Optical fiber cable and optical fiber unit

Abstract

This optical fiber cable comprises, a plurality of optical fiber ribbons, a plurality of water absorbing members, and an outer covering that covers the periphery of the plurality of optical fiber ribbons and the plurality of water absorbing members. The optical fiber ribbons each have a plurality of optical fiber cores, and a connecting resin that connects together the plurality of optical fiber cores arranged in parallel in a direction orthogonal to the longitudinal direction of the plurality of optical fiber cores. The connecting resin has at least one recess between the adjacent optical fiber cores, and the thickness of each water absorbing member is less than the center-to-center distance of two adjacent optical fiber cores in the parallel arrangement direction of the optical fiber cores.

Description

Optical fiber cable and optical fiber unit

[0001] This disclosure relates to an optical fiber cable and an optical fiber unit. This application claims priority to Japanese Application No. 2023-017611, filed February 8, 2023, and incorporates by reference all of the contents of said Japanese application.

[0002] Patent Document 1 discloses an optical fiber cable including an optical fiber unit assembly in which a plurality of optical fiber units, each of which is a bundle of a plurality of optical fiber cores, are assembled. The optical fiber cable disclosed in Patent Document 1 includes an external water-stopping material provided on the outer periphery of the optical fiber unit assembly and an internal water-stopping material provided inside the optical fiber unit assembly. The internal water-stopping material is a water-swellable fiber or string-like member.

[0003] Japanese Patent Application Publication No. 2013-088542

[0004] The optical fiber cable comprises a plurality of optical fiber ribbons, a plurality of water-absorbing members, and an outer jacket covering the plurality of optical fiber ribbons and the plurality of water-absorbing members, each of the optical fiber ribbons having a plurality of optical fiber core wires and a connecting resin connecting the plurality of optical fiber core wires arranged in parallel in a direction perpendicular to the longitudinal direction of the plurality of optical fiber core wires, the connecting resin having at least one recess between adjacent optical fiber core wires, and the thickness of each of the water-absorbing members being smaller than the center-to-center distance between two adjacent optical fiber core wires in the parallel direction of the optical fiber core wires.

[0005] The optical fiber unit comprises one or more optical fiber ribbons, a plurality of water-absorbing members, and a unit coating portion that coats the one or more optical fiber ribbons and the plurality of water-absorbing members, each of the optical fiber ribbons having a plurality of optical fiber core wires and a connecting resin that connects the plurality of optical fiber core wires that are arranged in parallel in a direction perpendicular to the longitudinal direction of the plurality of optical fiber core wires, the connecting resin having at least one recess between adjacent optical fiber core wires, and the thickness of each of the water-absorbing members being smaller than the center-to-center distance between two adjacent optical fiber core wires in the parallel direction of the optical fiber core wires.

[0006] Fig. 1 is a cross-sectional view perpendicular to the longitudinal direction of an optical fiber cable according to a first embodiment. Fig. 2 is a partial development view showing an optical fiber ribbon used in the optical fiber cable in the longitudinal direction. Fig. 3 is a partially enlarged cross-sectional view perpendicular to the longitudinal direction of some of the optical fiber cores among the multiple optical fiber cores forming the optical fiber ribbon. Fig. 4 is a cross-sectional view perpendicular to the longitudinal direction of an optical fiber cable according to a modified example of the first embodiment. Fig. 5 is a cross-sectional view perpendicular to the longitudinal direction of an optical fiber unit according to a second embodiment. Fig. 6 is a schematic diagram illustrating an evaluation experiment on the watertightness of an optical fiber cable.

[0007] (Problem to be Solved by the Present Disclosure) As an optical fiber core wire mounted in an optical fiber cable, an optical fiber ribbon is known, which includes a plurality of optical fibers and a connecting resin that connects the optical fibers arranged in parallel in a direction perpendicular to the longitudinal direction of the optical fibers. Water that has entered the cable may run longitudinally along the connecting resin. In particular, if the optical fiber ribbon has a recess between adjacent optical fibers, water may run along this recess for a longer distance.

[0008] An object of the present disclosure is to provide an optical fiber cable and an optical fiber unit with higher waterproof properties.

