Holding member, optical connector, and optical connection assembly

Abstract

A holding member (30) includes: a front end surface (31) that faces, in a first direction, an inner wall surface (201) of the interior of an optical connector ferrule; a rear end surface (32) that is disposed on a side opposite the front end surface in the first direction; a bottom surface (34) that contacts, in a second direction, a bottom wall surface (202) of the interior of the optical connector ferrule; a plurality of holding parts (37) that extend along the first direction between the front end surface and the rear end surface, are arranged along a third direction, and can each hold one of a plurality of optical fibers; and a stopper (40) that is formed on the surface of the holding member and maintains a distance in the first direction between the front end surface and the inner wall surface within a predetermined range when tip portions (14) of a plurality of optical fibers (10) extending from the holding member are respectively inserted into a plurality of insertion holes (24) in the first direction.

Description

Holding member, optical connector, and optical connection assembly

[0001] This application claims priority to Japanese Patent Application No. 2023-125980, filed on August 2, 2023, and incorporates by reference the entire contents of said Japanese application.

[0002] Conventionally, optical fiber holding members for holding multiple optical fibers (for example, Patent Document 1) are known. The multiple optical fibers are inserted into and held in multiple fiber holes formed in the optical fiber holding member. The tip ends of the optical fibers protrude from each fiber hole. In this state, the optical fiber holding member is placed inside a ferrule. The tip ends of the multiple optical fibers protruding from the optical fiber holding member are inserted into multiple insertion holes formed inside the ferrule, respectively. The optical fiber holding member is then fixed to the ferrule to form a connector.

[0003] International Publication No. 2016 / 031678

[0004] A holding member according to an embodiment of the present disclosure is a holding member that is disposed on a bottom wall surface inside an optical connector ferrule while holding a plurality of optical fibers, and in which tip ends of the plurality of optical fibers are inserted one by one into a plurality of insertion holes formed in the inner wall surface of the optical connector ferrule. The holding member includes: a front end surface that faces the inner wall surface in a first direction intersecting the inner wall surface; a rear end surface that is disposed on the opposite side of the first direction from the front end surface; a bottom surface that abuts the bottom wall surface in a second direction intersecting the first direction; a plurality of holding portions that extend between the front end surface and the rear end surface along the first direction and are aligned along a third direction intersecting the first and second directions, and are capable of holding one of the plurality of optical fibers; and a stopper formed on a surface of the holding member that maintains a distance in the first direction between the front end surface and the inner wall surface within a specified range when the tip ends of the plurality of optical fibers extending from the holding member are inserted into the plurality of insertion holes in the first direction.

[0005] FIG. 1 is a perspective view of an optical connector according to one embodiment. FIG. 2 is a cross-sectional view of the optical connector. FIG. 3 is another cross-sectional view of the optical connector. FIG. 4 is a front view of the optical connector. FIG. 5 is a cross-sectional view of an optical connector ferrule. FIG. 6 is another cross-sectional view of the optical connector ferrule. FIG. 7 is a cross-sectional view of a holding member. FIG. 8 is a front view of the holding member. FIG. 9 is a diagram showing a state in which the holding member is being inserted into the optical connector ferrule. FIG. 10 is a diagram showing a state after the holding member has been inserted into the optical connector ferrule. FIG. 11 is a graph showing the relationship between bend radius R and distance L. FIG. 12 is a perspective view of an optical connection assembly. FIG. 13 is a cross-sectional view of an optical connector according to Modification 1. FIG. 14 is another cross-sectional view of the optical connector of FIG. 13. FIG. 15 is a cross-sectional view of the optical connector according to Modification 2. FIG. 16 is another cross-sectional view of the optical connector of FIG. 15.

[0006] [Problem to be Solved by the Present Disclosure] When an optical fiber holding member such as that described above is disposed inside a ferrule, it is difficult to perfectly align the central axis of each fiber hole in the optical fiber holding member with the central axis of the insertion hole in the ferrule due to manufacturing tolerances, and therefore axial misalignment is likely to occur between the fiber holes. Such axial misalignment can cause bending of the optical fiber inserted from the insertion hole into the fiber hole. When bending stress applied to the optical fiber increases, problems such as increased transmission loss and damage to the optical fiber are more likely to occur. As a result, there is a risk of reducing the reliability of the optical fiber.

[0007] The present disclosure provides a holding member, an optical connector, and an optical connection assembly that can reduce deterioration in the reliability of optical fibers.

[0008] Effect of the Present Disclosure The holding member, optical connector, and optical connection assembly according to the present disclosure can reduce the deterioration of the reliability 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) According to an embodiment of the present disclosure, a holding member is disposed on a bottom wall surface of an interior of an optical connector ferrule while holding a plurality of optical fibers, and the tip ends of the plurality of optical fibers are inserted one by one into a plurality of insertion holes formed in the inner wall surface of the optical connector ferrule. The holding member includes: a front end surface facing the inner wall surface in a first direction intersecting the inner wall surface; a rear end surface disposed on the opposite side of the first direction from the front end surface; a bottom surface abutting the bottom wall surface in a second direction intersecting the first direction; a plurality of holding portions extending along the first direction between the front end surface and the rear end surface and aligned along a third direction intersecting the first and second directions, each capable of holding one of the plurality of optical fibers; and a stopper formed on a surface of the holding member that maintains a distance in the first direction between the front end surface and the inner wall surface within a specified range when the tip ends of the plurality of optical fibers extending from the holding member are inserted into the plurality of insertion holes in the first direction.

[0011] The holding member includes a stopper that maintains the distance in the first direction between the front end face of the holding member and the inner wall surface of the optical connector ferrule within a specified range when the tip ends of the optical fibers extending from the holding member are inserted into the insertion holes in the first direction. The distance between the front end face of the holding member and the inner wall surface of the optical connector ferrule significantly affects the bending stress on the optical fiber. If the distance between the front end face and the inner wall surface is too small, the optical fiber extending from the front end face to the inner wall surface is likely to bend sharply, thereby increasing the bending stress on the optical fiber. If the distance between the front end face and the inner wall surface is too large, the intermediate portion of the optical fiber between the front end face and the inner wall surface is likely to bend. Therefore, this also increases the bending stress on the optical fiber. In contrast, the holding member uses the stopper to maintain the distance between the front end face and the inner wall surface within a specified range, thereby easily and appropriately limiting the position of the holding member relative to the optical connector ferrule so as not to increase the bending stress on the optical fiber. As a result, problems such as increased transmission loss and damage to the optical fiber due to increased bending stress can be reduced. Therefore, the above-mentioned holding member can reduce the deterioration of the reliability of the optical fiber.

