JPH06208047A - Optical cable - Google Patents

Abstract

PURPOSE:To provide the optical cable which is housed in a pipeline and can prevent running water in the terminal part of the pipeline. CONSTITUTION:The optical cable 1 is forcibly fed by a pressure gas to the pipeline 4. After the optical cable is inserted therein, a water absorptive tape 5 for waterproofing is gently wound around the optical cable 1 and the optical cable is inserted into the pipeline. The inserted water absorptive tape 5 is fixed by the frictional force with the pipe wall of the pipelling 4 onto the insertion position. A connector 3 for connecting the pipeline is then passed onto the optical cable 1 and is connected to the end of the pipeline 4. An optical cable fixing jig 2 is fitted onto the optical cable 1 from its score and is pushed to the connector 3 for connecting the pipeline, by which the optical cable 1 is fixed as the optical cable is tightened by the optical cable fixing jig 2. The water absorptive tape for waterproofing swells to prevent the running water in case of wetting with water.

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 a pressure gas is used for carrying and laying it in a pipe line laid in advance.

[0002]

2. Description of the Related Art There is a method of laying an optical cable by laying a pipe in advance and using pressured gas in the pipe to feed an optical cable by a gas flow. The optical cable laid in the pipeline is retained in order to prevent movement in the pipeline or in the junction box of the pipeline.

FIG. 4 is an explanatory view of an example of a conventional retaining structure at the end of a pipeline. In the figure, 1 is an optical cable, 2 is an optical cable fixing jig, 3 is a connector for conduit connection, and 4 is a conduit. The optical cable 1 contains one or a plurality of optical fibers and is provided with a protective coating. One end of the conduit connection connector 3 is connected to the conduit 4, and a hole into which the optical cable fixing jig 2 can be inserted is formed at the other end. The optical cable fixing jig 2 is made of plastic and has a wedge-shaped plug shape, is provided with a cut, and has a hole formed at the center for passing the optical cable.

The method of retaining the optical cable is to connect the conduit connecting connector 3 to the end of the conduit 4, insert the optical cable fixing jig 2 into the optical cable 1 from a cut, and push it into the conduit connecting connector 3. The optical cable 1 is clamped and fixed to the optical cable fixing jig 2.

The conventional structure at the end of such a conduit does not have a waterproof effect because it is intended to prevent movement or to fix the optical cable. Therefore, for example, if the pipeline is damaged by natural disaster or man-made disaster, and water enters the pipeline inside and runs in the longitudinal direction of the pipeline, the water will flow from the end of the pipeline through the junction box. Since the water runs to the adjacent pipeline, there is a high possibility that the flooded section will be flooded not only in one pipeline section but also in multiple pipeline sections. As a result, the inside of the conduit is contaminated, and it becomes impossible to lay or collect the optical cable using gas, and there is a possibility that the optical cable and the conduit may have to be re-installed over a plurality of sections.

On the other hand, the optical cable described in Japanese Utility Model Laid-Open No. 62-49114 discloses a pipe in which a wrap tape is formed into a cylindrical shape and a polyethylene coating is applied to the outer peripheral surface of the wrap tape.
In an optical fiber core or a tape-shaped optical fiber core that is housed, the optical fiber core or tape-shaped optical fiber core may be made of continuous long fibers having a high water absorption property or a high water absorption property processed into a sheet shape. Adopts a structure in which short fibers are vertically or horizontally wound to prevent water running. In such a cable structure, when a certain section of the optical cable is damaged, the water-prevention material swells to fill the voids in the cable and has the effect of stopping the water so that the water does not spread over a wide area. The abnormal parts due to the accident are limited. Therefore, the structure has only to repair this abnormal section at an appropriate time after flooding.

[0007] However, such an optical cable cannot be applied to a pipeline that is pumped by gas.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and in an optical cable housed in a conduit, prevents running water at the conduit terminal portion, and
It is an object of the present invention to provide an optical cable capable of detecting water immersion.

[0009]

The present invention relates to an optical cable which is laid using a gas in a hollow conduit and is retained in the conduit by an optical cable fixing jig at the end of the conduit. The water absorbing and swelling substance is arranged around the optical cable near the end of the pipe or around the optical cable fixing jig.

Further, in an optical cable laid in a hollow conduit using gas and held at the end of the conduit by an optical cable fixing jig, the optical cable near the end of the conduit. The water absorbing and swelling substance is unevenly distributed between the pipe and the pipe. A water-swellable tape can be used as the water-swellable substance.

[0011]

According to the present invention, since the water running prevention treatment is applied at the end of the pipeline, even if water enters the pipeline, the water can be waterproofed at the pipeline end, and the inundation length can be reduced to 1 It can be stopped in the pipeline section. Further, by unevenly distributing the water-swellable substance between the optical cable and the conduit, when the water-swellable substance swells in contact with water, bending loss is given to the optical cable in the conduit, By monitoring
It is possible to detect water ingress into the pipeline.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory view of a first embodiment of a retaining structure at the end of a conduit of an optical cable of the present invention. In the figure,
The same parts as those in FIG. 4 are designated by the same reference numerals and the description thereof will be omitted. 5 is a water-absorbing tape for waterproofing. The conduit 4 is a thin conduit such as a PE tube having an inner diameter of 6 mm and an outer diameter of 8 mm, which is PVC-coated so as to have an outer diameter of 12 mm, or a weatherproof PE having an inner diameter of 4 mm and an outer diameter of 6 mm. The tube etc. which were able to be used can be used. Of course, the diameter may be larger than that. As the waterproof water-absorbing tape 5, an appropriate waterproof water-absorbing tape such as a tape made of a water-swelling fiber or a woven fabric containing a water-swelling material can be used.