[0009] (Explanation of One Form of the Present Disclosure) First, embodiments of the present disclosure will be listed and described. (1) An optical fiber cable according to one form of the present disclosure comprises: a plurality of optical fiber ribbons; a plurality of water-absorbing members; and an outer jacket covering the plurality of optical fiber ribbons and the plurality of water-absorbing members, wherein each of the optical fiber ribbons comprises a plurality of optical fibers and a connecting resin connecting the plurality of optical fibers arranged in parallel in a direction perpendicular to the longitudinal direction of the plurality of optical fibers, the connecting resin having at least one recess between adjacent optical fibers, and the thickness of each of the water-absorbing members being smaller than the center-to-center distance between two adjacent optical fibers in the parallel direction of the optical fibers.

[0010] According to the present disclosure, the connecting resin of each optical fiber ribbon has at least one recess between adjacent optical fibers, making it easy to separate some optical fibers from the optical fiber ribbon and install the optical fibers in the cable. Furthermore, water that enters the optical fiber cable is likely to run along the longitudinal direction by flowing along this recess. However, the thickness of each water-absorbing member of the present disclosure is smaller than the center-to-center distance between two adjacent optical fibers in the parallel direction of the optical fibers. Because the water-absorbing member is sized to easily enter the recess, water running within the cable can be suppressed.

[0011] (2) In the above (1), the optical fiber ribbon may be an intermittently connected optical fiber ribbon in which, among some or all of the plurality of optical fiber cores, connected sections in which adjacent optical fiber cores are connected and non-connected sections in which adjacent optical fiber cores are not connected are alternately arranged in the longitudinal direction.

[0012] When the optical fiber ribbons are intermittently connected optical fiber ribbons, the optical fiber ribbons can be packed densely within the optical fiber cable. However, if there are recesses between the optical fiber cores, water that has entered the optical fiber cable may run along the recesses and may run longer along the longitudinal direction. However, since the thickness of each water-absorbing member of the present disclosure is smaller than the center-to-center distance, such water running can be suppressed.

[0013] (3) In the above (1) or (2), each of the water-absorbing members may be twisted with one or more of the optical fiber ribbons. According to the present disclosure, since each of the water-absorbing members is twisted with one or more of the optical fiber ribbons, waterproofing in the circumferential direction of the cable can be improved compared to when the water-absorbing members are not twisted with the optical fiber ribbons.

[0014] (4) In any of the above (1) to (3), each of the water-absorbent members may be formed by assembling a plurality of water-absorbent fibers, and the diameter of the water-absorbent fibers may be 5 μm or more and 50 μm or less. According to the present disclosure, each of the water-absorbent members is formed by assembling a plurality of water-absorbent fibers, and the diameter of the water-absorbent fibers is 5 μm or more and 50 μm or less. Since the water-absorbent fibers are easily inserted between adjacent optical fiber cores or into recesses, the waterproofness of the cable can be improved.

[0015] (5) In any of (1) to (3) above, each of the water-absorbent members may have a tape shape, and the thickness of the tape may be 250 μm or less and the width of the tape may be 300 μm or more and 2500 μm or less in a cross section of the water-absorbent member. According to the present disclosure, each water-absorbent member has a tape shape with a thickness of 250 μm or less and a width of 300 μm or more and 2500 μm or less in a cross section. This makes it easy for the water-absorbent member to penetrate between adjacent optical fiber cores or into recesses, thereby improving the waterproofing of the cable. Furthermore, since the processing precision is not as high as in a shape formed by assembling a plurality of water-absorbent fibers, manufacturing costs can be reduced.

[0016] (6) In any of (1) to (5) above, the cable may further include a plurality of optical fiber units each including one or more of the optical fiber ribbons and a unit covering portion covering the optical fiber ribbon, and each of the water-absorbing members may be twisted with one or more of the optical fiber units. According to the present disclosure, since each of the water-absorbing members is twisted with one or more of the optical fiber units, waterproofness in the circumferential direction of the cable can be improved compared to when the water-absorbing members are not twisted with the optical fiber units.