[0012] (2) In the holding member described in (1) above, the specified range may be 0.5 mm or more and 3 mm or less. By maintaining the specified range of the distance between the front end face of the holding member and the inner wall surface of the optical connector ferrule at 0.5 mm or more, it is possible to effectively reduce an increase in bending stress caused by a sharp bend in the optical fiber. By maintaining the specified range of the distance between the front end face of the holding member and the inner wall surface of the optical connector ferrule at 3 mm or less, it is possible to effectively reduce an increase in bending stress caused by a deflection in the intermediate portion of the optical fiber.

[0013] (3) In the holding member described in (1) or (2), the stopper may be at least one front-end protrusion formed on the front end surface and protruding in a first direction from the front end surface. In this case, the front-end protrusion abuts against the inner wall surface of the optical connector ferrule in the first direction, thereby easily and reliably maintaining the distance between the front end surface of the holding member and the inner wall surface within a specified range.

[0014] (4) In the holding member described in (3) above, the stopper may be a plurality of front end protrusions. The plurality of front end protrusions may be arranged so as to be spaced apart in at least one of the second direction and the third direction along the front end face. In this case, when an adhesive is injected into the interior of the ferrule to fix the holding member to the ferrule, the adhesive is more likely to spread through the spaces between the plurality of front end protrusions and into the interior of the ferrule. In other words, the above configuration reduces the obstruction of the flow of adhesive by the stopper. This allows the plurality of optical fibers and the holding member to be more reliably fixed with the adhesive.

[0015] (5) In the holding member described in (4) above, the plurality of front-end protrusions may be arranged symmetrically in at least one of the second direction and the third direction with respect to the center of the front end face. In this case, the position of the holding member relative to the ferrule can be stabilized when the plurality of front-end protrusions abut the inner wall surface. As a result, an increase in bending stress due to instability in the position of the holding member can be reduced.

[0016] (6) The holding member described in (1) or (2) above may further include a pair of side surfaces spaced apart in the third direction between the front end face and the rear end face. The distance between the pair of side surfaces in the third direction may increase as the distance approaches the rear end face in the first direction. The pair of side surfaces may be stoppers and may abut against a pair of internal side wall surfaces of the optical connector ferrule in the first and third directions. In this case, the pair of side surfaces of the holding member abut against a pair of internal side wall surfaces of the optical connector ferrule in the first direction, thereby maintaining the distance between the front end face of the holding member and the inner wall surface of the optical connector ferrule within a specified range. Furthermore, the pair of side surfaces of the holding member abut against a pair of internal side wall surfaces of the ferrule in the third direction, thereby determining the position of the holding member relative to the optical connector ferrule in the third direction. In other words, in the above configuration, the pair of side surfaces of the holding member can serve both the function of positioning the holding member relative to the optical connector ferrule in the first direction and the function of positioning the holding member relative to the optical connector ferrule in the third direction.

[0017] (7) In the holding member described in (1) or (2) above, the stopper may be a rear end protrusion formed on the rear end face and protruding from the rear end face in at least one of the second and third directions. The rear end protrusion may abut in a first direction against the rear end face of the ferrule, which has an opening connecting to the interior of the optical connector ferrule. In this case, the rear end protrusion abuts in the first direction against the rear end face of the ferrule, thereby maintaining the distance between the front end face of the holding member and the inner wall surface of the optical connector ferrule within a specified range. Furthermore, in the above configuration, the stopper can be formed over a wider area outside the optical connector ferrule than in a configuration in which the stopper is formed inside the optical connector ferrule. In this case, the contact area between the rear end protrusion as a stopper and the rear end face of the ferrule can be maintained large. As a result, the position of the holding member relative to the ferrule can be stabilized when the rear end protrusion abuts against the rear end face of the ferrule. Therefore, in the above configuration, an increase in bending stress caused by instability in the position of the holding member can be reduced.

[0018] (8) An optical connector according to an embodiment of the present disclosure includes the holding member according to any one of (1) to (7) above, a plurality of optical fibers held by the holding member with their tip ends protruding from the holding member, and a ferrule including a plurality of insertion holes into which the tip ends of the plurality of optical fibers are inserted and fixed one by one. Because this optical connector includes any one of the holding members described above, it is possible to reduce the deterioration of the reliability of the optical fibers, as described above.

[0019] (9) In the optical connector described in (8) above, each of the multiple optical fibers may be a multi-core optical fiber. When such an optical fiber is used, rotational alignment of the optical fiber is required. In this case, the bending stress of the optical fiber is likely to increase further due to friction between the outer surface of the tip of the optical fiber and the inner surface of the insertion hole. In the above-mentioned optical connector, the increase in bending stress can be reduced as described above, thereby effectively reducing the risk of malfunctions caused by the increase in bending stress.

[0020] (10) An optical connection assembly according to an embodiment of the present disclosure includes a first optical connector and a second optical connector as the optical connectors described in (8) or (9). The first optical connector and the second optical connector are arranged to face each other along a first direction. Because this optical connection assembly includes the first optical connector and the second optical connector as the optical connectors described above, it is possible to reduce a decrease in the reliability of the optical fiber, as described above.

[0021] [Details of the embodiments of the present disclosure] Specific examples of a holding member, an optical connector, and an optical connection assembly 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, the same elements in the description of the drawings will be given the same reference numerals, and duplicate descriptions will be omitted as appropriate.

[0022] 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 referred to as the X direction (first direction), the lateral direction of the optical connector 1 is referred to as the Y direction (third direction), and the height direction of the optical connector 1 is referred to as the Z direction (second direction). The X direction, Y direction, and Z direction intersect with each other (in one example, are orthogonal). In the following description, the positive Z direction may be referred to as "up," the negative Z direction as "down," the positive X direction as "front," and the negative X direction as "rear."

[0023] As shown in Fig. 1, the optical connector 1 includes a plurality of optical fibers 10, an optical connector ferrule (hereinafter simply referred to as a "ferrule") 20, and a holding member 30. Each of the plurality of optical fibers 10 is a cable that transmits an optical signal. 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, for example, 4, 8, or 24. The plurality of optical fibers 10 may also be arranged in two or more rows.

[0024] 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 front view of the optical connector 1. However, for convenience, guide holes 26, 26 described later are omitted in FIGS. 2 and 4 . As shown in FIGS. 2 and 3 , each optical fiber 10 includes a coating-removed portion 12 and a coating portion 13. The coating-removed portion 12 is a portion of the optical fiber 10 from the tip surface 11 where a predetermined length of resin coating has been removed. The tip surface 11 is an end face located at the tip of the optical fiber 10 in the X direction. In the coating-removed portion 12, the cladding portion of the optical fiber 10 is exposed. The outer diameter of the coating-removed portion 12 (i.e., the diameter of the cladding portion) is, for example, 30 μm or more and 300 μm or less. The coating portion 13 is a portion of the optical fiber 10 where the resin coating remains. The outer diameter of the coating portion 13 is, for example, 50 μm or more and 500 μm or less.

