fiber optic cable

Abstract

An optical fiber cable (10A) comprises: an outer sheath (11) including an inner peripheral surface (11a) that forms a housing space (14); a coated optical fiber (12) housed in the housing space (14); and a plurality of tension members (13) provided in the outer sheath (11). Part of an outer peripheral surface (13a) of at least one of the plurality of tension members (13) is in contact with the inner peripheral surface (11a) of the outer sheath (11) from inside the outer sheath (11) or is exposed to the housing space (14) from the inner peripheral surface (11a).

Description

[Technical Field]

[0001] The present invention relates to optical fiber cables. [Background technology]

[0002] Optical fiber cables are widely used in the construction of optical communication networks. Patent Document 1 discloses an optical fiber cable in which optical fiber cores are bundled at high density. A strength member is provided in the outer jacket of the optical fiber cable to prevent breakage of the optical fiber cores due to excessive bending and to suppress an increase in transmission loss. Note that, as shown in Patent Document 2, multiple strength members may be used in some cases. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4774337 [Patent Document 2] Patent No. 6182091 Summary of the Invention [Problem to be solved by the invention]

[0004] When removing the optical fiber contained in the optical fiber cable, it is necessary to remove the jacket to expose the optical fiber. To make it easier to cut open the jacket during this process, the jacket is provided with a rip cord.

[0005] Unlike strength members, rip cords do not have strength that contributes to the mechanical strength of the optical fiber cable, and therefore, portions of the jacket where rip cords are provided are more vulnerable to external forces than portions where no rip cords are provided.

[0006] The present invention has been made in view of the above circumstances, and has as its object to provide an optical fiber cable that is easy to remove and in which weak spots against external forces are unlikely to occur in the sheath. [Means for solving the problem]

[0007] An optical fiber cable according to one embodiment of the present invention comprises an outer sheath including an inner surface that forms a storage space, an optical fiber core housed in the storage space, and a plurality of strength members provided in the outer sheath, wherein a portion of the outer surface of at least one of the plurality of strength members is in contact with the inner surface of the outer sheath from inside the outer sheath, or is exposed to the storage space from the inner surface. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide an optical fiber cable that is easy to remove and in which the sheath is less likely to have weak spots against external forces. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional view of an optical fiber cable according to a first embodiment. [Figure 2A] FIG. 2A is a perspective view of a first example in which a cross section of a part of the jacket and a tension member according to each embodiment is enlarged. [Figure 2B] FIG. 2B is a perspective view of a second example in which a cross section of a part of the jacket and the tension member according to each embodiment is enlarged. [Figure 3] FIG. 3 is a cross-sectional view of an optical fiber cable according to a modified example of the first embodiment. [Figure 4] FIG. 4 is a cross-sectional view of the optical fiber cable according to the second embodiment. [Figure 5] FIG. 5 is a cross-sectional view of the optical fiber cable according to the third embodiment. [Figure 6] FIG. 6 is a cross-sectional view of the optical fiber cable according to the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, optical fiber cables according to several embodiments of the present invention will be described. Note that common parts in the drawings are designated by the same reference numerals, and redundant explanations will be omitted. The following embodiments can be combined.

[0011] [First embodiment] First, the first embodiment will be described. FIG. 1 is a cross-sectional view of an optical fiber cable 10A according to this embodiment. FIG. 2A is a perspective view of a first example in which the cross sections of the jacket 11 and the tension member 13 according to this embodiment are enlarged. FIG. 2B is a perspective view of a second example. Note that FIGS. 2A and 2B also apply to other embodiments described later. FIG. 3 is a cross-sectional view of an optical fiber cable 10A according to a modified example of this embodiment.

[0012] As shown in Fig. 1, an optical fiber cable 10A includes a jacket 11, one or more optical fibers 12, and multiple tensile members 13. The jacket 11 is a tubular member formed from synthetic resin and extending in one direction. The jacket 11 includes an inner circumferential surface 11a that forms a storage space 14 for the optical fiber 12, and an outer circumferential surface 11b that forms the outer shape of the jacket 11. The jacket 11 stores the optical fiber 12 in the storage space 14 and protects the optical fiber 12. The jacket 11 is made of a polyolefin-based synthetic resin, such as polyethylene.

[0013] The type and number of the optical fiber 12 are arbitrary. For example, the optical fiber 12 may be a single-core optical fiber or a multi-core ribbon optical fiber. Furthermore, multiple optical fiber 12 may be bundled together with a holding tape or the like.

[0014] The tension members 13 are provided in the jacket 11. The tension members 13 bear the tension applied to the optical fiber cable 10A and prevent damage to the optical fiber cable 10A and, in turn, to the optical fiber core 12. The material of the tension members 13 is, for example, fiber-reinforced plastic (FRP) made of aramid fiber or glass fiber, or steel wire. However, the material of the tension members 13 is not limited to the above, as long as the desired performance is obtained.