[0017] (7) An optical fiber unit according to another aspect of the present disclosure comprises one or more optical fiber ribbons, a plurality of water-absorbing members, and a unit coating portion that coats the one or more optical fiber ribbons and the plurality of water-absorbing members, each of the optical fiber ribbons having a plurality of optical fiber core wires and a connecting resin that connects the plurality of optical fiber core wires arranged in parallel in a direction perpendicular to the longitudinal direction of the plurality of optical fiber core wires, the connecting resin having at least one recess between adjacent optical fiber core wires, and the thickness of each of the water-absorbing members being smaller than the center-to-center distance between two adjacent optical fiber core wires in the parallel direction of the optical fiber core wires.

[0018] According to the present disclosure, the connecting resin of each optical fiber ribbon has at least one recess between adjacent optical fibers, making it easy to separate some optical fibers from the optical fiber ribbon and to mount the optical fibers within the unit. Furthermore, water that enters the optical fiber unit is likely to run along the longitudinal direction by flowing down this recess. However, the thickness of each water-absorbing member of the present disclosure is smaller than the center-to-center distance between two adjacent optical fibers in the parallel direction of the optical fibers. Because the water-absorbing member is sized to easily enter the recess, water running within the unit can be suppressed.

[0019] (Effects of the Present Disclosure) According to the present disclosure, it is possible to provide an optical fiber cable and an optical fiber unit with higher waterproofing properties.

[0020] (Details of an embodiment of the present disclosure) Specific examples of an optical fiber cable according to an embodiment of the present disclosure will be described with reference to the drawings. Note that the present disclosure is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope of the claims.

[0021] First Embodiment With reference to FIG. 1, the configuration of an optical fiber cable 1 according to a first embodiment will be described.

[0022] Fig. 1 is a cross-sectional view perpendicular to the longitudinal direction of an optical fiber cable 1 according to a first embodiment. As illustrated in Fig. 1, the optical fiber cable 1 includes a plurality of optical fiber ribbons 21 formed of a plurality of coated optical fibers 2, a plurality of water-absorbent members 3, and an outer jacket 4. The optical fiber cable 1 of this embodiment is a slotless optical fiber cable. The plurality of coated optical fibers 2 and the plurality of water-absorbent members 3 are arranged in a storage space S inside the outer jacket 4. The outer diameter of the optical fiber cable 1 is, for example, 10 mm.

[0023] The optical fiber cores 2 form an optical fiber ribbon 21. In this embodiment, the storage section S of the optical fiber cable 1 stores 288 optical fiber ribbons 21, each formed of, for example, 12 optical fiber cores 2. Note that a plurality of optical fiber ribbons 21 may be twisted together to form an assembly, and a plurality of assemblies may be further twisted together. In this case, a bundling material may be wrapped around the assembly of optical fiber ribbons 21. The plurality of optical fiber ribbons 21 may be stored in the storage section S of the optical fiber cable 1 in a stacked state.

[0024] FIG. 2 is a partial development view showing an optical fiber ribbon 21 used in the optical fiber cable 1 in the longitudinal direction. As illustrated in FIG. 2 , the optical fiber ribbon 21 has a configuration in which multiple optical fibers 2 are arranged in parallel in a direction perpendicular to the longitudinal direction, and some adjacent optical fibers 2 are connected to form connection sections 211. The connection sections 211 are formed intermittently along the optical fibers 2, and connection sections 211 and non-connection sections 212 are formed alternately along the optical fibers 2. In other words, the optical fiber ribbon 21 is an intermittently connected optical fiber ribbon in which, among some or all of the multiple optical fibers 2, connection sections 211 where adjacent optical fibers 2 are connected and non-connection sections 212 where adjacent optical fibers 2 are not connected are alternately provided in the longitudinal direction. The optical fiber 2 is composed of, for example, a glass fiber consisting of a core and a cladding, and one or more coating layers surrounding the glass fiber. The optical fiber 2 has, for example, an outer diameter of 180 μm or more and 250 μm or less.

[0025] Returning to FIG. 1 , the description of the configuration of the optical fiber cable 1 will continue. The water-absorbent member 3 is formed by assembling a plurality of water-absorbent fibers. The water-absorbent fibers are, for example, polyester fibers. For example, polyester fibers having a water absorption rate of 30 g / min or less for tap water are used. The water absorption rate indicates the amount of water that can be absorbed per minute. The diameter of the water-absorbent fibers in this embodiment is 5 μm or more and 50 μm or less. The water-absorbent member 3 is twisted with one or more optical fiber ribbons 21.

