 7 is a side view of a tape fiber T including an optical fiber 10. FIG. 8 is a diagram illustrating how the tape fiber T is mounted in a ferrule 20. As described above, the longer the length L10 of the optical fiber 10 from the end face 13a, the greater the positional deviation of the tip 10a of the optical fiber 10. The positional deviation of the tip 10a can be expressed by the distance d (see FIG. 8 ) of the tip 10a from the central axis C1 of the insertion hole of the tape resin 13 into which the optical fiber 10 is inserted. Therefore, the longer the length L10, the greater the distance d. In particular, in a configuration in which the optical fiber 10 is held by the tape resin 13, as in this embodiment, the tape resin 13 must be removed to expose the tip 14 of the optical fiber 10 from the tape resin 13. Therefore, this removal is likely to cause the tip 10a to be misaligned, and the distance d is likely to be large.

[0052] As described above, the distance d depends on the length L10 of the optical fiber 10. Therefore, if the length L10 of the optical fiber 10 can be kept at 3.5 mm or less, the distance d can be kept at, for example, 100 μm or less. In contrast, since the inner diameter of the holding portion 27 is 200 μm or less, if the distance d can be kept small in this manner, even if the optical fiber 10 is advanced while the insertion hole 25 and the optical fiber 10 are axially aligned, the tip 14 of the optical fiber 10 can be prevented from coming into strong contact with the tapered portion 28, etc. Therefore, by setting the total length L+D to a short value, such as 3.5 mm or less, it is possible to sufficiently reduce the positional deviation of the tip 10 a of the optical fiber 10. Note that the length L of the insertion hole 25 may be set to a short value, such as 1 mm or less, in order to further reduce the positional deviation of the tip 10 a of the optical fiber 10 by shortening the total length L+D. Furthermore, taking into account the manufacturing accuracy of the insertion hole 25, the length L of the insertion hole 25 may be set to, for example, 0.5 mm or more. Therefore, the length L of the insertion hole 25 may be set to, for example, 0.5 mm or more and 1.5 mm or less. Alternatively, the length L of the insertion hole 25 may be set to a shorter range, for example, 0.5 mm or more and 1 mm or less.

[0053] If the distance d can be kept small in this way, it is possible to reduce the possibility of the tip end 14 of the optical fiber 10 being inserted into the insertion hole 25 in a significantly tilted position. As shown in Figure 8, when the resin tape 13 holding the optical fiber 10 is inserted into the ferrule 20 and the resin tape 13 is advanced, the tip end 14 of the optical fiber 10 can be inserted into the holding portion 27 without making strong contact with the tapered portion 28 or other parts.

[0054] When the resin tape 13 is inserted into the introduction hole 24, the optical fiber 10 held in the resin tape 13 is positioned with high precision by the lower surface 31, upper surface 32, side surface 33, and side surface 34 of the introduction hole 24. As the length L10 of the optical fiber 10 becomes shorter, the rigidity of the optical fiber 10 increases. Therefore, if there is a large axial misalignment between the optical fiber 10 and the insertion hole 25, there is a concern that the optical fiber 10 may be severely damaged by contact with the insertion hole 25 or the like. Therefore, by providing the lower surface 31, upper surface 32, side surface 33, and side surface 34 as a positioning mechanism for accurately positioning the optical fiber 10, it is possible to avoid such damage to the optical fiber.

[0055] 9 is a perspective view of an optical coupling structure 100 according to this embodiment. The optical coupling structure 100 includes 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.

[0056] 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.

[0057] The effects obtained by the ferrule 20, the optical connector 1, and the optical coupling structure 100 according to the present embodiment described above will be described together with the problems of the comparative example.

[0058] Fig. 10 is a cross-sectional view showing an optical connector 101 according to a comparative example. Fig. 11 is a side view showing a ribbon fiber T100 included in the optical connector 101. As shown in Fig. 10, in the optical connector 101, the length L100 of the insertion hole 125 of the ferrule 120 is set to, for example, 4 mm or more. The insertion hole 125 includes a holding portion 127 into which the tip portion 114 of the optical fiber 110 of the ribbon fiber T100 is inserted, and an introduction portion 128 into which the coating portion 115 of the optical fiber 110 is inserted.

