Optical Cable

Abstract

The present invention provides an optical cable. The optical cable (1) comprises: a cable body (10) having an optical fiber (14), a cylindrical outer sheath (40) accommodating the cable body (10), a protective layer (30) arranged between the cable body (10) and the outer sheath (40), and tear cords (20A, 20B) arranged between the cable body (10) and the protective layer (30), wherein the protective layer (30) has a groove (36) extending along the axial direction of the cable body 10 on its inner surface (302a), and the tear cords (20A, 20B) are arranged in the groove (36).

Description

Technical Field

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

[0002] Regarding designated countries that authorize citation of references, the contents described in Japanese Patent Application No. 2020-085734 filed in Japan on May 15, 2020 are incorporated into this specification by reference and made a part of the description of this specification. Background Art

[0003] The optical cable includes a cable body, a cylindrical outer sheath for accommodating the cable body, a metal reinforcement sheet disposed between the cable body and the outer sheath, and a tear cord disposed between the reinforcement sheet and the cable body (for example, see Patent Document 1). In the operation of removing the cable body from such an optical cable, the reinforcement sheet and the outer sheath are torn apart by the tear cord, thereby removing the cable body.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2017-72801

[0005] However, in the above-mentioned optical fiber cable, a gap is generated between the cable body and the reinforcing sheet. Therefore, when the outer sheath is torn by the tear cord, the tear cord often moves in the circumferential direction, which causes a problem that workability is deteriorated. Summary of the invention

[0006] An object of the present invention is to provide an optical fiber cable capable of improving workability by suppressing the movement of a tear cord.

[0007] [1] The optical cable of the present invention comprises: a cable body having an optical fiber; a cylindrical outer sheath accommodating the cable body; a protective layer disposed between the cable body and the outer sheath; and a tear cord disposed between the cable body and the protective layer, wherein the protective layer has a groove extending in the axial direction of the cable body on its inner surface, and the tear cord is arranged in the groove.

[0008] [2] In the above invention, the protective layer may have a corrugated shape having peaks and valleys alternately arranged along the axial direction of the cable body, the groove may include a plurality of recessed portions formed by recessing a portion of the peaks, the plurality of recessed portions may be arranged along the axial direction of the cable body, and the tear rope may be arranged in the recessed portions.

[0009] [3] In the above invention, the tear cord may include a first tear cord and a second tear cord, the groove may include a first groove and a second groove, the first tear cord may be arranged in the first groove, and the second tear cord may be arranged in the second groove.

[0010] [4] In the above invention, the following formula (1) may be satisfied.

[0011] θ1≥120°···(1)

[0012] Among them, in the above formula (1), θ1 is the angle between the first straight line and the second straight line, the above first straight line is a straight line passing through the center of the above cable main body and the center of the above first tear rope, and the above second straight line is a straight line passing through the center of the above cable main body and the center of the above second tear rope.

[0013] [5] In the above invention, it may also include: at least one anti-tension body, which is buried in the above outer sheath and sandwiched between the above cable body and facing each other. The above protective layer may also have an overlapping portion in which both ends overlap in the circumferential direction of the above cable body, and may also satisfy the following formula (2).

[0014] θ2≤70°···(2)

[0015] Among them, in the above formula (2), θ2 is the larger angle between the angle formed by the third straight line and the fourth straight line, and the angle formed by the third straight line and the fifth straight line, the third straight line is a neutral line defined by the above-mentioned tensile body, the fourth straight line is a straight line passing through the center of the above-mentioned cable main body and the first end of the above-mentioned overlapping portion, and the fifth straight line is a straight line passing through the center of the above-mentioned cable main body and the second end of the above-mentioned overlapping portion.

[0016] [6] In the above invention, it may further include: a film attached to the inner surface of the protective layer in a manner covering the tear cord, and the tear cord may be arranged between the film and the groove.

[0017] [7] In the above invention, the following formula (3) may also be satisfied.

[0018] d1 / D≥1 / 2···(3)

[0019] In the above formula (3), d1 is the depth of the above groove, and D is the diameter of the above tear cord.

[0020] [8] In the above invention, the protective layer may be formed in a cylindrical shape around the cable body.

[0021] In the optical fiber cable of the present invention, the grooves formed on the inner surface of the protective layer suppress the movement of the tear cord in the circumferential direction, thereby improving the workability. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a cross-sectional view showing an optical fiber cable according to a first embodiment of the present invention.

