JPH10319282A - Optical cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the optical cable which prevents a spacer on an external- layer side from falling in an opening for an internal-layer side spacer. SOLUTION: This optical cable 1 is formed in laminate structures of >=2 layers by annularly arraying U-sectioned spacers 4 and 7 containing coated optical fibers 5, and openings 4a and 7d to 7f of the spacers 4 and 7 are directed outward. In this case, when the spacers on the internal layer side and the spacer on the external layer side which are adjacent to each other inside and outside are compared with each other, the bottom surface width (A) of the spacer 7 positioned on the external layer side is made more than twice as large as the width (B) of the opening edge par ts of the spacers 4 which are positioned on the internal layer side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical cable in which optical fibers are mounted at high density.

[0002]

2. Description of the Related Art Conventionally, as a technique in such a field, there are JP-A-4-182611 and JP-A-4-77108. At the center of the optical cable described in these publications, a solid and columnar tensile member (tension member) is arranged, and spacers having a U-shaped cross section are arranged annularly so as to surround the tension member. It has a two-layer structure. The outer-layer-side spacers are arranged in a ring shape so as to close the openings of the inner-layer-side spacers. As described above, by arranging the spacers having a U-shaped cross section annularly in a laminated state of the inner and outer two layers, it is possible to increase the density of the optical fiber cores (optical fiber tapes) accommodated in the spacers. In addition, the optical fiber core wires are in a state of being laminated in the spacer.

[0003]

However, the conventional optical cable has the following problems because it is configured as described above.

That is, when manufacturing an optical cable, the position of the outer layer spacer with respect to the inner layer spacer is not strictly determined, and the outer layer spacer is simply placed on the annularly arranged inner layer spacer. That is, FIG.
As shown in FIG. 3, after the inner spacers 101 are densely arranged on the outer peripheral surface of the center tensile member 100,
The outer-layer spacers 102 are densely arranged so as to overlap with each other. Further, the presser winding tape 103 is firmly wound from the outside so that the arrangement of the outer layer side spacers 102 is not broken. At this time, the arrangement of the outer-layer-side spacer 102 may be disrupted by the winding force of the holding tape 103, and the outer-layer-side spacer 102 may fall into the opening 101 a of the inner-layer-side spacer 101 with the collapse. . As described above, the outer layer-side spacer 102 is
As a result, the arrangement of the outer layer side spacers 102 is not only disturbed, but also the inner layer side
The outer layer side spacer 102 may press down the inner optical fiber core wire 104 from above. Due to such a situation, there is a problem that the transmission characteristics of the optical fiber 104 are deteriorated. Note that, even when the inner layer side spacer is pressed and wound, there is a possibility that the outer layer side spacer 102 may fall into the inner layer side spacer 101 depending on the winding method.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and an object of the present invention is to provide an optical cable in which an outer-layer spacer is prevented from dropping into an opening of an inner-layer spacer.

[0006]

According to a first aspect of the present invention, there is provided an optical cable in which a plurality of U-shaped spacers accommodating a plurality of optical fiber cores are annularly arranged in a laminated structure of two or more layers. In an optical cable in which the openings of the spacers are directed outward, when the inner spacer and the outer spacer adjacent in and outside are compared in the circumferential direction, the width of the opening edge of the spacer located on the inner layer is determined by On the other hand, the width of the bottom surface of the spacer located on the outer layer side is at least twice as large.

In this optical cable, when the outer-layer spacers are annularly arranged on the inner-layer spacers arranged annularly, the position of the outer-layer spacers relative to the inner-layer spacers is not strictly determined, and the annular spacers are arranged annularly. The outer spacer is simply placed on the inner spacer.
At this time, the width of the bottom surface of the outer layer side spacer is made wider than the width of the opening edge of the inner layer side spacer so that the outer layer side spacer does not fall into the opening of the inner layer side spacer. When the diameter is set to twice or less, the arrangement diameter of the inner layer side and outer layer side spacers changes depending on the diameter of the optical cable itself, and there is a possibility that the outer layer side spacer may fall into the opening of the inner layer side spacer. By the judgment, to be able to cope with any diameter of the optical cable,
The width of the bottom surface of the outer-layer spacer is specified to be at least twice as large as the width of the opening edge of the inner-layer spacer, thereby providing versatility. In this manner, by defining the relationship between the inner layer and the outer layer of the spacer, the bottom surface of the outer-layer spacer is reliably supported by the opening edge of the inner-layer spacer. There is no need to consider the arrangement relationship between the spacers and the spacers on the outer layer side at all. Therefore, the manufacture of the optical cable becomes extremely easy.