[0025] The optical fiber 10 is, for example, an optical fiber that requires rotational alignment about a central axis C10. In this embodiment, a multi-core optical fiber (MCF) is exemplified as the optical fiber 10 that requires rotational alignment. In this case, as shown in FIG. 4 , the optical fiber 10 includes multiple cores 10 a and a cladding 10 b that covers the multiple cores 10 a. In the optical fiber 10, at least one of the multiple cores 10 a is disposed at a position shifted from the central axis C10. The number and arrangement of the multiple cores 10 a are not limited to the example shown in FIG. 4 and can be changed as appropriate. For example, the number of the multiple cores 10 a is not limited to 6, but may be 2, 4, 8 or more.

[0026] The optical fiber 10 does not necessarily have to include a core 10a disposed on the central axis C10. Examples of optical fibers 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 C10. In this case, for example, the optical fiber 10 has a core disposed on the central axis C10, and a pair of stress-applying portions are disposed on both sides of the core.

[0027] FIG. 5 is a cross-sectional view showing the XZ cross section of the ferrule 20. FIG. 6 is a cross-sectional view showing the XY cross section of the ferrule 20. The ferrule 20 is, for example, an MT ferrule that holds multiple optical fibers 10. The ferrule 20 has a substantially rectangular parallelepiped appearance. The ferrule 20 is formed, for example, from PPS (Polyphenylene Sulfide). The ferrule 20 includes, for example, a ferrule front end face 21 and a ferrule rear end face 22. The ferrule front end face 21 is an end face located at the front end of the ferrule 20 in the X direction. The ferrule rear end face 22 is an end face located on the opposite side of the ferrule front end face 21. The ferrule rear end face 22 is aligned with the ferrule front end face 21 in the X direction. The ferrule rear end face 22 is, for example, a flat surface extending along the Y and Z directions. An opening 22a capable of receiving multiple optical fibers 10 is formed in the ferrule rear end face 22.

[0028] The ferrule 20 includes an introduction hole 23 and a plurality of insertion holes 24 therein. The introduction hole 23 extends in the X direction from an opening 22a in the ferrule rear end face 22 to an inner wall surface 201 formed inside the ferrule 20. The introduction hole 23 has a space capable of introducing a holding member 30 for holding a plurality of optical fibers 10. The inner wall surface 201 is formed between the ferrule front end face 21 and the ferrule rear end face 22 in the X direction. The inner wall surface 201 is, for example, a flat surface extending along the Y and Z directions, similar to the ferrule rear end face 22. The inner wall surface 201 extends, for example, parallel to the ferrule rear end face 22. In addition to the inner wall surface 201, a bottom wall surface 202, a top wall surface 203, a side wall surface 204, and a side wall surface 205 are formed inside the ferrule 20. The bottom wall surface 202, the top wall surface 203, the side wall surface 204, and the side wall surface 205 extend in the X direction from the inner wall surface 201 to the opening 22a in the ferrule rear end surface 22, and together with the inner wall surface 201, define the internal space of the introduction hole 23. Therefore, the internal space of the introduction hole 23 is a space surrounded by the inner wall surface 201, the bottom wall surface 202, the top wall surface 203, the side wall surface 204, and the side wall surface 205.

[0029] As shown in FIG. 5 , the bottom wall surface 202 and the top wall surface 203 face each other in the Z direction and are spaced apart from each other in the Z direction. Each of the bottom wall surface 202 and the top wall surface 203 is, for example, a flat surface extending along the X and Y directions and perpendicular to the inner wall surface 201 and the ferrule rear end surface 22. Each of the bottom wall surface 202 and the top wall surface 203 extends, for example, parallel to each other. A window 25 for injecting adhesive is formed in the top wall surface 203. The window 25 is located in a portion of the top wall surface 203 close to the inner wall surface 201. As shown in FIG. 6 , the side wall surface 204 and the side wall surface 205 face each other in the Y direction and are spaced apart from each other in the Y direction. Each of the side wall surface 204 and the side wall surface 205 is, for example, a flat surface extending along the X and Z directions and perpendicular to the inner wall surface 201 and the ferrule rear end surface 22.

[0030] As shown in FIGS. 5 and 6 , each of the multiple insertion holes 24 is, for example, a through-hole penetrating in the X direction from the inner wall surface 201 to the ferrule front end face 21. The insertion holes 24 are, for example, lined up in a row in the Y direction corresponding to each optical fiber 10. Each insertion hole 24 is, for example, a circular hole centered on the central axis C24. A pair of guide holes 26, 26 (see FIG. 1 ) extending in the X direction from the ferrule front end face 21 toward the ferrule rear end face 22 are formed at positions sandwiching the multiple insertion holes 24 in the Y direction. Each insertion hole 24 opens at the ferrule front end face 21 and the inner wall surface 201. Each insertion hole 24 is connected to the introduction hole 23 in the X direction at the inner wall surface 201. The tip ends 14 of the multiple optical fibers 10 introduced into the introduction hole 23 are inserted into each insertion hole 24 (see FIGS. 2 and 3 ). The tip portion 14 may be, for example, a part of the coating removal portion 12 that includes the tip surface 11 .

[0031] Each insertion hole 24 includes a position defining portion 24a that defines the position of the coating removal portion 12 of the optical fiber 10, and a tapered portion 24b (introduction portion) for guiding the coating removal portion 12 into the position defining portion 24a. The position defining portion 24a is a small-diameter circular hole extending in the X direction from the ferrule front end face 21. The position defining portion 24a has a constant inner diameter at each position along the X direction. The inner diameter of the position defining portion 24a is large enough to hold the tip end 14. The distance between the inner circumferential surface of the position defining portion 24a and the outer circumferential surface of the tip end 14 in the YZ plane is sufficiently small. The position defining portion 24a opens at the ferrule front end face 21. The tip end face 11 of the optical fiber 10 inserted into the position defining portion 24a of the insertion hole 24 is exposed from the opening in the ferrule front end face 21 (see FIG. 4 ).

[0032] The tapered portion 24b is disposed between the position defining portion 24a and the inner wall surface 201. The tapered portion 24b extends in the X direction from the position defining portion 24a to the inner wall surface 201 and connects the position defining portion 24a and the inner wall surface 201 in the X direction. The tapered portion 24b has an inner diameter larger than the inner diameter of the position defining portion 24a. The inner diameter of the tapered portion 24b becomes smaller as it approaches the position defining portion 24a from the inner wall surface 201 in the X direction. In other words, the diameter of the tapered portion 24b gradually decreases as it approaches the position defining portion 24a. The tapered portion 24b opens at the inner wall surface 201 and receives the optical fiber 10 through the opening of the inner wall surface 201. When the optical fiber 10 is inserted into the insertion hole 24, the tip end 14 of the optical fiber 10 is guided to the position defining portion 24a by the tapered portion 24b and inserted into the position defining portion 24a.

