JPH0587672A - Airtightness inspecting method for optical fiber unit - Google Patents

Abstract

PURPOSE:To make it possible to perform the airtightness inspection of an airtight tube without cutting communication by connecting the ends of optical fibers to the opening parts of the airtight tubes, surrounding and covering the ends of the optical fibers with tubular bodies, which can be divided into the axial direction and have an inspecting hole, connecting the and sealing the tubes tubular bodies to the opening parts of the CONSTITUTION:The ends of optical fibers 5a and 5b are connected. Thereafter, the fibers are surrounded and covered with tubular bodies 10a and 10b, which are divided into two parts in the axial direction of the fiber. The tubular body 10b has an inspecting hole 11. The inspecting hole 11 is closed, and the airtightness of the inside is maintained. The connecting parts are contained in an airtight case 7. In the airtightness test of the optical fibers, air is sealed through the inspecting hole 11 of the tubular body 10b, and an air gage 8 is attached. The air pressure in an aluminum pipe 3 is measured. Since the optical fiber is not cut when the airtightness test is conducted, the inspection can be performed without stopping communication.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an airtightness inspection method performed at a connecting portion of an optical fiber unit.

[0002]

2. Description of the Related Art Conventionally, an optical fiber consisting of a core and a clad is covered with nylon or the like to form a core wire, or a plurality of these core wires are combined into a unit structure and used as a communication cable or the like. .. In particular, since the optical fiber is non-inductive, it can also be combined with a power cable, and an optical overhead line that has an optical fiber unit for long-distance communication built into the overhead ground wire laid in the uppermost part of the long-distance transmission line. Ground line (OPG
W) is also widely used.

As shown in an example in FIG. 2, an optical overhead ground wire C
Is formed by incorporating the optical fiber unit 1 in the center of the optical overhead ground wire C, and the aluminum pipe 3 in the center of the aluminum-coated steel wire 2.
A plurality of optical fiber cables 4 are housed in the structure. As shown in FIG. 3, the connection of the optical fiber unit of the optical overhead ground wire is sufficient for the reconnection of the end of each optical fiber 5 of the optical fiber cable exposed from the aluminum pipe 3. Then, the optical fibers are connected at the connecting portion 6 by heat fusion or the like. The cable box and the end of the aluminum pipe 3 are housed in the connection box 7 so that water and moisture do not enter, and the optical fiber 5 is not subjected to external stress. The connection box 7 is installed on the utility pole or the wall of the building. Has been done.

[0004]

When a crack or a pinhole occurs in the aluminum pipe of such an optical fiber unit, water penetrates into the aluminum pipe and freezes in the winter, causing a break in the optical fiber. Must be kept airtight. For this reason, aluminum pipes are regularly inspected for airtightness.

To perform the airtightness test, air is sealed from one end of the aluminum pipe in the connection box, and a barometer is attached to the other end of the aluminum pipe installed in the adjacent connection box to inspect for air leakage. Therefore, the airtightness is judged. At this time, as shown in FIG. 4, it is necessary to make the opening of the aluminum pipe 3 airtight because the optical fiber becomes an obstacle, so the connecting portion 6 of the optical fiber 5 is once cut off, and the end of the optical fiber 5 is set to the end. The air gauge 8 is inserted into the pressure-resistant hose 9 that is airtightly attached, and the pressure-resistant hose 9 is connected to the aluminum pipe 3 for inspection.

However, according to this method, the communication must be temporarily stopped in order to cut the optical fiber.
In addition, after the test was completed, the optical fiber had to be re-connected, and in the case of a multi-core wire, it took a long working time. Moreover, when the reconnection is performed, the optical fiber becomes short, and there is a limit to the excess length, so the number of tests at the same point was limited.

The present invention has been made in order to solve the above-mentioned drawbacks, and the airtightness inspection between adjacent diameters can be performed without cutting the optical fiber, and therefore the inspection can be repeated efficiently without interruption of communication. It is an object of the present invention to provide an airtightness inspection method for an optical fiber unit capable of performing the above.

[0008]

In order to achieve the above-mentioned object, the airtightness inspection method for an optical fiber unit according to the present invention comprises the first and second optical fiber units each having an optical fiber housed in an airtight tube. After inspecting the airtightness of the airtight tube after exposing the end of the optical fiber from the opening of each of the airtight tubes and connecting, the connected end of the optical fiber can be divided in the axial direction and the inspection port on the side wall. Surrounding and covering with a tubular body provided with, connecting both ends of the tubular body to the opening of the airtight tube for sealing, and connecting an instrument to the inspection hole to inspect the airtightness of the airtight tube in a repeatable manner. To do.

