Fiber bundle connector and method of manufacturing the fiber connector

Abstract

This fiber bundle connector 1 comprises a plurality of optical fibers 30 and a ferrule 20 that has a connecting end surface 20a and a fiber bore 21 that extends to the connecting end surface and has the plurality of optical fibers passed therethrough. At least at the connecting end surface, the plurality of optical fibers passed through the fiber bore are closely arranged such that adjacent optical fibers are in contact, and among the closely arranged optical fibers, all of the optical fibers positioned on the outermost periphery are pressed against the inner wall 22 of the fiber bore so as to induce the elasto-plastic deformation of the inner wall.

Description

[Technical Field]

[0001] The present invention relates to a fiber bundle connector and a method for manufacturing a fiber connector. This application claims priority based on Japanese Patent Application No. 2022-014270, filed on February 1, 2022, the contents of which are incorporated herein by reference. [Background technology]

[0002] In recent years, with the expansion of data transmission volumes, there has been a trend toward denser arrangements of multiple optical fibers for data communication. Patent Document 1 discloses a bundle fiber connector, in which multiple optical fibers are bundled and inserted into fiber holes of a ferrule, as one method for densely arranging multiple optical fibers. The multiple optical fibers inserted into the fiber holes are exposed at the connecting end surface of the ferrule. In such a bundle fiber connector, the connecting end surface of the bundle fiber connector is butted against the connecting end surface of another optical fiber connector, thereby optically connecting the optical fibers exposed at the connecting end surfaces of these two connectors. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2013-125195 Summary of the Invention [Problem to be solved by the invention]

[0004] In this type of fiber bundle connector, it is necessary to position the multiple optical fibers at the connection end face of the ferrule with high precision. If this cannot be done, there is a problem that the connection loss between the optical fibers of the fiber bundle connector and the optical fibers of another optical fiber connector will be large.

[0005] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a fiber bundle connector capable of suppressing connection loss, and a method for manufacturing the fiber connector. [Means for solving the problem]

[0006] A bundle fiber connector according to a first aspect of the present invention comprises a plurality of optical fibers, a connection end face, and a ferrule having fiber holes extending to the connection end face and through which the plurality of optical fibers are inserted, wherein at least at the connection end face, the plurality of optical fibers inserted into the fiber holes are closely packed so that adjacent optical fibers are in contact with each other, and all of the optical fibers located at the outermost periphery of the plurality of closely packed optical fibers are pressed against an inner wall of the fiber hole, causing elastic-plastic deformation of the inner wall.

[0007] A method for manufacturing a fiber connector according to a second aspect of the present invention is a method for manufacturing a fiber connector including an optical fiber, a ferrule having a connection end face and a fiber hole extending to the connection end face and through which the optical fiber is inserted, the method comprising the steps of: preparing insertion optical fibers each having a tip end and a base end having a diameter larger than that of the tip end, the insertion optical fibers being arranged in succession, the insertion optical fibers being configured so that, in a cross section perpendicular to the longitudinal direction of the insertion optical fibers, the circumscribing circle when the tip ends are closely packed is smaller than at least the inscribing circle of the fiber hole in the connection end face, and the circumscribing circle when the base ends are closely packed is larger than at least the inscribing circle of the fiber hole in the connection end face; and The fiber connector includes a fiber insertion step of inserting the base end of the insertion optical fiber into the fiber hole by inserting the tip end of the insertion optical fiber into the fiber hole and extracting it from the connection end face, and a cutting step of cutting the insertion optical fiber at the connection end face after the fiber insertion step to remove the tip end of the insertion optical fiber extracted from the connection end face, wherein in a state after the fiber insertion step, the base ends of all of the insertion optical fibers located at the outermost periphery among the base ends of the insertion optical fibers inserted into the fiber hole are pressed against the inner wall of the fiber hole, causing elastic-plastic deformation of the inner wall, and in a state after the cutting step, the base ends of the insertion optical fibers form the optical fibers in the fiber connector.

