Optical fiber cable

Abstract

This optical fiber cable comprises at least one fiber unit that includes a plurality of optical fibers and a holding member that holds the plurality of optical fibers in a state in which the plurality of optical fibers are arranged in a row in a linear direction orthogonal to the longitudinal direction of the optical fibers. The tips in the longitudinal direction of the plurality of optical fibers held by the same holding member protrude from the holding member.

Description

Optical fiber cable

[0007] ,

[0006] ,

[0001] The present invention relates to an optical fiber cable. This application claims priority based on Japanese Patent Application No. 2024-174243 filed in Japan on October 3, 2024, and incorporates its content herein.

[0002] Patent Document 1 discloses an optical fiber cable in which a large number of optical fibers are wrapped by an outer skin. When laying this type of optical fiber cable, several of the large number of optical fibers (hereinafter referred to as "a plurality of optical fibers") may be fused and connected to other plural optical fibers as one group.

[0003] Conventionally, when fusing and connecting an optical fiber of an optical fiber cable to another optical fiber, at the laying site, first, a plurality of optical fibers in the same group among the large number of optical fibers drawn out from the outer skin are aligned in a tape shape. Also, the coating of the tip portions of the plurality of optical fibers to be made into a tape is removed, and further, the tip positions of these plural optical fibers are processed so as to be aligned. Then, the plurality of optical fibers made into a tape are set in a holder for a fusion splicer, the holder is attached to the fusion splicer, and fusion splicing is performed to other plural optical fibers.

[0004] Japanese Patent Application Laid-Open No. 2013-097320

[0005] However, at the laying site of the optical fiber cable, there is a problem that the work man-hours at the laying site increase due to the process of aligning a plurality of optical fibers in the same group in a tape shape. If the work man-hours at the laying site are large, the laying period and work cost of the optical fiber cable become problems, which is not preferable.

[0006] The present invention has been made in view of the above circumstances, and an object thereof is to provide an optical fiber cable capable of reducing the work man-hours at the laying site.

[0007] A first aspect of the present invention comprises at least one fiber unit including a plurality of optical fibers and a holding member that holds the plurality of optical fibers in a line in a straight line perpendicular to the longitudinal direction of the optical fibers, wherein the longitudinal ends of the plurality of optical fibers held by the same holding member protrude from the holding member.

[0008] A second aspect of the present invention provides an optical fiber cable comprising at least one fiber unit including a plurality of multicore fibers, each having a plurality of cores, and a holding member that holds the plurality of multicore fibers in a line in a linear direction perpendicular to the longitudinal direction of the multicore fibers, wherein the multicore fibers have bare fibers and a covering that covers the bare fibers, the longitudinal ends of the plurality of multicore fibers held by the same holding member protrude from the holding member, and at least the tip-side portion of the multicore fibers of the plurality of multicore fibers protruding from the same holding member consists only of bare fibers, the plurality of multicore fibers held by the same holding member are each held non-rotatably with respect to the holding member with the core positions being the same, and the positions of the tips of the plurality of bare fibers protruding from the same holding member are aligned.

[0009] A third aspect of the present invention provides an optical fiber cable comprising at least one fiber unit including a plurality of polarization-maintaining fibers and a holding member that holds the plurality of polarization-maintaining fibers in a line in a linear direction perpendicular to the longitudinal direction of the polarization-maintaining fibers, wherein the polarization-maintaining fibers have a bare fiber and a covering that covers the bare fiber, the longitudinal ends of the plurality of polarization-maintaining fibers held by the same holding member protrude from the holding member, and at least the tip-side portion of the tips of the plurality of polarization-maintaining fibers protruding from the same holding member consists only of the bare fiber, the plurality of polarization-maintaining fibers held by the same holding member are each held non-rotatably with respect to the holding member in a rotationally centered state, and the positions of the tips of the plurality of bare fibers protruding from the same holding member are aligned.

[0010] According to the present invention, it is possible to reduce the amount of work required at the site where optical fiber cables are laid.

[0011] This is a perspective view showing the main part of the optical fiber cable according to the first embodiment. This is a perspective view showing one fiber unit of the optical fiber cable of Figure 1. This is a front view showing the fiber unit of Figure 2 with a reinforcing sleeve attached. This is a front view showing the fiber unit of Figure 2 mounted on the holder of a fusion splicer. This is a side cross-sectional view showing the fiber unit of Figure 2 mounted on the holder of a fusion splicer. This is a front view showing a modified structure of the first embodiment in which a reinforcing sleeve is attached to the fiber unit. This is a perspective view showing an example of the first embodiment in which a protective cover is attached to the fiber unit. This is a perspective view showing a modified fiber unit of the first embodiment. This is a perspective view showing the main part of the optical fiber cable according to the second embodiment. This is a view of the two fiber units of the optical fiber cable according to the second embodiment, viewed from the thickness direction. This is a diagram showing another example of the optical fiber unit of the second embodiment. This is a diagram showing another example of the optical fiber unit of the second embodiment. This is a front view showing a fiber unit of the optical fiber cable according to the third embodiment. This is a front view showing another example of the fiber unit of the optical fiber cable according to the third embodiment. This is an enlarged front view showing the multicore fiber of the fiber unit of Figure 11A. This is a front view showing a fiber unit of the optical fiber cable according to the fourth embodiment.

[0012] [First Embodiment] (Optical Fiber Cable) The first embodiment will be described below with reference to Figures 1 to 5. As shown in Figure 1, the optical fiber cable 1 of the first embodiment is constructed by housing a large number of optical fibers 4 inside a cylindrical outer sheath 2. In the optical fiber cable 1, a large number of optical fibers 4 are drawn out from the end of the outer sheath 2. The large number of optical fibers 4 drawn out from the end of the outer sheath 2 constitute a fiber unit 3. The number of fiber units 3 may be, for example, one or more. In Figure 1, the number of fiber units 3 is four, but it is not limited to this, and may be, for example, less than four or more than four.

[0013] As shown in Figure 2, each fiber unit 3 has multiple optical fibers 4 and one holding member 5. The number of optical fibers 4 in the same fiber unit 3 can be two or more, and less than or equal to the total number of optical fibers 4 in the optical fiber cable 1. In the illustrated example, the number of optical fibers 4 in the same fiber unit 3 is four.

[0014] Each optical fiber 4 has a bare fiber 41 and a cladding 42 that covers the bare fiber 41. The bare fiber 41 is made of, for example, silica-based glass. Although not shown in the figures, the bare fiber 41 in this embodiment has one core and a cladding that surrounds the core. That is, the optical fiber 4 in this embodiment is a single-core fiber. The cladding 42 is made of a UV-curable resin or the like and covers the bare fiber 41. The cladding 42 may be made of only a single layer or of multiple layers. If the cladding 42 is made of multiple layers, the optical fiber 4 may have a primary layer 4p that covers the bare fiber 41 and a secondary layer 4s that covers the primary layer 4p. For illustrative purposes, the primary layer 4p and secondary layer 4s are shown for only one of the optical fibers 4 shown in Figure 2. The secondary layer 4s is made of a resin with a higher Young's modulus than the primary layer 4p. The cladding 42 may further include a colored layer made of a colored UV-curable resin or the like. The outer diameter of the optical fiber 4 (i.e., the outer diameter of the coating 42) is, for example, about 200 μm or about 250 μm.