[0033] Fig. 7 is a cross-sectional view showing an XZ cross section of the holding member 30 that holds a plurality of optical fibers 10. Fig. 8 is a front view of the holding member 30. The holding member 30 is, for example, a rectangular parallelepiped member that holds a plurality of optical fibers 10. The holding member 30 is arranged on the bottom wall surface 202 inside the ferrule 20 while holding a plurality of optical fibers 10. The holding member 30 is formed, for example, from a resin or quartz glass that is transmissive to ultraviolet (UV) light with a wavelength of 200 nm or more and 400 nm or less, or visible light with a wavelength of 400 nm or more and 850 nm or less. The holding member 30 may also be formed, for example, from a metal material.

[0034] The holding member 30 includes, for example, a front end surface 31, a rear end surface 32, a top surface 33, a bottom surface 34, side surfaces 35, and side surfaces 36. These surfaces constitute the surface of the holding member 30. The front end surface 31 and the rear end surface 32 are, for example, flat surfaces extending along the Y and Z directions and aligned along the X direction. The front end surface 31 and the rear end surface 32 extend, for example, parallel to each other. The top surface 33 and the bottom surface 34 are, for example, flat surfaces extending along the X and Y directions and aligned along the Z direction. The top surface 33 and the bottom surface 34 extend, for example, parallel to each other and are formed perpendicular to the front end surface 31 and the rear end surface 32. As shown in FIG. 8 , the side surfaces 35 and 36 are, for example, flat surfaces extending along the X and Z directions and aligned along the Y direction. The side surface 35 and the side surface 36 extend, for example, parallel to each other and are formed perpendicular to the front end surface 31 and the rear end surface 32 .

[0035] As shown in FIG. 7 , the holding member 30 further includes a plurality of holding holes 37 (holding portions) penetrating in the X direction from the front end face 31 to the rear end face 32. The plurality of holding holes 37 are aligned in the Y direction corresponding to the alignment of the plurality of optical fibers 10 (see FIG. 8 ). Each holding hole 37 includes, for example, a small diameter portion 37 a and a large diameter portion 37 b. The coating removal portion 12 of the optical fiber 10 is inserted into the small diameter portion 37 a. The inner diameter of the small diameter portion 37 a is the same as or slightly larger than the outer diameter of the coating removal portion 12. The large diameter portion 37 b has an inner diameter larger than the inner diameter of the small diameter portion 37 a. The coating portion 13 of the optical fiber 10 is inserted into the large diameter portion 37 b. The inner diameter of the large diameter portion 37 b is the same as or slightly larger than the outer diameter of the coating portion 13.

[0036] When multiple optical fibers 10 are mounted on the holding member 30, rotational alignment of the optical fibers 10 is performed with the coating removal portion 12 and the coating portion 13 inserted into the small diameter portion 37a and the large diameter portion 37b, respectively, and the optical fibers 10 are fixed to the inner surfaces of the holding holes 37 by adhesive injected into the holding holes 37. In this way, the holding member 30 that holds multiple optical fibers 10 is obtained. When the holding member 30 holds the multiple optical fibers 10, the tip portion 14 of the coating removal portion 12 protrudes in the X direction from the front end face 31. The tip portion 14 may be, for example, a portion of the optical fiber 10 that protrudes forward from the front end face 31.

[0037] The adhesive for fixing the plurality of optical fibers 10 to the holding member 30 may be, for example, an ultraviolet (UV) curable resin, a thermosetting resin, or an anaerobic resin. Instead of using an adhesive, the plurality of optical fibers 10 may be fixed to the holding member 30 by laser welding. Only the coating-removed portion 12 of the optical fiber 10 may be inserted into the holding hole 37, or only the coating portion 13 of the optical fiber 10 may be inserted.

[0038] 7 and 8 , the holding member 30 further includes a plurality of front end protrusions 40 (stoppers) that protrude in the X direction from the front end face 31. The plurality of front end protrusions 40 function as stoppers that determine the position of the holding member 30 relative to the ferrule 20. In other words, when the holding member 30 is inserted into the ferrule 20, each of the front end protrusions 40 protruding from the front end face 31 abuts against an inner wall surface 201 of the ferrule 20, which will be described later, thereby stopping movement of the holding member 30 in the X direction relative to the ferrule 20 (see FIGS. 2 and 3 ). For convenience, in each drawing, the plurality of front end protrusions 40 that function as stoppers are hatched with a dotted pattern that differs from the other components.

[0039] Each front end protrusion 40 is, for example, a rectangular parallelepiped protrusion formed on the front end face 31. Each front end protrusion 40 is, for example, formed integrally with the holding member 30. Alternatively, each front end protrusion 40 may be formed separately from the holding member 30. As shown in FIG. 7 , each front end protrusion 40 includes an abutment surface 40a disposed at a position protruding from the front end face 31 in the X direction. The abutment surface 40a is, for example, a flat surface extending along the Y and Z directions. The abutment surface 40a is parallel to the front end face 31 and perpendicular to the bottom surface 34. When the holding member 30 is inserted into the ferrule 20, the abutment surface 40a of each front end protrusion 40 abuts against the inner wall surface 201 in the X direction (see FIGS. 2 and 3 ). This determines the position of the holding member 30 in the X direction relative to the ferrule 20. The protrusion amount D40 in the X direction of each front end protrusion 40, that is, the distance in the X direction between each abutting surface 40a and the front end surface 31, may be the same for each.

[0040] 8 shows four front end protrusions 401, 402, 403, and 404 as the multiple front end protrusions 40. The front end protrusions 401, 402, 403, and 404 are arranged at positions spaced apart from one another on the front end face 31. For example, the front end protrusions 401, 402, 403, and 404 are arranged at positions where the distances from the center CP of the rectangular front end face 31 to the respective front end protrusions 401, 402, 403, and 404 are equal. For example, the front end protrusions 401, 402, 403, and 404 are arranged symmetrically in at least one of the Y direction and the Z direction with respect to the center CP of the front end face 31.

[0041] The two front end protrusions 401, 402 are spaced apart from each other along the Y direction. The two front end protrusions 401, 402 are, for example, arranged symmetrically with respect to an imaginary plane VL1 that passes through the center CP and is perpendicular to the Y direction. The distance d11 in the Y direction between the front end protrusion 401 and the imaginary plane VL1 is the same as the distance d12 in the Y direction between the front end protrusion 402 and the imaginary plane VL1. The two front end protrusions 403, 404 are spaced apart from each other in the Z direction from the two front end protrusions 401, 402, and are arranged spaced apart from each other along the Y direction. The two front end protrusions 403, 404 are, for example, arranged symmetrically with respect to the imaginary plane VL1 that passes through the center CP, similar to the two front end protrusions 401, 402. A distance d21 in the Y direction between the front end protrusion 403 and the imaginary plane VL1 is the same as a distance d22 in the Y direction between the front end protrusion 404 and the imaginary plane VL1.