[0008] A manufacturing method of a fiber connector according to a third aspect of the present invention is a manufacturing method of a fiber connector including an optical fiber, and a ferrule having a connection end face and a fiber hole extending to the connection end face and through which the optical fiber is inserted, the manufacturing method comprising: a ferrule preparation step of preparing a ferrule molded from resin, the ferrule having an inscribed circle of the fiber hole at least at the connection end face in a cross section perpendicular to the longitudinal direction of the fiber hole that is larger than the circumscribed circle when the optical fibers are closely packed; a fiber insertion step of inserting the optical fibers into the fiber holes after the ferrule preparation step; and an annealing step of annealing the ferrule after the fiber insertion step to make the inscribed circle of the fiber hole at least at the connection end face smaller than the circumscribed circle when the optical fibers are closely packed, wherein in a state after the annealing step, the optical fibers located at the outermost periphery among the optical fibers inserted into the fiber holes are pressed against an inner wall of the fiber hole, causing elastic-plastic deformation of the inner wall. [Effects of the Invention]

[0009] According to the above aspects of the present invention, when the connection end face of a bundle fiber connector or a fiber connector is butted against another optical fiber connector, connection loss between the optical fibers of these connectors can be suppressed. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a perspective view showing a fiber bundle connector according to an embodiment of the present invention; [Figure 2] FIG. 2 is an enlarged view of part II in FIG. [Figure 3] 3 is a side view showing an insertion optical fiber used in a first manufacturing method for manufacturing the bundle fiber connector of FIGS. [Figure 4] 10A to 10C are cross-sectional views showing a manufacturing process of a first manufacturing method for a bundle fiber connector. [Figure 5] FIG. 5 is a view taken along the line VV in FIG. 4. [Figure 6]5A to 5C are cross-sectional views showing a manufacturing process of the first manufacturing method for the bundle fiber connector, following FIG. 4. [Figure 7] FIG. 7 is a view taken along the line VII-VII in FIG. 6. [Figure 8] 7A to 7C are cross-sectional views showing a manufacturing process of the first manufacturing method for the bundle fiber connector, following FIG. 6. [Figure 9] 3A to 3C are cross-sectional views showing a manufacturing process of a second manufacturing method for manufacturing the bundle fiber connector of FIGS. [Figure 10] FIG. 10 is a view taken along the line XX in FIG. 9. [Figure 11] 11A to 11C are cross-sectional views showing the manufacturing process of the second manufacturing method for the bundle fiber connector following FIGS. [Figure 12] FIG. 10 is an enlarged view showing a first modified example of the bundle fiber connector. [Figure 13] FIG. 10 is an enlarged view showing a second modified example of the bundle fiber connector. [Figure 14] FIG. 10 is an enlarged view showing a third modified example of the bundle fiber connector. [Figure 15] FIG. 10 is an enlarged view showing a fourth modified example of the bundle fiber connector. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, one embodiment of the present invention will be described with reference to FIGS. As shown in FIGS. 1 and 2, the bundle fiber connector 1 includes a plurality of optical fibers 10 and a ferrule 20.

[0012] As shown in Fig. 2, the multiple optical fibers 10 are single-core fibers each having a glass body including a core 11 and a cladding 12. The glass body of each optical fiber 10 has a circular shape in a cross section perpendicular to the longitudinal direction of the optical fiber 10. The glass body of the optical fiber 10 is inserted into a fiber hole 21 of a ferrule 20, which will be described later. In this embodiment, each optical fiber 10 has a coating 13 that coats the glass body. The coating 13 is provided on a portion of the optical fiber 10 that extends outside the ferrule 20.

[0013] 1 and 2, the ferrule 20 has a connection end face 20a and a fiber hole 21. The fiber hole 21 penetrates the ferrule 20 and extends to the connection end face 20a. A plurality of optical fibers 10 are inserted into one fiber hole 21. End faces of the glass bodies of the plurality of optical fibers 10 inserted into the fiber hole 21 are exposed at the connection end face 20a of the ferrule 20. The number of fiber holes 21 in the ferrule 20 in this embodiment is one, but may be, for example, multiple.

[0014] The ferrule 20 of this embodiment has two guide holes 23. Like the fiber holes 21, the two guide holes 23 penetrate the ferrule 20 and extend to the connection end face 20a. The two guide holes 23 are parallel to the fiber holes 21. The two guide holes 23 are arranged so that the fiber hole 21 is located between them. A guide pin (not shown) can be inserted into the guide holes 23. The guide holes 23 and guide pins are used for alignment when connecting the bundle fiber connector 1 to another optical fiber connector.