[0059] 11 , when the length L100 of the insertion hole 125 is set long, the length L110 of the optical fiber 110 from the end face 113a of the resin tape 113 also becomes long, and accordingly, the deviation of the central axis C110 of the optical fiber 110 from the central axis C100 of the insertion hole of the resin tape 113, i.e., the deviation (distance d100) of the tip 110a of the optical fiber 110 from the central axis C100, also becomes large. When the positional deviation of the tip 110a becomes large, the optical fiber 110 is inserted into the insertion hole 125 with its posture tilted significantly. Therefore, the optical fiber 110 is more likely to come into strong contact with the insertion hole 125.

[0060] 12 is a cross-sectional view showing how the ribbon fiber T100 is mounted in the ferrule 120. As shown in FIG. 12 , when the optical fiber 110 is advanced while the tip 110a of the optical fiber 110 is significantly misaligned, the tip 114 of the optical fiber 110 comes into strong contact with the insertion section 128 of the insertion hole 125, and friction between the tip 114 and the insertion section 128 causes twisting and rotation of the optical fiber 110. As a result, an angular deviation (rotational deviation) occurs in the rotational direction of the optical fiber 110. Such rotational deviation may cause a core deviation at the tip 110a of the optical fiber 110, which may cause fluctuations in the installation state of the optical fiber 110. Such fluctuations in the installation state of the optical fiber 110 may cause deterioration of optical characteristics, such as increased splice loss.

[0061] On the other hand, when the length L of the insertion hole 25 is set to a short value of 1.5 mm or less, as in this embodiment, the length L10 of the optical fiber 10 from the end face 13a of the tape-formed resin 13 can be shortened. Therefore, the positional deviation of the tip 10a of the optical fiber 10 can also be reduced (see FIG. 8 ). This allows the tip 14 of the optical fiber 10 to be inserted into the insertion hole 25 while suppressing tilt of the tip 14. This reduces the occurrence of fluctuations in the installation state, such as twisting and rotation of the optical fiber 10, due to friction between the insertion hole 25 and the tip 14. As a result, the occurrence of deterioration of the optical characteristics, such as an increase in splice loss, caused by fluctuations in the installation state of the optical fiber 10 can be reduced.

[0062] As in this embodiment, the insertion hole 25 may include a tapered portion 28 whose diameter decreases from the inner wall surface 26 toward the holding portion 27. In this case, it is possible to easily insert the tip portion 14 into the holding portion 27. Furthermore, with this configuration, the length L of the insertion hole 25 can be made shorter compared to a configuration in which the insertion hole 25 has another portion between the tapered portion 28 and the inner wall surface 26. Therefore, with this configuration, it is possible to further reduce the positional deviation of the tip of the optical fiber 10. This makes it possible to more effectively reduce the occurrence of fluctuations in the installation state of the optical fiber 10.

[0063] As in this embodiment, the introduction hole 24 may include an abutting surface 37a against which the tape-formed resin 13 introduced from the rear end face 22 abuts in the X direction. If the distance from the tape-formed resin 13 to the inner wall surface 26 is too close, the optical fiber 10 between the tape-formed resin 13 and the inner wall surface 26 is likely to be sharply bent due to axial alignment between the optical fiber 10 protruding from the tape-formed resin 13 and the insertion hole 25 on the inner wall surface 26. On the other hand, if the abutting surface 37a is formed at a position away from the inner wall surface 26 as in the above configuration, the distance between the end face 13a of the tape-formed resin 13 and the inner wall surface 26 can be maintained. This reduces the occurrence of sharp bending of the optical fiber 10 between the end face 13a and the inner wall surface 26. This reduces the application of excessive bending stress to the optical fiber 10.

