Manufacturing method of ferrule structure and ferrule-attached fiber

Abstract

[Problem] To suppress deformation of a ferrule. [Solution] A boot (20) according to the present disclosure is attached to a ferrule (10). The boot comprises: a fiber insertion hole (21) which is disposed to correspond to the disposition of a plurality of fiber holes (12) of the ferrule, and through which a plurality of optical fibers (1) are inserted; a lower part (22) which is disposed on one side with respect to the fiber insertion hole; and an upper part (23) which is disposed on the other side with respect to the fiber insertion hole. The upper part has a protruding section (231) protruding farther than an end surface of the lower part in a fiber insertion direction.

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing boots, ferrule structures, and fibers with ferrules. This application claims priority based on Japanese Patent Application No. 2021-008665 filed in Japan on January 22, 2021, the content of which is incorporated herein by reference.

Background Art

[0002] As a ferrule for collectively connecting multi-core optical fibers, a so-called MT ferrule is known. Such a ferrule is provided with an adhesive filling portion. By filling the adhesive filling portion with an adhesive, the optical fiber is fixed to the ferrule. For example, Patent Document 1 describes a ferrule capable of filling an adhesive from an adhesive injection port.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When the adhesive filled in the ferrule shrinks, the ferrule may deform. In contrast, Patent Document 1 describes molding fiber holes, guide pin holes, etc. of the ferrule with a resin insert-molded in a metal frame. However, the configuration of the ferrule described in Patent Document 1 is complicated and the manufacturing cost is high.

[0005] The present invention provides a novel configuration capable of suppressing deformation of the ferrule.

Means for Solving the Problems

[0006] The boot according to the first aspect of the present invention is a boot attached to a ferrule provided with a plurality of fiber holes arranged in one direction, an adhesive filling portion for filling an adhesive, and a step portion for guiding an optical fiber into the fiber hole, and includes a fiber insertion hole that is arranged corresponding to the arrangement of the plurality of fiber holes and through which the plurality of optical fibers are inserted, a lower portion arranged on one side with reference to the fiber insertion hole, and an upper portion arranged on the other side with reference to the fiber insertion hole, and the upper portion has a protruding portion that protrudes from the end surface of the lower portion in the fiber insertion direction.

[0007] Other features of the present invention will be clarified by the description of the specification and drawings described later.

Effects of the Invention

[0008] According to the present invention, by reducing the amount of the adhesive filled in the adhesive filling portion, deformation of the ferrule can be suppressed.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Embodiments for Carrying Out the Invention

[0010] An embodiment that is an example of the invention of the present application will be described based on the descriptions in the specification and drawings described below.

[0011] ===First Embodiment=== FIG. 1A is a perspective view of the ferrule structure 100. FIG. 1B is an exploded explanatory view of the ferrule structure 100. FIG. 2 is a cross-sectional perspective view of the ferrule structure 100. FIG. 3A is a top view of the ferrule structure 100. FIG. 3B is a cross-sectional view of the ferrule structure 100. In FIG. 1A, an optical fiber tape composed of a plurality of optical fibers 1 is shown by a dotted line.

[0012] In the following description, the directions are defined as follows. The insertion direction of the optical fiber 1 inserted into the boot 20 (or ferrule 10) is defined as the "fiber insertion direction" or the "front-back direction". Based on the optical fiber 1 inserted into the boot 20 (or ferrule 10), the tip side of the optical fiber 1 is defined as "front", and the opposite side is defined as "back". Note that the optical axis direction (the direction of the longitudinal axis) of the optical fiber 1 inserted into the boot 20 (or ferrule 10) is the fiber insertion direction (or the front-back direction). Also, the direction in which a plurality of optical fibers 1 inserted into the boot 20 (or ferrule 10) are arranged, that is, the direction orthogonal to the optical axis direction (the direction of the longitudinal axis) is defined as the "width direction" or the "left-right direction". When viewed from the back side to the front side, the right side is defined as "right", and the opposite side is defined as "left". Further, the direction perpendicular to the fiber insertion direction (front-back direction) and the width direction (left-right direction), that is, the direction orthogonal to the plane formed by the optical axis direction (the direction of the longitudinal axis) and the width direction is defined as the "up-down direction". Based on the fiber insertion hole 21 of the boot 20, the upper side is defined as "up", and the opposite side is defined as "down". Note that the upper side may also be referred to as the "filling window side", and the lower side may also be referred to as the "bottom side".

[0013] The ferrule structure 100 has a ferrule 10 and a boot 20. Note that the member that fixes the optical fiber 1 to the ferrule structure 100 may also be referred to as a fiber with ferrule.

[0014] The ferrule 10 is a member that holds the ends of a plurality of optical fibers 1. The ferrule 10 of the present embodiment is an MT connector (MT ferrule) defined in JIS C 5981 or IEC 61754-5. The main body of the ferrule 10 has a connection end face 10A and an outer wall. The connection end face 10A is the front end face of the ferrule 10 and is the end face that is connected to a mating ferrule (not shown here). The outer wall constitutes the outer surface connected to the connection end face 10A (the main upper, lower, left, and right outer surfaces of the main body of the ferrule 10). A pair of guide holes 11 are provided on the left and right of the ferrule 10. Also, at the rear of the ferrule 10, a flange portion 10B (flange portion) protruding outward from the side surface of the main body of the ferrule 10 is provided.