[0023] Figure 2It is a perspective view showing the optical fiber unit according to the first embodiment of the present invention.

[0024] Figure 3 It is a perspective view showing an intermittently fixed type optical fiber ribbon core according to the first embodiment of the present invention.

[0025] Figure 4 (A) Yes Figure 1 The expanded view of the protective layer shown, Figure 4 (B) is Figure 4 (A) is a development view showing a state in which a tear cord is arranged in a concave portion of the protective layer.

[0026] Figure 5 It is along Figure 4 (B) is a cross-sectional view taken along line VV.

[0027] Figure 6 It is a cross-sectional view showing an optical fiber cable according to a second embodiment of the present invention.

[0028] Figure 7 It is a cross-sectional view showing an optical fiber cable according to a third embodiment of the present invention.

[0029] Figure 8 is a cross-sectional view of a state in which a tear cord is arranged in a concave portion of the protective layer in the third embodiment of the present invention, which is equivalent to a cross-sectional view along Figure 4 (B) is a cross-sectional view taken along line VV. DETAILED DESCRIPTION

[0030] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0031] <First embodiment>

[0032] Figure 1 It is a cross-sectional view showing the optical fiber cable according to the present embodiment. Figure 2 It is a perspective view showing the optical fiber unit according to the present embodiment. Figure 3 It is a perspective view showing an intermittently fixed type optical fiber ribbon core according to the present embodiment.

[0033] like Figure 1 As shown, the optical cable 1 includes a cable body 10, tear cords (lips) 20A and 20B, a protective layer 30, an outer sheath 40, and tensile members 50A to 50D.

[0034] The cable main body 10 of the present embodiment includes an optical fiber aggregate 11 , a crimping tape 17 , and an inner sheath 18 .

[0035] The optical fiber assembly 11 is an assembly of a plurality of optical fibers 14. Specifically, in the present embodiment, the optical fiber assembly 11 is formed by bundling a plurality of optical fiber units 12. Figure 2As shown, each optical fiber unit 12 includes a plurality of optical fiber ribbon cores 13 and a bundling member 16 .

[0036] like Figure 3 As shown, each optical fiber ribbon core 13 is an intermittently bonded optical fiber ribbon in which a plurality of (four in this example) optical fibers (optical fiber wires) 14 are arranged side by side and intermittently connected. Specifically, mutually adjacent optical fibers 14 are intermittently bonded to each other at a predetermined interval by a bonding portion 15. The bonding portion 15 is formed, for example, of an ultraviolet curing resin or a thermoplastic resin. The bonding portions 15 are arranged to be staggered relative to the long side direction of the optical fiber ribbon core 13. Furthermore, in the optical fiber ribbon core 13, the area outside the bonding portion 15 becomes a non-bonded area where the optical fibers 14 are not bound to each other. Therefore, the optical fiber ribbon core 13 can be rolled into a tube (bundle) or folded, and a plurality of optical fibers 14 can be bundled at a high density.

[0037] like Figure 2 As shown, the optical fiber unit 12 is composed of a plurality of optical fiber ribbon cores 13 bundled by a bundling material 16. The bundling material 16 is a member wound in a mesh shape around the outer periphery of the bundle of optical fiber ribbon cores 13. In addition, although not particularly shown in the figure, as the bundling material 16, a rope-like member wound in a spiral shape around the outer periphery of the bundle of optical fiber ribbon cores 13 may also be used.

[0038] Moreover, if Figure 1 As shown, the optical fiber assembly 11 is formed by twisting a plurality of optical fiber units 12 with each other. Specific examples of the twisting method of the optical fiber unit 12 include SZ twisting and unidirectional twisting. SZ twisting is a twisting method of twisting a plurality of linear bodies while reversing the twisting direction at a predetermined interval. Unidirectional twisting is a twisting method of twisting a plurality of linear bodies with only the twisting direction being unidirectional, that is, a twisting method of twisting a plurality of linear bodies in a spiral shape.

[0039] In addition, the structure of the optical fiber ribbon core 13 is not limited to the above-mentioned case. For example, the optical fiber 14 may be bonded intermittently, or the entire optical fiber 14 may be bonded to each other. In addition, the structure of the optical fiber unit 12 is not particularly limited to the above-mentioned structure. For example, the optical fiber ribbon core 13 may not be used, and the optical fiber unit 12 may be formed by simply bundling a plurality of optical fibers 14. In addition, the structure of the optical fiber assembly 11 is not particularly limited to the above-mentioned structure. For example, the optical fiber unit 12 may not be used, and the optical fiber assembly 11 may be formed by simply twisting a plurality of optical fibers 14 together. In addition, the optical fiber assembly 11 may be formed by a loose tube that accommodates the optical fibers.