[0015] As shown in Fig. 2, when a plurality of glass bodies of optical fibers 10 (hereinafter, sometimes simply referred to as optical fibers 10) are inserted into one fiber hole 21, the adjacent optical fibers 10 are arranged so as to be in contact with each other. Hereinafter, this state in which adjacent optical fibers 10 are arranged so as to be in contact with each other will be referred to as the optical fibers 10 being closely packed. Furthermore, of the plurality of optical fibers 10 closely packed arranged in one fiber hole 21, all of the optical fibers 10 located at the outermost periphery are in contact with the inner wall 22 of the fiber hole 21. Within the fiber hole 21, the optical fibers 10 located at the outermost periphery among the plurality of optical fibers 10 are pressed against the inner wall 22, causing the inner wall 22 to undergo elastic-plastic deformation.

[0016] In this embodiment, the shape of the inner surface 21a of the fiber hole 21 when viewed in the longitudinal direction of the fiber hole 21 is circular. Four optical fibers 10 (glass bodies) are inserted into the fiber hole 21. The four optical fibers 10 that are closely packed in the fiber hole 21 are all located on the outermost periphery. Therefore, these four optical fibers 10 are pressed against the inner wall 22 of the fiber hole 21.

[0017] The structure including the fiber hole 21 of the ferrule 20 will be described below. The inner wall 22 of the fiber hole 21 of the ferrule 20 is the inner surface 21a of the fiber hole 21 and a portion of the ferrule 20 located in the vicinity thereof, and is formed to be elastically and plastically deformable. The elastic modulus of the inner wall 22 of the fiber hole 21 is preferably lower than the elastic modulus of the optical fiber 10 (glass body). That is, the inner wall 22 of the fiber hole 21 is more easily elastically deformed than the glass body of the optical fiber 10. Furthermore, in a cross section perpendicular to the longitudinal direction of the fiber hole 21, the inscribed circle 20C (see FIG. 2) of the fiber hole 21 is smaller than the circumscribed circle (not shown) when the multiple optical fibers 10 inserted into the fiber hole 21 are closely packed. As shown in FIG. 2, the inscribed circle 20C of the fiber hole 21 in this embodiment is the same as the outline of the fiber hole 21, which is circular. The fiber hole 21 may be substantially circular after the optical fiber 10 is inserted and the inner wall 22 is elastically and plastically deformed. For example, the inner diameter of the fiber hole 21 in the portion that contacts the optical fiber 10 may be equal to the diameter of the circumscribing circle of the optical fiber 10, and the other portion that does not contact the optical fiber 10 may be smaller than the diameter of the circumscribing circle of the optical fiber 10. In this case, the inscribing circle 20C is a circle inscribed at the point with the smallest inner diameter in the fiber hole 21 after elastically and plastically deformed.

[0018] The specific material and manufacturing method of the ferrule 20 may be arbitrary. The ferrule 20 of this embodiment is manufactured by resin molding. The resin forming the ferrule 20 may be, for example, a thermoplastic resin. Examples of thermoplastic resins include PPS (polyphenylene sulfide), PBT (polybutylene terephthalate), PEEK (polyether ether ketone), LCP (liquid crystal polymer), PEI (polyetherimide), COP (cyclic olefin polymer), and COC (cyclic olefin copolymer). PPS, PBT, PEEK, and LCP are crystalline resins, while PEI is an amorphous resin. COC and COP are amorphous optical resins that are light-transmitting.

[0019] In the bundle fiber connector 1 of this embodiment, the inner wall 22 of the fiber hole 21 is elastically and plastically deformed by the pressure of the optical fiber 10, and the relative positions of the optical fiber 10 and the fiber hole 21 are fixed with absolutely no clearance between the optical fiber 10 and the fiber hole 21. This makes it possible to fix the optical fiber 10 at a desired position with high precision relative to the ferrule 20. This makes it possible to suppress connection loss between the optical fibers of these connectors when the connection end face 20a of the bundle fiber connector 1 is butted against another optical fiber connector.

[0020] The above-described bundle fiber connector 1 can be manufactured by two different manufacturing methods. The two manufacturing methods for the bundle fiber connector 1 will be described below.