[0015] The holding member 5 holds multiple optical fibers 4 in a line in a linear direction D2 perpendicular to the longitudinal direction D1 of the optical fibers 4. In other words, the holding member 5 aligns the multiple optical fibers 4 in a tape-like manner. The "linear direction D2" is the direction in which the multiple optical fibers 4 held by the same holding member 5 are arranged. In the following explanation, the side of the longitudinal direction D1 that goes from the outer sheath 2 toward the tip 4a of the optical fiber 4 is referred to as the "tip side," and the opposite side is referred to as the "rear side." In the drawings, the tip side of the longitudinal direction D1 is indicated by "+D," and the rear side is indicated by "-D."

[0016] The holding member 5 holds a plurality of optical fibers 4 so that they cannot move in their longitudinal direction D1. In this embodiment, the holding member 5 holds the optical fibers 4 from above the coating 42. The holding member 5 may hold each optical fiber 4 so that it can rotate around its axis, or it may hold it so that it cannot rotate. The holding member 5 may also be removable from the plurality of optical fibers 4, or it may not be removable. If the holding member 5 is removable from the plurality of optical fibers 4, the holding member 5 may be configured to be separable in the thickness direction perpendicular to both the longitudinal direction D1 and the linear direction D2, for example. The material constituting the holding member 5 may be arbitrary, for example, an elastomer, plastic, epoxy resin, UV-curable resin, etc. Here, the Young's modulus of at least one layer of the coating 42 is lower than the Young's modulus of the holding member 5. In particular, if the coating 42 has a primary layer 4p and a secondary layer 4s, the Young's modulus of the primary layer 4p is lower than the Young's modulus of the holding member 5. This makes it possible to reliably hold the optical fibers 4 while suppressing the increase in loss of the optical fibers 4 when the optical fibers 4 are fixed with the holding member 5. Furthermore, if the coating 42 has a primary layer 4p and a secondary layer 4s, it is more preferable that the Young's moduli of both the primary layer 4p and the secondary layer 4s are lower than the Young's moduli of the holding member 5. This allows the optical fiber 4 to be held more securely.

[0017] The ends 4A of the multiple optical fibers 4 held by the same holding member 5 protrude from the holding member 5 in the longitudinal direction D1. The holding member 5 also holds the end portions of the multiple optical fibers 4 that are drawn out from the outer sheath 2. Therefore, the multiple optical fibers 4 held by the holding member 5 also extend to the rear side of the holding member 5.

[0018] Of the tip portions 4A of multiple optical fibers 4 protruding from the same holding member 5, the tip portions of the optical fibers 4 consist only of bare fiber 41 and do not have a coating 42. In other words, the tip portion 4A has an exposed portion 4b where the coating 42 is removed over a certain length from the tip 4a of the optical fiber 4 toward the rear, exposing the bare fiber 41, and a coated portion 4c provided behind the exposed portion 4b. The length of the exposed portion 4b in the longitudinal direction D1 is, for example, the length required to remove the coating 42 when fusion splicing is performed with a fusion splicer. Furthermore, the positions of the tip portions 4a of multiple bare fiber 41 protruding from the same holding member 5 are aligned. More specifically, the tip portions 4a of multiple optical fibers 4 included in the fiber unit 3 are aligned at equivalent positions in the longitudinal direction D1, and multiple optical fibers 4 can be fused together. Here, in order to enable batch fusion splicing, the distance D1 in the longitudinal direction between the tip 4a located furthest forward and the tip 4a located furthest back among the multiple tips 4a of the multiple optical fibers 4 is preferably 20 μm or less. Furthermore, it is even more preferable that this distance be 10 μm or less. Note that, for example, the entire tip portions 4A of the multiple optical fibers 4 protruding from the holding member 5 may consist only of bare fiber 41. In other words, the tip portions 4A do not need to be provided with a covering portion 4c.

[0019] As shown in Figure 3, the optical fiber cable 1 of this embodiment further includes a reinforcing sleeve 7. The reinforcing sleeve 7 protects the fusion splice portion of the optical fiber 4 after the multiple optical fibers 4 held by the holding member 5 have been fusion spliced ​​together with other multiple optical fibers.

[0020] The reinforcing sleeve 7 only needs to have a cylindrical member through which at least several optical fibers 4 can be inserted and which can be heat-shrinkable. The reinforcing sleeve 7 illustrated in Figure 3 has an outer tube 71, an inner tube 72, and a tensile strength member 73. Both the outer tube 71 and the inner tube 72 are heat-shrinkable members. The tensile strength member 73 is made of a material with higher rigidity than the outer tube 71 and the inner tube 72, and reinforces the fusion splice portion of the optical fibers 4. The inner tube 72 and the tensile strength member 73 are arranged inside the outer tube 71. The tensile strength member 73 is arranged outside the inner tube 72 and inside the outer tube 71. Multiple optical fibers 4 are inserted through the inner tube 72.

[0021] In this embodiment, the size of the holding member 5 is smaller than the size of the inside of the inner tube 72 (cylindrical member) when viewed from the longitudinal direction D1 of the optical fiber 4. Therefore, the holding member 5 holding multiple optical fibers 4 can also pass through the inside of the inner tube 72.

[0022] Although not shown in the figures, in the optical fiber cable 1 of this embodiment, the reinforcing sleeve 7 described above surrounds the multiple optical fibers 4 that extend to the rear side of the holding member 5. That is, at the rear side of the holding member 5, the multiple optical fibers 4 extending from the holding member 5 are inserted into the reinforcing sleeve 7.

[0023] (Method for Manufacturing Optical Fiber Cables) Next, an example of a method for manufacturing the optical fiber cable 1 according to this embodiment will be described. When manufacturing the optical fiber cable 1, first, several optical fibers 4 (multiple optical fibers 4) from the numerous optical fibers 4 drawn out from the end of the outer sheath 2 are aligned in a straight line direction D2, that is, aligned in a tape shape (optical fiber alignment step). Next, the multiple optical fibers 4 aligned in a tape shape are inserted into a reinforcing sleeve 7 (reinforcing sleeve insertion step). After that, holding members 5 are attached to these multiple optical fibers 4 to hold the multiple optical fibers 4 in a tape-shaped alignment state (holding member attachment step). In this state, the tip portions 4A of the multiple optical fibers 4 protrude from the holding members 5. Note that the reinforcing sleeve insertion step may be performed before the optical fiber alignment step or after the holding member attachment step.