[0040] The core is covered with a crimping tape 17. In the present embodiment, the crimping tape 17 is longitudinally wound around the outer periphery of the optical fiber assembly 11 in such a manner that the long side direction of the crimping tape 17 is substantially consistent with the axial direction of the optical cable 1, and the width direction of the crimping tape 17 is substantially consistent with the circumferential direction of the optical cable 1. By setting the crimping tape 17 to longitudinal winding, the workability of the optical fiber 14 taken out from the optical cable 1 is improved. In addition, the winding method of the crimping tape 17 is not limited to longitudinal winding, and for example, it may be transverse winding (spiral winding).

[0041] The pressing belt 17 is made of nonwoven fabric or film. Although there is no particular limitation on the specific example of the nonwoven fabric constituting the pressing belt 17, for example, nonwoven fabrics made of fibers such as polyester, polyethylene, and polypropylene can be cited. Although there is no particular limitation on the specific example of the film constituting the pressing belt 17, for example, films made of resins such as polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), or nylon can be cited.

[0042] The inner sheath 18 is a cylindrical member covering the outer circumference of the crimping tape 17, and the optical fiber assembly 11 surrounded by the crimping tape 17 is accommodated in the inner sheath 18. The inner sheath 18 is made of a resin material such as polyvinyl chloride (PVC), polyethylene (PE), nylon, ethylene fluoride or polypropylene (PP).

[0043] In addition, the structure of the cable main body 10 is not particularly limited to the above situation, for example, it can also be a cable with a slot structure, a loose tube structure or a slotless structure. In addition, the outer shape of the cable main body 10 is not particularly limited either. For example, the outer shape of the cable main body 10 can also be circular, flat, shaped or amorphous. In addition, in the present embodiment, although the central tube structure with an inner sheath 18 is illustrated, it is not particularly limited to the above structure, and the inner sheath 18 can also be used to form the optical fiber aggregate 11. That is, the cable main body 10 only needs to have at least one optical fiber.

[0044] A pair of tear cords 20A and 20B are rope-shaped components for tearing the protective layer 30 and the outer sheath 40 in the middle of the optical cable 1 to remove the optical fiber 14. The tear cords 20A and 20B are configured to extend substantially parallel to the cable body 10. In the case where the outer sheath 40 is provided with a tensile body (tensile bodies 50A to 50D described later), the tear cords 20A and 20B are substantially opposed to each other in a direction orthogonal to the opposing direction of the tensile bodies 50A to 50D. In the present embodiment, since the tear cords 20A and 20B do not overlap with the tensile bodies 50A to 50B, the tearing workability can be further improved.

[0045] The tear cords 20A and 20B are not particularly limited, but are formed of twisted yarns made of polyester, or fiber ropes such as aramid fibers or glass fibers. The outer diameter (diameter) of the tear cords 20A and 20B can be set to 0.2 mm to 1.0 mm, for example.

[0046] Figure 4 (A) Yes Figure 1 An expanded view of the protective layer 30 is shown. Figure 4 (B) is Figure 4 (A) is an expanded view of a state in which a tear cord is arranged in a concave portion of the protective layer. Figure 5 It is along Figure 4 (B) is a cross-sectional view along line VV.

[0047] like Figure 1 , Figure 4 (A) and Figure 4 As shown in (B), the protective layer 30 covers the cable body 10 and the ripcords 20A and 20B. The protective layer 30 is provided to protect the cable body 10. The protective layer 30 prevents damage to the cable body 10 when the optical cable 1 is bitten by an animal, for example.

[0048] like Figure 5 As shown in the cross-sectional view of , the protective layer 30 comprises: a reinforcing sheet 301, a resin film 302 bonded to the inner peripheral surface 301a of the reinforcing sheet 301, and a resin film 303 bonded to the outer peripheral surface 301b of the reinforcing sheet 301. As the reinforcing sheet 301, for example, a metal sheet, a fiber sheet, or a fiber reinforced plastic (FRP) sheet can be used. As materials constituting the metal sheet, for example, stainless steel, copper, or a copper alloy can be cited. In addition, as materials constituting the fiber sheet, glass fiber, aramid fiber, etc. can be cited. The thickness of the reinforcing sheet can be set to 0.1 to 0.3 mm, for example. In addition, as the resin films 302 and 303, for example, a hot melt adhesive film can be used. The thickness of the resin film can be set to 0.01 to 0.1 mm, for example. Therefore, the thickness of the protective layer 30 can be set to 0.12 mm to 0.5 mm, for example. In addition, the resin film 302 can also be omitted from the protective layer 30.