[0015] The ferrule 10 of this embodiment has a plurality of fiber holes 12, an adhesive filling portion 13, an inner wall 14, a step portion 15, and a boot insertion port 17.

[0016] The fiber hole 12 is a hole for inserting the end portion of the optical fiber 1. The end portion of the optical fiber 1 is fixed to each fiber hole 12. The plurality of fiber holes 12 are arranged side by side in the width direction (arranged side by side in one direction). Here, 24 fiber holes 12 are arranged in a row in the width direction. However, the number of fiber holes 12 is not limited to 24. Also, the row of fiber holes 12 may be one row or two or more rows. One end portion (rear end) of the fiber hole 12 opens at the inner wall 14 (specifically, the first surface 14A) of the adhesive filling portion 13. The other end portion (front end) of the fiber hole 12 opens at the connection end surface 10A of the ferrule 10. Note that the fiber hole 12 communicates with a guide groove 15A described later.

[0017] The adhesive filling portion 13 is a portion (space) for filling the adhesive. An upper opening 131 (adhesive filling window) is provided on the upper surface of the ferrule 10. The upper opening 131 is an opening that leads from the outer wall of the ferrule 10 to the adhesive filling portion 13. The adhesive is filled into the adhesive filling portion 13 through this upper opening 131. Also, a lower opening 132 is provided on the lower surface of the ferrule 10. The lower opening 132 is an opening that leads from the outer wall of the ferrule 10 to the adhesive filling portion 13. The lower opening 132 is arranged on the side opposite to the upper opening 131. As will be described later, by providing openings on the upper and lower surfaces of the ferrule 10, distortion of the ferrule 10 due to shrinkage accompanying the curing of the adhesive can be suppressed. However, the lower opening 132 may not be provided on the lower surface of the ferrule 10. The fiber hole 12 opens at the front inner wall surface (first surface 14A) of the adhesive filling portion 13. Also, a pressing portion 131A is provided on the upper wall surface of the adhesive filling portion 13.

[0018] The inner wall 14 has openings of a plurality of fiber holes 12 and is disposed within the body of the ferrule 10. A space disposed on the side opposite to the connection end face 10A with respect to the inner wall 14 is the adhesive filling portion 13. That is, the inner wall 14 is the wall surface on the side of the connection end face 10A (the front side of the adhesive filling portion 13; the side where the fiber holes 12 open) among the wall surfaces constituting the adhesive filling portion 13. In the present embodiment, the inner wall 14 has a first surface 14A and a second surface 14B. The first surface 14A is a surface along the edge on the side (front side) of the connection end face 10A at the upper opening 131. The upper opening 131 opens at a position along the first surface 14A. The second surface 14B is a surface protruding toward the side (rear side) of the adhesive filling portion 13 from the first surface 14A and is the rear end face of the step portion 15. In the first embodiment, the second surface 14B is a surface along the edge on the side (front side) of the connection end face 10A at the lower opening 132. The lower opening 132 opens at a position along the second surface 14B.

[0019] The step portion 15 is a step provided inside the adhesive filling portion 13 and guides the optical fiber 1 into the fiber hole 12. A plurality of guide grooves 15A are provided on the upper surface of the step portion 15. The guide grooves 15A are grooves for guiding the optical fiber 1 into the fiber hole 12. The guide grooves 15A are grooves along the fiber insertion direction (front-rear direction). The plurality of guide grooves 15A are arranged side by side in the width direction. Here, the guide grooves 15A are formed as round grooves with a semicircular cross section. However, the guide grooves 15A may have other shapes such as V-grooves, round grooves with a semicircular cross section, U-grooves, or square grooves. Note that the guide grooves 15A may not be provided on the upper surface of the step portion 15. The front end of the guide groove 15A reaches the front inner wall 14 (specifically, the first surface 14A) of the adhesive filling portion 13. The front end of the guide groove 15A communicates with the opening of the fiber hole 12. The rear end of the guide groove 15A reaches the second surface 14B which is the rear end face of the step portion 15. The rear end face (the second surface 14B) of the step portion 15 is configured by a surface perpendicular to the fiber insertion direction. This second surface 14B functions as an alignment surface for aligning the mounting direction (front-rear direction) of the boot 20.

[0020] The guide groove 15A is provided on the upper surface of the stepped portion 15 (the surface on the side of the upper opening 131). Therefore, if there is no boot 20 inside the adhesive filling portion 13, when the operator inserts the optical fiber 1 into the fiber hole 12, while checking the inside of the adhesive filling portion 13 from the upper opening 131, the operator can check the state where the end of the optical fiber 1 is guided by the guide groove 15A. However, in the present embodiment, as will be described later, the end of the boot 20 is inserted into the adhesive filling portion 13, and a part of the upper opening 131 is blocked by the upper surface of the boot 20 (see FIGS. 1A, 2, and 3B).