[0024] Next, the coating 42 located on the tip side of the tip portions 4A of the multiple optical fibers 4 protruding from the holding member 5 is removed. Furthermore, the portion of the optical fiber 4 from which the coating 42 has been removed (i.e., the portion consisting only of bare fiber 41) is cleaned, and then a screening test is performed. Finally, the tip portions of the multiple exposed bare fibers 41 are cut (tip preparation step). This makes it possible to obtain a fiber unit 3 in which the positions of the tips 4a of the multiple bare fibers 41 are aligned. It also makes possible to obtain a fiber unit 3 in which the coating 42 has been removed from a predetermined range from the tip 4a. With this, the method for manufacturing the optical fiber cable 1 according to this embodiment is completed.

[0025] (Fusion Splicing Method) Next, an example of a method for fusion splicing each fiber unit 3 (multiple optical fibers 4 held by the same holding member 5) to multiple other optical fibers at the site where the optical fiber cable 1 is laid will be described. When fusion splicing multiple optical fibers 4 held by the same holding member 5, first, as shown in Figures 4 and 5, the holding member 5 holding the multiple optical fibers 4 is attached to a holder 100 for a fusion splicer (holder attachment step). The holder 100 comprises a base portion 101 and a cover portion 102.

[0026] The base portion 101 has a receiving recess 103 that is recessed from its upper surface 101a. A part of the retaining member 5 is housed in the receiving recess 103. When the retaining member 5 is housed in the receiving recess 103, the retaining member 5 is positioned so as to be immovable relative to the base portion 101 with respect to the longitudinal direction D1 and the linear direction D2 of the optical fiber 4. The structure of the base portion 101 for positioning the retaining member 5 relative to the base portion 101 is not limited to the receiving recess 103 and may be arbitrary. The lid portion 102 sandwiches the retaining member 5 housed in the receiving recess 103 between itself and the base portion 101, preventing the retaining member 5 from coming out of the receiving recess 103. In the illustrated example, the lid portion 102 is rotatable relative to the base portion 101 about a rotation axis 104, so that it can move between a first position P1 in which the retaining member 5 is sandwiched between itself and the base portion 101 and a second position P2 in which the retaining member 5 is released. In the example shown in Figures 4 and 5, the entire holding member 5 is held by the holder 100 in the longitudinal direction D1 during fusion splicing. This increases the contact area between the holding member 5 and the holder 100, making it easier to fix the optical fiber 4 by the holder 100. The example is not limited to this, and at least a portion of the holding member 5 may be held by the holder 100 in the longitudinal direction D1.

[0027] After attaching the holding member 5 to the holder 100, the holder 100 is attached to a fusion splicer to fusion splice the multiple optical fibers 4 held by the holding member 5 to multiple other optical fibers (fusion splicing step). Then, the holding member 5 is removed from the holder 100 and the reinforcing sleeve 7 is moved from the rear side of the holding member 5 to the fusion splice portion. After that, the inner tube 72 and outer tube 71 (cylindrical member) of the reinforcing sleeve 7 are heat-shrinked to reinforce the fusion splice portion (fusion splice reinforcement step). With this, the fusion splicing method of this embodiment is completed. As described above, since the tips 4a of the multiple optical fibers 4 are aligned, the tip preparation step at the optical fiber cable 1 laying site and the steps prior to the tip preparation step can be omitted. In other words, at the laying site, by setting the holding member 5 of the fiber unit 3 in the holder 100 and appropriately positioning the fiber unit 3 in the fusion splicer, it becomes possible to fusion splice multiple other optical fibers at once.

[0028] As described above, the optical fiber cable 1 according to the first embodiment includes at least one fiber unit 3 which includes a plurality of optical fibers 4 and a holding member 5 that holds the plurality of optical fibers 4 in a line in a linear direction D2 perpendicular to the longitudinal direction D1 of the optical fibers 4, and the ends 4A in the longitudinal direction D1 of the plurality of optical fibers 4 held by the same holding member 5 protrude from the holding member 5. In other words, the ends 4A of the plurality of optical fibers 4 in the same fiber unit 3 (same group) are aligned in a tape shape by the holding member 5. For this reason, the process of aligning the plurality of optical fibers 4 of the same fiber unit 3 in a tape shape is unnecessary at the optical fiber cable 1 laying site. Accordingly, the amount of work required at the optical fiber cable 1 laying site can be reduced.

[0029] Furthermore, the optical fiber 4 has a bare fiber 41 and a covering 42 that covers the bare fiber 41. Of the tip portions 4A of the multiple optical fibers 4 protruding from the same holding member 5, at least the tip-side portions of the optical fibers 4 consist only of bare fiber 41, and the positions of the tip portions 4a of the multiple bare fibers 41 protruding from the same holding member 5 are aligned. In other words, in the optical fiber cable 1 according to the first embodiment, the covering 42 is removed from the tip-side portions of the tip portions 4A of the multiple optical fibers 4 arranged in a tape shape by the same holding member 5, leaving only bare fiber 41. Also, the positions of the tip portions 4a of these multiple bare fibers 41 are aligned. For this reason, at the optical fiber cable 1 installation site, the process of processing the tip portions 4A of the multiple optical fibers 4 of the same fiber unit 3 (same group) (i.e., the process of removing the covering 42 and the process of aligning the tip positions of the optical fibers 4) is unnecessary. Therefore, the amount of work required at the optical fiber cable 1 installation site can be further reduced.

[0030] In the first embodiment, the size of the holding member 5 may be larger than the inner size of the inner tube 72 (cylindrical member) of the reinforcing sleeve 7, for example, as shown in Figure 6. That is, the holding member 5 that holds the multiple optical fibers 4 does not need to be able to pass through the inside of the inner tube 72. In this case, in the fusion splicing method for the optical fibers 4, the holding member 5 can be removed from the multiple optical fibers 4 after the fusion splicing step in which the multiple optical fibers 4 held by the holding member 5 are fusion spliced ​​to the other multiple optical fibers. This allows the reinforcing sleeve 7 located behind the holding member 5 to be moved to the fusion splicing portion. If the size of the holding member 5 is larger than the inner size of the inner tube 72 of the reinforcing sleeve 7, it is preferable that the reinforcing sleeve insertion step be performed before the holding member mounting step.

[0031] Furthermore, the optical fiber 4 has a bare fiber 41 and a covering 42 that covers the bare fiber 41, and the holding member 5 holds the optical fiber 4 from above the covering 42, and the covering 42 has a region having a Young's modulus lower than the Young's modulus of the holding member 5. As a result, when the optical fiber 4 is fixed by the holding member 5, the optical fiber 4 can be held securely while suppressing an increase in the loss of the optical fiber 4.

[0032] Furthermore, the optical fiber cable 1 may further include a protective cover 8 that covers the tips 4A of at least multiple optical fibers 4 protruding from the same holding member 5. In the first embodiment, the optical fiber cable 1 may include a protective cover 8 that covers the tips 4A of multiple optical fibers 4 protruding from the same holding member 5, as shown in Figure 7, for example. The protective cover 8 may be detachably attached to the holding member 5, for example. The protective cover 8 may also cover multiple fiber units 3 located outside the end of the outer sheath 2, for example. In the manufacturing method of the optical fiber cable 1 described above, the protective cover 8 may cover the tips 4A of multiple optical fibers 4 after, for example, a tip preparation step in which the positions of the tips 4a of multiple bare fibers 41 are aligned.