[0042] The two front end protrusions 401, 403 aligned in the Z direction are positioned symmetrically with respect to an imaginary plane VL2 that passes through the center CP and is perpendicular to the Z direction. The distance d31 in the Z direction between the front end protrusion 401 and the imaginary plane VL2 is the same as the distance d32 in the Z direction between the front end protrusion 403 and the imaginary plane VL2. The two front end protrusions 402, 404 aligned in the Z direction are positioned symmetrically with respect to the imaginary plane VL2 that passes through the center CP. The distance d41 in the Z direction between the front end protrusion 402 and the imaginary plane VL2 is the same as the distance d42 in the Z direction between the front end protrusion 404 and the imaginary plane VL2.

[0043] In one example, the front end protrusions 401, 402, 403, and 404 are disposed at the corners 31a, 31b, 31c, and 31d of the rectangular front end face 31. The front end protrusion 401 is disposed at the corner 31a of the front end face 31, which is formed by a side of the front end face 31 that contacts the top surface 33 and a side of the front end face 31 that contacts the side surface 36. The front end protrusion 40 is disposed at the corner 31b of the front end face 31, which is formed by a side of the front end face 31 that contacts the top surface 33 and a side of the front end face 31 that contacts the side surface 35. In other words, the two front end protrusions 401 and 402 are disposed at a first end of the front end face 31 in the Z direction and at both ends in the Y direction. The front end protrusion 403 is disposed at the corner 31c of the front end face 31, which is formed by a side of the front end face 31 that contacts the side surface 36 and a side of the front end face 31 that contacts the bottom surface 34. The front end protrusion 404 is disposed at a corner 31d of the front end face 31, which is formed by a side of the front end face 31 that contacts the side face 35 and a side of the front end face 31 that contacts the bottom face 34. In other words, the two front end protrusions 403, 404 are disposed at a second end in the Z direction and at both ends in the Y direction of the front end face 31. In the following description, when the front end protrusions 401, 402, 403, and 404 are not to be distinguished from one another, each of the front end protrusions 401, 402, 403, and 404 will be referred to as a "front end protrusion 40."

[0044] FIG. 9 is a diagram showing the state of the holding member 30 in the middle of being inserted into the ferrule 20. FIG. 10 is a diagram showing the state of the holding member 30 after it has been inserted into the ferrule 20. As shown in FIG. 9 , when inserting the holding member 30 into the ferrule 20, for example, the bottom surface 34 of the holding member 30, which holds the rotationally aligned optical fiber 10, is placed on the bottom wall surface 202. The bottom surface 34 of the holding member 30 abuts against the bottom wall surface 202 in the Z direction, thereby determining the Z-direction position of the holding member 30 relative to the ferrule 20. Here, by aligning the flat bottom surface 34 with the flat bottom wall surface 202, the position and rotation angle of the holding member 30 relative to the ferrule 20 can be stabilized, allowing the holding member 30 to be mounted on the ferrule 20 with high precision. Furthermore, the Y-direction position of the holding member 30 relative to the ferrule 20 is determined by adjusting the Y-direction position of the holding member 30 so that each insertion hole 24 of the ferrule 20 corresponds to each holding hole 37 of the holding member 30.

[0045] In this state, because it is difficult to perfectly align the central axis C24 of each insertion hole 24 with the central axis C37 of each holding hole 37 due to the influence of manufacturing tolerances, an axial misalignment may occur between each insertion hole 24 and each holding hole 37, as shown in Fig. 9. In this case, when the tip portion 14 of the optical fiber 10 protruding from the holding member 30 is inserted into each insertion hole 24 from the introduction hole 23, a bend is imparted to the tip portion 14 due to the misalignment between the central axes C24 and C37. When the holding member 30 is moved further forward from the state shown in Fig. 9, the abutment surfaces 40a of each front end protrusion 40 formed on the front end face 31 of the holding member 30 abut against the inner wall surface 201 of the ferrule 20 in the X direction, as shown in Fig. 10.

[0046] When the abutment surface 40 a of each front end protrusion 40 abuts against the inner wall surface 201, movement of the holding member 30 relative to the ferrule 20 in the X direction is stopped, and the distance L between the inner wall surface 201 and the front end face 31 is maintained. The protrusion amount D40 of each front end protrusion 40 from the front end face 31 is equal to the distance L. Therefore, the distance L can be adjusted by adjusting the protrusion amount D40 of each front end protrusion 40. In this manner, in this embodiment, each front end protrusion 40 is used to adjust the distance L. The distance L significantly affects the bending radius R of the optical fiber 10 (hereinafter simply referred to as the “bending radius R”). For example, if the distance L is too small, the optical fiber 10 will be bent too sharply, increasing the bending stress on the optical fiber 10. On the other hand, if the distance L is too large, bending will be more likely to occur in the intermediate portion of the optical fiber 10 between the inner wall surface 201 and the front end face 31, increasing the bending stress on the optical fiber 10.

[0047] 11 is a graph showing the relationship between the bending radius R of the optical fiber 10 and the distance L between the front end face 31 and the inner wall surface 201. The horizontal axis of FIG. 11 represents the distance L [mm]. The vertical axis of FIG. 11 represents the bending radius R [mm]. Plot P shows the calculated values ​​(simulation results) of the bending radius R when the distance L is changed. Curve La is an approximation curve of plot P. As is clear from curve La, the smaller the distance L, the smaller the bending radius R and the greater the bending stress. The larger the distance L, the smaller the bending radius R and the greater the bending stress. Thus, it can be seen that the bending stress of the optical fiber 10 increases whether the distance L is too small or too large.

[0048] In FIG. 11 , the reference line Lb indicates the line where the bending radius R is 10 mm. When the bending radius R of the optical fiber 10 is 10 mm or less, the bending stress on the optical fiber 10 increases, making the optical fiber 10 more susceptible to problems such as breakage or increased transmission loss. This problem occurs equally in the coated portion 13 and the coated-removed portion 12 of the optical fiber 10. Therefore, from the viewpoint of maintaining the long-term reliability of the optical fiber 10, the bending radius R of the optical fiber 10 may be greater than 10 mm. In other words, the plots P may be located above the reference line Lb. The plots P above the reference line Lb are distributed in a range where the distance L is equal to or greater than 0.5 mm and equal to or less than 3 mm. On the other hand, the plots P below the reference line Lb are distributed in a range where the distance L is less than 0.5 mm and greater than 3 mm.