[0064] As in this embodiment, the distance D between the inner wall surface 26 and the abutting surface 37a in the X direction may be 0.5 mm or more and 2 mm or less. By setting the distance D to 0.5 mm or more, it is possible to more reliably reduce the occurrence of abrupt bending of the optical fiber 10. Therefore, it is possible to more reliably reduce the application of excessive bending stress to the optical fiber 10. Furthermore, by setting the distance D to 2 mm or less, it is possible to prevent the length L10 of the tip portion 14 of the optical fiber 10 from the end surface 13a of the tape-formed resin 13 from becoming excessively long. As a result, it is possible to more reliably reduce the occurrence of fluctuations in the installation state of the optical fiber 10 when it is mounted in the ferrule 20.

[0065] As in the present embodiment, the upper surface 32 may be inclined with respect to the lower surface 31 so that the distance between the upper surface 32 and the lower surface 31 becomes narrower toward the inner wall surface 26. In this case, when inserting the resin tape 13 into the introduction hole 24, the optical fiber 10 held in the resin tape 13 can be easily guided into the insertion hole 25 by advancing the resin tape 13 along the upper surface 32 and the lower surface 31. At the same time, the position of the optical fiber 10 relative to the insertion hole 25 can be determined with high precision. This more reliably reduces the occurrence of fluctuations in the installation state of the optical fiber 10 when it is mounted in the ferrule 20.

[0066] As in the present embodiment, the side surfaces 33 and 34 may be inclined with respect to the XZ plane so that the distance between the side surfaces 33 and 34 becomes narrower toward the inner wall surface 26. In this case, when inserting the resin tape 13 into the introduction hole 24, the resin tape 13 is advanced along the side surfaces 33 and 34, so that the optical fiber 10 held in the resin tape 13 can be easily guided into the insertion hole 25. At the same time, the position of the optical fiber 10 relative to the insertion hole 25 can be determined with high precision. This more reliably reduces the occurrence of fluctuations in the installation state of the optical fiber 10 when it is mounted in the ferrule 20.

[0067] As in the present embodiment, the resin tape 13 may be a resin layer that bundles together and surrounds only the coatings 15 of the tip ends 14 and coatings 15 of the multiple optical fibers 10. In this case, by holding the coatings 15 of the optical fibers 10, which have a relatively high strength, with the resin tape 13, it is possible to reduce damage to the optical fibers 10 due to stress concentration at the boundary between the resin tape 13 and the optical fibers 10.

[0068] As in this embodiment, each of the multiple optical fibers 10 may be any one of a multicore fiber, a polarization-maintaining fiber, and a bundle fiber. When such optical fibers 10 are used, rotational alignment of the optical fibers 10 is required. Therefore, fluctuations in the installation state, such as twisting and rotation of the optical fibers 10 due to friction between the insertion hole 25 and the tip end 14, are likely to become a problem. In contrast, the optical connector 1 can reduce such fluctuations in the installation state of the optical fibers 10, thereby effectively achieving the above-mentioned effects.

[0069] The ferrule 20, the optical connector 1, and the optical coupling structure 100 according to the present disclosure are not limited to the above-described embodiment. The specific aspects of the ferrule 20, the optical connector 1, and the optical coupling structure 100 according to the present disclosure may be modified within the scope of the claims.

[0070] <Modification 1> Figure 13 is a cross-sectional view of an optical connector 1A according to Modification 1. In the optical connector 1A, the tape resin 13 bundles and surrounds only the tip portion 14 of the optical fiber 10, which is a part of the tip portion 14 and the coating 15. In this case, a portion of the tip portion 14 protrudes from the end face 13a of the tape resin 13, and the remaining portion of the tip portion 14 is covered by the tape resin 13. The coating 15 is located, for example, behind the tape resin 13. Even when only the tip portion 14 of the optical fiber 10 is held by the tape resin 13, the same effect as in the above-described embodiment can be obtained. Furthermore, in the optical connector 1A, the clearance between the tape resin 13 and the tip portion 14 can be relatively small, thereby further reducing the positional deviation of the tip of the optical fiber 10. This more reliably reduces the occurrence of fluctuations in the installation state of the optical fiber 10 when mounted in the ferrule 20.