[0021] The boot insertion port 17 is an opening for inserting the boot 20. The boot insertion port 17 is provided at the rear end of the ferrule 10. The boot insertion port 17 communicates with the adhesive filling portion 13. The boot insertion port 17 allows a plurality of optical fibers 1 to be inserted therethrough. The optical fiber 1 inserted from the boot insertion port 17 crosses the adhesive filling portion 13 and is inserted into the fiber hole 12. In the present embodiment, by utilizing the fact that the boot insertion port 17 communicates with the adhesive filling portion 13, the end of the boot 20 is inserted into the adhesive filling portion 13.

[0022] FIG. 11 is an explanatory diagram of a comparative example. As shown in FIG. 11, the boot 20 is usually attached to the boot insertion port 17 so that the end does not reach the adhesive filling portion 13. The boot is arranged to block the rear portion of the adhesive filling portion 13 as shown in FIG. 11. This prevents the adhesive from leaking from the rear end of the ferrule 10. In the case of the comparative example, due to the shrinkage of the adhesive filled in the adhesive filling portion 13 as it cures, the ferrule 10 may be deformed. In order to suppress such deformation of the ferrule 10 due to the shrinkage of the adhesive, it is desirable to reduce the amount of the adhesive filled in the adhesive filling portion 13. On the other hand, simply reducing the amount of the adhesive may result in insufficient fixing of the optical fiber 1. Therefore, in the present embodiment, as shown in FIGS. 2 and 3B, a part of the boot 20 (specifically, the protruding portion 231) is disposed to face the upper surface of the stepped portion 15. Thereby, while reducing the amount of the adhesive filled in the adhesive filling portion 13, the adhesive necessary for fixing the optical fiber 1 can be applied around the optical fiber 1. Hereinafter, this point will be described.

[0023] FIG. 4 is an orthographic projection view of the boot 20 of the present embodiment in each direction. FIGS. 5A and 5B are perspective views of the boot 20 alone.

[0024] The boot 20 is a member that protects the optical fiber 1. The boot 20 is made of a flexible material (for example, resin) and is elastically deformable. Thereby, the boot 20 can suppress the load (for example, bending stress) applied to the plurality of optical fibers 1. As shown in FIGS. 2 and 3B, in a state where the boot 20 is attached to the ferrule 10, the central portion in the fiber insertion direction (front-rear direction) of the boot 20 is disposed so as to be sandwiched between the upper and lower inner wall surfaces of the ferrule 10. In the present embodiment, as shown in FIGS. 2 and 3B, the front portion of the boot 20 (the portion on the front side of the portion sandwiched between the upper and lower inner wall surfaces of the ferrule 10) is disposed inside the adhesive filling portion 13. Further, the portion on the rear side of the portion sandwiched between the upper and lower inner wall surfaces of the ferrule 10 protrudes rearward of the ferrule 10 and serves as a portion (strain relief) that suppresses the bending stress applied to the optical fiber 1.

[0025] The boot 20 has a fiber insertion hole 21. The fiber insertion hole 21 is a through hole for inserting a plurality of optical fibers 1. Therefore, the fiber insertion hole 21 is configured as a through hole along the fiber insertion direction (front-rear direction; the optical axis direction of the optical fiber 1). Further, the fiber insertion hole 21 is configured to be able to insert an optical fiber tape composed of a plurality of optical fibers 1. Therefore, the fiber insertion hole 21 is configured to have a cross-sectional shape extending in the width direction (left-right direction).

[0026] Further, the fiber insertion hole 21 is arranged corresponding to the arrangement of the fiber hole 12 of the ferrule 10. Therefore, the fiber insertion hole 21 is arranged so as to conform to the same height as the fiber hole 12 or the upper surface (or the guide groove 15A) of the stepped portion 15 of the ferrule 10 when the boot 20 is attached to the ferrule 10.

[0027] The boot 20 has a lower portion 22 and an upper portion 23. Note that the boot 20 has a shape in which two block-shaped lower portions 22 and upper portions 23 are connected at both ends in the width direction. In the following description, the portion connecting the lower portion 22 and the upper portion 23 outside the width direction of the fiber insertion hole 21 may be referred to as a connecting portion 24. The space surrounded by the lower portion 22, the upper portion 23, and the pair of connecting portions 24 becomes the fiber insertion hole 21.

[0028] The lower portion 22 is arranged on one side (lower side, bottom side) with respect to the fiber insertion hole 21. In other words, the lower portion 22 is arranged on the side opposite to the side of the upper opening 131 of the ferrule 10 when the boot 20 is attached to the ferrule 10. The lower portion 22 is a block-shaped (plate-shaped) portion constituting the lower side of the boot 20, and may also be called a "lower block" or a "first block". The lower portion 22 is arranged at the bottom of the adhesive filling portion 13 and fills the space at the bottom side of the adhesive filling portion 13. Note that a lower opening 132 is provided on the lower surface of the ferrule 10 of the present embodiment. However, in the case of a ferrule 10 without the lower opening 132, the lower portion 22 is arranged to face the bottom surface of the ferrule 10 (the bottom surface of the adhesive filling portion 13).

[0029] The front end face 22A of the lower portion 22 is composed of a surface perpendicular to the fiber insertion direction (the mounting direction of the boot 20; the front-rear direction). The front end face 22A of the lower portion 22 becomes a contact surface that contacts the second surface 14B (the rear end face of the stepped portion 15) of the inner wall 14 of the ferrule 10, and functions as an alignment surface for performing alignment in the mounting direction (the front-rear direction) of the boot 20.