[0033] In an optical fiber cable 1 equipped with a protective cover 8, the protective cover 8 can suppress or prevent damage to the tip portion 4A (especially the bare fiber 41) of the optical fiber 4 held by the holding member 5 during the period from when the optical fiber cable 1 is transported to the installation site until the fusion splicing work of the multiple optical fibers 4 of each fiber unit 3 begins.

[0034] In the first embodiment, for example, as shown in Figure 8, the entire tip portions 4A of multiple optical fibers 4 protruding from the same holding member 5 may be configured such that the bare fibers 41 are covered with a covering 42. Even in the configuration illustrated in Figure 8, the tip portions 4A of the multiple optical fibers 4 may be covered with the protective cover 8 shown in Figure 7. In this case as well, the optical fiber alignment process, the holding member attachment process, and / or the reinforcing sleeve insertion process can be omitted at the installation site. Therefore, the amount of work required at the installation site of the optical fiber cable 1 can be reduced.

[0035] Furthermore, the manufacturing method of the optical fiber cable 1 of the first embodiment includes an optical fiber alignment step of arranging a plurality of optical fibers 4 drawn out from the end of the outer sheath 2 in a linear direction D2 perpendicular to the longitudinal direction D1 of the optical fibers 4, a holding member attachment step of attaching a holding member 5 to the optical fibers 4 to hold the optical fibers 4 in an aligned state, and a tip preparation step of removing at least a portion of the coating 42 of the tip portion 4A of the optical fibers 4 protruding from the holding member 5 to expose the bare fiber 41, and cutting the tip portion of the bare fiber 41. The holding member 5 holds the optical fiber 4 immovably in the longitudinal direction D1, and after the tip preparation step, the holding member 5 is sandwiched in the holder 100 of the fusion splicer, and the holder 100 is installed in the fusion splicer, thereby enabling the optical fiber 4 to be fusion spliced ​​together with a plurality of optical fibers to be connected. With the optical fiber cable 1 manufactured in this way, the amount of work required for connecting the optical fibers 4 at the installation site can be reduced.

[0036] [Second Embodiment] Next, the second embodiment will be described with reference to Figures 9 and 10A to 10C, but the basic configuration is the same as that of the first embodiment. For this reason, the same reference numerals are used for similar components and their descriptions are omitted, and only the differences will be described.

[0037] In the second embodiment, the optical fibers 4 mounted on the optical fiber cable 1 form an optical fiber ribbon cable 4R connected by connecting portions 4R1. The optical fiber ribbon cable 4R includes N optical fibers 4 and connecting portions 4R1, where N is an integer of 2 or more. The connecting portions 4R1 connect two adjacent optical fibers 4 in the linear direction D2. In this embodiment, multiple connecting portions 4R1 are intermittently arranged two-dimensionally in the longitudinal direction D1 and the linear direction D2. In other words, it is a so-called intermittently fixed ribbon cable. The connecting portions 4R1 may also continuously connect the optical fibers 4 along the entire length of the longitudinal direction D1. In this case, the optical fiber ribbon cable 4R becomes a ribbon cable in which multiple optical fibers 4 are covered together.

[0038] The material of the connecting portion 4R1 may be, for example, a UV-curing resin or a thermosetting resin. However, the material of the connecting portion 4R1 is not particularly limited and can be changed as appropriate, as long as it can fix adjacent optical fibers 4 together. The Young's modulus of the connecting portion 4R1 is lower than that of the holding member 5. That is, the Young's modulus of the holding member 5 is higher than that of the connecting portion 4R1. This ensures that the holding member 5 can securely hold multiple optical fibers 4 in a straight line.

[0039] The connecting portion 4R1 is configured to hold the unit structure of the optical fibers 4 within the optical fiber cable 1. For this reason, the connecting portion 4R1 is also provided inside the outer sheath 2 of the optical fiber cable 1. In contrast, the holding member 5 holds the tip portion 4A of the optical fiber 4 and is provided only in a predetermined range on the tip side of the optical fiber 4 in order to align the position of the tip 4a. Furthermore, the holding member 5 is held by the holder 100 in whole or at least in part during fusion splicing. Thus, the connecting portion 4R1 and the holding member 5 have different purposes and can be said to be different from each other in the respects described above. In addition, although the optical fibers 4 are intermittently fixed to each other by the connecting portion 4R1 within the optical fiber cable 1, the arrangement of the optical fibers 4 is not fixed, and the bundle state of the optical fiber ribbon core 4R is deformable. In contrast, the holding member 5 fixes the arrangement of the optical fibers 4 at the tip portion 4A. For this reason, as mentioned above, the Young's modulus of the holding member 5 is higher than that of the connecting portion 4R1, and in this respect as well, the connecting portion 4R1 and the holding member 5 are different.

[0040] The connecting portion 4R1 may or may not be provided within the holding member 5. Furthermore, there may be a section extending rearward from the holding member 5 where the connecting portion 4R1 is not located. In other words, the holding member 5 and the connecting portion 4R1 located at the very end of the connecting portion 4R1 may be spaced apart in the longitudinal direction D1. Hereafter, the section between the holding member 5 and the connecting portion 4R1 located at the very end will be referred to as the unconnected section T. In the optical fiber cable 1, the connecting portion 4R1 may be removed and the unconnected section T adjusted to an appropriate length depending on the rigidity and workability of the optical fiber ribbon core 4R. The length of the unconnected section T may be the same for all optical fibers 4 included in the optical fiber cable 1, or it may be different for each. In the example in Figure 9, since the connecting portions 4R1 are intermittently arranged two-dimensionally in the longitudinal direction D1 and the linear direction D2, the lengths of the unconnected sections T are different for each.

[0041] The optical fiber 4 may have elastic torsion applied to it behind the holding member 5. For example, the optical fiber 4 may be twisted by a predetermined angle around the axis O, thereby applying elastic torsion to the optical fiber 4 in the unconnected section T. All of the multiple optical fibers 4 held by one holding member 5 may have the same elastic torsion, or at least one of the multiple optical fibers 4 may have elastic torsion. By applying elastic torsion to the optical fiber 4, polarization mode dispersion of the optical fiber 4 can be suppressed.

[0042] Figure 10A shows two optical fiber ribbons 4R of this embodiment as viewed from the thickness direction. In the example in Figure 10A, multiple optical fibers 4 contained in one optical fiber ribbon 4R are each held by one holding member 5.

[0043] The example in Figure 10A is not limited to this; as shown in Figure 10B, the optical fibers 4 contained in a single optical fiber ribbon cable 4R may be branched and held by multiple holding members 5. In the example in Figure 10B, an 8-core optical fiber ribbon cable 4R is shown, having a first subunit 4Ra with four optical fibers 4 and a second subunit 4Rb with the remaining four optical fibers 4. The first subunit 4Ra is held by the first holding member 5A, and the second subunit 4Rb is held by the second holding member 5B.