[0071] <Modification 2> Figure 14 is a cross-sectional view of an optical connector 1B according to Modification 2. In the ferrule 20A of the optical connector 1B, the upper surface 32A of the introduction hole 24A is not inclined but extends parallel to the lower surface 31. That is, like the lower surface 31, the upper surface 32A extends along the X and Y directions between the inner wall surface 26 and the rear end surface 22. The upper surface 32A is, for example, a flat surface parallel to the XY plane and formed perpendicular to the inner wall surface 26 and the rear end surface 22. As in the above-described embodiment, the side surfaces 33 and 34 may be inclined with respect to the XZ plane so that the distance between the side surfaces 33 and 34 in the Y direction becomes narrower as they approach the inner wall surface 26 (see Figure 6). Even with this configuration, the same effects as those of the above-described embodiment can be obtained.

[0072] <Modification 3> Figure 15 is a cross-sectional view of an optical connector 1C according to Modification 3. Figure 16 is another cross-sectional view of the optical connector 1C. In the ferrule 20B of the optical connector 1C, the upper surface 32B, the side surface 33A, and the side surface 34A of the introduction hole 24B extend in the X direction without inclining. As shown in Figure 15, the upper surface 32B extends, for example, parallel to the lower surface 31. The distance in the Z direction between the upper surface 32B and the lower surface 31 is constant at each position along the X direction. The distance in the Z direction between the upper surface 32B and the lower surface 31 is set to be slightly larger than the width in the Z direction of the tape-formed resin 13 so that the tape-formed resin 13 that holds the optical fiber 10 can be positioned in the Z direction.

[0073] As shown in FIG. 16 , the side surfaces 33A and 34A are, for example, flat surfaces along the XZ plane and extend parallel to each other. The side surfaces 33A and 34A are, for example, formed perpendicular to the inner wall surface 26 and the rear end surface 22. The distance in the Y direction between the side surfaces 33A and 34A is constant at each position along the X direction. The distance in the Y direction between the side surfaces 33A and 34A is set to be slightly larger than the width in the Y direction of the tape-formed resin 13 so that the tape-formed resin 13 holding the optical fiber 10 can be positioned in the Y direction. Therefore, the lower surface 31, the upper surface 32B, the side surfaces 33A, and the side surfaces 34A can function as a positioning mechanism for determining the position of the optical fiber 10 in the YZ plane. Even with this configuration, the same effects as those of the above-described embodiment can be obtained.

[0074] <Modification 4> Figure 17 is a cross-sectional view of an optical connector 1D according to Modification 4. Figure 18 is another cross-sectional view of the optical connector 1D. Figure 19 is a cross-sectional view of the optical connector 1D taken along line XIX-XIX in Figure 17. In a ferrule 20C of the optical connector 1D, an introduction hole 24C includes a convex portion 45 on a lower surface 31. An upper surface 32C, a side surface 33B, and a side surface 34B of the introduction hole 24C extend in the X direction without inclining. The upper surface 32C extends, for example, parallel to the lower surface 31. The distance in the Z direction between the upper surface 32B and the lower surface 31 is constant at each position along the X direction. The side surfaces 33B and 34B extend, for example, parallel to each other. The distance in the Y direction between the side surfaces 33B and 34B is constant at each position along the X direction.

[0075] FIG. 20 is a cross-sectional view of the ferrule 20C. FIG. 21 is another cross-sectional view of the ferrule 20C. As shown in FIGS. 20 and 21 , the convex portion 45 protrudes upward from the lower surface 31 toward the upper surface 32C. The height of the top surface of the convex portion 45 from the lower surface 31 is lower than the height of the top surface of the protrusion 37 from the lower surface 31. The convex portion 45 extends linearly in the X direction from the abutting surface 37a of the protrusion 37 to the rear end surface 22 at the Y-direction center of the lower surface 31. The width of the convex portion 45 in the Y direction is smaller than the width of the protrusion 37 in the Y direction, for example. As shown in FIG. 19 , for example, the convex portion 45 is rectangular when viewed in the X direction. The tape resin 13A that holds the optical fiber 10 includes a recess 46 in the bottom surface 13b that can fit into the convex portion 45. The recess 46 extends linearly in the X direction from the end surface 13a on the bottom surface 13b.