[0049] like Figure 1 As shown in FIG. 1 , the protective layer 30 is formed into a cylindrical shape by longitudinally wrapping around the cable body 10. A portion of the protective layer 30 is bonded (thermally melted) to the outer sheath 40 by a resin film 303 provided on the outer peripheral surface 301b. The circumferential direction (width direction) of the protective layer 30 is substantially consistent with the circumferential direction of the optical cable 1. In addition, the long side direction of the protective layer 30 is substantially consistent with the axial direction of the optical cable 1.

[0050] The first end portion 31 of the protective layer 30 overlaps with the second end portion 32 of the protective layer 30 in the radial direction of the optical cable 1, thereby forming an overlapping portion 33 of the protective layer 30. In the overlapping portion 33, the resin films 302 and 303 are bonded (thermally fused) to each other.

[0051] The overlapping portion 33 overlaps the tensile members 50A and 50B in the radial direction of the optical cable 1. On the other hand, the overlapping portion 33 does not overlap the tear cords 20A and 20B. Thus, in this embodiment, the overlapping portion 33 does not overlap the tear cords 20A and 20B, so that the tearing workability can be further improved.

[0052] like Figure 4 As shown in (A), the protective layer 30 includes a plurality of peaks 34 and a plurality of valleys 35. The peaks 34 face the center C1 of the cable body 10 (see Figure 1 ) protrudes and has an annular shape along the circumferential direction of the cable body 10. On the other hand, the valley portion 35 is spaced away from the center C1 of the cable body 10 (see Figure 1 ) direction, and has an annular shape along the circumferential direction of the cable body 10. In this embodiment, a corrugated shape is formed by alternately arranging the peaks 34 and the valleys 35 along the longitudinal direction. The protective layer 30 has a corrugated shape, thereby having flexibility.

[0053] A linear groove 36 extending along the longitudinal direction of the optical cable 1 is formed on the inner peripheral surface (inner surface) 302a of the protective layer 30. Figure 1 As shown, a plurality of (two in this example) grooves 36 are formed on the inner circumferential surface 302a of the protective layer 30 according to the number of tear cords 20A and 20B. Figure 4 As shown in (A), the groove 36 includes a plurality of recessed portions 341 formed by recessing a portion of the mountain portion 34 , and the plurality of recessed portions 341 are arranged in a row along the longitudinal direction of the protective layer 30 .

[0054] like Figure 4 As shown in (B), the tear cord 20A (20B) is arranged in the concave portion 341 of the groove 36. Figure 5 As shown in FIG. 1 , the recess 341 has a width sufficient to accommodate at least a portion of the tear cord 20A (20B) therein. Thus, the recess 341 suppresses the rip cord 20A (20B) from moving in the circumferential direction. The recess 341 is formed by causing a portion of the mountain portion 34 to move away from the center C1 (refer to FIG. 1 ) of the cable body 10. Figure 1 ) direction. In addition, in the present embodiment, the recessed portion 341 is recessed into an arc shape to match the outer peripheral shape of the tear cord 20A (20B).

[0055] The height h1 of the peak 34 of the protective layer 30 is not particularly limited, but is preferably 0.1 mm to 0.6 mm (0.1 mm ≤ h1 ≤ 0.6 mm) in consideration of the flexibility of the optical cable 1 . Here, the height h1 refers to the distance from the bottom of the valley 35 to the top of the peak 34 .

[0056] The depth d1 of the recess 341 is not particularly limited, but is preferably 0.10 mm to 0.34 mm (0.10 mm ≤ d1 ≤ 0.34 mm). By setting the depth d1 of the recess 341 within this range, the movement of the rip cord 20A (20B) can be more reliably suppressed.