[0049] When the plots P are distributed in a range smaller than 0.5 mm and larger than 3 mm, breakage of the optical fiber 10 is more likely to occur due to increased bending stress on the optical fiber 10, as described above. In light of this, the distance L is adjusted to be within a specified range, for example, not less than 0.5 mm and not more than 3 mm. From the viewpoint of more effectively reducing the increase in bending stress on the optical fiber 10, the distance L may be, for example, within a range not less than 1 mm and not more than 3 mm, or within a range not less than 1.5 mm and not more than 2.5 mm. In the present embodiment, when the tip ends 14 of the multiple optical fibers 10 are inserted into the multiple insertion holes 24 in the X direction, the multiple front end protrusions 40 serving as stoppers abut against the inner wall surface 201, thereby maintaining the distance L within the specified range.

[0050] After each front end protrusion 40 abuts against the inner wall surface 201, adhesive is injected through the window 25 of the ferrule 20. As the adhesive hardens, the holding member 30 and the optical fiber 10 are fixed to the ferrule 20. For convenience, the adhesive is not shown in the drawings. Then, after the ferrule front end face 21 is polished, the spring and housing are assembled to obtain the optical connector 1.

[0051] 12 is a perspective view of an optical connection assembly 100 according to this embodiment. The optical connection assembly 100 includes a first optical connector 1a, a second optical connector 1b, a pair of guide pins 50, 50, and a spacer 60. 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 connection assembly 100, the ferrule front end face 21 of the first optical connector 1a and the ferrule 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 50, 50 fit into a pair of guide holes 26, 26 of the first optical connector 1a and a pair of guide holes 26, 26 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.

[0052] The spacer 60 is a plate-like member having an opening 60a. The spacer 60 is disposed between the ferrule front end face 21 of the first optical connector 1a and the ferrule front end face 21 of the second optical connector 1b. The opening 60a 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 60 abuts against the ferrule front end face 21 of the first optical connector 1a and the ferrule front end face 21 of the second optical connector 1b. This defines the distance between the first optical connector 1a and the second optical connector 1b in the X direction.

[0053] The effects obtained by the holding member 30, the optical connector 1, and the optical connection assembly 100 according to this embodiment described above will be described together with the problems with the related art.

[0054] As described above, when mounting the holding member 30 on the ferrule 20, an axial misalignment may occur between the insertion hole 24 of the ferrule 20 and the holding hole 37 of the holding member 30. In this case, the optical fiber 10 is bent due to this axial misalignment. The distance L between the front end face 31 of the holding member 30 and the inner wall surface 201 of the ferrule 20 greatly affects the increase or decrease in bending stress on the optical fiber 10. When mounting the holding member 30 on the ferrule 20, if the holding member 30 is pushed into the ferrule 20 until the front end face 31 of the holding member 30 abuts against the inner wall surface 201, the bending stress on the optical fiber 10 will be extremely large, making the optical fiber 10 more likely to break. To address this issue, it is conceivable that the position of the holding member 30 relative to the ferrule 20 can be managed by an operator through observation and adjustment so that the front end face 31 of the holding member 30 does not come too close to the inner wall surface 201. However, in this case, the difficulty of mounting the holding member 30 on the ferrule 20 increases, and the number of steps required may increase.

[0055] In this embodiment, the holding member 30 includes a plurality of front end protrusions 40 as stoppers that stop the movement of the holding member 30 relative to the ferrule 20 so that the distance L in the X direction between the front end face 31 of the holding member 30 and the inner wall surface 201 of the ferrule 20 is within a specified range when the tip ends 14 of the plurality of optical fibers 10 are inserted into the plurality of insertion holes 24 in the X direction. As described above, the distance L between the front end face 31 of the holding member 30 and the inner wall surface 201 of the ferrule 20 has a significant effect on the bending stress on the optical fiber 10. If the distance L is too small, the optical fiber 10 extending from the front end face 31 to the inner wall surface 201 is likely to be sharply bent, thereby increasing the bending stress on the optical fiber 10. If the distance L is too large, the intermediate portion of the optical fiber 10 between the front end face 31 and the inner wall surface 201 is likely to bend. Therefore, in this case as well, the bending stress on the optical fiber 10 increases. In this embodiment, by using multiple front end protrusions 40 to maintain the distance L within a specified range, the position of the holding member 30 relative to the ferrule 20 can be easily and appropriately limited so as to prevent an increase in bending stress on the optical fiber 10. As a result, it is possible to reduce the occurrence of problems such as increased transmission loss and damage to the optical fiber 10 caused by an increase in bending stress. Therefore, the holding member 30 can reduce a decrease in the reliability of the optical fiber 10.

[0056] As in the present embodiment, the specified range may be 0.5 mm or more and 3 mm or less. By setting the distance L to 0.5 mm or more, it is possible to effectively reduce the increase in bending stress caused by a sharp bend in the optical fiber 10. By maintaining the distance L at 3 mm or less, it is possible to effectively reduce the increase in bending stress caused by deflection in the intermediate portion of the optical fiber 10.

[0057] As in the present embodiment, at least one front end protrusion 40 protruding in the X direction from the front end face 31 may be used as a stopper. In this case, the front end protrusion 40 abuts against the inner wall surface 201 of the ferrule 20 in the X direction, thereby easily and reliably maintaining the distance L between the front end face 31 and the inner wall surface 201 within a specified range.

[0058] As in the present embodiment, multiple front end protrusions 40 may be used as stoppers. The multiple front end protrusions 40 may be arranged to be spaced apart in at least one of the Z direction and the Y direction. In this case, when an adhesive is injected into the ferrule 20 to fix the holding member 30 to the ferrule 20, the adhesive is more likely to spread through the spaces between the multiple front end protrusions 40 and into the interior of the ferrule 20. In other words, the above configuration reduces the obstruction of the flow of adhesive by the stopper. This makes it possible to more reliably fix the multiple optical fibers 10 and the holding member 30 with the adhesive.

[0059] As in the present embodiment, the multiple front end protrusions 40 may be arranged symmetrically in at least one of the Z direction and the Y direction with respect to the center CP of the front end face 31. In this case, the posture of the holding member 30 relative to the ferrule 20 can be stabilized with the multiple front end protrusions 40 in contact with the inner wall surface 201. As a result, an increase in bending stress caused by instability in the posture of the holding member 30 can be reduced.

[0060] As in the present embodiment, each of the multiple optical fibers 10 may be a multi-core optical fiber. When such an optical fiber 10 is used, rotational alignment of the optical fiber 10 becomes necessary. In this case, the bending stress of the optical fiber 10 is likely to increase further due to friction between the outer circumferential surface of the tip portion 14 of the optical fiber 10 and the inner circumferential surface of the insertion hole 24. In the present embodiment, the increase in bending stress can be reduced as described above, and therefore the risk of defects caused by the increase in bending stress can be effectively reduced.