[0044] Furthermore, as shown in Figure 10C, a single holding member 5 may hold optical fibers 4 included in multiple optical fiber ribbon cables 4R. In the example in Figure 10C, a total of four optical fibers 4 are held in the first holding member 5A: two of the four optical fibers 4 of the first optical fiber ribbon cable 4Rf and two of the four optical fibers 4 of the second optical fiber ribbon cable 4Rs. A total of four optical fibers 4 are held in the second holding member 5B: the remaining two optical fibers 4 of the first optical fiber ribbon cable 4Rf and the remaining two optical fibers 4 of the second optical fiber ribbon cable 4Rs. Note that the number of optical fibers 4 held by a single holding member 5, and the number of optical fiber ribbon cables 4R containing the optical fibers 4 held by each holding member 5, are not limited to the examples in Figures 10A to 10C and can be changed as appropriate.

[0045] (Method for manufacturing an optical fiber cable) Next, an example of a method for manufacturing the optical fiber cable 1 according to the second embodiment will be described. Similar to the first embodiment, first, an optical fiber alignment step is performed. At this time, since the optical fibers 4 are connected by the connecting portion 4R1, a plurality of optical fibers 4 can be easily aligned in a tape shape.

[0046] When applying elastic twist to the optical fiber 4, if necessary, the connecting portion 4R1 on the tip side of the optical fiber 4 is removed, a non-connected section T of a predetermined length is provided, and then a twist of a target angle is applied to the optical fiber 4 (twist application step). The twist application step is performed before the holding member attachment step. In order to hold the elastic twist of the optical fiber 4, in the holding member attachment step after the twist application step, the optical fiber 4 is held non-rotatably with respect to the holding member 5. Since the other steps are the same as those in the first embodiment, detailed description thereof is omitted.

[0047] As described above, the optical fiber cable 1 according to the second embodiment further has a connecting portion 4R1 that adheres the optical fibers 4 to each other, and the Young's modulus of the holding member 5 is higher than the Young's modulus of the connecting portion 4R1. Thereby, when the optical fiber 4 is fixed by the holding member 5, it is possible to reliably hold the optical fiber 4 and suppress an increase in loss of the optical fiber 4.

[0048] Further, the optical fiber cable 1 according to the second embodiment further has a connecting portion 4R1 that adhesively connects the optical fibers 4 to each other. The holding member 5 holds the optical fibers 4 in a non-rotatable manner, and at least one of the optical fibers 4 is elastically twisted in a non-connected section T between the holding member 5 and the connecting portion 4R1. Thereby, the optical fibers 4 pre-loaded with elastic twist can be fusion-connected in a batch at the work site. Conventionally, a fusion connection machine for the optical fiber 4 may have a function of adjusting the rotation angle of the optical fiber 4, but it may be difficult to rotate a plurality of optical fibers 4 around the axis O to such an extent that the polarization mode dispersion can be improved. On the other hand, according to the fiber unit 3 held by the holding member 5 in a state where elastic twist is applied, the work of fusion-connecting a plurality of optical fibers 4 with elastic twist can be performed in a short time at the laying site.

[0049] [Third Embodiment] Next, the third embodiment will be described with reference to FIGS. 11A, 11B, and 12. The basic configuration is the same as that of the first and second embodiments. Therefore, the same components are denoted by the same reference numerals and their descriptions are omitted, and only the differences will be described.

[0050] As shown in FIGS. 11A and 11B, the optical fiber cable 1E of the third embodiment includes a fiber unit 3E including a plurality of optical fibers 4E and one holding member 5 that holds these plurality of optical fibers 4E, similar to the first embodiment. Further, the holding member 5 holds the plurality of optical fibers 4E in a state where they are arranged in a line in the linear direction D2. However, the optical fiber 4E in the third embodiment is a multi-core fiber 4E.

[0051] As shown in Figure 12, the multicore fiber 4E has a bare fiber 41E extending in its longitudinal direction D1 and a covering 42 that covers the bare fiber 41E. Each bare fiber 41E has a plurality of cores 43E, a cladding 44E, and one mark 45E. The plurality of cores 43E are spaced apart from each other in a cross-section of the bare fiber 41E perpendicular to the longitudinal direction D1. In Figure 12, the plurality of cores 43E are located on the same circumference centered on the axis O of the bare fiber 41E. In Figure 12, there are four cores 43E, but there should be at least two or more.

[0052] The cladding 44E surrounds the multiple cores 43E. Mark 45E is located inside the cladding 44E in the cross-section of the bare fiber 41E, away from the axis O of the bare fiber 41E, and is positioned at different distances from Mark 45E to each of the multiple cores 43E. This allows the rotational position of the multicore fiber 4E to be determined using Mark 45E as an indicator. Different optical signals can be transmitted between the multiple cores 43E of the multicore fiber 4E.

[0053] As shown in Figures 11A and 11B, in the fiber unit 3E of the third embodiment, a plurality of multicore fibers 4E held by the holding member 5 are held non-rotatably with respect to the holding member 5, with the cores 43E in the same position. The same position of the cores 43E means that when a straight line L passes through the multiple axes O of the plurality of multicore fibers 4E, the position of the core 43E of each multicore fiber 4E is congruent with respect to the straight line L. More specifically, in the plurality of multicore fibers 4E, when one multicore fiber 4E is translated along the straight line L, the core 43E of one multicore fiber 4E coincides with the position of the corresponding core 43E of the other multicore fibers 4E. The same position of the cores 43E includes a state in which the plurality of multicore fibers 4E held by the holding member 5 are held non-rotatably with respect to the holding member 5, with each being rotationally aligned. Rotational alignment of the multicore fibers 4E means determining the rotational position of the multicore fibers 4E.

[0054] In Figure 11A, the multiple multicore fibers 4E held by the holding member 5 are held in a state where they are rotationally aligned so that the marks 45E of the multiple multicore fibers 4E are positioned at the same location in the circumferential direction around the axis O. Note that the rotational position of each of the multiple multicore fibers 4E held by the holding member 5 is not limited to the position illustrated in Figure 11A. For example, as shown in Figure 11B, the marks 45E of the multiple multicore fibers 4E may be located at different positions in the circumferential direction, and the marks 45E may not overlap when the multicore fibers 4E are translated along a straight line L. Even in such a case, since the arrangement of the cores 43E contained in each multicore fiber 4E is congruent with respect to the straight line L, it is possible to connect with other multiple multicore fibers 4E.

[0055] Multiple multicore fibers 4E may be included in the optical fiber ribbon 4R described in the second embodiment. Furthermore, elastic torsion may be applied to the multicore fibers 4E in the unconnected section T. In this case, a predetermined elastic torsion is applied to the multicore fibers 4E and rotational alignment is performed before the holding member 5 holds the multicore fibers 4E. This makes it possible to suppress polarization mode dispersion of the multicore fibers 4E while keeping the positions of the cores 43E similar in multiple multicore fibers 4E.