[0026] The jacket 4 covers the plurality of optical fiber ribbons 21 and the plurality of water-absorbing members 3. The jacket 4 is formed of a hard resin with a relatively high Young's modulus, such as high-density polyethylene. A plurality of tension members 5 and a plurality of tear cords 6 may be embedded in the jacket 4. The tension members 5 may be formed of, for example, fiber-reinforced plastic (FRP) such as aramid FRP, glass FRP, or carbon FRP, or metal wire.

[0027] The optical fiber cable 1 of this embodiment may include a pressing member 7 disposed between the jacket 4 and the plurality of optical fiber ribbons 21 and the plurality of water-absorbent members 3. The pressing member 7 covers the periphery of the plurality of optical fiber ribbons 21 and the plurality of water-absorbent members 3. The pressing member 7 is formed, for example, from a nonwoven fabric made of polyester or the like. The pressing member 7 may have water-absorbent properties. If the pressing member 7 has water-absorbent properties, the pressing member 7 is formed, for example, by adhering water-absorbent powder to a base fabric made of polyester or the like. The pressing member 7 may be wound longitudinally or spirally around the periphery of the plurality of optical fiber ribbons 21. Note that "wound longitudinally" means that the pressing member 7 is wound around the optical fiber ribbons 21 so that the longitudinal direction of the pressing member 7 is parallel to the longitudinal direction of the optical fiber cable 1 and the width direction of the pressing member 7 is aligned with the circumferential direction of the optical fiber cable 1.

[0028] 3 is a partially enlarged cross-sectional view perpendicular to the longitudinal direction of some of the optical fiber core wires 2 among the plurality of optical fiber core wires 2 that form the optical fiber ribbon 21. As illustrated in FIG. 3, the optical fiber ribbon 21 includes a plurality of optical fiber core wires 2 and a connecting resin 22.

[0029] The connecting resin 22 is configured to connect the plurality of optical fiber cores 2 arranged in parallel in a direction perpendicular to the longitudinal direction of the plurality of optical fiber cores 2. The connecting resin 22 coats the outer peripheries of the plurality of optical fiber cores 2. The connecting resin 22 is, for example, an ultraviolet curing resin. The connecting resin 22 may also be a thermoplastic resin, an adhesive resin, or another coating resin.

[0030] The recess 23 is formed in the connecting resin 22 between two adjacent optical fiber cores 2, and is a depression when the position of the top of the optical fiber core 2 is used as a reference. As shown in Fig. 3, the recess 23 is formed in the connecting resin 22 that covers the optical fiber core 2. The recess 23 extends along the longitudinal direction of the optical fiber core 2.

[0031] When the outer diameter of the optical fiber 2 is 250 μm, the center-to-center distance D between two adjacent optical fiber cores 2 in the parallel arrangement direction of the optical fiber cores 2 is, for example, 244 μm or more and 256 μm or less, including tolerances. The smaller the outer diameter of the optical fiber cores 2, the shorter the center-to-center distance D. Note that, although the multiple optical fiber cores 2 illustrated in FIG. 3 are arranged in parallel so as to be in contact with each other, the connecting resin 22 may penetrate between the two adjacent optical fiber cores 2 so that the two optical fiber cores 2 do not contact each other, or the centers of the optical fiber cores 2 may be arranged slightly off-center from the parallel arrangement direction. When the connecting resin 22 is applied to fill the depressions formed between the two adjacent optical fiber cores 2, the depth of the recesses 23 may be shallow. The depth of the recesses 23 is, for example, 20 μm or more and 70 μm or less. The thickness (diameter) of the water-absorbent member 3 in this embodiment is smaller than the center-to-center distance D.