[0030] The upper part 23 is arranged on the other side (the lower side, the bottom side; the side opposite to the lower part 22) with reference to the fiber insertion hole 21. In other words, the upper part 23 is arranged on the side of the upper opening 131 of the ferrule 10 in a state where the boot 20 is attached to the ferrule 10. The upper part 23 is a block-shaped (plate-shaped) part that constitutes the upper side of the boot 20 and may also be called the "upper block" or the "second block". The upper part 23 fills the space above the adhesive filling part 13.

[0031] The upper part 23 has a protruding part 231. The protruding part 231 protrudes compared to the end face 22A of the lower part 22 in the fiber insertion direction. The protruding part 231 is arranged at the front end of the upper part 23. The fiber insertion hole 21 is arranged corresponding to the arrangement of the fiber hole 12 of the ferrule 10. Also, the protruding part 231 protrudes forward compared to the end face 22A of the lower part 22 (the part below the fiber insertion hole 21). Thereby, in a state where the boot 20 is attached to the ferrule 10, the protruding part 231 faces the upper surface (or the guide groove 15A) of the step part 15 inside the adhesive filling part 13. That is, the lower surface of the protruding part 231 becomes the opposing surface that faces the upper surface of the step part 15. By arranging the protruding part 231 to face the upper surface of the step part 15 inside the adhesive filling part 13, the upper part 23 can fill the space of the adhesive filling part 13 on the upper opening 131 side (the upper side) compared to the step part 15.

[0032] FIG. 6A is an enlarged cross-sectional view near the gap between the end face 231A of the protruding part 231 and the first face 14A of the ferrule 10. Note that FIG. 6A is an enlarged explanatory view of the region A in FIG. 3B. The end face 231A of the protruding portion 231 is disposed to face the first face 14A having the opening of the fiber hole 12. Since the protruding portion 231 protrudes from the lower portion 22, the gap between the end face 231A of the boot 20 (protruding portion 231) and the first face 14A can be narrowed as compared with the case where the protruding portion 231 is not provided in the boot 20. The gap between the end face 231A of the protruding portion 231 and the first face 14A opens upward at the upper opening 131. Adhesive will be filled from this gap. When the adhesive is filled from the gap that opens at the upper opening 131 (the gap between the end face 231A of the protruding portion 231 and the first face 14A), it will penetrate inside by capillary action (described later).

[0033] In the present embodiment, the length by which the protruding portion 231 protrudes from the end face 22A of the lower portion 22 (the protruding length L2 shown in FIG. 7A; the dimension between the end face 22A of the lower portion 22 and the end face 231A of the upper portion 23 in the fiber insertion direction) is the length of the stepped portion 15 in the fiber insertion direction (the length L1 shown in FIG. 7A; the length of the guide groove 15A; the dimension between the first face 14A and the second face 14B in the fiber insertion direction). That is, the protruding length L2 of the protruding portion 231 is less than the length L1 of the stepped portion 15 in the fiber insertion direction (L2 < L1). Thereby, in a state where the end face 22A of the lower portion 22 of the boot 20 is in contact with the second face 14B of the stepped portion 15 (see FIGS. 2 and 3B), as shown in FIG. 6A, a gap for filling the adhesive can be formed between the end face 231A of the protruding portion 231 and the first face 14A of the ferrule 10. In the present embodiment, since the protruding length L2 of the protruding portion 231 is less than the length L1 of the stepped portion 15 in the fiber insertion direction (L2 < L1), by bringing the end face 22A of the lower portion 22 of the boot 20 into contact with the second face 14B of the stepped portion 15, it becomes possible to align the position of the boot 20 in the mounting direction (front-rear direction) with respect to the ferrule 10.

[0034] Incidentally, as shown in FIG. 6A (and FIG. 2), a pressing portion 131A is provided on the upper wall surface of the adhesive filling portion 13 of the ferrule 10. The pressing portion 131A presses the protruding portion 231 of the boot 20 from above. The pressing portion 131A is provided at both ends in the width direction near the front edge of the upper opening 131. The pressing portion 131A is disposed above both edges (both corners) in the width direction of the protruding portion 231 of the boot 20 in a state where the boot 20 is attached to the ferrule 10. In other words, the protruding portion 231 of the boot 20 is configured to be disposed below the upper wall surface (pressing portion 131A) of the adhesive filling portion 13 of the ferrule 10. By disposing the pressing portion 131A above the protruding portion 231 of the boot 20, it is possible to suppress the upward displacement of the protruding portion 231 of the boot 20 inside the adhesive filling portion 13, and the protruding portion 231 is stably disposed inside the adhesive filling portion 13. Note that the pressing portion 131A is provided only above both edges in the width direction of the protruding portion 231 of the boot 20, and is not provided above the central portion in the width direction of the protruding portion 231. Thereby, as shown in FIG. 6A, the upper part of the gap between the end face 231A of the protruding portion 231 and the first surface 14A of the ferrule 10 can be opened, and the adhesive can be filled from this gap. Note that the ferrule 10 may not include the pressing portion 131A.