[0021] <First manufacturing method> First, a first manufacturing method of the bundle fiber connector 1 will be described with reference to FIGS. In the first manufacturing method, first, a fiber preparation step is carried out to prepare an insertion optical fiber 30 shown in Fig. 3. In the insertion optical fiber 30, a tip portion 31 and a base portion 32 having a larger diameter than the tip portion 31 are continuously arranged in the longitudinal direction of the insertion optical fiber 30. The tip portion 31 and the base portion 32 are made of glass bodies (the core 11 and the cladding 12 shown in Fig. 2). The diameters of the tip portion 31 and the base portion 32 are constant in the longitudinal direction of the insertion optical fiber 30. The diameters of the tip portion 31 and the base portion 32 are different due to the difference in thickness of the cladding 12.

[0022] The distal end 31 and the proximal end 32 of the insertion optical fiber 30 may be connected in a stepped manner, for example. In the insertion optical fiber 30 of this embodiment, a tapered portion 33 made of a glass body is located between the distal end 31 and the proximal end 32. The tapered portion 33 is formed in a tapered shape with a diameter that increases from the distal end 31 toward the proximal end 32. In the insertion optical fiber 30 of this embodiment, a tip portion 31, a base portion 32, and a tapered portion 33 made of a glass body protrude from the coating portion 13 that covers the glass body. The base portion 32, the tapered portion 33, and the tip portion 31 are arranged in this order from the end of the coating portion 13.

[0023] In the first manufacturing method of this embodiment, four of the above-mentioned insertion optical fibers 30 are prepared. The diameters of the tip end 31 and the base end 32 of the four insertion optical fibers 30 are set so as to satisfy the following two conditions. First condition: As shown in FIG. 5, in a cross section perpendicular to the longitudinal direction of the insertion optical fiber 30, the circumscribing circle 31C when the tip ends 31 of four insertion optical fibers 30 are closely packed is smaller than the inscribing circle 20C of the fiber hole 21. Second condition: The circumscribing circle (not shown) when the base ends 32 of the four insertion optical fibers 30 are closely packed is larger than the inscribing circle 20C (see FIG. 7) of the fiber hole 21. More specifically, the circumscribing circle when the base ends 32 of the insertion optical fibers 30 are closely packed is larger than the inscribing circle 20C of the fiber hole 21 before the optical fibers 10 are inserted, and is also larger than the inscribing circle 20C of the fiber hole 21 after elastic-plastic deformation. In the example shown in FIG. 7, the inscribing circle 20C of the fiber hole 21 is the same as the outline of the fiber hole 21, which is circular.

[0024] After the above-described fiber preparation step, a fiber insertion step is carried out in which four insertion optical fibers 30 are inserted into the fiber holes 21 of the ferrule 20, as shown in FIGS. 4 to 7. In the fiber insertion step, first, as shown in FIGS. 4 and 5, the tip ends 31 of the four insertion optical fibers 30 are inserted into the fiber holes 21 of the ferrule 20 and protrude from the connection end face 20a of the ferrule 20. Here, as described above, when the tip ends 31 of the four insertion optical fibers 30 are arranged closest together, the circumscribing circle 31C is smaller than the inscribing circle 20C of the fiber hole 21. Therefore, the tip ends 31 of the four insertion optical fibers 30 can be easily inserted into the fiber holes 21.

[0025] 6, in the fiber insertion step, the tip ends 31 of the four insertion optical fibers 30 inserted into the fiber hole 21 are extracted from the connection end face 20a of the ferrule 20. As a result, the base ends 32 of the four insertion optical fibers 30 are inserted into the fiber hole 21, as shown in FIGS. 6 and 7. Here, as described above, the circumscribing circle (not shown) when the base ends 32 of the four insertion optical fibers 30 are closest packed is larger than the inscribing circle 20C of the fiber hole 21. Therefore, in a state where the base ends 32 of the four insertion optical fibers 30 are inserted into the fiber hole 21, the base ends 32 located on the outermost periphery among these four base ends 32, i.e., all four base ends 32, are pressed against the inner wall 22 of the fiber hole 21, causing elastic-plastic deformation of the inner wall 22.