[0057] The ratio (d1 / D) of the depth d1 of the recess 341 to the diameter D of the tear cord 20A (20B) is more preferably 1 / 6 or more (d1 / D≥1 / 6), more preferably 1 / 2 or more (d1 / D≥1 / 2), and particularly preferably 2 / 3 or more (d1 / D≥2 / 3). By making the ratio (d1 / D) of the depth d1 of the recess 341 to the diameter D of the tear cord 20A (20B) within any of the above ranges, the movement of the tear cord 20A (20B) in the circumferential direction can be further suppressed.

[0058] The protective layer 30 having the corrugated shape of the recessed parts 341 as described above can be produced by, for example, roll forming. Specifically, the protective layer 30 can be produced by lowering the height of the mountain corresponding to the recessed parts 341 in the processing roller.

[0059] Furthermore, in the present embodiment, the recessed portions 341 are formed in all the ridges 34 , and the recessed portions 341 are continuously arranged in the longitudinal direction, but the present invention is not particularly limited thereto.

[0060] The recessed portion 341 need not be formed in all the mountain portions 34 as long as it can suppress the movement of the tear cord 20A (20B). For example, the recessed portion 341 may be formed only in a part of the mountain portions 34, so that the recessed portions 341 are arranged intermittently in the long side direction. In this case, the grooves 36 including at least one recessed portion 341 are arranged intermittently along the long side direction. When the optical cable 1 is cut to a predetermined length for use, the intervals between the recessed portions 341 can be set according to the length of the optical cable after cutting. In this case, the intervals between the recessed portions 341 can be set in such a way that the optical cable after cutting contains a plurality of recessed portions 341.

[0061] In addition, in the present embodiment, the plurality of mountain portions 34 are formed independently of each other, and the plurality of valley portions 35 are also formed independently of each other, but the present invention is not limited thereto. For example, the plurality of mountain portions 34 may be connected to each other in a spiral shape, and the plurality of valley portions 35 may be connected to each other in a spiral shape.

[0062] In addition, the protective layer 30 may not have a corrugated shape. For example, the protective layer 30 may have a cylindrical shape with a flat main surface. In this case, by recessing a portion of the protective layer, grooves extending in the longitudinal direction can be formed on the inner surface of the protective layer.

[0063] like Figure 1 As shown, the outer sheath 40 is a cylindrical member located outside the inner sheath 18 of the cable body 10, and a gap 41 is formed between the inner sheath 18 and the outer sheath 40. The cable body 10, the protective layer 30, and the tear cords 20A and 20B are accommodated in the internal space formed inside the outer sheath 40. The outer sheath 40 is not particularly limited, but is made of the same material as the inner sheath 18.

[0064] A plurality of (four in this example) tensile members (tensile members) 50A to 50D are embedded in the outer sheath 40. The tensile members 50A to 50D are arranged along the longitudinal direction (see FIG. Figure 3 ) is a linear member extending from the outer sheath 40 to suppress deformation and bending applied to the optical fiber 14 due to the contraction of the outer sheath 40. In addition, the tensile member can also be omitted from the outer sheath 40.

[0065] The pair of tensile bodies 50A and 50B are opposed to each other with the cable main body 10 interposed therebetween, and are arranged to be line-symmetrical with respect to the first straight line L1. On the other hand, the pair of tensile bodies 50C and 50D are opposed to each other with the cable main body 10 interposed therebetween, and are arranged to be line-symmetrical with respect to the second straight line L2. In addition, the angle θ1 formed by the first straight line L1 and the second straight line L2 refers to the smaller angle of the angles formed by the first straight line L1 and the second straight line L2, and θ1 is 180° or less (θ1≤180°).

[0066] In addition, the tensile body 50A is adjacent to the tensile body 50C along the circumferential direction of the outer sheath 40 and is arranged to be line-symmetrical with the tensile body 50C with respect to the third straight line L3. Similarly, the tensile body 50B is adjacent to the tensile body 50D along the circumferential direction of the outer sheath 40 and is arranged to be line-symmetrical with the tensile body 50D with respect to the third straight line L3.

[0067] As materials constituting the tension bodies 50A to 50D, non-metallic materials and metal materials can be exemplified. Specific examples of non-metallic materials are not particularly limited, but examples thereof include fiber reinforced plastics (FRPs) such as glass fiber reinforced plastics (GFRP), aramid fiber reinforced plastics (KFRP) reinforced with Kevlar (registered trademark), polyethylene fiber reinforced plastics reinforced with polyethylene fibers, and carbon fiber reinforced plastics (CFRP) reinforced with carbon fibers. Specific examples of metal materials are not particularly limited, but examples thereof include metal wires such as steel wires.

