JP2002139632A - Connection box having projection-restraining metal fitting for winding type opgw - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a connection box, having a projection restraining metal fitting for a wound type OPGW which prevents a tension member from projecting, without increasing transmission loss in an optical fiber. SOLUTION: The connection box is provided with the projection-restraining metal fitting, consisting of a protective tube by which an optical cable, is inserted into the connecting box for the wound type OPGW and a terminal fixture which clamps the protective tube.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wrapping type OPGW connection box, and more particularly to a wrapping type OPGW connection box with protrusion suppression fittings for suppressing protrusion of a tension member.

[0002]

2. Description of the Related Art A wrapping type OPGW is formed by winding an optical cable around an overhead ground wire which is laid between steel towers.
The optical cable is used to monitor the tower and communicate information. The optical cable is composed of a plurality of optical fiber strands, and the connection of the optical fiber strands is performed inside a connection box, that is, a connection box for a winding type OPGW.

FIG. 4 is a sectional view of an optical cable related to a conventional wrapping type OPGW connection box. 11 is external intervention, 1
2 is an optical fiber, 13 is a center interposed, 14 is an outer sheath, and 15 is a tension member.

There are 24 optical fiber strands 12,
Numbers up to 4 are given. First, the center intervention 6
3 are twisted around each other to form one group. Then, a total of four optical fiber groups are twisted together with the external intervention 11 around the tension member 15 and the outer sheath 14 is provided on the outermost layer to constitute an optical cable. The outer sheath 14 is made of a fluorine resin in consideration of weather resistance.

[0005] The connection of the optical cable in the wrapping type OPGW connection box is as follows.

[0006] Only the tension member 15 is fixed to a tension member fixing jig provided in the winding type OPGW connection box. The reason for fixing only the tension member 15 is that the work is easy. And the outer sheath 1
4 is peeled off, the optical fiber strands 12 are taken out one by one, and the respective optical fiber strands are fusion-spliced. Finally, the fusion spliced portion is housed together with the reinforcing component at a predetermined location in the wrapping type OPGW connection box.

[0007]

SUMMARY OF THE INVENTION A conventional wound type OPGW
The connection box has the following problems.

Since only the center tension member 15 is fixed, the protrusion of the tension member due to the contraction of the outer sheath 14 cannot be prevented. The protrusion of the tension member means that the outer sheath 14
Is a phenomenon in which the tension member 15 projects together with the optical fiber 12 at the terminal portion due to the contraction of the optical fiber. If the protrusion amount is large, the tension member 15 is fixed, so that the tension member 15 meanders and swells in the optical cable. In the worst case, the tension member 15 is bent (buckled).

If the tension member 15 meanders, undulates, or buckles in the optical cable, the tension member 15 comes into contact with the optical fiber 12 and increases the transmission loss of the optical fiber 12 or in the worst case. Causes disconnection.

In order to avoid the above-mentioned problem, a method of fixing the optical cable by a metal fitting (referred to as an optical cable holder) for holding the optical cable in the connection box for the wrap-type OPGW is adopted. This is a method of holding the optical cable from above the outer sheath with a metal optical cable holder. However, since the optical cable is made of metal, it is difficult to suppress the protrusion of the tension member without increasing the transmission loss of the optical fiber.

In order to prevent the transmission loss of the optical fiber from increasing, the optical cable holder is required to have high dimensional accuracy. However, the optical fiber and the optical cable generally have a variation in outer diameter, and the variation is absorbed. It is difficult.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned drawbacks of the prior art and to provide a protrusion for a wire-wrapped OPGW which prevents the tension member from projecting without increasing the transmission loss of the optical fiber. To provide a junction box.

[0013]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention is provided with a protrusion-suppressing metal fitting in a wrapping type OPGW connection box.

[0014] The protrusion suppressing metal fitting includes a protective tube into which the optical cable is inserted and a terminal fixing metal fitting which clamps the protective tube.

The protection tube is made of a flexible material.

[0016]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a front view showing an embodiment of a connection box with a protrusion suppressing metal fitting for a wrap-type OPGW of the present invention.
FIG. 2 is a cross-sectional view of the protrusion suppressing metal fitting of FIG. 1
Is a protrusion suppressing bracket, 2 is a connection box, 3 is a protective tube with a reinforcing wire, 4 is a protective tube, 5 is an optical cable, 6 is a terminal fixing bracket, 7 is a bolt, 8 is a nut, and 9 is a ground wire.

The connection box with the protrusion-suppressing fitting for the wrap-type OPGW of the present invention has a configuration in which the protrusion-suppression fitting 1 is added to the connection box for the conventional wrap-type OPGW. The protrusion suppressing metal fitting 1 includes a protective tube 4 for inserting the optical cable 5, a terminal fixing metal 6 for holding the protective tube 4, a bolt 7, and a nut 8. In this embodiment, the protection tube 4 is mounted collectively in the protection tube 3 with the reinforcing wire, but these may be separately provided.