[0026] Moreover, the insertion optical fiber 30 of this embodiment has a tapered portion 33 between its tip portion 31 and base portion 32. Therefore, the tapered portion 33 of the insertion optical fiber 30 gradually presses the inner wall 22 of the fiber hole 21, and then the base portion 32 of the insertion optical fiber 30 can be easily inserted into the fiber hole 21. In the fiber insertion process, as shown in Figure 6, the insertion optical fiber 30 is inserted into the fiber hole 21 so that the base end 32 of the insertion optical fiber 30 reaches a position corresponding to the connection end face 20a of the ferrule 20, i.e., so that the tip end 31 and tapered portion 33 of the insertion optical fiber 30 are positioned outside the ferrule 20 and away from the connection end face 20a.

[0027] After the above-described fiber insertion step, a cutting step is carried out to cut the insertion optical fiber 30 at the splicing end face 20a of the ferrule 20. As a result, as shown in FIG. 8, the tip portion 31 of the insertion optical fiber 30 extracted from the splicing end face 20a is removed. The tapered portion 33 extracted from the splicing end face 20a is also removed. A portion of the base end portion 32 extracted from the splicing end face 20a may also be removed. In other words, each of the multiple optical fibers 10 in the manufactured bundle fiber connector 1 has a cut portion (cut surface) at the splicing end face 20a of the ferrule 20 where the insertion optical fiber 30 is cut. This cut portion is exposed at the splicing end face 20a. By carrying out this cutting step, the bundle fiber connector 1 is manufactured. In the cutting step, the tip portion 31 and the tapered portion 33 of the insertion optical fiber 30 are removed so that the base end portion 32 of the insertion optical fiber 30 is positioned corresponding to the splicing end face 20a.

[0028] 8, in the state after the cutting process, the base ends 32 of the insertion optical fibers 30 are configured as the optical fibers 10 (glass bodies) of the bundle fiber connector 1. That is, the base ends 32 of the four insertion optical fibers 30 are arranged as closely packed as the four optical fibers 10 of the bundle fiber connector 1. Furthermore, the base ends 32 of all of the insertion optical fibers 30 located at the outermost periphery among the multiple insertion optical fibers 30 arranged as closely packed are pressed against the inner wall 22 of the fiber hole 21. In this embodiment, there are four insertion optical fibers 30, and all four insertion optical fibers 30 are located at the outermost periphery. Therefore, the base ends 32 of all of the insertion optical fibers 30 are pressed against the inner wall 22 of the fiber hole 21. After the cutting step, the connection end face 20a of the ferrule 20 and the end face of the base end portion 32 of the insertion optical fiber 30 exposed at the connection end face 20a (end face of the optical fiber 10) may be polished.

[0029] The plurality of optical fibers 10 in the bundle fiber connector 1 manufactured by the above-described first manufacturing method each comprise an inserting optical fiber 30 configured by continuously arranging a tip end 31 and a base end 32 having a diameter larger than that of the tip end 31, and inserted into a fiber hole 21 of the ferrule 20. Then, the plurality of optical fibers 10 in the bundle fiber connector 1 each have a cut portion (cut surface) exposed at the connection end face 20a by cutting the inserting optical fiber 30 and removing the tip end 31 of the inserting optical fiber 30 with the base end 32 of the inserting optical fiber 30 positioned at the connection end face 20a of the ferrule 20.

[0030] In the first manufacturing method of the bundle fiber connector 1 described above, a plurality of insertion optical fibers 30 are prepared, each having a tip end 31 and a base end 32 that is larger in diameter than the tip end 31 and that are arranged in succession. The tip ends 31 of the plurality of insertion optical fibers 30 are inserted into the fiber holes 21 of the ferrule 20 and extracted from the connection end face 20a, thereby inserting the base ends 32 of the plurality of insertion optical fibers 30 into the fiber hole 21. In this state, the base ends 32 of the plurality of insertion optical fibers 30 are closely packed in the fiber hole 21, and all of these base ends 32 located at the outermost periphery are pressed against the inner wall 22 of the fiber hole 21. Accordingly, the inner wall 22 of the fiber hole 21 is elastically and plastically deformed. Furthermore, after the base ends 32 of the plurality of insertion optical fibers 30 are inserted into the fiber holes 21, the plurality of insertion optical fibers 30 are cut at the splicing end face 20a, and the tip ends 31 of the plurality of insertion optical fibers 30 that have been pulled out from the splicing end face 20a to the outside of the ferrule 20 are removed. Then, the base ends 32 of the plurality of insertion optical fibers 30 inserted into the fiber holes 21 become the plurality of optical fibers 10 in the bundle fiber connector 1. The bundle fiber connector 1 may be manufactured by the first manufacturing method for the bundle fiber connector 1 described above. This makes it possible to easily manufacture the bundle fiber connector 1 in which the multiple optical fibers 10 are positioned in the fiber holes 21 with high precision.