[0032] As described above, the optical fiber cable 1 of this embodiment includes multiple optical fiber ribbons 21, allowing the optical fiber cores 2 to be mounted in the housing section S of the optical fiber cable 1. Furthermore, the optical fiber ribbon 21 has at least one recess 23 in the connecting resin 22, making it easy to separate some of the optical fiber cores 2 from the optical fiber ribbon 21 and handle them easily. Water that enters the housing section S of the optical fiber cable 1 is likely to run long distances by flowing down the recess 23 extending in the longitudinal direction of the optical fiber cores 2. However, the optical fiber cable 1 of this embodiment also includes multiple water-absorbing members 3, each of which has a thickness (diameter) smaller than the center-to-center distance D between two adjacent optical fiber cores 2 in the parallel direction of the optical fiber cores 2. Because the size of the water-absorbing members 3 allows them to easily enter the recess 23, water running within the housing section S can be suppressed.

[0033] Because the optical fiber ribbon 21 of this embodiment is an intermittently connected optical fiber ribbon, it can be packed more densely in the housing section S of the optical fiber cable 1. Note that water that has entered the housing section S of the optical fiber cable 1A is likely to run long distances by traveling along the connecting portions 211 of the intermittently connected optical fiber ribbon. In addition, the infiltrating water is likely to pass between two adjacent optical fibers 2 in the non-connecting portions 212 and run downward in an unintended direction or due to gravity. However, because the water-absorbing member 3 of this embodiment is sized to easily enter the recess 23, water running in the housing section S can be suppressed even if the optical fiber ribbon 21 is an intermittently connected optical fiber ribbon.

[0034] The water-absorbing member 3 in this embodiment is twisted with one or more optical fiber ribbons 21. Therefore, compared to when the water-absorbing member 3 is not twisted with the optical fiber ribbons 21, the water-absorbing member 3 is distributed evenly in the circumferential direction, and the waterproofness of the optical fiber cable 1 in the circumferential direction can be improved.

[0035] The water-absorbent member 3 of this embodiment is formed by assembling a plurality of water-absorbent fibers, the thickness (diameter) of which is 5 μm or more and 50 μm or less, and the thickness of the water-absorbent member 3 formed by assembling the water-absorbent fibers is smaller than the center-to-center distance D between two adjacent optical fiber cores 2. Because the thickness (diameter) of the water-absorbent member 3 is smaller than the center-to-center distance D, the water-absorbent fibers of the water-absorbent member 3 can easily enter the recesses 23 of the optical fiber ribbon 21, thereby improving the waterproofness of the optical fiber cable 1.

[0036] Although the water-absorbent member 3 in the first embodiment is formed by assembling a plurality of water-absorbent fibers, the form of the water-absorbent member 3 is not limited to this. Fig. 4 is a cross-sectional view perpendicular to the longitudinal direction of the optical fiber cable 1A. The optical fiber cable 1A is a modified example of the optical fiber cable 1 according to the first embodiment. In the configuration shown in Fig. 4, the same components as those shown in Figs. 1 to 3 are designated by the same reference numerals, and their description will be omitted.

[0037] As illustrated in FIG. 4 , the optical fiber cable 1A includes a plurality of optical fiber ribbons 21, a plurality of water-absorbing members 3A, and an outer jacket 4. The water-absorbing members 3A extend in the longitudinal direction of the optical fiber cable 1A. The water-absorbing members 3A are tape-shaped. In the cross section of the water-absorbing member 3A, the thickness of the tape is 250 μm or less, and the width of the tape is 300 μm or more and 2500 μm or less. Here, the thickness of the tape is the sum of the dimensions of the base fabric material (nonwoven fabric tape, PET tape, etc.) and the dimensions of the water-absorbing material (water-absorbent polymer, etc.) provided on the base fabric material. The width of the tape is the length of the tape in the longitudinal direction of the optical fiber cable 1A and in a direction perpendicular to the thickness of the tape.

[0038] The water-absorbing member 3A has a tape shape and a thickness of 250 μm or less, so that the corners of the water-absorbing member 3A can easily fit into the recesses 23 between adjacent optical fibers 2. This improves the waterproofing of the optical fiber cable 1A. Furthermore, compared to the water-absorbing member 3 having a shape formed by assembling a plurality of water-absorbing fibers, the water-absorbing member 3A having a tape shape does not require high processing precision, and therefore manufacturing costs can be reduced.