The optical cable 1 is pressure-fed to the pipe line 4 by compressed gas, for example, compressed air. After inserting the optical cable, the waterproof water-absorbing tape 5 having an appropriate width is loosely wound around the optical cable 1 and inserted into the conduit. The inserted water-absorbing tape 5 for waterproofing is fixed at the insertion position by the frictional force with the pipe wall of the pipe line 4. Then, the conduit connecting connector 3 is passed through the optical cable 1 to be connected to the end of the conduit 4, and the optical cable fixing jig 2 is fitted into the optical cable 1 through the cut and pushed into the conduit connecting connector 3. The optical cable 1 is clamped and fixed by the optical cable fixing jig 2.

A specific example will be described. As the conduit, a thin polyethylene conduit having an outer diameter of about 8 mm and an inner diameter of about 6 mm was used. After inserting an optical cable having an outer diameter of about 2 mm into the conduit, a waterproof water-absorbing tape having a thickness of about 0.2 mm and a width of about 50 mm was wrapped around the optical cable and inserted from the end of the conduit. Then, the conduit connection connector was attached to the conduit, and the optical cable was held by the optical cable fixing jig.

A head pressure of 1 m of water column, which is a typical waterproofing test method for a cable, was attached to one end of the small diameter pipe, and the inside of the pipe was flooded. After 24 hours, no water permeation was observed, indicating good waterproof property.

FIG. 2 is an explanatory view of a second embodiment of the retaining structure at the conduit end of the optical cable of the present invention. In the figure, the same parts as those in FIG. In this example, the optical cable fixing jig 2 was fixed using a waterproof water absorbing tape 5. That is, after inserting the optical cable 1 into the conduit 4, the connector 3 for conduit connection was passed through the optical cable 1 and connected to the end of the conduit 4. Then,
The optical cable fixing jig 2 was fitted into the optical cable 1 through the cut, and the water absorbing tape 5 for waterproofing was wound and pushed into the conduit connection connector 3.

For concrete examples, the pipeline and the optical cable are
This is the same as the specific example described in FIG. A waterproof water-absorbing tape having a thickness of about 0.2 mm was used, and a tape having a width of about 10 mm was wound around the optical cable fixing jig. Also in this specific example, the result of the waterproof test method is similar to the above-mentioned result,
It showed good waterproof properties.

FIG. 3 is an explanatory view of an embodiment capable of detecting water in the second embodiment described with reference to FIG. In the figure, the same parts as those in FIG. 6 is a half-type jig, and 7 is a water absorbing tape. Half-divided jigs 6 are attached to the inside of the pipe 4 through which the optical cable 1 is inserted at intervals, and a water-absorbing tape 7 is placed at an intermediate position so as to face the half-divided jigs 6. It was attached over the half circumference. The attachment of the conduit connection connector 3, the optical cable fixing jig 2 and the waterproof water absorbing tape 5 is the same as in the second embodiment. Since the water-absorbing tape 7 is not arranged all around the optical cable but is unevenly distributed, when water leaks in the conduit, the optical cable is locally bent, and the transmission loss increases. By measuring this, inundation can be detected.

In the concrete example described in the second embodiment,
Half-division jigs having a width of about 5 mm were attached at intervals of about 10 mm, and a water absorbing tape was placed in the middle. When the inside of the pipe was submerged, the water absorbing tape swelled and the optical cable was locally bent, resulting in loss. Also, the water absorbing tape was swollen and the waterproof effect was confirmed.

[0020]

As is apparent from the above description, according to the present invention, even if water enters the pipeline, waterproofing can be carried out at the end of the pipeline, and running over one pipeline section or more can be achieved. Can prevent water. In addition, there is an effect that it is possible to detect water ingress into the pipeline.

[Brief description of drawings]

FIG. 1 is an explanatory view of a first embodiment of a retaining structure at a conduit end of an optical cable of the present invention.

FIG. 2 is an explanatory view of a second embodiment of the retaining structure at the conduit end of the optical cable of the present invention.

FIG. 3 is an explanatory diagram of an embodiment capable of detecting water immersion in the second embodiment.

FIG. 4 is an explanatory diagram of an example of a conventional retaining structure at a pipe end.

[Explanation of symbols]

 1 Optical cable 2 Optical cable fixing jig 3 Pipe line connection connector 4 Pipe line 5 Water absorbing tape for waterproof 6 Half-divided jig 7 Water absorbing tape

Claims (3)

[Claims] 1. An optical cable laid in a hollow conduit using gas and retained at the end of the conduit by an optical cable fixing jig, wherein the optical cable is near the end of the conduit. An optical cable characterized in that a water-swelling substance is arranged around the circumference of the. 2. An optical cable laid in a hollow conduit using gas and retained at the end of the conduit by an optical cable fixing jig, wherein water is absorbed around the optical cable fixing jig. An optical cable characterized in that a swelling substance is arranged. 3. An optical cable laid in a hollow conduit using gas and retained at the end of the conduit by an optical cable fixing jig, wherein the optical cable is near the end of the conduit. An optical cable in which a water-swelling substance is unevenly distributed between the pipe and the conduit.