[0015] As shown in Fig. 1, the multiple strength members 13 are arranged in pairs, for example, symmetrically positioned with respect to the central axis Z of the jacket 11. In the example shown in Fig. 1, two strength members 13A form one pair, and two strength members 13B form another pair. A plane 21A including the strength members 13A and a plane 21B including the strength members 13B intersect with each other at a predetermined angle (e.g., 90°). In other words, the multiple strength members 13 are arranged in positions that are symmetrical with respect to the central axis Z or a plane including the central axis Z.

[0016] In this embodiment, a portion of the outer peripheral surface 13a of at least one of the multiple strength members 13 contacts the inner peripheral surface 11a of the outer sheath 11 from inside the outer sheath 11 (see FIG. 2A), or is exposed from the inner peripheral surface 11a to the accommodation space 14 (see FIG. 2B). In the example shown in FIG. 1, all of the strength members 13 constituting a pair contact the inner peripheral surface 11a of the outer sheath 11 from inside the outer sheath 11, or are exposed from the inner peripheral surface 11a to the accommodation space 14.

[0017] As shown in Fig. 2A, the minimum gap between the outer peripheral surface 13a of the strength member 13 and the inner peripheral surface 11a of the jacket 11 is extremely narrow, for example, about 0 to 0.1 mm, but preferably about 0 to 0.01 mm, which makes it easier to tear. Alternatively, as shown in Fig. 2B, when the outer peripheral surface 13a of the strength member 13 is exposed to the accommodation space 14, a slit 15 is formed in the inner peripheral surface 11a of the jacket 11. The width of the slit 15 is at most about one-fourth the diameter of the strength member 13. In either case, the strength member 13 is strongly adhered to the jacket 11 so that it will not come off when the optical fiber cable 10A is deformed, such as by bending.

[0018] The optical fiber cable 10A according to this embodiment does not have a rip cord. Therefore, when removing the optical fiber 12 from the optical fiber cable 10A, the jacket 11 is scraped with a tool such as a blade, exposing the strength members 13 at the scraped portion. The exposed strength members 13 are then peeled away from the jacket 11, causing the jacket 11 to split in the longitudinal direction. As a result, the optical fiber 12 can be removed from the split portion of the jacket 11.

[0019] In the optical fiber cable 10A according to this embodiment, no rip cord is provided in the jacket 11. Therefore, the jacket 11 is less likely to have any weak points against external forces.

[0020] When the strength members 13 are provided in pairs symmetrically positioned with respect to the central axis Z of the outer jacket 11, the distance between each pair of the strength members 13 and the central axis Z may be different. That is, the spacing between each pair of the strength members 13, 13 provided symmetrically with respect to the central axis Z may be different. For example, as shown in FIG. 3 , the outer peripheral surface 13a of each of the strength members 13A, 13A may be in contact with the inner peripheral surface 11a of the outer jacket 11 or may be exposed from the inner peripheral surface 11a to the accommodation space 14, while the entire strength members 13B, 13B may be provided inside the outer jacket 11.

[0021] In this case, the strength members 13B, 13B are located farther away from the central axis Z than the strength members 13A, 13A. In other words, in a cross section perpendicular to the central axis Z, the distance between the two strength members 13B, 13B is greater than the distance between the two strength members 13A, 13A. This difference in position results in a difference in bending rigidity between the plane 21A including the strength members 13A, 13A and the plane 21B including the strength members 13B, 13B. Using this difference in bending rigidity, an operator or the like can identify the position of the strength member 13 that is in contact with the inner circumferential surface 11a of the outer jacket 11 from inside the outer jacket 11 or that is exposed from the inner circumferential surface 11a to the accommodation space 14.

[0022] [Second embodiment] Next, a second embodiment will be described. 4 is a cross-sectional view of an optical fiber cable 10B according to this embodiment. As shown in this figure, in the optical fiber cable 10B according to this embodiment, a plurality of rip cords 16 are provided in the jacket 11 so as to contact each of a plurality of tensile members 13. The other configurations are the same as those in the first embodiment, and therefore description thereof will be omitted.

[0023] The rip cord 16 is a string-like member made of a synthetic resin such as nylon (registered trademark) or polyester. The rip cord 16 can be exposed by scraping away the jacket 11 with a tool such as a blade. The exposed rip cord 16 is pulled out to expose the strength members 13. The exposed strength members 13 can be easily peeled off from the jacket 11. As a result, the jacket 11 is torn in the longitudinal direction, and the optical fiber 12 can be taken out from the torn portion.

[0024] In this embodiment, the rip cord 16 is provided on the jacket 11 in a state where it is in contact with the strength members 13. In other words, the rip cord 16 is interposed between the jacket 11 and the strength members 13. Therefore, the adhesive force between the jacket 11 and the strength members 13 is reduced. Even if the strength members 13 are made of a material that is prone to fraying, such as fiber-reinforced plastic, fraying or unexpected breakage of the strength members 13 can be suppressed when pulling out the strength members 13, making it possible to extract the optical fiber 12. Furthermore, because the rip cord 16 is close to the strength members 13, the jacket 11 is less likely to have any weak spots against external forces.