[0068] In the past, in the tearing operation of the outer sheath, the tear rope moved in the circumferential direction, so the workability sometimes deteriorated. In addition, in the manufacturing process of the optical cable, the tear rope moved, and the position of the tear rope needed to be readjusted, which deteriorated the workability. In contrast, in the present embodiment, the protective layer 30 has a groove 36, and the tear ropes 20A and 20B are arranged in the groove 36, so that the contact area between the protective layer 30 and the tear ropes 20A and 20B can be increased. Therefore, the movement of the tear ropes 20A and 20B in the circumferential direction can be suppressed, and the workability can be improved.

[0069] In addition, in the past, when the optical cable is short (e.g., less than 10 m), the pull-out force of the tear rope is weak, so if one end of the tear rope is not fixed during the tearing operation, the tear rope may be pulled out of the optical cable. In contrast, in the optical cable 1 of this embodiment, since the contact area between the protective layer 30 and the tear rope 20A, 20B is larger than before, the pull-out force of the tear rope 20A, 20B can be increased, and the tear rope 20A, 20B is difficult to be pulled out of the optical cable.

[0070] In this embodiment, if Figure 1 As shown, the angle θ1 formed by the first straight line L1 and the second straight line L2 is 180°. The first straight line L1 is a straight line passing through the center C1 of the cable body and the center C2 of the first rip cord 20A, and the second straight line L2 is a straight line passing through the center C1 of the cable body and the center C3 of the second rip cord 20B.

[0071] The angle θ1 is not particularly limited, but is preferably greater than 120° (θ1 ≥ 120°). The pair of tear cords 20A and 20B are separated by a certain distance in the circumferential direction of the optical cable 1, thereby increasing the width of the open portion of the protective layer 30 and the outer sheath 40, thereby improving the removal workability of the cable body 10.

[0072] Here, the optical cable was manufactured by changing the value of θ1 within the range shown in Table 1 below, and its removal workability was evaluated. That is, the protective layer 30 and the outer sheath 40 were torn by a pair of tear cords to remove the cable body from the optical cable. In this test, the removal workability of the cable body was evaluated as either ○ or ×. "○" means that the workability is good. "×" means that the cable body cannot be removed. The results are shown in Table 1.

[0073] [Table 1]

[0074] Table 1

[0075] <![CDATA[θ1[°]]]> Removal workability 30 × 60 × 90 × 120 ○ 150 ○ 180 ○

[0076] It can be seen from Table 1 that the removal workability is improved by setting θ1 to 120° or more. This range of θ1 can also be applied to the second embodiment described later.

[0077] In addition, it is preferred that the first end 33a of the overlapping portion 33 is separated from the tear cord 20A in the circumferential direction of the optical cable 1. More specifically, it is preferred that the angle θ2 formed by the third straight line L3 and the fourth straight line L4 is less than 70° (θ2≤70°). θ2 is less than 70° (θ2≤70°), thereby further improving the tearing workability.

[0078] In addition, the third straight line L3 is a neutral line defined by the tensile members 50A to 50D, and the fourth straight line L4 is a straight line passing through the center C1 of the cable body 10 and the first end 33a of the overlapping portion 33. More specifically, the neutral line is a straight line extending along a neutral plane in a transverse cross section of the optical cable 1. The neutral plane is a plane that does not extend or contract when the optical cable 1 is bent in a direction substantially perpendicular to the opposing direction of the tensile members 50A to 50D.

[0079] In the present embodiment, the neutral line is a straight line passing through the midpoint M1 between the center C4 of the tensile body 50A and the center C5 of the tensile body 50C, and the midpoint M2 between the center C6 of the tensile body 50B and the center C7 of the tensile body 50D. In the present embodiment, the neutral line is defined by the two counter-tensile bodies 50A to 50D, but the present invention is not limited thereto. For example, when only one counter-tensile body is provided in the outer sheath 40 to counter the cable body 10, the straight line passing through the centers of the respective tensile bodies becomes the neutral line.

[0080] Here, the optical cable was manufactured by changing the value of θ2 within the range shown in Table 2 below, and its tearing workability was evaluated. In this test, the tearing workability of the cable body was evaluated as any one of ◎, ○, △, and ×. "◎" means good workability. "○" means no problem with workability. "△" means that the tearing operation takes more time than necessary, and the workability is slightly deteriorated. "×" means that tearing cannot be performed. The results are shown in Table 2.