[0031] <Second manufacturing method> Next, a second manufacturing method for the bundle fiber connector 1 will be described with reference to FIGS. 9 and 10, a ferrule preparation step is first performed to prepare a ferrule 20. The ferrule 20 has fiber holes 21 that extend to its connection end face 20a and through which four optical fibers 10 (glass bodies) are inserted. The ferrule 20 is molded from resin. In the molded ferrule 20, in a cross section perpendicular to the longitudinal direction of the fiber holes 21, an inscribed circle 20C of the fiber holes 21 is larger than a circumscribed circle 10C when the four optical fibers 10 are arranged closest together.

[0032] After the ferrule preparation step described above, a fiber insertion step is carried out in which four optical fibers 10 are inserted into the fiber holes 21. Here, as described above, the inscribed circle 20C of the fiber hole 21 is larger than the circumscribed circle 10C when the four optical fibers 10 are arranged closest together. Therefore, the four optical fibers 10 can be easily inserted into the fiber holes 21. In FIG. 9, the end face of the optical fiber 10 is positioned to correspond to the connection end face 20a of the ferrule 20, but this is not limitative.

[0033] After the above-described fiber insertion step, an annealing step is performed in which the ferrule 20 is annealed. In the annealing step, the ferrule 20 is annealed to make the inscribed circle 20C (see FIG. 11) of the fiber hole 21 smaller than the circumscribed circle 10C (see FIG. 10) when the four optical fibers 10 are closely packed. As a result, in the state after the annealing step, all of the optical fibers 10 located at the outermost periphery among the four optical fibers 10 inserted into the fiber hole 21 (i.e., the four optical fibers 10) are pressed against the inner wall 22 of the fiber hole 21, causing the inner wall 22 to undergo elastic-plastic deformation. In the example shown in FIG. 11, the inscribed circle 20C of the fiber hole 21 is the same as the outline of the fiber hole 21, which is circular.

[0034] By carrying out the above-described annealing process, the bundle fiber connector 1 is manufactured. After the annealing process, for example, the connection end face 20a of the ferrule 20 and the end face of the optical fiber 10 exposed at the connection end face 20a may be polished.

[0035] In the second manufacturing method of the bundle fiber connector 1 described above, a ferrule 20 molded from resin and having fiber holes 21 through which multiple optical fibers 10 are inserted is prepared. The inscribed circle 20C of the fiber holes 21 in the prepared ferrule 20 is larger than the circumscribed circle 10C when the multiple optical fibers 10 are closely packed. After the multiple optical fibers 10 are inserted into the fiber holes 21, the ferrule 20 is annealed to make the inscribed circle 20C of the fiber holes 21 smaller than the circumscribed circle 10C when the multiple optical fibers 10 are closely packed. As a result, all of the optical fibers 10 located at the outermost periphery among the multiple optical fibers 10 closely packed in the fiber hole 21 are pressed against the inner wall 22 of the fiber hole 21. Accordingly, the inner wall 22 of the fiber hole 21 is elastically and plastically deformed. The bundle fiber connector 1 may be manufactured by the second manufacturing method of the bundle fiber connector 1 described above. Therefore, the bundle fiber connector 1 in which the multiple optical fibers 10 are positioned in the fiber holes 21 with high precision can be easily manufactured.

[0036] Furthermore, in the second manufacturing method described above, after the optical fiber 10 is inserted into the fiber hole 21 of the ferrule 20, simply by performing an annealing treatment with the ferrule 20 housed in a heating chamber, the inscribed circle 20C of the fiber hole 21 can be reduced and the optical fiber 10 can be fitted into the fiber hole 21. This makes it easier to fit the optical fiber 10 into the fiber hole 21 than when the inscribed circle 20C of the fiber hole 21 is increased by heating the ferrule 20 housed in a chamber and then the optical fiber 10 is inserted into the fiber hole 21 in the chamber.