[0039] The optical fiber cable 1 or 1A may include a plurality of optical fiber units, each of which includes one or a plurality of optical fiber ribbons 21 and a unit coating portion that coats the optical fiber ribbons 21. The water-absorbing member 3 or 3A may be twisted with one or a plurality of optical fiber units.

[0040] With this configuration, the waterproofing in the circumferential direction of the cable can be improved compared to when the water-absorbing member 3 or the water-absorbing member 3A is not twisted with the optical fiber unit.

[0041] Second Embodiment In the above embodiment, the optical fiber cable 1 or the optical fiber cable 1A is described, but the configuration of this embodiment can be applied to cables other than the optical fiber cable 1 or the optical fiber cable 1A. Fig. 5 is a cross-sectional view perpendicular to the longitudinal direction of the optical fiber unit 11 according to the second embodiment. In the configuration shown in Fig. 5, the same components as those shown in Figs. 1 to 4 are designated by the same reference numerals, and their description will be omitted.

[0042] 5, the optical fiber unit 11 includes a plurality of optical fiber ribbons 121 formed of a plurality of optical fiber cores 12, a plurality of water-absorbing members 13, and a unit sheath 14. The plurality of optical fiber cores 12 and the plurality of water-absorbing members 13 are arranged in a storage section S10 inside the unit sheath 14. The outer diameter of the optical fiber unit 11 is, for example, 3 mm.

[0043] The optical fiber core wires 12 form an optical fiber ribbon 121. A plurality of optical fiber ribbons 121 are bundled together by being twisted together. In this example, in the optical fiber unit 11, three optical fiber ribbons 121 formed by twelve optical fiber core wires 12 are twisted together.

[0044] The optical fiber ribbon 121 is configured in the same manner as the optical fiber ribbon 21 in Fig. 2. That is, the optical fiber ribbon 121 is an intermittently connected optical fiber ribbon in which, in some or all of the multiple optical fiber cores 12, connected portions 211 where adjacent optical fiber cores 12 are connected and non-connected portions 212 where adjacent optical fiber cores 12 are not connected are alternately provided in the longitudinal direction. The optical fiber cores 12 are configured, for example, with a glass fiber consisting of a core and a cladding and one or more coating layers covering the glass fiber. The optical fiber cores 12 have, for example, an outer diameter of 180 µm or more and 250 µm or less.

[0045] The water-absorbing member 13 is formed by assembling a plurality of water-absorbing fibers, similar to the water-absorbing member 3 described above. The water-absorbing fibers are, for example, polyester. For example, polyester fibers having a water absorption rate of 30 g / min or less for tap water are used. The diameter of the water-absorbing fibers in this embodiment is 5 μm or more and 50 μm or less. The water-absorbing member 3 is twisted with one or more optical fiber ribbons 21.

[0046] The unit covering portion 14 covers the peripheries of the plurality of optical fiber ribbons 121 and the plurality of water-absorbent members 13. The unit covering portion 14 can be formed of, for example, a hard resin with a relatively high Young's modulus, such as high-density polyethylene. For example, when a tear string (not shown) is embedded in the unit covering portion 14, the unit covering portion 14 may be made of a material with low strength and low elongation so that it can be torn by the tear string.

[0047] As described above, the optical fiber unit 11 of this embodiment includes an optical fiber ribbon 121, and optical fibers 12 can be mounted in the storage section S10 of the optical fiber unit 11. Furthermore, like the optical fiber ribbon 21 of the first embodiment, the optical fiber ribbon 121 has at least one recess 23 in the connecting resin 22, making it easy to separate some of the optical fibers 12 from the optical fiber ribbon 121 and handle them easily. Water that enters the storage section S10 of the optical fiber unit 11 tends to run along the longitudinal direction by flowing down the recess 23. However, the thickness of each water-absorbent member 13 of this embodiment is smaller than the center-to-center distance D between two adjacent optical fibers 12 in the parallel direction of the optical fibers 12. Because the water-absorbent member 13 is sized to easily fit into the recess 23, water running within the storage section S10 can be suppressed.