[0081] [Table 2]

[0082] Table 2

[0083] <![CDATA[θ2[°]]]> Tearing workability 10 ◎ 30 ◎ 50 ◎ 70 ○ 80 △ 90 △ 100 ×

[0084] As shown in Table 2, if the angle θ2 formed by the third straight line L3 and the fourth straight line L4 is 70° or less, there is no problem with tearing workability, and in particular, if the angle θ2 is 50° or less, good tearing workability can be obtained. This range of θ2 can also be applied to the second embodiment described below.

[0085] In addition, it is preferred that the second end 33b of the overlapping portion 33 is also separated from the tear cord 20B in the circumferential direction of the optical cable 1, similarly to the first end 33a. More specifically, it is preferred that the angle θ3 formed by the fifth straight line L5 and the fourth straight line L4 is 70° or less (θ3≤70°). Here, the fifth straight line L5 is a straight line passing through the center C1 of the cable body 10 and the second end 33b of the overlapping portion 33. In this embodiment, θ2 is an angle greater than θ3 (θ2>θ3). In addition, the range of θ3 can also be applied to the second embodiment described later.

[0086] <Second Embodiment>

[0087] Figure 6 2 is a cross-sectional view of an optical cable according to a second embodiment. In this embodiment, the cable body 10B is different from the first embodiment in that it further includes an interposition 60, and the other structures are the same as those of the first embodiment. Hereinafter, only the interposition 60 of the second embodiment will be described, and the same reference numerals are given to the same parts as those of the first embodiment, and the description thereof will be omitted.

[0088] In the optical cable 1B, the inclusion 60 is, for example, a fiber sheet having a belt shape extending in the longitudinal direction. In the present embodiment, a plurality of (eight in this example) inclusions 60 are provided on the outer periphery of the inner sheath 18 of the cable body 10B. The inclusions 60 may be added longitudinally, or may be twisted by SZ twisting or unidirectional twisting. The material of the inclusions 60 is not particularly limited, but glass fiber, aramid fiber, carbon fiber, metal fiber, etc. may be used.

[0089] Thus, by arranging the interlayer 60 around the cable body 10, the tensile tension of the cable body 10 can be increased. This enables the tension members 50A to 50D to be reduced in diameter, so that the optical cable 1B can be reduced in diameter and weight.

[0090] In addition, the inclusion 60 may also be given waterproof properties. In addition, although not specifically shown in the figure, a compression tape may be used instead of the inclusion. In addition, a compression tape may be provided on the outside of the inclusion 60. As the compression tape, the same component as the compression tape 17 can be used. In addition, the compression tape may also be given waterproof properties. In addition, a water-absorbent inclusion such as a water-absorbent yarn may also be provided between the inclusions 60.

[0091] In this embodiment, as in the first embodiment, the tear cords 20A and 20B are arranged in the grooves 36 of the protective layer 30, so that the contact area between the protective layer 30 and the tear cords 20A and 20B can be increased. Therefore, the movement of the tear cords 20A and 20B in the circumferential direction can be suppressed, and the workability can be improved.

[0092] <<Third Embodiment>>

[0093] Figure 7 is a cross-sectional view showing an optical cable according to a third embodiment, Figure 8 This is a cross-sectional view of a state where a tear cord is arranged in a concave portion of the protective layer, which is equivalent to Figure 4 (B) is a cross-sectional view taken along line VV.

[0094] In this embodiment, the optical cable 1C is different from the first embodiment in that it further includes a resin film 70, and the other structures are the same as those of the first embodiment. Hereinafter, only the resin film 70 of the third embodiment will be described, and the same reference numerals are given to the same components as those of the first embodiment and the description thereof will be omitted.

[0095] like Figure 7 as well as Figure 8 As shown in FIG. 1 , the optical cable 1C of this embodiment further includes a cylindrical resin film 70 on the innermost periphery of the protective layer 30C. Figure 8 As shown in FIG. 1 , the resin film 70 is attached to the resin film 302 of the protective layer 30C. The resin film 70 covers the tear cords 20A and 20B, and the regions corresponding to the tear cords 20A and 20B are bent along the outer periphery of the tear cords 20A and 20B. Thus, the tear cords 20A and 20B are arranged between the resin film 70 and the groove 36. The resin film 70 is made of a hot melt adhesive film or the like, similar to the resin films 302 and 303. The resin film 70 is bonded to the resin film 302.