In this case, it is preferable to twist the spacer on the inner layer side and the spacer on the outer layer side in the same direction. When such a configuration is adopted, in the operation of taking out a desired optical fiber core wire from the middle of the laid optical cable (intermediate rear branch), the twist of the spacer is returned after removing a part of the jacket of the optical cable. By twisting and expanding the optical cable core wire outward (so-called "laughing"), the inner-layer spacer and the outer-layer spacer can be made to laugh at the same time. This is based on the fact that the width of the bottom surface of the outer-layer spacer is at least twice the width of the opening edge of the inner-layer spacer, so that the outer-layer spacer does not fall into the opening of the inner-layer spacer. Technology. As described above, by making the twist of the spacers inside and outside the same, the strength member located at the center of the optical cable can be easily taken out, and the workability of the intermediate branching operation can be improved. In order to prevent the outer spacer from falling into the inner spacer, the inner spacer and the outer spacer are alternately twisted (for example, one is S twisted and the other is Z twisted). When the screw is twisted so as to return, the spacer on the outer layer side laughs, but the spacer on the inner layer side tightens on the contrary.

It is preferable that the spacers on the inner layer side and the spacers on the outer layer side are twisted at the same pitch in the length direction. In the case of employing such a configuration, if the optical cable is twisted at the time of the intermediate rear branch, the take-out amounts of the inner-layer spacer and the outer-layer spacer become equal. Therefore, the work of collecting the spacers taken out of the optical cable is simplified.

Further, it is preferable that the outermost diameter when the inner spacers are arranged in a ring is substantially equal to the curvature of the bottom surface of the outer spacers. When such a configuration is adopted, the outer-layer spacer is stably seated on the inner-layer spacer, and the inner-layer spacer and the outer-layer spacer can be brought into close contact with each other, thereby reducing a gap between members. This can reduce the amount of water running through the gap.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of an optical cable according to the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a sectional view showing an optical cable according to the present invention. The optical cable 1 shown in FIG. 1 has a cylindrical central tensile member 2 disposed at the center thereof.
Are embedded with seven steel strands 3 at the center. Further, an elongated inner-layer-side spacer 4 is disposed so as to abut on the outer peripheral surface of the center tensile member 2, and the inner-layer-side spacer 4 has a cross section U.
It is formed in a letter shape and is densely arranged so that the openings 4a face outward. In addition, the inner layer side spacer 4 includes:
An optical fiber housing recess 4b is formed, and a tape core 5 as an optical fiber core is provided in each optical fiber housing recess 4b.
Are laminated. A tape-shaped or linear pressing member 6 is tightly wound around the annularly arranged inner-layer spacers 4 to prevent the inner-layer spacers 4 from being broken.

Further, three optical fiber receiving recesses 7 are formed on the presser winding member 6 so as to overlap the inner layer side spacer 4.
The outer layer spacers 7 having a, 7b, and 7c are arranged in a ring shape, and in each of the optical fiber receiving recesses 7a, 7b, and 7c,
Tape core wires 5 are stacked. Further, a tape-shaped or linear holding member 8 is tightly wound around the annularly arranged outer-layer-side spacers 7 to prevent the outer-layer-side spacers 7 from being broken. And the inside of the optical cable 1
A polyethylene jacket 9 surrounding the presser winding member 8.
Protected.

As shown in FIG. 2, the inner layer side spacer 4 is formed of a plastic long member having a U-shaped cross section and has a pair of right and left ribs 10 extending in the longitudinal direction of the optical cable 1. The opening 4a is formed at the free end of the rib 10. Further, in the optical fiber accommodating recess 4b of the inner layer side spacer 4, ten laminated tape cores (optical fiber cores) 5 are accommodated. As shown in FIG. 3, the outer layer side spacer 7 is formed of a plastic long member and has four ribs 11 a to 11 d extending in the longitudinal direction of the optical cable 1. Each rib 11
a to 11d are erected substantially perpendicularly to the curved bottom wall 12, and three optical fiber receiving recesses 7a, 7b, 7c are formed between the ribs 11a to 11d.