[0035] FIG. 6B is an explanatory view of the protruding portion 231 of the modified example. In the protruding portion 231 of the modified example, an inclined surface 231B is provided between the upper surface of the protruding portion 231 (the surface on the side of the upper opening 131) and the end face 231A of the protruding portion 231. That is, in the protruding portion 231 of the modified example, an inclined surface 231B is provided at the upper edge of the end face 231A. Thereby, it becomes easier to fill the adhesive between the end face 231A of the protruding portion 231 and the first surface 14A of the ferrule 10. Note that as shown in FIG. 6B, even when the inclined surface 231B is provided on the protruding portion 231, it is desirable that the pressing portion 131A of the ferrule 10 presses the protruding portion 231 of the boot 20 from above.

[0036] FIG. 7A is an enlarged view of the vicinity of the front end of the fiber insertion hole 21. FIG. 7B is an enlarged view of the vicinity of the front end of the fiber insertion hole 21 with the optical fiber 1 inserted therethrough. Note that FIG. 7A is an enlarged explanatory view of the region B in FIG. 3B.

[0037] As shown in FIG. 7B, the fiber insertion hole 21 is formed to conform to the diameter of the coated optical fiber 1. For example, the diameter (outer diameter of the coating) of the optical fiber 1 is 250 μm, and the vertical dimension (distance between the lower part 22 and the upper part 23) of the fiber insertion hole 21 is 260 μm. Therefore, the vertical position of the lower surface of the upper part 23 is approximately the same as the upper edge of the optical fiber 1 (coated optical fiber 1) inserted into the fiber insertion hole 21. The tip end (front end) of the optical fiber 1 is a bare optical fiber with the coating removed. For example, the diameter of the bare optical fiber is 125 μm. The stripping edge 1A (front end of the coating of the optical fiber 1) is arranged on the rear side (side of the boot insertion port 17) of the second surface 14B (or the guide groove 15A) of the step portion 15. Therefore, as shown in FIG. 7B, the stripping edge 1A of the coating is arranged inside the fiber insertion hole 21. Further, the bare optical fiber extends forward from the opening of the fiber insertion hole 21. Also, the bare optical fiber is arranged on the upper surface (guide groove 15A) of the step portion 15.

[0038] As shown in FIG. 7A, the lower surface of the protruding portion 231 serves as an opposing surface facing the upper surface of the stepped portion 15. Also, as shown in FIG. 7A, the lower surface of the protruding portion 231 is provided on the extension of the upper edge of the fiber insertion hole 21. Since the fiber insertion hole 21 is formed to conform to the diameter of the optical fiber 1 having a coating, when the lower surface of the protruding portion 231 (the opposing surface facing the upper surface of the stepped portion 15) is provided on the extension of the upper edge of the fiber insertion hole 21 as in the present embodiment, as shown in FIG. 7A, a gap corresponding to the diameter of the optical fiber 1 having a coating is formed between the lower surface of the protruding portion 231 and the upper surface of the stepped portion 15 (here, the guide groove 15A). Then, as shown in FIG. 7B, when a bare optical fiber is disposed between the lower surface of the protruding portion 231 and the upper surface of the stepped portion 15 (guide groove 15A), a narrow gap about the thickness of the coating is formed around the bare optical fiber. Thereby, it becomes easier for the adhesive to penetrate around the bare optical fiber by capillary action.

[0039] As shown in FIG. 7B, since the stripping edge 1A of the coating is disposed on the rear side (the side of the boot insertion port 17) rather than the second surface 14B of the stepped portion 15 (or the guide groove 15A), it is positioned inside the fiber insertion hole 21. As a result, as shown in FIG. 3B, when the ferrule structure 100 is viewed from above, the stripping edge 1A of the coating is hidden by the upper portion 23 of the boot 20, and the position of the stripping edge 1A of the coating in the fiber insertion direction (front-rear direction) cannot be confirmed from the upper opening 131. Therefore, as will be described next, it is desirable to provide an exposed portion 232 on the boot 20.

[0040] FIGS. 8A and 8B are explanatory views of the exposed portion 232. The boot 20 shown in FIGS. 8A and 8B has an exposed portion 232. The exposed portion 232 exposes the area above the optical fiber 1 inserted into the fiber insertion hole 21. The exposed portion 232 is disposed on the rear side of the front end face 22A of the lower portion 22. That is, the exposed portion 232 is disposed on the rear side of the second surface 14B (or the guide groove 15A) of the step portion 15 when the boot 20 is attached to the ferrule 10. Further, the exposed portion 232 is disposed on the front side of the rear edge of the upper opening 131 when the boot 20 is attached to the ferrule 10. By disposing the exposed portion 232 between the second surface 14B (or the guide groove 15A) of the step portion 15 and the rear edge of the upper opening 131 when the boot 20 is attached to the ferrule 10, as shown in FIGS. 8A and 8B, it becomes possible to confirm from the upper opening 131 through the exposed portion 232 the position in the fiber insertion direction (front-rear direction) at the time of stripping the coating 1A.