[0048] The optical fiber unit 11 may be mounted in the housing S of the optical fiber cable 1 or the optical fiber cable 1A. The water-absorbing member 3 or the water-absorbing member 3A may be twisted with one or more optical fiber units 11. The optical fiber unit 11 may include one optical fiber ribbon 121 instead of multiple optical fiber units.

[0049] Although the present disclosure has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present disclosure. Furthermore, the number, position, shape, etc. of the components described above are not limited to the above embodiments, and can be changed to the number, position, shape, etc. that are suitable for implementing the present disclosure.

[0050] The number of coated optical fibers 2 forming the optical fiber ribbon 21 and the number of coated optical fibers 12 forming the optical fiber ribbon 121 can be changed as appropriate.

[0051] (Evaluation Experiment) For the optical fiber cable 1 according to the first embodiment, multiple samples No. 4 to No. 6 were prepared, each having a different diameter (thickness) of the water-absorbent member 3. The diameter of the water-absorbent member for Sample No. 4 was 5 μm or more and 16 μm or less. The diameter of the water-absorbent member for Sample No. 4 was also the diameter of the water-absorbent fiber. The diameter of the water-absorbent member for Sample No. 5 was 190 μm or more and 200 μm or less. The diameter of the water-absorbent member for Sample No. 6 was 500 μm or more and 550 μm or less. The water-absorbent members for Sample No. 5 and Sample No. 6 were each made of an aggregate of water-absorbent fibers with a diameter of 5 μm or more and 16 μm or less. Furthermore, for the optical fiber cable 1A according to the modified example, multiple samples No. 2, No. 3, and No. 7 were prepared, each having a different tape width for the water-absorbent member 3A. Sample No. The thickness of the water-absorbent member 3A of sample No. 2 was 250 μm and the width was 300 μm. The thickness of the water-absorbent member 3A of sample No. 3 was 250 μm and the width was 1000 μm. The thickness of the water-absorbent member 3A of sample No. 7 was 300 μm and the width was 3000 μm. As a comparative example, sample No. 1, an optical fiber cable without a water-absorbent member 3 or a water-absorbent member 3A, was also prepared. The outer diameter of the optical fiber 2 was 250 μm, and the center-to-center distance D between two adjacent optical fiber 2 in the optical fiber ribbon 21 was 250 μm.

[0052] Fig. 6 is a schematic diagram illustrating an evaluation experiment of watertightness. As illustrated in Fig. 6, the hose X has a cylindrical portion X1 extending vertically and a cylindrical portion X2 extending horizontally. The diameter of the hose X is larger than the diameters of the optical fiber cables 1 and 1A. A waterproof seal X3 is provided at the end of the cylindrical portion X2, which holds the cables and seals the hose X to prevent leakage of water stored in the hose X. Because this waterproof seal X3 is provided, the hose X is configured to be able to store liquids such as water or artificial seawater inside the cylindrical portions X1 and X2.

[0053] In the evaluation experiment, a sample optical fiber cable was first held at the end of the cylindrical portion X2, and tap water or artificial seawater was stored inside the hose X. At this time, the height H between the center point of the held optical fiber cable and the water surface of the cylindrical portion X1 was 1 m. Each sample was left at room temperature with tap water or artificial seawater stored inside the hose X for 24 hours. After that, the optical fiber cable was removed from the end of the cylindrical portion X2, and the length of the cable that was submerged in tap water or artificial seawater was measured in the longitudinal direction. If the submerged length was less than 3 m, the watertightness was deemed good and rated A. Conversely, if the submerged length was 3 m or more, the watertightness was deemed poor and rated B. The measurement results are shown in Table 1.

[0054]

[0055] As shown in Table 1, in Sample No. 1, which had no water-absorbent member at all, the length to which water was submerged was 9 m in the case of tap water and 15 m in the case of artificial seawater, and the water-stopping ability was evaluated as B.

[0056] In sample No. 6, which had a relatively thick water-absorbent member with a diameter of 500 μm or more and 550 μm or less, the length of water penetration was 3.5 m for tap water and 6 m for artificial seawater, and the water-stopping ability was evaluated as B. On the other hand, in sample No. 4, which had a water-absorbent member with a diameter of 5 μm or more and 16 μm or less, and sample No. 5, which had a water-absorbent member with a diameter of 190 μm or more and 200 μm or less, the length of water penetration was less than 3 m, and they were evaluated as A, confirming high water-stopping ability.