The optical cable 5 is the same as the optical cable shown in FIG. That is, a total of 24 optical fiber strands are divided into four groups of six and twisted around the tension member.

The optical cable 5 is inserted into the protection tube 4 mounted on the protection tube 3 with the reinforcing wire. Then, the protection tube 4 and the protection tube 3 with a reinforcing wire are clamped by the terminal fixing bracket 6 together with the ground wire 9 having substantially the same diameter. The pinching strength is configured to be adjustable by the bolt 7 and the nut 8. The terminal fitting 6 is configured to be fixed to the connection box 2. The protection tube 4 is formed of a flexible material, for example, rubber or plastic.

The bolt 7 and the nut 8 were tightened with a torque of 800 kgf · cm. At this time, the transmission loss of the optical fiber did not increase. This is because the dimensions and the material of the protection tube 3 containing the reinforcing wire and the dimensions and the material of the protection tube are appropriately designed, and no side pressure or bending is applied to the optical fiber in the optical cable.

FIG. 3 relates to the connection box with the protrusion suppressing metal fitting for the wrapping type OPGW according to the present invention, and is an explanatory view of the change over time of the protrusion amount of the tension member. The horizontal axis is time (hr),
The vertical axis is the protrusion amount (mm). The protrusion amount indicates the length (mm) of the tension member protruding from the terminal portion.

The case where only the tension member of the prior art is pressed is described as "only the tension member is pressed".
Further, a case where the conventional optical cable is held by a metal optical cable holder is described as “with optical cable holder”.
And the case where the protrusion suppression metal fitting of FIG. 2 was used was described as "there is a protrusion suppression metal fitting."

By using the protrusion suppressing metal fitting of the present invention, the protrusion amount of the tension member could be suppressed to about 1 mm for several thousand hours. When a conventional optical cable holder is used, the amount of protrusion can be suppressed to about 1 mm, but transmission loss increases in the optical fiber. In other words, if an increase in transmission loss can be tolerated, it is possible to suppress the protrusion amount of the tension member to about 1 mm.

As described above, it is possible to provide a connection box with a protrusion-type fitting for a wire-wound OPGW that prevents a tension member from protruding without causing an increase in transmission loss of an optical fiber. Although the description has been given of the case where the optical cable has 24 cores, it goes without saying that the present invention can be applied to various types of optical cables irrespective of 24 cores.

In FIGS. 1 and 2, a protective tube containing a reinforcing wire is used together. However, even if the optical cable 5 is simply inserted into the protective tube 4 and held down by the terminal fixing bracket 6, the structure may be modified. I do not care. In short, the gist of the present invention lies in that the optical cable is inserted into the protective tube and gripped by the terminal fixing bracket.

[0027]

According to the present invention, there is provided a connection box with a protrusion-controlling member for a wrap-type OPGW, comprising a protective tube for inserting an optical cable into the connection box for a wrap-type OPGW and a terminal fixing member for clamping the protective tube. The provision of the restraining fitting makes it possible to prevent the tension member from protruding without causing an increase in the transmission loss of the optical fiber.

[Brief description of the drawings]

FIG. 1 is a front view showing one embodiment of a connection box with a protrusion-suppressing metal fitting for a wrap-type OPGW of the present invention.

FIG. 2 is a cross-sectional view of the protrusion suppressing fitting of FIG.

FIG. 3 is an explanatory view of a change over time of a protrusion amount of a tension member, which relates to a connection box with a protrusion-suppressing metal fitting for a winding type OPGW of the present invention.

FIG. 4 is a cross-sectional view of an optical cable related to a conventional wrapping type OPGW connection box.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Protrusion suppressing metal fitting 2 Connection box 3 Protective tube with reinforcing wire 4 Protective tube 5 Optical cable 6 Terminal fixing metal fitting 7 Bolt 8 Nut 9 Ground wire 11 External intervention 12 Optical fiber 13 Central intervention 14 External sheath 15 Tension member

Claims (3)

[Claims] 1. A connection box with a protrusion-suppressing fitting for a wrap-type OPGW, wherein the connection box for a wrap-type OPGW is provided with a protrusion-suppression fitting. 2. The wrapping mold O according to claim 1, wherein the protrusion suppressing metal fitting comprises a protective tube into which the optical cable is inserted, and a terminal fixing metal fitting which clamps the protective tube.
Connection box with protrusion suppression fitting for PGW. 3. The connection box according to claim 2, wherein the protection tube is made of a flexible material.