[0037] The first and second manufacturing methods described above may be combined as appropriate. For example, the annealing step of the second manufacturing method, in which the ferrule 20 is annealed, may be performed after the fiber insertion step of the first manufacturing method, in which the base end 32 of the insertion optical fiber 30 is inserted into the fiber hole 21.

[0038] As described above, in the bundle fiber connector 1 and its manufacturing method of this embodiment, the multiple optical fibers 10 inserted into the fiber hole 21 are closely packed so that adjacent optical fibers 10 are in contact with each other in a cross section perpendicular to the longitudinal direction of the fiber hole 21. Furthermore, all of the optical fibers 10 located at the outermost periphery among the multiple closely packed optical fibers 10 are pressed against the inner wall 22 of the fiber hole 21. Furthermore, the inner wall 22 of the fiber hole 21 against which the optical fibers 10 are pressed undergoes elastic-plastic deformation. Then, the elastic force of the elastic-plastically deformed inner wall 22 presses adjacent optical fibers 10, thereby maintaining the multiple optical fibers 10 inserted into the fiber hole 21 in a closely packed state. This allows the multiple optical fibers 10 to be positioned in the fiber hole 21 with high accuracy. Therefore, when the connection end face 20a of the bundle fiber connector 1 is butted against the connection end face of another optical fiber connector, it is possible to minimize the connection loss between the optical fibers of these connectors. The "another optical fiber connector" mentioned above may be the bundle fiber connector 1 of this embodiment, or may be, for example, a multi-fiber connector in which a multi-core fiber is held in a ferrule.

[0039] Furthermore, in this embodiment, the elastic modulus of the inner wall 22 of the fiber hole 21 is lower than the elastic modulus of the optical fiber 10 (glass body). This prevents the optical fiber 10 from being deformed even if the optical fiber 10 inserted into the fiber hole 21 is pressed against the inner wall 22 of the fiber hole 21. In other words, the optical fiber 10 can be protected.

[0040] Although the present invention has been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

[0041] In the above-described embodiment, the number of optical fibers 10 inserted into the fiber hole 21 is not limited to four. Furthermore, all of the optical fibers 10 inserted into the fiber hole 21 do not have to be pressed against the inner wall 22 of the fiber hole 21. For example, as shown in FIG. 12 , for a fiber hole 21 having a circular cross section perpendicular to the longitudinal direction of the optical fibers 10 and the fiber hole 21, six optical fibers 10 may be arranged in the circumferential direction of the fiber hole 21, and another optical fiber 10 may be arranged inside these six optical fibers 10. In the structure illustrated in FIG. 12 , the seven optical fibers 10 inserted into the fiber hole 21 are closely packed so that adjacent optical fibers 10 are in contact with each other. Furthermore, of these seven optical fibers 10, the six optical fibers 10 located at the outermost periphery are pressed against the inner wall 22 of the fiber hole 21.

[0042] In the above-described embodiment, the cross-sectional shape of the fiber hole 21 perpendicular to the longitudinal direction of the fiber hole 21 is not limited to a circle, and may be various shapes as exemplified in FIGS. 13 to 15. The cross-sectional shape of the fiber hole 21 exemplified in FIG. 13 is a shape in which a part of the circumferential direction of the circle is replaced with a straight line. The cross-sectional shape of the fiber hole 21 exemplified in FIG. 14 is a rectangle. In FIGS. 13 and 14, the number of optical fibers 10 inserted into the fiber hole 21 is four, but this is not limited to this. The cross-sectional shape of the fiber hole 21 exemplified in FIG. 15 is a triangle. In FIG. 15, the number of optical fibers 10 inserted into the fiber hole 21 is three, but this is not limited to this.