[0076] 17 and 19 , when the resin tape 13A holding the optical fiber 10 is inserted into the ferrule 20C, the recess 46 of the resin tape 13A fits into the protrusion 45 of the introduction hole 24C, thereby determining the position of the resin tape 13A in the introduction hole 24C in the YZ plane, i.e., the position of the optical fiber 10 in the YZ plane relative to the insertion hole 25. With the recess 46 fitted into the protrusion 45, the resin tape 13A moves forward until the end face 13a of the resin tape 13A abuts against the abutment surface 37a, thereby positioning the optical fiber 10 relative to the insertion hole 25. Therefore, the protrusion 45 and the recess 46 can function as a positioning mechanism for determining the position of the optical fiber 10 in the YZ plane.

[0077] Even with this configuration, the same effects as those of the above-described embodiment can be obtained. That is, in the optical connector 1D, when inserting the resin tape 13A into the introduction hole 24C, the resin tape 13A is advanced along the convex portion 45 and the concave portion 46, so that the optical fiber 10 held in the resin tape 13A can be easily guided into the insertion hole 25. At the same time, the position of the optical fiber 10 relative to the insertion hole 25 can be determined with high precision. This more reliably reduces the occurrence of fluctuations in the installation state of the optical fiber 10 when it is mounted in the ferrule 20C.

[0078] <Modification 5> FIG. 22 is a cross-sectional view of an optical connector 1E according to Modification 5. FIG. 23 is another cross-sectional view of the optical connector 1E. FIG. 24 is a cross-sectional view of a ferrule 20D of the optical connector 1E. FIG. 25 is another cross-sectional view of the ferrule 20D. The optical connector 1E has a configuration in which the arrangement of the protrusion 37 of the optical connector 1D is changed. In the optical connector 1E, the protrusion 37A is formed in the introduction hole 24D at a position spaced apart from the inner wall surface 26 in the X direction. That is, the protrusion 37A is disposed between the inner wall surface 26 and the rear end surface 22, at a position offset from the inner wall surface 26 in the X direction. As shown in FIG. 25 , the protrusion 37A extends linearly in the Y direction from the side surface 33B to the side surface 34B, for example, at the center of the lower surface 31 in the X direction. The convex portion 45A extends linearly in the X direction from the abutting surface 37a of the protrusion 37A to the rear end surface 22.

[0079] As shown in Figure 22, the resin tape 13B that holds the optical fiber 10 includes a recess 46A in its bottom surface 13b that can fit onto the protrusion 45A. The recess 46A extends linearly in the X direction from the end surface 13a on the bottom surface 13b of the resin tape 13B. As shown in Figures 22 and 23, the resin tape 13B that holds the optical fiber 10 has a step surface 13c that is recessed rearward from the end surface 13a. The step surface 13c is, for example, a flat surface along the YZ plane. The step surface 13c is, for example, formed between the optical fiber 10 and the lower surface 31 in the Z direction.

[0080] When the tape-like resin 13B holding the optical fiber 10 is inserted into the introduction hole 24D, the step surface 13c moves in the X direction and abuts against the abutting surface 37a. When the step surface 13c abuts against the abutting surface 37a, the distance between the end face 13a and the inner wall surface 26 is set to distance D. As described above, distance D is, for example, 0.5 mm or more and 2 mm or less. The distance between the abutting surface 37a and the inner wall surface 26 is set to distance D1. Distance D1 is set to the sum of distance D and the Z-direction distance from the end face 13a to the step surface 13c. Therefore, the distance D between the end face 13a and the inner wall surface 26 can be adjusted by adjusting the distance D1 between the abutting surface 37a and the inner wall surface 26. In other words, the abutting surface 37a has the function of adjusting the distance (distance D) between the end face 13a and the inner wall surface 26, as in the above-described embodiment.