[0096] In the present embodiment, the tear cords 20A and 20B are fixed to the groove 36 by the resin film 70, so that the movement of the tear cords 20A and 20B in the circumferential direction can be further suppressed. Therefore, the workability can be further improved.

[0097] In addition, in the present embodiment, the resin film 70 is provided on the entire inner periphery of the protective layer, but the present invention is not limited thereto. The resin film 70 may also be provided on a portion of the inner periphery of the protective layer 30. Specifically, for example, the resin film 70 may also cover the tear cords 20A and 20B and be attached only to a portion of the protective layer 30 located near the tear cords 20A and 20B.

[0098] In addition, the embodiments described above are described to facilitate understanding of the present invention, and are not described to limit the present invention. Therefore, the gist of each element disclosed in the above embodiments also includes all design changes and equivalents belonging to the technical scope of the present invention.

[0099] Description of Reference Numerals

[0100] 1, 1B, 1C…optical cable

[0101] 10, 10B…Cable body

[0102] 11…Optical fiber assembly

[0103] 12...Fiber Optic Unit

[0104] 13…Fiber optic ribbon core

[0105] 14…Fiber Optic

[0106] 15… Adhesion

[0107] 16…Bundle

[0108] 17…Compression tape

[0109] 18…Inner sheath

[0110] 20A, 20B…Rip cord

[0111] 30…Protection layer

[0112] 301…Reinforcement film

[0113] 301a…Inner Surface

[0114] 301b…Outer surface

[0115] 302, 303…resin film

[0116] 302a…Inner Surface

[0117] 31…first end

[0118] 32…Second end

[0119] 33…Overlapping

[0120] 33a…First end

[0121] 33b…Second end

[0122] 34…Yamabe

[0123] 341…concave

[0124] 35…Tanibe

[0125] 36... slots

[0126] 40…Outer sheath

[0127] 41…Gap

[0128] 50A~50D…Tensile strength

[0129] 60…Inclusions

[0130] 70…Resin film

[0131] L1~L5…first to fifth straight lines.

Claims

1. An optical cable comprising: a cable body having an optical fiber; A cylindrical outer sheath that accommodates the cable body; A protective layer disposed between the cable body and the outer sheath; a rip cord disposed between the cable body and the protective layer; and At least one tension-resistant body is embedded in the outer sheath and sandwiches the cable main body and faces each other. The protective layer has a groove extending in the axial direction of the cable body on the inner surface. The tear cord is arranged in the groove. The protective layer has an overlapping portion in which both ends overlap in the circumferential direction of the cable main body. Satisfies the following formula (2): θ2≤70°・・・(2) in, In the above formula (2), θ2 is the larger angle between the angle between the third straight line and the fourth straight line and the angle between the third straight line and the fifth straight line. The third straight line is the neutral line defined by the tension body. The fourth straight line is a straight line passing through the center of the cable main body and the first end of the overlapping portion. The fifth straight line is a straight line passing through the center of the cable main body and the second end of the overlapping portion.

2. The optical cable according to claim 1, wherein The protective layer has a corrugated shape with peaks and valleys alternately arranged along the axial direction of the cable body. The groove includes a plurality of concave portions formed by depressing a portion of the mountain portion. The plurality of recesses are arranged along the axial direction of the cable body. The tear cord is disposed in the recessed portion.

3. The optical cable according to claim 1 or 2, wherein: The tear cord comprises a first tear cord and a second tear cord, The above-mentioned groove comprises a first groove and a second groove, The first rip cord is disposed in the first groove, and the second rip cord is disposed in the second groove.

4. The optical cable according to claim 3, wherein: Satisfies the following formula (1): θ1 ≥ 120°・・・(1) In the above formula (1), θ1 is the angle between the first straight line and the second straight line. The first straight line is a straight line passing through the center of the cable body and the center of the first tear cord, The second straight line is a straight line passing through the center of the cable main body and the center of the second rip cord.

5. The optical cable according to claim 1 or 2, wherein: Also available: a film, which is attached to the inner surface of the protective layer in a manner covering the tear cord, The tear cord is disposed between the film and the groove.

6. The optical cable according to claim 1 or 2, wherein: Satisfies the following formula (3): d1 / D≥1 / 2・・・(3) In the above formula (3), d1 is the depth of the above groove, and D is the diameter of the above tear cord.

7. The optical cable according to claim 1 or 2, wherein: The protective layer is formed in a cylindrical shape around the cable main body.

Images