[0057] In sample No. 7, which had a relatively thick and wide tape-shaped water-absorbent member with a tape thickness of 300 μm and a tape width of 3,000 μm, the length of water penetration was 4.6 m for tap water and 8 m for artificial seawater, and the water-stopping ability was evaluated as B. On the other hand, sample No. 2, which had a tape-shaped water-absorbent member with a tape thickness of 250 μm and a tape width of 300 μm, and sample No. 3, which had a tape-shaped water-absorbent member with a tape thickness of 250 μm and a tape width of 1,000 μm, both had a water-submerged length of less than 3 m, and were evaluated as A, confirming high water-stopping ability.

[0058] According to the evaluation experiment in Table 1, samples No. 2 to No. 5 had good water stoppage properties. This shows that optical fiber cables equipped with a water-absorbing member having a diameter of 5 μm or more and 200 μm or less, or a tape-shaped water-absorbing member having a thickness of 250 μm and a width of 300 μm or more and 1000 μm or less, have good water stoppage properties.

[0059] DESCRIPTION OF SYMBOLS 1, 1A: Optical fiber cable 2: Optical fiber core 3, 3A: Water-absorbing member 4: Jacket 5: Tension member 6: Tear string 7: Pressing member 11: Optical fiber unit 12: Optical fiber core 13: Water-absorbing member 14: Unit coating portion 21: Optical fiber ribbon 22: Connecting resin 23: Recess 121: Optical fiber ribbon 211: Connecting portion 212: Non-connecting portion S, S10: Storage portion

Claims

1. a plurality of optical fiber ribbons; A plurality of water-absorbent members; an outer jacket that covers the plurality of optical fiber ribbons and the plurality of water-absorbing members; Each of the optical fiber ribbons is A plurality of optical fiber cores; a connecting resin that connects the plurality of optical fiber cores arranged in parallel in a direction perpendicular to the longitudinal direction of the plurality of optical fiber cores, the connecting resin has at least one recess between adjacent optical fibers, An optical fiber cable, wherein the thickness of each of the water-absorbing members is smaller than the center-to-center distance between two adjacent optical fibers in the parallel arrangement direction of the optical fibers.

2. The optical fiber cable of claim 1, wherein the optical fiber ribbon is an intermittently connected optical fiber ribbon in which, among some or all of the plurality of optical fiber cores, connected sections in which adjacent optical fiber cores are connected and non-connected sections in which adjacent optical fiber cores are not connected are alternately arranged in the longitudinal direction.

3. 3. The optical fiber cable according to claim 1, wherein each of the water-absorbent members is twisted with one or more of the optical fiber ribbons.

4. Each of the water-absorbent members is formed by assembling a plurality of water-absorbent fibers, 3. The optical fiber cable according to claim 1, wherein the diameter of the water-absorbent fiber is 5 μm or more and 50 μm or less.

5. Each of the water-absorbent members has a tape shape, 3. The optical fiber cable according to claim 1, wherein the thickness of the tape-shaped tape is 250 μm or less and the width of the tape-shaped tape is 300 μm or more and 2500 μm or less in a cross section of the water-absorbing member.

6. a plurality of optical fiber units each including one or more of the optical fiber ribbons and a unit coating portion that coats the optical fiber ribbon; 3. The optical fiber cable according to claim 1, wherein each of the water-absorbent members is twisted with one or more of the optical fiber units.

7. one or more optical fiber ribbons; A plurality of water-absorbent members; a unit covering portion that covers the periphery of one or more of the optical fiber ribbons and the plurality of water-absorbing members, Each of the optical fiber ribbons is A plurality of optical fiber cores; a connecting resin that connects the plurality of optical fiber cores arranged in parallel in a direction perpendicular to the longitudinal direction of the plurality of optical fiber cores, the connecting resin has at least one recess between adjacent optical fibers, An optical fiber unit, wherein the thickness of each of the water-absorbing members is smaller than the center-to-center distance between two adjacent optical fibers in the parallel arrangement direction of the optical fibers.