[0009]

[Operation] When connecting and laying an optical fiber unit in which an optical fiber is housed in an airtight tube, the optical fiber terminals exposed from the airtight tube are connected, and then connected by an axially separable tubular body. The optical fiber is surrounded and coated. When the tubular body is integrated and both ends are connected to cover the opening of the airtight tube, the inside can be kept airtight. The side wall of the tubular body is provided with an inspection hole, which is normally closed so that air can be enclosed or an instrument can be connected during the airtightness inspection.
Therefore, without cutting the optical fiber during inspection,
The test can be performed efficiently and repeatedly.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment to which the airtightness inspection method for an optical fiber unit of the present invention is applied will be described with reference to the drawings. When connecting the optical fiber unit 1 shown in FIG.
, The first optical fiber unit 1a and the second optical fiber unit 1a
Aluminum pipe opening 3a of the optical fiber unit 1b
And 3b expose the first optical fiber 5a and the second optical fiber 5b, respectively. In the figure, only one each of the first optical fiber 5a and the second optical fiber 5b is shown, but the core wires are taken out from the optical fiber unit to expose all the optical fibers. The terminal of the first optical fiber 5a and the terminal of the second optical fiber 5b are connected.

The connection is made by fusion. After the fusion of the optical fibers, the optical fibers 5a and 5b connected by the tubular bodies 10a and 10b divided into two in the axial direction are surrounded and covered. The tubular bodies 10a and 10b are made of plastic,
The structures may be fitted to each other, or they may be fused, as long as they can keep the inside airtight. The tubular body 10b has an inspection hole 11, and the inspection hole 11 is mechanically closed to keep the inside airtight. Such a connecting portion is housed in an airtight connecting box 7.

In order to carry out the airtightness test of the optical fiber unit thus connected, air is filled from the inspection hole 11 of the tubular body 10b. Then, the air gauge 8 as a measuring instrument is attached to the inspection hole 11 of the adjacent or desired connection portion which is similarly connected, and the air pressure in the aluminum pipe 3 is measured.
The presence or absence of pinholes or cracks in the aluminum pipe 3 is detected from the measured values. Since the optical fiber is not cut when performing the air tightness test, the inspection can be performed without stopping the communication. Further, since the complicated optical fiber connection is not performed after the inspection, the inspection can be performed efficiently and very easily.

In the above description, the optical fiber unit is an OPG.
However, the present invention is not limited to this, and can be applied to any optical fiber unit. Further, the measuring instrument is not limited to the air gauge, and any pressure sensor can be applied.

[0014]

As is apparent from the above description, according to the airtightness inspection method for an optical fiber unit of the present invention, after connecting the optical fiber terminal exposed from the airtight tube, it is surrounded by a tubular body which can be divided into two parts. Since the both ends of the tubular body and the opening of the airtight tube are covered by the coating and connected, the optical fiber is not cut at the time of inspecting the airtightness in the airtight tube. Therefore, the inspection can be performed without stopping the communication, and the optical fiber is not shortened due to cutting and bonding, so that the inspection can be repeated any number of times. Moreover, since there is no connection work of the optical fiber after the inspection, the inspection time is very short and can be easily performed.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment to which an airtightness inspection method for an optical fiber unit according to the present invention is applied.

FIG. 2 is a sectional view of an optical overhead ground wire.

FIG. 3 is a configuration diagram showing a connection state of a conventional optical fiber unit.

FIG. 4 is a diagram showing a conventional optical fiber unit inspection method.

[Explanation of symbols]

 1 --- optical fiber unit 1a --- first optical-fiber unit 1b --- second optical-fiber unit 3 ---... aluminum pipe (airtight tube) ) 3a, 3b ... Opening 5 Optical fiber 5a First optical fiber 5b Second optical fiber 8 ... Air gauge (meter) 10a 10b ... Tubular body

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Jun Sato 2-1-1 Oda Sakae, Kawasaki-ku, Kawasaki City, Kanagawa Prefecture, Showa Electric Wire & Cable Co., Ltd. 2-1-1 No. 1 Showa Electric Wire & Cable Co., Ltd.

Claims (1)

[Claims] 1. An airtight tube after exposing the ends of the optical fibers of the first and second optical fiber units each having an optical fiber housed in the airtight tube so as to be exposed from the openings of the respective airtight tubes. When inspecting the airtightness of the tube, the end of the connected optical fiber is surrounded and covered by a tubular body which can be divided in the axial direction and has an inspection port on the side wall, and both ends of the tubular body are opened by the airtight tube. An airtightness inspection method for an optical fiber unit, characterized in that the airtightness of the airtight tube is repeatably inspected by connecting an instrument to the inspection hole and sealing it.