Further, when the inner spacer 4 adjacent to the inner and outer spacers and the outer spacer 7 are compared in the circumferential direction, the chord length (bottom width) A at the bottom surface 12a of the outer spacer 7 is determined.
Is set to be at least twice the width B (see FIG. 2) of the opening edge of the inner layer side spacer 4. This is because the outer spacer 7 is simply placed on the inner spacer 4 when the optical cable 2 is assembled.
That is, no matter how the outer spacer 7 is placed with respect to the inner spacer 4, the outer spacer 7 is prevented from falling into the opening 4 a of the inner spacer 4. The bottom width A of the outer spacer 7 is made larger than the width B of the opening edge of the inner spacer 4.
The inner and outer spacers 4,
There is a possibility that the arrangement diameter of the spacers 7 changes and the outer-layer-side spacer 7 falls into the opening 4 a of the inner-layer-side spacer 4. Therefore, the width A of the bottom surface of the outer layer side spacer 7 is specified to be at least twice as large as the width B of the opening edge of the inner layer side spacer 4 so as to be able to cope with any size of the optical cable 1. And it has versatility.

When the relationship between the inner-layer spacer 4 and the outer-layer spacer 7 is defined in this manner, the bottom surface 12a of the outer-layer spacer 7 is reliably supported by the ribs 10 of the inner-layer spacer 4. That is, as shown in FIG. 4, no matter where the outer layer-side spacer 7 is located, the outer-layer-side spacer 7 falls into the opening 4 a of the inner-layer-side spacer 4 such that the outer-layer spacer 7 comes off from the presser winding member 6. There is no. Therefore,
When the optical cable 1 is manufactured, there is no need to consider the arrangement relationship between the inner spacer 4 and the outer spacer 7 at all, and the manufacturing of the optical cable 1 is facilitated. Further, when the optical cable 1 is manufactured, even if the outer-layer spacer 7 is assembled on the inner-layer spacer 4 in a tilted state, the outer-layer spacer 7 is attached to the rib 10 of the inner-layer spacer 4 by the presser winding member 8. Since the outer spacers 7 are pressed, the outer layer spacers 7 are correctly arranged so as to match the arrangement state of the ribs 10.
Openings 7d to 7f correctly face outward.

In the optical cable 1, the inner spacer 4 and the outer spacer 7 are S-twisted and Z-twisted S-twisted.
Either Z twist (meandering right and left alternate twist) is adopted, but when either S twist or Z twist is adopted, the inner layer side spacer 4 and the outer layer side spacer 7 are moved in the same direction. Twist. Therefore, in the work of removing the sheath 9 from the middle of the laid optical cable 1 and taking out the desired tape core 5 (intermediate rear branch), if the twist of the outer-layer spacer 7 is twisted back, the inner-layer spacer 4 Can also be returned at the same time, the center tensile member 2 can be easily taken out, and the workability of the intermediate rear branch is improved. Thus, the same kind of twist can be adopted between the inner layer spacer 4 and the outer layer spacer 7 only when there is a configuration in which the outer layer spacer 7 does not fall into the inner layer spacer 4.

Further, in the length direction of the optical cable 1,
The inner layer side spacer 4 and the outer layer side spacer 7 are twisted at the same pitch. That is, the inner spacer 4 and the outer spacer 7 that are twisted in a predetermined length of the optical cable 1 have the same length, and the inner spacer 4 has a shorter pitch than the outer spacer 7. It is twisted. Therefore, when the optical cable 1 is twisted at the time of the intermediate rear branch, the take-out amounts of the inner spacer 4 and the outer spacer 7 become equal. In other words, when the optical cable 1 is twisted at the time of the intermediate rear branch to make the inner layer side and outer layer side spacers 4 and 7 laugh, the distances at which the respective spacers 4 and 7 depart from the central tensile strength member 2 become equal. As a result, the inner spacer 4 and the outer spacer 7 taken out of the optical cable 1
And the work of coordination is simplified.