[0056] Except for the configuration described above, the fiber unit 3E of the third embodiment is configured in the same way as the first or second embodiment. That is, in the fiber unit 3E of the second embodiment, the tip portions 4A in the longitudinal direction D1 of the multiple multicore fibers 4E held by the holding member 5 protrude from the holding member 5. Furthermore, of the tip portions 4A of the multiple multicore fibers 4E protruding from the holding member 5, at least the tip-side portion of the multicore fibers 4E is bare fiber 41E only. Also, the positions of the tip 4a of the multiple bare fibers 41E protruding from the holding member 5 are aligned. Furthermore, in the fiber unit 3E of the third embodiment, similar to the first embodiment, at the rear side of the holding member 5, the multiple optical fibers 4E extending to the rear side of the holding member 5 are inserted into a reinforcing sleeve 7 (see Figure 3, etc.).

[0057] (Method for Manufacturing Optical Fiber Cables) Next, an example of a method for manufacturing an optical fiber cable 1E according to the third embodiment will be described. When manufacturing an optical fiber cable 1E including a multicore fiber 4E, first, several of the many multicore fibers 4E drawn out from the end of the outer sheath 2 (multiple multicore fibers 4E) are inserted into a reinforcing sleeve 7 (see Figure 3, etc.) similar to that of the first embodiment (reinforcing sleeve insertion step). Next, the coating 42 located at the tip end of the multiple multicore fibers 4E is removed. Furthermore, the portion of the multiple multicore fibers 4E from which the coating 42 has been removed (i.e., the portion consisting only of bare fibers 41E) is cleaned, and then a screening test is performed. After that, the tip portions of the exposed multiple bare fibers 41E are cut to align the positions of the tips 4a of the multiple bare fibers 41E (tip preparation step).

[0058] Next, rotational alignment is performed on each of the multiple multicore fibers 4E to determine the rotational position of each multicore fiber 4E so that the positions of the cores 43E of the multiple multicore fibers 4E are the same (alignment step). In this rotational alignment, for example, as shown in Figure 11A, the rotational positions of the multiple multicore fibers 4E may be determined so that the marks 45E of the multiple multicore fibers 4E face in the same direction. Alternatively, as shown in Figure 11B, the rotational positions of the multiple multicore fibers 4E may be determined so that the positional relationship of only the cores 43E included in the multiple multicore fibers 4E is the same. After this rotational alignment, the holding members 5 are attached to these multiple multicore fibers 4E (holding member attachment step). As a result, the multiple multicore fibers 4E are held by the holding members 5 in a state where they are aligned in a tape-like manner and each has been rotationally aligned, and are held in a state where they cannot rotate. In addition, the positions of the tips 4a of the multiple bare fibers 41E protruding from the holding members 5 are aligned.

[0059] Furthermore, when imparting elastic torsion to the multicore fiber 4E, the torsion imparting step is performed before the retaining member attachment step, as in the second embodiment. With this, the manufacturing method of the optical fiber cable 1E according to the third embodiment is completed.

[0060] (Fusion splicing method) In the optical fiber cable 1E of the third embodiment, multiple multicore fibers 4E held by the same holding member 5 can be fusion spliced ​​to multiple other optical fibers at the optical fiber cable 1E installation site using the same fusion splicing method as in the first embodiment.

[0061] As described above, the fiber unit 3E of the third embodiment includes at least one fiber unit 3E that includes a plurality of multicore fibers 4E, each having a plurality of cores 43E, and a holding member 5 that holds the plurality of multicore fibers 4E in a line in a linear direction D2 perpendicular to the longitudinal direction D1 of the multicore fibers 4E. Each multicore fiber 4E has a bare fiber 41E and a covering 42 that covers the bare fiber 41E. The tip portions 4A in the longitudinal direction D1 of the plurality of multicore fibers 4E held by the same holding member 5 protrude from the holding member 5, and of the tip portions 4A of the plurality of multicore fibers 4E protruding from the same holding member 5, at least the tip-side portion of the multicore fiber 4E is bare fiber 41E only. The plurality of multicore fibers 4E held by the same holding member 5 are held non-rotatably with respect to the holding member 5 with the core 43E in the same position, and the positions of the tip 4a of the plurality of bare fibers 41E protruding from the same holding member 5 are aligned. As a result, the optical fiber cable 1E according to the third embodiment provides the same effects as the first embodiment. That is, in the optical fiber cable 1E according to the third embodiment, the steps of aligning multiple multicore fibers 4E of the same fiber unit 3E (same group) into a tape shape and processing the tip portions 4A of multiple multicore fibers 4E of the same fiber unit 3E (i.e., the steps of removing the coating 42 and aligning the tip positions of the multicore fibers 4E) are eliminated at the optical fiber cable 1E installation site. Therefore, the amount of work required at the optical fiber cable 1E installation site can be reduced.

[0062] Furthermore, in the optical fiber cable 1E according to the third embodiment, the fusion splicing of multiple multicore fibers 4E can be performed in a short amount of time. Moreover, it becomes possible to perform the fusion splicing of multiple multicore fibers 4E at a low cost. This point will be explained below. Conventionally, dedicated fusion splicers for fusion splicing multicore fibers 4E have a rotational alignment function, but can only fusion splice one multicore fiber 4E at a time. For this reason, the work of fusion splicing multiple multicore fibers 4E at the optical fiber cable 1E installation site takes a long time. In addition, dedicated fusion splicers for multicore fibers with an alignment function are expensive, so the cost required for fusion splicing multiple multicore fibers 4E becomes high.

[0063] In contrast, in the optical fiber cable 1E of the third embodiment, in the multiple multicore fibers 4E aligned in a tape shape by the holding member 5, the cores 43E in each are arranged in the same state and held in a non-rotatable state. Therefore, it is possible to fusion splice multiple multicore fibers 4E aligned in a tape shape using a general-purpose fusion splicer (a fusion splicer without a rotational alignment function) that fusion splices multiple single-core fibers aligned in a tape shape. As a result, the work of fusion splicing multiple multicore fibers 4E can be performed in a short time at the installation site of the optical fiber cable 1E including the multicore fibers 4E. Furthermore, since a general-purpose fusion splicer is less expensive than a fusion splicer dedicated to multicore fibers, it is also possible to perform fusion splicing of multiple multicore fibers 4E at a low cost.

[0064] Furthermore, the holding member 5 has connecting portions 4R1 that bond the multicore fibers 4E together, and the Young's modulus of the holding member 5 is higher than that of the connecting portions 4R1. This makes it possible to more reliably maintain the multicore fibers 4E in a straight line while suppressing an increase in the loss of the multicore fibers 4E.