[0041] Note that the exposed portion 232 may have a shape that exposes the area above a part of the plurality of optical fibers 1 inserted into the fiber insertion hole 21. This is because the coating of the optical fiber tape is removed so that the positions at the time of stripping the coating 1A of the optical fibers 1 are aligned, and it is sufficient if the position in the fiber insertion direction at the time of stripping the coating 1A of a part of the optical fibers 1 can be confirmed. For this reason, the exposed portion 232 does not have to expose the area above all of the optical fibers 1.

[0042] As shown in FIG. 8A, the exposed portion 232 can be configured by a recess provided at an end in the width direction of the boot 20. According to the exposed portion 232 shown in FIG. 8A, the position in the fiber insertion direction at the time of stripping the coating 1A of the optical fiber 1 located at the end in the width direction of the fiber insertion hole 21 can be confirmed. Further, as shown in FIG. 8A, it is desirable to provide recesses at both ends in the width direction. Thereby, the position in the fiber insertion direction at the time of stripping the coating 1A of the optical fibers 1 located at both ends in the width direction can be confirmed, and as a result, it can be inferred that the stripping 1A of the other optical fibers 1 (the optical fibers 1 located at the center in the width direction) is located on the line connecting the stripping 1A at both ends.

[0043] As shown in FIG. 8B, the exposed portion 232 can be configured by a window (opening) provided at the central portion in the width direction of the boot 20. According to the exposed portion 232 shown in FIG. 8B, the position in the fiber insertion direction at the time of stripping 1A of the coating of the optical fiber 1 located at the central portion in the width direction of the fiber insertion hole 21 can be confirmed. As shown in FIG. 8B, since the exposed portion 232 is provided at the central portion in the width direction of the boot 20, the stripping 1A of the coating of the optical fiber 1 can be confirmed at the central portion in the width direction of the upper opening 131, making it easier for the operator to perform the confirmation work. Also, as shown in FIG. 8B, since the exposed portion 232 is provided at the central portion in the width direction of the boot 20, the protruding portion 231 of the boot 20 can be easily arranged below the pressing portion 131A of the ferrule 10.

[0044] As shown in FIGS. 1A and 1B, the boot 20 of the present embodiment has a recess 20A. The recess 20A is a dent provided at the rear portion of the boot 20. As shown in FIG. 3A, in the state where the boot 20 is attached to the ferrule 10, the recess 20A is located on the front side of the rear end surface of the ferrule 10. Thereby, when the adhesive filled in the adhesive filling portion 13 penetrates into the ferrule 10 (described later), even if the adhesive penetrates between the boot insertion port 17 of the ferrule 10 and the boot 20, it is possible to suppress the adhesive from leaking to the rear side of the rear end surface of the ferrule 10. However, the boot 20 may not be provided with the recess 20A.

[0045] <Manufacturing method> FIGS. 9A to 9D are explanatory diagrams of a method for manufacturing a ferrule-attached fiber.

[0046] First, the operator prepares the ferrule 10 and the boot 20 respectively. Note that as already described, the ferrule 10 includes a plurality of fiber holes 12 arranged side by side in one direction, an adhesive filling portion 13 for filling an adhesive, and a step portion 15 for guiding the optical fiber 1 into the fiber hole 12. Also, as already described, the boot 20 includes a fiber insertion hole 21, a lower portion 22 disposed on one side of the fiber insertion hole 21, and an upper portion 23 disposed on the other side of the fiber insertion hole 21. The upper portion 23 has a protruding portion 231 that protrudes compared to the end face 22A of the lower portion 22 in the fiber insertion direction. Also, the operator performs pretreatment on the plurality of optical fibers 1. For example, as pretreatment of the optical fiber 1, the operator removes the coating of the optical fiber tape (removes the coating of each of the plurality of optical fibers 1) and cuts the bare optical fiber so that the bare optical fiber has a predetermined length.

[0047] Next, as shown in FIG. 9A, the operator inserts the plurality of optical fibers 1 (optical fiber tape) into the fiber insertion hole 21 of the boot 20. Note that the operator inserts the plurality of optical fibers 1 (optical fiber tape) into the boot 20 such that the tip end portion (bare optical fiber) of the optical fiber 1 protrudes in front of the protruding portion 231 of the boot 20.

[0048] Also, as shown in FIG. 9A, the operator applies an adhesive near the opening of the fiber hole 12 on the side of the adhesive filling portion 13 and applies the adhesive to the fiber hole 12. Note that after applying the adhesive near the opening of the fiber hole 12 on the side of the adhesive filling portion 13, the operator may apply the adhesive inside the fiber hole 12 by sucking the adhesive from the side of the connection end face 10A of the ferrule 10. By applying the adhesive to the fiber hole 12 in advance, it is possible to suppress the mixing of air bubbles into the inside of the fiber hole 12.

[0049] Next, as shown in FIG. 9B, the operator inserts the plurality of optical fibers 1 inserted through the boots 20 into the respective fiber holes 12 of the ferrule 10. At this time, the operator inserts the optical fiber 1 into the fiber hole 12 while guiding the optical fiber 1 by the upper surface (here, the guide groove 15A) of the stepped portion 15 of the ferrule 10.