[0081] In this way, the abutting surface 37a does not need to be configured to abut against the end face 13a of the resin tape 13B, and may be configured to abut against another portion, such as the stepped surface 13c of the resin tape 13B. Even in this case, the distance D can be precisely controlled to maintain the distance between the end face 13a and the inner wall surface 26. As a result, it is possible to reduce the occurrence of a sudden bending of the optical fiber 10 between the end face 13a and the inner wall surface 26 due to the axial alignment of the optical fiber 10 with the insertion hole 25. This reduces the application of excessive bending stress to the optical fiber 10.

[0082] <Modification 6> Fig. 26 is a cross-sectional view of an optical connector 1F according to Modification 6. Fig. 27 is a perspective view of an optical fiber holding member 30 (holding member) included in the optical connector 1F. As shown in Figs. 26 and 27 , the optical connector 1F includes an optical fiber holding member 30 instead of the tape-formed resin 13. The optical fiber holding member 30 is a member that holds multiple optical fibers 10 in the introduction hole 24E of the ferrule 20E. The optical fiber holding member 30 is made of a material such as resin or metal. The optical fiber holding member 30 includes, for example, a front end face 30a, a rear end face 30b, an upper face 30c, a lower face 30d, a side face 30e, and a side face 30f. The front end face 30a and the rear end face 30b are, for example, flat faces along the YZ plane and are arranged side by side along the X direction. The upper face 30c and the lower face 30d are, for example, flat faces along the XY plane and are arranged side by side along the Z direction. The side surface 30e and the side surface 30f are, for example, flat surfaces along the XZ plane, and are arranged side by side along the Y direction.

[0083] The optical fiber holding member 30 includes a fixing surface 30g for collectively fixing the coatings 15 of the multiple optical fibers 10 in a portion close to the rear end face 30b in the X direction. The fixing surface 30g is, for example, a flat surface along the XY plane and forms a step with respect to the top surface 30c. The fixing surface 30g and the top surface 30c are connected via a step surface 30s. The step surface 30s is, for example, a flat surface along the YZ plane and is formed perpendicular to the fixing surface 30g and the top surface 30c. The fixing surface 30g extends from the step surface 30s to the rear end face 30b in the X direction. The optical fiber holding member 30 includes a plurality of V-grooves 30h for respectively holding the tip ends 14 of the multiple optical fibers 10 in a portion close to the front end face 30a in the X direction. The plurality of V-grooves 30h are formed in the top surface 30c. The plurality of V-grooves 30h extend in the X direction from the front end surface 30a to the step surface 30s on the upper surface 30c and are arranged side by side along the Y direction.

[0084] As shown in FIG. 26 , the tip portions 14 of the optical fibers 10 are placed in the V-grooves 30h, respectively, and the coatings 15 of the optical fibers 10 are placed on the fixing surface 30g. By placing the tip portions 14 in the respective V-grooves 30h, the position of the optical fibers 10 in the YZ plane relative to the optical fiber holding member 30 is determined. With the tip portions 14 placed in the V-grooves 30h, rotational alignment of the optical fibers 10 is performed. Each V-groove 30h is configured to hold the tip portions 14 rotatably about the central axis C. With all rotationally aligned optical fibers 10 placed in their respective V-grooves 30h, adhesive is applied to the optical fibers 10, and the tip portions 14 are pressed against the V-grooves 30h by a rectangular plate-shaped cover 29 provided on the tip portions 14. As the adhesive hardens in this state, the tip portions 14 are fixed to the V-grooves 30h via the adhesive. Similarly, the coatings 15 are fixed to the fixing surface 30g via the adhesive. As a result, an optical fiber holding member 30 that holds a plurality of optical fibers 10 is obtained.

[0085] Even with this configuration, the same effects as those of the above-described embodiment can be obtained. Furthermore, in the optical connector 1F, by placing the optical fiber holding member 30 inside the ferrule 20E with the rotationally aligned optical fibers 10 placed and fixed in the V-grooves 30h of the optical fiber holding member 30, the tip end 14 of the optical fiber 10 can be inserted into the insertion hole 25 with the orientation of the optical fiber 10 aligned in the X direction. This more reliably reduces friction between the insertion hole 25 and the tip end 14 and facilitates the installation of the optical fiber 10 in the ferrule 20A. Furthermore, since the optical fiber holding member 30 holds both the tip end 14 and the coating 15, the orientation of the optical fiber 10 can be more stabilized.