[0065] Furthermore, the multicore fiber 4E has a bare fiber 41E and a covering 42 that covers the bare fiber 41E, and the holding member 5 holds the multicore fiber 4E from above the covering 42, and the covering 42 has a region having a Young's modulus lower than the Young's modulus of the holding member 5. As a result, when the multicore fiber 4E is fixed by the holding member 5, the multicore fiber 4E can be held securely while suppressing an increase in the loss of the multicore fiber 4E.

[0066] Furthermore, the device has connecting parts 4R1 that bond the multicore fibers 4E together, and at least one of the multicore fibers 4E is given an elastic twist in the unconnected section T between the holding member 5 and the connecting part 4R1. This allows the multicore fibers 4E, which have been given an elastic twist in advance, to be fused together in bulk at the work site.

[0067] [Fourth Embodiment] Next, the fourth embodiment will be described with reference to Figure 13, but the basic configuration is the same as that of the first and second embodiments. For this reason, the same reference numerals are used for similar components and their descriptions are omitted, and only the differences will be described.

[0068] As shown in Figure 13, the optical fiber cable 1F of the fourth embodiment includes a fiber unit 3F that includes a plurality of optical fibers 4F and a holding member 5 that holds these plurality of optical fibers 4F, similar to the first embodiment. The holding member 5 holds the plurality of optical fibers 4F in a straight line in the linear direction D2. However, the optical fibers 4F in the fourth embodiment are polarization-maintaining fibers 4F.

[0069] The polarization-maintaining fiber 4F has a bare fiber 41F extending in its longitudinal direction D1 and a covering 42 that covers the bare fiber 41F. The bare fiber 41F has one core 43F, a pair of stress-applying portions 46F, and a cladding 44F. The core 43F is positioned on the axis of the bare fiber 41F in a cross-section of the bare fiber 41F perpendicular to the longitudinal direction D1. The pair of stress-applying portions 46F are positioned spaced apart on both sides of the core 43F in the cross-section of the bare fiber 41F. The cladding 44F surrounds the core 43F and the pair of stress-applying portions 46F. In the illustrated example, the polarization-maintaining fiber 4F is of the PANDA (Polarization-maintaining AND Absorption-reducing fiber) type, in which the stress-applying portion 46F has a circular cross-section, but it may also be of the bowtie type, elliptical cladding type, etc.

[0070] The polarization-maintaining fiber 4F has two polarization axes, namely a fast axis and a slow axis, that pass through the axis of the core 43F and are mutually orthogonal in a cross section perpendicular to the longitudinal direction D1. The fast axis extends in the direction in which a pair of stress-applying sections 46F are aligned. The core 43F of the polarization-maintaining fiber 4F can transmit transverse polarization of light vibrating in the direction of the fast axis, and longitudinal polarization of light vibrating in the direction of the slow axis.

[0071] In the fiber unit 3F of the fourth embodiment, a plurality of polarization-maintaining fibers 4F held by the holding member 5 are held non-rotatably relative to the holding member 5 in a state where each is rotationally aligned. Rotational alignment of the polarization-maintaining fibers 4F means determining the rotational position of the polarization-maintaining fibers 4F, in other words, it means determining the orientation of the two polarization axes of the polarization-maintaining fibers 4F. In Figure 13, the plurality of polarization-maintaining fibers 4F held by the holding member 5 are held by the holding member 5 in a state where each pair of stress-applying portions 46F is rotationally aligned in the arrangement direction (linear direction D2) of the plurality of polarization-maintaining fibers 4F. Note that the rotational position of each of the plurality of polarization-maintaining fibers 4F held by the holding member 5 is not limited to the position illustrated in Figure 13.

[0072] As described in the second embodiment, the multiple polarization-maintaining fibers 4F may be included in the optical fiber ribbon core 4R. In this embodiment, it is preferable not to impart elastic torsion in the unconnected section T in order to maintain the polarization of the light guiding the polarization-maintaining fibers 4F.

[0073] Except for the configuration described above, the fiber unit 3F of the fourth embodiment is configured in the same way as the first embodiment. That is, in the fiber unit 3F of the fourth embodiment, the longitudinal tip portions 4A of the multiple polarization-maintaining fibers 4F held by the holding member 5 protrude from the holding member 5. Furthermore, of the tip portions 4A of the multiple polarization-maintaining fibers 4F protruding from the holding member 5, at least the tip-side portion of the polarization-maintaining fibers 4F consists only of bare fibers 41F. Also, the positions of the tip portions 4a of the multiple bare fibers 41F protruding from the holding member 5 are aligned. In addition, in the fiber unit 3F of the fourth embodiment, similar to the first embodiment, at the rear side of the holding member 5, the multiple polarization-maintaining fibers 4F extending to the rear side of the holding member 5 are inserted into a reinforcing sleeve 7 (see Figure 3, etc.).

[0074] (Manufacturing Method for Optical Fiber Cables) The optical fiber cable 1F according to the fourth embodiment can be manufactured by the same manufacturing method as in any of the first to third embodiments. In this manufacturing method, when aligning the rotation of the plurality of polarization-maintaining fibers 4F, the rotational positions of the plurality of polarization-maintaining fibers 4F may be set such that, for example, as shown in Figure 13, the pair of stress-applying portions 46F of the polarization-maintaining fibers 4F are aligned in the arrangement direction (linear direction D2) of the plurality of polarization-maintaining fibers 4F.

[0075] (Fusion splicing method) In the optical fiber cable 1F of the fourth embodiment, multiple polarization-maintaining fibers 4F held by the same holding member 5 can be fusion-spliced ​​to multiple other optical fibers at the optical fiber cable 1F laying site by a fusion splicing method similar to that of any of the first to third embodiments.

[0076] As described above, the optical fiber cable 1F according to the fourth embodiment provides at least one optical fiber unit 3F including a plurality of polarization-maintaining fibers 4F and a holding member 5 that holds the plurality of polarization-maintaining fibers 4F in a line in a linear direction D2 perpendicular to the longitudinal direction D1 of the polarization-maintaining fibers 4F. Each polarization-maintaining fiber 4F has a bare fiber 41F and a covering 42 that covers the bare fiber 41F. The ends 4A in the longitudinal direction D1 of the plurality of polarization-maintaining fibers 4F held by the same holding member 5 protrude from the holding member 5, and of the ends 4A of the plurality of polarization-maintaining fibers 4F protruding from the same holding member 5, at least the portion on the tip side of the polarization-maintaining fiber 4F is bare fiber 41F only. The plurality of polarization-maintaining fibers 4F held by the same holding member 5 are each held non-rotatably with respect to the holding member 5 in a rotationally centered state, and the positions of the ends 4a of the plurality of bare fibers 41F protruding from the same holding member 5 are aligned. In other words, in the optical fiber cable 1F according to the fourth embodiment, the steps of aligning multiple polarization-maintaining fibers 4F of the same fiber unit 3F (same group) in a tape-like manner, and processing the tip portions 4A of multiple polarization-maintaining fibers 4F of the same fiber unit 3F (i.e., the steps of removing the coating 42 and aligning the tip positions of the polarization-maintaining fibers 4F) are eliminated at the optical fiber cable 1F installation site. Therefore, the amount of work required at the optical fiber cable 1F installation site can be reduced.