[0043] In the above-described embodiment, it is sufficient that the optical fibers 10 are closely packed so that adjacent ones are in contact with each other, and that all of the optical fibers 10 located at the outermost periphery among the plurality of closely packed optical fibers 10 are pressed against the inner wall 22 of the fiber hole 21, thereby causing elastic-plastic deformation of the inner wall 22, at least at the connection end face 20a of the ferrule 20. For this reason, the fiber hole 21 is not limited to being formed to have the same size along its longitudinal direction, and may be formed, for example, so that the size increases with increasing distance from the connection end face 20a along the longitudinal direction of the fiber hole 21.

[0044] In the above-described embodiment, the number of optical fibers 10 (or insertion optical fibers 30) inserted into the fiber holes 21 of the ferrule 20 may be, for example, one. That is, the above-described embodiment is not limited to being applied to a bundle fiber connector 1 in which a plurality of optical fibers 10 are bundled and held in the ferrule 20, but may also be applied to a fiber connector in which one optical fiber 10 is held in the ferrule 20. When the fiber connector is manufactured by the first manufacturing method, the circumscribing circles when the tip ends 31 and base ends 32 of the insertion optical fibers 30 are closest packed may be the circumscribing circles of the tip end 31 and base end 32 of one insertion optical fiber 30, respectively. Furthermore, when the fiber connector is manufactured by the second manufacturing method, the circumscribing circles when the optical fibers 10 are closest packed may be the circumscribing circles of one optical fiber 10.

[0045] In the above-described embodiment, the inner wall 22 of the fiber hole 21 is not limited to being configured to be elastically deformable, but may be configured to be elastically deformable, for example. [Explanation of symbols]

[0046] 1... fiber bundle connector, 10... optical fiber, 10C... circumscribing circle, 20... ferrule, 20a... connection end face, 21... fiber hole, 22... inner wall, 20C... inscribing circle, 30... insertion optical fiber, 31... tip portion, 31C... circumscribing circle, 32... base end portion

Claims

1. a plurality of optical fibers; a ferrule having a connection end surface and fiber holes extending to the connection end surface and through which the optical fibers are inserted, at least at the connection end face, the plurality of optical fibers inserted into the fiber holes are closely packed so that adjacent optical fibers are in contact with each other, and all of the optical fibers positioned at the outermost periphery among the plurality of closely packed optical fibers are pressed against an inner wall of the fiber hole, causing elastic deformation of the inner wall; a circumscribing circle of the connection end face when the optical fibers are closely packed is larger than an inscribing circle of the fiber hole from which a plurality of the optical fibers have been removed;

2. 2. The fiber bundle connector according to claim 1, wherein the modulus of elasticity of the inner wall of the fiber hole is lower than the modulus of elasticity of the optical fiber.

3. 3. The fiber bundle connector according to claim 1, wherein a portion of the inner peripheral surface of the fiber hole that is not in contact with the optical fiber is located radially inward of the circumscribing circle of the optical fiber.

4. A method for manufacturing a fiber connector including an optical fiber, a ferrule having a connection end face and a fiber hole extending to the connection end face and through which the optical fiber is inserted, comprising: a fiber preparation step of preparing an insertion optical fiber in which a tip end portion and a base end portion having a diameter larger than that of the tip end portion are arranged continuously, and in which, in a cross section perpendicular to the longitudinal direction of the insertion optical fiber, a circumscribing circle when the tip ends are closely packed is smaller than at least the inscribing circle of the fiber holes in the splicing end face, and a circumscribing circle when the base ends are closely packed is larger than at least the inscribing circle of the fiber holes in the splicing end face; a fiber insertion step of inserting the tip end portion of the insertion optical fiber into the fiber hole and extracting it from the connection end face after the fiber preparation step, thereby inserting the base end portion of the insertion optical fiber into the fiber hole; a cutting step of cutting the insertion optical fiber at the connection end surface after the fiber insertion step, and removing the tip portion of the insertion optical fiber extracted from the connection end surface, In a state after the fiber insertion step, of the base ends of the insertion optical fibers inserted into the fiber holes, the base ends of all the insertion optical fibers located at the outermost periphery are pressed against the inner wall of the fiber hole, causing the inner wall to elastically deform, In a state after the cutting step, the base end portion of the insertion optical fiber forms the optical fiber in the fiber connector, a circumscribing circle when the base ends of the optical fibers are closely packed is larger than an inscribing circle of the fiber hole from which a plurality of the optical fibers have been removed.

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