[0061] The holding member, optical connector, and optical connection assembly of the present disclosure are not limited to the above-described embodiments, and specific aspects of the holding member, optical connector, and optical connection assembly of the present disclosure may be modified without departing from the spirit of the claims.

[0062] <Modification 1> Fig. 13 is a cross-sectional view showing an XZ cross-section of an optical connector 1A according to Modification 1. Fig. 14 is a cross-sectional view showing an XY cross-section of the optical connector 1A. In the optical connector 1 according to the above-described embodiment, the case where the multiple front end protrusions 40 formed on the front end face 31 of the holding member 30 are used as stoppers has been described. In the optical connector 1A according to this modification, a pair of side faces 35A, 36A of the holding member 30A are used as stoppers.

[0063] 14 , the side surfaces 35A, 36A are inclined with respect to the XZ plane so that the distance between the side surfaces 35A, 36A in the Y direction increases as the side surfaces 35A, 36A approach the rear end surface 32 in the X direction. The distance between the side surface 35A and the side wall surface 204 in the Y direction decreases as the side surfaces 35A, 36A approach the rear end surface 32 in the X direction. The side surface 35A abuts against a connection portion P1 between the ferrule rear end surface 22 and the side wall surface 204 in the X and Y directions. The distance between the side surface 36A and the side wall surface 205 in the Y direction decreases as the side surfaces 35A, 36A approach the rear end surface 32 in the X direction. The side surface 36A abuts against a connection portion P2 between the ferrule rear end surface 22 and the side wall surface 205 in the X and Y directions.

[0064] When the holding member 30A is inserted into the ferrule 20 in the X direction, if the holding member 30A is advanced a certain distance inside the ferrule 20, the side surfaces 35A and 36A of the holding member 30A come into contact with the side wall surfaces 204 and 205 in the X direction. This stops the movement of the holding member 30A in the X direction relative to the ferrule 20. The side surfaces 35A and 36A of the holding member 30A determine the position of the holding member 30A in the X direction relative to the ferrule 20 so that the distance L between the front end face 31 of the holding member 30A and the inner wall surface 201 of the ferrule 20 is maintained within the specified range (e.g., 0.5 mm or more and 3 mm or less). In this way, the side surfaces 35A and 36A maintain the distance L within the specified range when the multiple optical fibers 10 are inserted into the multiple insertion holes 24 in the X direction, respectively. By using the side surfaces 35A and 36A to maintain the distance L within a specified range, the position of the holding member 30A relative to the ferrule 20 can be easily and appropriately limited so as not to increase bending stress on the optical fiber 10. Therefore, with the holding member 30A, the same effects as those of the above-described embodiment can be obtained.

[0065] Furthermore, in the holding member 30A, the side surfaces 35A, 36A abut against the side wall surfaces 204, 205 in the Y direction, thereby determining the position of the holding member 30A in the Y direction relative to the ferrule 20. In other words, the side surfaces 35A, 36A are inclined so that the distance between the side surfaces 35A, 36A in the Y direction increases as the holding member 30A approaches the rear end face 32, and therefore the position of the holding member 30A in the Y direction relative to the ferrule 20 is determined with greater precision as the holding member 30A is advanced inside the ferrule 20. In this way, the side surfaces 35A, 36A of the holding member 30A can serve both the function of positioning the holding member 30A in the X direction relative to the ferrule 20 and the function of positioning the holding member 30A in the Y direction relative to the ferrule 20.

[0066] In the holding member 30A, both the side surfaces 35A and 36A do not necessarily have to be inclined. For example, only one of the side surfaces 35A and 36A may be inclined with respect to the XZ plane so that the distance between the side surfaces 35A and 36A in the Y direction increases as the side surfaces 35A and 36A approach the rear end face 32 in the X direction. In the holding member 30A, instead of the side surfaces 35A and 36A, one or both of the top surface 33 and the bottom surface 34 may be inclined. For example, the top surface 33 may be inclined with respect to the XY plane so that the distance between the top surface 33 and the bottom surface 34 in the Z direction increases as the top surface 33 approaches the rear end face 32 in the X direction. In this case, the distance between the top surface 33 and the top wall surface 203 in the Z direction decreases as the top surface 33 approaches the rear end face 32 in the X direction. The top surface 33 abuts against the connection portion of the top wall surface 203 with the ferrule rear end face 22 in the X and Z directions. In this configuration, the top surface 33 and the bottom surface 34 can serve both to position the holding member 30A relative to the ferrule 20 in the X direction and to position the holding member 30A relative to the ferrule 20 in the Z direction.

[0067] <Modification 2> Fig. 15 is a cross-sectional view showing an XZ cross-section of an optical connector 1B according to Modification 2. Fig. 16 is a cross-sectional view showing an XY cross-section of the optical connector 1B. In the optical connector 1 according to the above-described embodiment, the case where the multiple front end protrusions 40 formed on the front end surface 31 of the holding member 30 are used as stoppers has been described. In the optical connector 1B according to this modification, the rear end protrusions 40A formed on the rear end surface 32 of the holding member 30B are used as stoppers.

[0068] In the optical connector 1B, the holding member 30B includes a rear end protrusion 40A as a stopper instead of the multiple front end protrusions 40. The rear end protrusion 40A is formed on the rear end surface 32 of the holding member 30B. The rear end protrusion 40A protrudes from the rear end surface 32 in at least one of the Y and Z directions. As shown in FIGS. 15 and 16 , the rear end protrusion 40A protrudes from the rear end surface 32 in both the Y and Z directions. In this case, the rear end protrusion 40A extends in a planar shape along the YZ plane. When viewed in the X direction, the rear end protrusion 40A has a rectangular shape that is larger than the opening 22a of the ferrule rear end surface 22. The rear end protrusion 40A includes an abutment surface 40b that faces the rear end surface 32. The abutment surface 40b of the rear end protrusion 40A, which extends in the Y and Z directions from the rear end face 32, faces the ferrule rear end face 22 in the X direction. In other words, the abutment surface 40b faces the rear end face 32 and the ferrule rear end face 22 in the X direction. The abutment surface 40b is fixed to the rear end face 32, for example, and abuts against the ferrule rear end face 22 in the X direction.