[0077] Furthermore, in the optical fiber cable 1F according to the fourth embodiment, the fusion splicing of multiple polarization-maintaining fibers 4F can be performed in a short amount of time, similar to the third embodiment. Moreover, it becomes possible to perform the fusion splicing of multiple polarization-maintaining fibers 4F at a low cost.

[0078] Furthermore, the holding member 5 has connecting portions 4R1 that bond the polarization-maintaining fibers 4F together, and the Young's modulus of the holding member 5 is higher than that of the connecting portions 4R1. This makes it possible to more reliably maintain the polarization-maintaining fibers 4F in a straight line while suppressing an increase in the loss of the polarization-maintaining fibers 4F.

[0079] Furthermore, the polarization-maintaining fiber 4F has a bare fiber 41F and a covering 42 that covers the bare fiber 41F, and the holding member 5 holds the polarization-maintaining fiber 4F from above the covering 42, and the covering 42 has a region having a Young's modulus lower than the Young's modulus of the holding member 5. As a result, when the polarization-maintaining fiber 4F is fixed by the holding member 5, the polarization-maintaining fiber 4F can be held securely while suppressing an increase in the loss of the polarization-maintaining fiber 4F.

[0080] The optical fiber cables 1, 1E, and 1F of the second to fourth embodiments described above may be equipped with a protective cover 8 (see Figure 7) similar to that of the first embodiment. The protective cover 8 may, for example, collectively cover the tip portions 4A of multiple multicore fibers 4E or the tip portions 4A of multiple polarization-maintaining fibers 4F (especially the bare fibers 41E and 41F) that protrude from the holding member 5.

[0081] The technical scope of the present invention is not limited to the embodiments described above, and various modifications can be made without departing from the spirit of the invention. Furthermore, without departing from the spirit of the invention, the components in the above embodiments can be replaced with well-known components as appropriate, and the above embodiments and modifications can be combined as appropriate.

[0082] 1, 1E, 1F... Fiber optic cable, 3, 3E, 3F... Fiber unit, 4... Optical fiber, 4A... Tip, 4a... Tip, 4E... Multicore fiber (optical fiber), 4F... Polarization-maintaining fiber (optical fiber), 4R... Optical fiber ribbon core, 4R1... Connecting part, 5... Holding member, 7... Reinforcement sleeve, 8... Protective cover, 41, 41E, 41F... Bare fiber, 42... Covering, D1... Longitudinal direction, D2... Linear direction

Claims

1. An optical fiber cable comprising at least one fiber unit including a plurality of optical fibers and a holding member that holds the plurality of optical fibers in a straight line in a direction perpendicular to the longitudinal direction of the optical fibers, wherein the longitudinal ends of the plurality of optical fibers held by the same holding member protrude from the holding member.

2. The optical fiber cable according to claim 1, wherein the optical fiber has a bare fiber and a covering that covers the bare fiber, and of the tip portions of a plurality of optical fibers protruding from the same holding member, at least the tip portions of the optical fibers consist only of the bare fiber, and the positions of the tips of the plurality of bare fibers protruding from the same holding member are aligned.

3. The optical fiber cable according to claim 1 or 2, further comprising a connecting portion for bonding the optical fibers together, wherein the Young's modulus of the holding member is higher than the Young's modulus of the connecting portion.

4. The optical fiber cable according to any one of claims 1 to 3, wherein the optical fiber comprises a bare fiber and a covering covering the bare fiber, the holding member holds the optical fiber from above the covering, and the covering comprises a region having a Young's modulus lower than that of the holding member.

5. The optical fiber cable according to any one of claims 1 to 4, further comprising a connecting portion for bonding the optical fibers together, wherein the holding member holds the optical fibers so as not to rotate, and at least one of the optical fibers is subjected to elastic torsion in the unconnected section between the holding member and the connecting portion.

6. The optical fiber cable according to any one of claims 1 to 5, further comprising a protective cover that collectively covers the tips of at least a plurality of optical fibers protruding from the same holding member.

7. An optical fiber cable comprising at least one fiber unit including a plurality of multicore fibers, each having a plurality of cores, and a holding member that holds the plurality of multicore fibers in a line in a linear direction perpendicular to the longitudinal direction of the multicore fibers, wherein the multicore fibers have bare fibers and a covering covering the bare fibers, the longitudinal ends of the plurality of multicore fibers held by the same holding member protrude from the holding member, at least the tip-side portion of the multicore fibers protruding from the same holding member consists only of bare fibers, the plurality of multicore fibers held by the same holding member are each held non-rotatably with respect to the holding member with the core positions being the same, and the positions of the ends of the plurality of bare fibers protruding from the same holding member are aligned.

8. The optical fiber cable according to claim 7, further comprising a connecting portion for bonding the multicore fibers together, wherein the Young's modulus of the holding member is higher than the Young's modulus of the connecting portion.

9. The optical fiber cable according to claim 7 or 8, wherein the multicore fiber comprises the bare fiber and a covering covering the bare fiber, the holding member holds the multicore fiber from above the covering, and the covering comprises a region having a Young's modulus lower than that of the holding member.

10. The optical fiber cable according to any one of claims 7 to 9, further comprising a connecting portion for bonding the multicore fibers together, wherein at least one of the multicore fibers is subjected to elastic torsion in the unconnected section between the holding member and the connecting portion.

11. The optical fiber cable according to claim 7, further comprising a protective cover that collectively covers the tips of at least a plurality of multicore fibers protruding from the same retaining member.

12. An optical fiber cable comprising at least one fiber unit including a plurality of polarization-maintaining fibers and a holding member that holds the plurality of polarization-maintaining fibers in a straight line perpendicular to the longitudinal direction of the polarization-maintaining fibers, wherein the polarization-maintaining fibers have a bare fiber and a covering that covers the bare fiber, the longitudinal ends of the plurality of polarization-maintaining fibers held by the same holding member protrude from the holding member, at least the tip-side portion of the tips of the plurality of polarization-maintaining fibers protruding from the same holding member consists only of the bare fiber, the plurality of polarization-maintaining fibers held by the same holding member are each held non-rotatably with respect to the holding member in a rotationally centered state, and the positions of the tips of the plurality of bare fibers protruding from the same holding member are aligned.

13. The optical fiber cable according to claim 12, further comprising a connecting portion for bonding the polarization-maintaining fibers together, wherein the Young's modulus of the retaining member is higher than the Young's modulus of the connecting portion.

14. The optical fiber cable according to claim 12 or 13, wherein the polarization-maintaining fiber comprises the bare fiber and a covering covering the bare fiber, the holding member holds the polarization-maintaining fiber from above the covering, and the covering comprises a region having a Young's modulus lower than that of the holding member.

15. The optical fiber cable according to any one of claims 12 to 14, further comprising a protective cover that collectively covers the tips of at least a plurality of polarization-maintaining fibers protruding from the same retaining member.

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