[0050] Next, as shown in FIG. 9C, the operator inserts the boots 20 into the boot insertion port 17 of the ferrule 10 and attaches the boots 20 to the ferrule 10. At this time, as shown in FIG. 9C, the operator inserts the boots 20 into the ferrule 10 until the end face 22A of the lower portion 22 of the boots 20 contacts the second face 14B of the stepped portion 15 of the ferrule 10. When the end face 22A of the lower portion 22 of the boots 20 contacts the second face 14B of the stepped portion 15 of the ferrule 10, a gap for filling an adhesive is formed between the end face 231A of the protruding portion 231 and the first face 14A of the ferrule 10. Further, the lower surface of the protruding portion 231 is disposed to face the upper surface of the stepped portion 15 with a gap about the diameter of the optical fiber 1 (see FIGS. 7A and 7B). At this time, the operator disposes both edges (both corners) in the width direction of the protruding portion 231 of the boots 20 below the lower side of the upper wall surface (pressing portion 131A) of the adhesive filling portion 13 of the ferrule 10. When the boots 20 have the exposed portion 232 (see FIGS. 8A and 8B), after the operator attaches the boots 20 to the ferrule 10, the operator can confirm the position in the fiber insertion direction (front-rear direction) at the time of stripping the coating 1A through the exposed portion 232 from the upper opening 131.

[0051] Next, as shown in FIG. 9D, the operator applies an adhesive to the gap between the end face 231A of the protruding portion 231 and the first face 14A of the ferrule 10. The adhesive applied to the gap penetrates inside by capillary action, and the adhesive is applied around the guide groove 15A and the optical fiber 1 disposed in the guide groove 15A. After applying the adhesive, by curing the adhesive, the optical fiber 1 is fixed to the ferrule 10, and the production of the fiber with ferrule is completed.

[0052] In this embodiment, since the boot 20 is disposed inside the adhesive filling portion 13, the amount of the adhesive filled in the adhesive filling portion 13 can be reduced. As a result, even when the adhesive shrinks during curing, deformation of the ferrule 10 can be suppressed. On the other hand, in this embodiment, since the boot 20 is provided with the protruding portion 231, the gap between the protruding portion 231 of the boot 20 and the first surface 14A of the ferrule 10 can be narrowed, so that the adhesive easily penetrates inside due to capillary action. In addition, in this embodiment, the gap between the lower surface of the protruding portion 231 and the upper surface (or the guide groove 15A) of the stepped portion 15 can be narrowed, and the gap around the optical fiber 1 (bare optical fiber) disposed on the upper surface of the stepped portion 15 can be narrowed. Therefore, the adhesive easily penetrates around the upper surface of the stepped portion 15 and around the optical fiber 1 disposed on the upper surface of the stepped portion 15 due to capillary action. Thus, in this embodiment, even when the amount of the adhesive is small, it is possible to apply the adhesive around the upper surface of the stepped portion 15 and around the optical fiber 1, and the optical fiber can be fixed to the ferrule with sufficient strength.

[0053] ===Second Embodiment=== FIG. 10A is a cross-sectional view of a ferrule structure 100 according to the second embodiment. FIG. 10B is a partially enlarged view of the ferrule structure 100 according to the second embodiment. Note that FIG. 10B is an enlarged explanatory view of region C in FIG. 10A.

[0054] Also in the second embodiment, the ferrule structure 100 includes a ferrule 10 and a boot 20. Also in the second embodiment, the ferrule 10 includes a plurality of fiber holes 12, an adhesive filling portion 13, and a stepped portion 15 provided with a plurality of guide grooves 15A. In the second embodiment, the ferrule 10 has two rows of a plurality of fiber holes 12 (fiber rows) arranged side by side in one direction (a direction perpendicular to the paper surface in the figure). The two fiber rows are arranged side by side in the vertical direction. A plurality of optical fibers 1 of an optical fiber tape are inserted into the plurality of fiber holes 12 of each fiber row. In the second embodiment, the plurality of optical fibers 1 are fixed to the ferrule 10 in a state where two optical fiber tapes are overlapped.

[0055] The stepped portion 15 has two rows of a plurality of guide grooves 15A arranged side by side in one direction (a direction perpendicular to the plane of the drawing in the figure) (guide groove rows). The two guide groove rows are configured in a stepped shape. In either guide groove row, the front end of the guide groove 15A reaches the front inner wall 14 of the adhesive filling portion 13. Also, in either guide groove row, the front end of the guide groove 15A communicates with the opening of the fiber hole 12. The rear end of the guide groove 15A in the lower guide groove row reaches the second surface 14B of the stepped portion 15. On the other hand, the rear end of the guide groove 15A in the lower guide groove row is provided up to the central portion in the fiber insertion direction of the stepped portion 15 and does not reach the second surface 14B. Note that also in the second embodiment, the guide groove 15A may not be provided on the upper surface of the stepped portion 15.