[0069] When the holding member 30B is inserted into the ferrule 20 in the X direction, if the holding member 30B is advanced a certain distance inside the ferrule 20, the abutment surface 40b of the rear end protrusion 40A formed on the rear end face 32 of the holding member 30B abuts against the ferrule rear end face 22 in the X direction. This stops the movement of the holding member 30B in the X direction relative to the ferrule 20. The rear end protrusion 40A of the holding member 30B determines the X-direction position of the holding member 30B relative to the ferrule 20 so as to maintain the distance L between the front end face 31 of the holding member 30B and the inner wall surface 201 of the ferrule 20 within a specified range. In this way, the rear end protrusion 40A maintains the distance L within a specified range when multiple optical fibers 10 are inserted into the multiple insertion holes 24 in the X direction. By maintaining the distance L within the specified range using the rear end protrusion 40A, the position of the holding member 30B relative to the ferrule 20 can be easily and appropriately limited so as to prevent an increase in bending stress on the optical fibers 10. Therefore, the holding member 30B also provides the same effects as those of the above-described embodiment.

[0070] Furthermore, in the holding member 30B, the stopper (i.e., the rear end protrusion 40A) can be formed over a wider area outside the ferrule 20 compared to a configuration in which the stopper is formed inside the ferrule 20. In this case, the contact area between the rear end protrusion 40A and the ferrule rear end face 22 can be maintained large, so the position of the holding member 30B relative to the ferrule 20 can be stabilized when the rear end protrusion 40A is in contact with the ferrule rear end face 22. Therefore, according to this modification, it is possible to reduce an increase in bending stress caused by instability in the position of the holding member 30B.

[0071] The present disclosure is not limited to the above-described embodiments and modifications, and various modifications are possible. For example, the above-described embodiments and modifications may be combined with each other to a consistent extent depending on the required purpose and effect. For example, in the above-described embodiments, the case where the insertion hole of the holding member holds both the coating-removed portion and the coating portion of the optical fiber has been described. However, the insertion hole of the holding member may hold only the coating-removed portion or only the coating portion. The holding member may have multiple V-grooves as "holding portions" instead of multiple insertion holes.

[0072] The holding member may include a tapered portion (introduction portion) at the opening of the insertion hole at the front end face or the opening of the insertion hole at the rear end face to facilitate insertion of the optical fiber into the position determining portion. The introduction portion may be a tapered hole, a hole larger than the position determining portion, a groove with a larger radius of curvature than the hole diameter of the position determining portion, or a combination thereof. The holding member may include a mounting portion (fiber holding portion) on which the coating portion of the optical fiber is mounted at a position lower than the position determining portion to prevent unnecessary bending of the optical fiber. The holding member may further include multiple injection holes for injecting adhesive into the multiple insertion holes. In this case, each injection hole is formed to extend from the surface of the holding member toward each insertion hole and is individually connected to each insertion hole.

[0073] DESCRIPTION OF SYMBOLS 1, 1A, 1B...Optical connector 1a...First optical connector 1b...Second optical connector 10...Optical fiber 10a...Core 10b...Cladding 11...Tip surface 12...Coating removal portion 13...Coating portion 14...Tip portion 20...Optical connector ferrule 21...Ferrule front end surface 22...Ferrule rear end surface 22a, 60a...Opening 23...Introduction hole 24...Insertion hole 24a...Position determining portion 24b...Tapered portion 25...Window 26...Guide hole 30, 30A, 30B...Holding member 31...Front end surface 31a, 31b, 31c, 31d...Corner portion 32...Rear end surface 33...Top surface 34...Bottom surface 35, 35A...Side surface 36, 36A...Side surface 37...Holding hole (holding portion) 37a...Narrow diameter portion 37b...Thick diameter portion 40, 401, 402, 403, 404...Front end protrusion (stopper) 40A...Rear end protrusion (stopper) 40a, 40b...Abutment surface 50...Guide pin 60...Spacer 100...Optical connection assembly 201...Inner wall surface 202...Bottom wall surface 203...Top wall surface 204...Side wall surface 205...Side wall surface C10, C24, C37...Central axis CP...Center d11, d12, d21, d22, d31, d32, d41, d42...Distance D40...Protrusion amount L...Distance La...Curve Lb...Reference line P...Plot P1, P2...Connection portion VL1, VL2...Virtual plane

Claims

1. A holding member disposed on an internal bottom wall surface of an optical connector ferrule while holding a plurality of optical fibers, the tip ends of the plurality of optical fibers being inserted one by one into a plurality of insertion holes formed in the inner wall surface of the optical connector ferrule, the holding member comprising: a front end face facing said inner wall surface in a first direction intersecting with said inner wall surface; a rear end face disposed on the opposite side of the first direction from the front end face; a bottom face abutting said bottom wall surface in a second direction intersecting with the first direction; a plurality of holding portions extending along the first direction between the front end face and the rear end face and aligned along a third direction intersecting with the first direction and the second direction, the plurality of holding portions being capable of holding each of the plurality of optical fibers one by one; and a stopper formed on a surface of the holding member for maintaining the distance in the first direction between the front end face and the inner wall surface within a specified range when the tip ends of the plurality of optical fibers extending from the holding member are inserted into the plurality of insertion holes, respectively, in the first direction.

2. The retaining member according to claim 1, wherein the specified range is 0.5 mm or more and 3 mm or less.

3. A retaining member according to claim 1 or 2, wherein the stopper is at least one front end protrusion formed on the front end surface and protruding from the front end surface in the first direction.

4. A retaining member as described in claim 3, wherein the stopper is a plurality of the front end protrusions, and the plurality of the front end protrusions are arranged so as to be spaced apart in at least one of the second direction and the third direction along the front end surface.

5. A retaining member according to claim 4, wherein the plurality of front end protrusions are arranged symmetrically in at least one of the second direction and the third direction with respect to the center of the front end surface.

6. A retaining member as described in claim 1 or claim 2, further comprising a pair of side surfaces as the surface, spaced apart in the third direction between the front end face and the rear end face, the spacing between the pair of side surfaces in the third direction increasing toward the rear end face in the first direction, and the pair of side surfaces being the stoppers and abutting against a pair of side wall surfaces inside the optical connector ferrule in the first direction and the third direction.

7. A holding member as described in claim 1 or claim 2, wherein the stopper is a rear end protrusion formed on the rear end face and protruding from the rear end face in at least one of the second direction and the third direction, and the rear end protrusion abuts in the first direction against a ferrule rear end face having an opening connected to the interior of the optical connector ferrule.

8. An optical connector comprising: the holding member according to any one of claims 1 to 7; a plurality of optical fibers held by the holding member with their tips protruding from the holding member; and the ferrule including a plurality of insertion holes into which the tips of the plurality of optical fibers are inserted and fixed one by one.

9. The optical connector according to claim 8, wherein each of said plurality of optical fibers is a multi-core optical fiber.

10. An optical connection assembly comprising a first optical connector and a second optical connector as the optical connectors according to claim 8 or 9, the first optical connector and the second optical connector being arranged to face each other along the first direction.

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