[0025] [Third embodiment] Next, a third embodiment will be described. 5 is a cross-sectional view of an optical fiber cable 10C according to this embodiment. In the optical fiber cable 10C according to this embodiment, the strength members 13 all have the same outer diameter, but the strength members 13 are arranged in pairs symmetrically positioned with respect to the central axis Z of the jacket 11, and the strength members 13 are made of different materials for each pair. The rest of the configuration is the same as that of the first embodiment, and therefore a description thereof will be omitted.

[0026] 5, the multiple strength members 13 are divided into a pair of strength members 13A, 13A and another pair of strength members 13B, 13B. The strength members 13A, 13A are positioned symmetrically with respect to the central axis Z, and the strength members 13B, 13B are also positioned symmetrically with respect to the central axis Z. A plane 21A including the strength members 13A, 13A and a plane 21B including the strength members 13B, 13B intersect at a predetermined angle (e.g., 90°) as in the other embodiments.

[0027] In this embodiment, the material of the strength members 13A and the material of the strength members 13B are different. Therefore, a difference occurs in the bending rigidity between the two. As a result, a difference occurs in the bending rigidity between the plane 21A including the strength members 13A and the plane 21B including the strength members 13B. Using this difference in bending rigidity, an operator or the like can identify the position of the strength members 13 that are in contact with the inner circumferential surface 11a of the outer sheath 11 from inside the outer sheath 11 or that are exposed from the inner circumferential surface 11a to the accommodation space 14.

[0028] In this embodiment, no rip cord is provided on the outer sheath 11. Therefore, the outer sheath 11 is less likely to have any areas that are vulnerable to external forces.

[0029] [Fourth embodiment] Next, a fourth embodiment will be described. 6 is a cross-sectional view of an optical fiber cable 10D according to this embodiment. As shown in this figure, in the optical fiber cable 10D according to this embodiment, the multiple strength members 13 are all formed of the same material, but the multiple strength members 13 are provided in multiple pairs symmetrically positioned with respect to the central axis Z of the jacket 11, and the multiple strength members 13 have different outer diameters for each pair. The rest of the configuration is the same as that of the first embodiment, so a description thereof will be omitted.

[0030] 6, the multiple strength members 13 are divided into a pair of strength members 13A, 13A and another pair of strength members 13B, 13B. The strength members 13A, 13A are positioned symmetrically with respect to the central axis Z, and the strength members 13B, 13B are also positioned symmetrically with respect to the central axis Z. A plane 21A including the strength members 13A, 13A and a plane 21B including the strength members 13B, 13B intersect at a predetermined angle (e.g., 90°) as in the other embodiments.

[0031] In this embodiment, the outer diameter of the strength members 13A and the outer diameter of the strength members 13B are different. This causes a difference in bending rigidity between the two. As a result, a difference occurs between the bending rigidity of the plane 21A including the strength members 13A and 13A and the bending rigidity of the plane 21B including the strength members 13B and 13B. Using this difference in bending rigidity, an operator or the like can identify the position of the strength members 13 that are in contact with the inner circumferential surface 11a of the outer sheath 11 from inside the outer sheath 11 or that are exposed from the inner circumferential surface 11a to the accommodation space 14.

[0032] As in the first and third embodiments, in this embodiment, no rip cord is provided in the outer sheath 11. Therefore, the outer sheath 11 is less likely to have any weak spots against external forces.

[0033] Furthermore, in any of the embodiments, the jacket 11 can be torn by cutting the jacket 11 to expose the strength members 13 and then pulling out the exposed strength members 13. Furthermore, in the embodiment in which the difference in bending rigidity can be confirmed, the position of the strength members 13 can be identified by bending the optical fiber cable in multiple directions. Therefore, there is no need to intentionally provide protrusions or other undulations on the outer surface 11b of the jacket 11 to indicate the position to be cut. This improves the ease of handling of the optical fiber cable during installation work, etc. [Explanation of symbols]

[0034] 10A fiber optic cable 10B fiber optic cable 10C fiber optic cable 10D fiber optic cable 11 Outer cover 11a Inner surface 11b Outer surface 12 Optical fiber core 13 Tensile strength body 13a Outer surface 13A tensile strength body 13B Tensile strength body 14 Containment Space 15 Slit 16 Ripper 21A plane 21B plane Z center axis

Claims

1. an outer cover including an inner circumferential surface that forms an accommodation space; an optical fiber core housed in the housing space; a plurality of strength members provided in the outer jacket as a first pair and a second pair that are symmetrically positioned with respect to the central axis of the outer jacket and that intersect with each other, the strength members having the same outer diameter and made of the same material; Equipped with a portion of an outer peripheral surface of the plurality of strength members forming the first pair is in contact with the inner peripheral surface of the outer sheath from inside the outer sheath, or is exposed from the inner peripheral surface to the accommodation space, the second pair of strength members are entirely provided within the interior of the outer jacket; The plurality of strength members forming the first pair and the plurality of strength members forming the second pair are arranged so that there is a difference in bending rigidity between the respective planes including the plurality of strength members. Fiber optic cable.

2. a rip cord provided on the outer sheath and in contact with each of the plurality of tension members; Further provided with 2. The optical fiber cable according to claim 1.

3. The materials of the plurality of tensile members are different for each pair.

3. The optical fiber cable according to claim 1 or 2.

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