[0056] Also in the second embodiment, the boot 20 includes a fiber insertion hole 21, a lower portion 22, and an upper portion 23. The upper portion 23 has a protruding portion 231 that protrudes compared to the end face 22A of the lower portion 22 in the fiber insertion direction. Also in the second embodiment, the fiber insertion hole 21 is arranged corresponding to the arrangement of the fiber hole 12 of the ferrule 10. In the second embodiment, two optical fiber tapes in a stacked state are to be inserted into the fiber insertion hole 21. For this reason, in the second embodiment, the fiber insertion hole 21 is formed to conform to two optical fiber tapes in a stacked state. Also, the vertical dimension (the distance between the lower portion 22 and the upper portion 23) of the fiber insertion hole 21 corresponds to the thickness of two optical fiber tapes. Note that when two optical fiber tapes are arranged separated in the vertical direction and the two fiber rows of the ferrule 10 are arranged relatively separated in the vertical direction, two vertically separated fiber insertion holes 21 may be provided in the boot 20. Also in the second embodiment, an adhesive is applied to the gap between the end face 231A of the protruding portion 231 and the first surface 14A of the ferrule 10, and the adhesive applied to the gap penetrates inside by capillary action.

[0057] Also in the second embodiment, the lower surface of the protruding portion 231 serves as a facing surface facing the upper surface of the stepped portion 15 (here, the guide groove 15A). Also in the second embodiment, the lower surface of the protruding portion 231 is provided on an extension of the upper edge of the fiber insertion hole 21. As a result, also in the second embodiment, a gap corresponding to the diameter of the optical fiber 1 having a coating is formed between the lower surface of the protruding portion 231 and the upper surface of the upper stage of the stepped portion 15 (the upper guide groove 15A). In the second embodiment, the gap between the lower surface of the protruding portion 231 and the upper surface of the lower stage of the stepped portion 15 (the lower guide groove 15A) becomes relatively large. However, a plurality of optical fibers 1 (bare optical fibers) arranged in two upper and lower rows are disposed between the lower surface of the protruding portion 231 and the upper surface of the lower stage of the stepped portion 15, and narrow gaps of about the thickness of the coating are formed around these bare optical fibers. For this reason, also in the second embodiment, it becomes easy for the adhesive to penetrate around the bare optical fiber due to capillary action.

[0058] ===Other Embodiments=== The above embodiments are for facilitating the understanding of the present invention and are not for limiting the interpretation of the present invention. The present invention can be changed and improved without departing from its gist, and it goes without saying that equivalents of the present invention are included therein.

Explanation of Reference Numerals

[0059] 1 Optical fiber, 1A Stripping 10 Ferrule, 10A Connection end face, 10B Flange portion 11 Guide hole, 12 Fiber hole 13 Adhesive filling portion, 131 Upper opening, 131A Pressing portion, 132 Lower opening 14 Inner wall, 14A First surface, 14B Second surface 15 Stepped portion, 15A Guide groove 17 Boot insertion port, 20 Boot 20A Concave portion, 21 Fiber insertion hole 22 Lower part, 22A End face 23 Upper part, 231 Protruding portion 231A End face, 231B Inclined surface 232 exposed part, 24 connecting part 100 ferrule structure

Claims

1. A ferrule having a plurality of fiber holes arranged side by side in one direction, an adhesive filling portion for filling an adhesive, and a stepped portion for guiding an optical fiber into the fiber holes, a boot attached to the ferrule, characterized in that: the stepped portion is a step provided inside the adhesive filling portion; the boot has: fiber insertion holes arranged corresponding to the arrangement of the plurality of fiber holes and through which the plurality of optical fibers are inserted, a lower portion arranged on one side with respect to the fiber insertion holes, an upper portion arranged on the other side with respect to the fiber insertion holes, wherein: the upper portion has a protruding portion that protrudes compared to the end face of the lower portion in the fiber insertion direction; the protruding length of the protruding portion is less than the length of the stepped portion in the fiber insertion direction; an upper opening communicating with the adhesive filling portion is provided on the upper surface of the ferrule; when the end face of the lower portion is in contact with the end face of the stepped portion, the front end face of the upper portion is arranged in front of the rear edge of the upper opening. A ferrule structure characterized by the above.

2. The ferrule structure according to claim 1, wherein the ferrule has a pressing portion on the upper wall surface of the adhesive filling portion, and the protruding portion is arranged below the pressing portion in a state where the boot is attached to the ferrule.

3. Preparing a ferrule having a plurality of fiber holes arranged side by side in one direction, an adhesive filling portion for filling an adhesive, and a stepped portion for guiding an optical fiber into the fiber holes, and having an upper opening communicating with the adhesive filling portion provided on the upper surface; preparing a boot having fiber insertion holes arranged corresponding to the arrangement of the plurality of fiber holes and through which the plurality of optical fibers are inserted, a lower portion arranged on one side with respect to the fiber insertion holes, and an upper portion arranged on the other side with respect to the fiber insertion holes, having a protruding portion that protrudes compared to the end face of the lower portion in the fiber insertion direction, and the protruding length of the protruding portion being less than the length of the stepped portion in the fiber insertion direction; attaching the boot to the ferrule such that the end face of the lower portion is in contact with the end face of the stepped portion and the front end face of the upper portion is arranged in front of the rear edge of the upper opening, and opposing the protruding portion to the stepped portion inside the adhesive filling portion; and Filling an adhesive into the gap between the inner wall of the adhesive filling portion and the protruding portion to fix the optical fiber to the ferrule A method for manufacturing an optical fiber with a ferrule, characterized by performing the above.

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