[0086] FIG. 28 is a perspective view showing a modified example of the optical fiber holding member 30 included in the optical connector 1F. The optical connector 1F may include the optical fiber holding member 30A shown in FIG. 28 instead of the optical fiber holding member 30 shown in FIG. 27. Unlike the optical fiber holding member 30, the optical fiber holding member 30A does not have a fixing surface 30g. The upper surface 30c extends from the front end face 30a to the rear end face 30b, and multiple V-grooves 30i formed on the upper surface 30c extend from the front end face 30a to the rear end face 30b. The coatings 15 of the multiple optical fibers 10 are placed in the multiple V-grooves 30i, respectively. The multiple rotationally aligned optical fibers 10 are then accommodated and fixed in the multiple V-grooves 30i. Rectangular plate-shaped covers 29 (see FIG. 26) are provided on the multiple V-grooves 30i to cover the coatings 15 of the multiple optical fibers 10. Even with this configuration, the same effects as those of the optical connector 1F described above can be obtained.

[0087] FIG. 29 is a perspective view showing another modified example of the optical fiber holding member 30 included in the optical connector 1F. The optical connector 1F may include the optical fiber holding member 30B of FIG. 29 instead of the optical fiber holding member 30 of FIG. 27. Unlike the optical fiber holding member 30, the optical fiber holding member 30B does not have a fixing surface 30g, and the upper surface 30c extends from the front end face 30a to the rear end face 30b. The optical fiber holding member 30B includes a plurality of through holes 301 instead of the plurality of V-grooves 30h. The plurality of through holes 301 penetrate in the X direction from the front end face 30a to the rear end face 30b and are aligned along the Y direction. For example, the tip end 14 and coating 15 of the optical fiber 10 are inserted into each through hole 301, and the tip end 14 and coating 15 are fixed in the through hole 301 with an adhesive. Even with this configuration, the same effects as those of the optical connector 1F described above can be obtained. Only the tip portion 14 of the optical fiber 10 may be inserted into the through-hole 301, or only the coating portion 15 of the optical fiber 10 may be inserted.

[0088] 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. Furthermore, the configuration of the optical connector is not limited to the above-described embodiments and modifications. For example, the insertion hole may include, in addition to the tapered portion described above, a thickened portion between the tapered portion and the inner wall surface. In this case, the thickened portion has a constant inner diameter that is larger than the inner diameter of the holding portion and is capable of holding the coating portion of the optical fiber. The tapered portion and the thickened portion may be configured as an introduction portion for introducing the tip of the optical fiber into the holding portion.

[0089] DESCRIPTION OF SYMBOLS 1, 1A, 1B, 1C, 1D, 1E, 1F...Optical connector 1a...First optical connector 1b...Second optical connector 10...Optical fiber 10a...Tip 11...Glass portion 11a...Core 11b...Cladding 12...Resin coating 13, 13A, 13B...Tape-shaped resin (holding member) 13a...End face 13b...Bottom face 13c...Step surface 14...Tip portion 15...Coated portion 15a...Coated end 20, 20A, 20B, 20C, 20D, 20E...Optical connector ferrule 21...Front end face 22...Rear end face 22a...Opening 23...Guide hole 24, 24A, 24B, 24C, 24D, 24E...Introduction hole 25...Insertion hole 26...Inner wall surface 27...Holding portion 28...Tapered portion 29...Cover 30, 30A, 30B...Optical fiber holding member (holding member) 30a...Front end surface 30b...Rear end surface 30c...Top surface 30d...Bottom surface 30e...Side surface 30f...Side surface 30g...Fixing surface 30h, 30i...V groove 30s...Step surface 31...Bottom surface 32, 32A, 32B, 32C...Top surface 33, 33A, 33B... Side surface (first side surface) 34, 34A, 34B... Side surface (second side surface) 35... Window 37, 37A... Protrusion 37a... Abutment surface 45, 45A... Convex portion 46, 46A... Concave portion 50... Spacer 50a... Opening 100... Optical coupling structure 301... Through hole C, C1... Central axis D, D1...distance d...distance T...tape fiber