Further, the inner layer spacers 4 are arranged annularly on the center tensile member 2, and the outermost diameter at this time is substantially equal to the curvature of the bottom surface 12 a of the outer layer spacer 7.
Therefore, the outer layer spacer 7 is stably seated on the inner layer spacer 4, and the inner layer spacer 4 and the outer layer spacer 7 can be brought into close contact with each other. To block. In addition, the amount of the water absorbing material interposed between the inner spacer 4 and the outer spacer 7 can be reduced, which contributes to the cost reduction of the optical cable 1.

The optical cable of the present invention is not limited to the embodiment described above. For example, as shown in FIG. 5, a W-shaped outer layer side spacer 14 in which two optical fiber housing recesses 16a and 16b are formed by three ribs 15a to 15c may be employed. Further, the optical cable 1 may be an arbitrary combination of the outer layer spacer 14 and the outer layer spacer 7 shown in FIG.

As shown in FIG. 6, two ribs 20 are provided.
The outer-layer-side spacer 22 in which one optical fiber accommodating concave portion 21 is formed wide in a and 20b may be employed. In this case, three sets of tape core units 23 are arranged in the optical fiber receiving recess 21. Each tape core unit 23
Is formed into a unit by winding a holding coil or tape 24 around the laminated state of ten tape cores 5.

Further, in the optical cable 1 shown in FIG. 1, the spacer structure has two layers, but may have three or more layers. In this case, it is determined whether the inner layer or the outer layer is adjacent in the radial direction. It is determined whether the spacers are inside or outside. Furthermore,
In some cases, a single-core optical fiber is used as the optical fiber core.

[0023]

As described above, the optical cable according to the present invention has the following effects. That is, U-shaped cross-section spacers accommodating a plurality of optical fiber cores are arranged in a ring to form a laminated structure of two or more layers, and in an optical cable in which the openings of the spacers are directed outward, inside and outside are adjacent. When the inner layer side spacer and the outer layer side spacer are compared in the circumferential direction, the width of the bottom surface of the outer layer side spacer is at least twice as large as the width of the opening edge of the inner layer side spacer. By doing so, the outer-layer-side spacer does not fall into the opening of the inner-layer-side spacer, the arrangement of the spacers is not disturbed, and the situation of deteriorating the transmission characteristics of the optical fiber is also avoided.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of an optical cable according to the present invention.

FIG. 2 is a cross-sectional view showing an inner layer side spacer applied to the optical cable of FIG.

FIG. 3 is a sectional view showing an outer-layer-side spacer applied to the optical cable of FIG. 1;

FIG. 4 is an enlarged sectional view of a main part of the optical cable according to the present invention.

FIG. 5 is an enlarged sectional view of a main part showing another embodiment of the optical cable according to the present invention.

FIG. 6 is an enlarged sectional view of a main part showing still another embodiment of the optical cable according to the present invention.

FIG. 7 is an enlarged sectional view showing a main part of a conventional optical cable.

[Explanation of symbols]

A: bottom width, B: width of opening edge, 1: optical cable, 4 ...
Inner layer side spacer, 4a, 7d to 7f ... opening, 5 ... tape core wire (optical fiber core wire), 7, 14, 22 ... outer layer side spacer, 12a ... bottom surface.

Claims (4)

[Claims] 1. An optical cable in which U-shaped spacers accommodating a plurality of optical fiber cores are arranged in a ring to form a laminated structure of two or more layers, and the openings of the spacers are directed outward. When the spacer on the inner layer side and the spacer on the outer layer side adjacent to each other inside and outside are compared in the circumferential direction, the width of the opening edge portion of the spacer on the inner layer side is larger than the width of the opening edge of the spacer on the outer layer side. An optical cable characterized in that the bottom width is at least twice as large. 2. The spacer according to claim 1, wherein the spacer on the inner layer side and the spacer on the outer layer side are twisted in the same direction.
Optical cable as described. 3. The optical cable according to claim 2, wherein, in the length direction, the spacer on the inner layer side and the spacer on the outer layer side are twisted at the same pitch. 4. The spacer according to claim 1, wherein the outermost diameter when the spacers on the inner layer side are arranged in a ring is substantially equal to the curvature of the bottom surface of the spacers on the outer layer side. Optical cable according to the item.