Claims

1. An optical connector ferrule into which a holding member can be inserted, the holding member holding a plurality of optical fibers, each having a coating portion covered with a resin coating and a tip end of a glass portion protruding from a coating end of the coating portion, A front end surface and a rear end surface aligned with the front end surface in a first direction; an inner wall surface formed between the front end surface and the rear end surface and intersecting the first direction; an introduction hole extending in the first direction from the rear end surface to the inner wall surface, through which the holding member can be introduced from the rear end surface; a plurality of insertion holes extending in the first direction from the inner wall surface toward the front end surface and aligned in a second direction intersecting the first direction, into which the tip ends of the plurality of optical fibers protruding from the end surface of the holding member can be inserted, respectively; Equipped with Each of the plurality of insertion holes is the holding portion includes at least a holding portion having a constant inner diameter that extends in the first direction between the inner wall surface and the front end surface and is capable of holding the tip portion; The length of the insertion hole in the first direction is 1.5 mm or less. Optical connector ferrule.

2. Each of the plurality of insertion holes is The holding portion further includes a tapered portion extending in the first direction from the holding portion to the inner wall surface, the tapered portion having a diameter that decreases as it moves from the inner wall surface toward the holding portion.

2. The optical connector ferrule according to claim 1.

3. The introduction hole is The holding member includes an abutment surface configured to abut in the first direction, The abutting surface is formed at a position spaced apart from the inner wall surface in the first direction.

2. The optical connector ferrule according to claim 1.

4. The distance between the inner wall surface and the abutting surface in the first direction is 0.5 mm or more and 2 mm or less. The optical connector ferrule according to claim 3 .

5. The introduction hole is a lower surface extending in the first direction and the second direction between the inner wall surface and the rear end surface; an upper surface facing the lower surface, the upper surface is inclined with respect to the lower surface such that the distance between the upper surface and the lower surface becomes narrower from the rear end surface toward the inner wall surface; 2. The optical connector ferrule according to claim 1.

6. The introduction hole is a first side surface and a second side surface facing each other in the second direction between the inner wall surface and the rear end surface, the first side surface and the second side surface are inclined with respect to a plane perpendicular to the second direction such that a distance between the first side surface and the second side surface becomes narrower from the rear end surface toward the inner wall surface; 2. The optical connector ferrule according to claim 1.

7. The introduction hole is a lower surface configured to face a bottom surface of the holding member introduced into the introduction hole, the lower surface extends between the inner wall surface and the rear end surface in the first direction and the second direction, a convex portion extending in the first direction is formed on the lower surface or the bottom surface, a recess that can be fitted into the protrusion is formed on the lower surface or the bottom surface, When the convex portion is formed on the lower surface, the concave portion is formed on the bottom surface, When the convex portion is formed on the bottom surface, the concave portion is formed on the lower surface.

2. The optical connector ferrule according to claim 1.

8. The optical connector ferrule according to any one of claims 1 to 7, the plurality of optical fibers; the holding member that is inserted into the optical connector ferrule while holding the plurality of optical fibers; Equipped with Optical connector.

9. the holding member is a resin layer that surrounds only the coating portions of the plurality of optical fibers; 9. The optical connector according to claim 8.

10. the holding member is a resin layer that surrounds only the tip portions of the plurality of optical fibers; 9. The optical connector according to claim 8.

11. the holding member has a plurality of V-grooves extending in the first direction and aligned in the second direction, each of which accommodates one of the plurality of optical fibers; 9. The optical connector according to claim 8.

12. the holding member has a plurality of through holes that penetrate the holding member in the first direction and are arranged in the second direction, and into which the plurality of optical fibers are inserted, respectively.

9. The optical connector according to claim 8.

13. 9. The optical connector according to claim 8, wherein each of the plurality of optical fibers is one of a multicore fiber, a polarization-maintaining fiber, and a bundle fiber.

14. A first optical connector and a second optical connector as the optical connector according to claim 8, The first optical connector is disposed opposite the second optical connector in the first direction and is optically coupled to the second optical connector.