JPH01191109A - Optical fiber cable for composite overhead earth wire - Google Patents

Abstract

PURPOSE:To improve heat resistance and workability at the time of connection and to prevent impairment of the characteristics of a cable in spite of a change in tension as the cable elongates or contracts by winding a tape having a high heat resisting temp. on the outside circumference of doubled and twisted optical fibers and disposing a tension member to the center thereof. CONSTITUTION:Plural pieces of the optical fibers 4 are doubled and twisted on the outside circumference of the tension member 3 and the heat resisting tape 5 consisting of a polyimide system is wound on the outside circumference of these fibers to constitute the cable. The heat resistance is thereby improved and since a stripping operation is easy, the workability at the time of connection is improved as well. Further, the tension member 3 is disposed to prevent the change in the tension arising when the cable elongates or contracts at the time of a high temp. or strong wind from being directly exerted upon the optical fibers 4.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a composite optical fiber cable for overhead ground wires, and in particular, it improves heat resistance and workability during connection, and improves the cable's performance. The present invention relates to a composite optical fiber cable for overhead ground wire that can handle changes in tension due to expansion and contraction.

(Prior Art) In recent years, an optical fiber composite overhead ground wire that combines an overhead ground wire and an optical fiber has been developed, and its practical use is rapidly progressing.

Generally, this optical fiber composite overhead ground wire is a groove in which the optical fiber cable is stored inside an aluminum pipe, and a plurality of aluminum covered steel wires are twisted around the pipe.

However, such an optical fiber composite overhead ground wire is always 1
00~150'C1 Because the temperature reaches over 300°C during an abnormality, conventionally, optical fiber cables are coated with a silicone resin coated with a heat-resistant silicone resin, as shown in Figure 3. A fluororesin 2 of polytetrafluoroethylene (PTFE) W, which is known as a heat-resistant resin, is extruded and coated on the outer periphery of the fibers.

In addition, optical fiber composite overhead ground wires stretch at high temperatures or strong winds, resulting in a large tension burden, so it is necessary to prevent this stress from being applied directly to the optical fibers. This is dealt with by setting it up.

(Problem to be solved by the invention) However, in the conventional optical fiber cable as mentioned above, the heat resistance of the fluororesin is limited to around 300°C, so if the temperature is higher than this, it will melt and damage surrounding aluminum pipes, etc. There was a problem in that when the optical fiber was fused and returned to room temperature, microbending occurred in the optical fiber, increasing transmission loss.

Furthermore, it is necessary to peel off the fluororesin coating 2 during connection, but since the coating is formed by extrusion, there is also the problem of poor workability.

In order to improve heat resistance, it may be possible to increase the thickness of the fluororesin coating 2, but this is not preferable as it would greatly reduce workability during connection.

In general, the conventional provision of extra length was insufficient to cope with changes in cable tension during high temperatures and strong winds.

The present invention was made in response to these conventional problems, and has excellent heat resistance that can withstand use at high temperatures exceeding 300°C, and also has good workability during connection. Moreover, it is an object of the present invention to provide a composite optical fiber cable for an overhead ground wire that can sufficiently cope with changes in tension caused by expansion and contraction of the cable at high temperatures.

[Structure of the Invention] (Means for Solving the Problems) The optical fiber cable for a composite overhead ground wire of the present invention has a plurality of optical fiber cores twisted around the outer periphery of a tension member, and a polyimide heat-resistant material is applied to the outer periphery of the optical fiber cables. It is characterized by being made by winding tape.

The tension members used in the present invention include metal wires such as steel wires, non-metal wires made of glass fiber reinforced plastics, carbon fibers, etc., or stranded wires thereof, and the outer periphery of these wires is generally coated with silicone resin or fluorine. It is also possible to use a material coated with a heat-resistant resin such as resin.

Further, examples of the polyimide heat-resistant tape used in the present invention include polyimide tape and polyamide-imide tape, which can be used at high temperatures exceeding 300'C. Examples of commercially available products include various Kapton tapes (trade name) manufactured by DuPont, and Upilex C (trade name) manufactured by Ube Industries.

(Function) In the composite optical fiber cable for overhead ground wire of the present invention, the above-described tape having a high heat resistance temperature is wound around the outer periphery of the optical fiber core wire, so that heat resistance is improved. Furthermore, since the stripping work is easy, the workability during connection is also improved. Furthermore, a tension member is placed in the center, and the tension applied to the cable can be borne by this tension member, preventing changes in tension caused by expansion and contraction of the cable at high temperatures or strong winds from being applied directly to the optical fiber. can do.

(Example) An embodiment of the present invention shown in the drawings will be described below.

FIG. 1 is a longitudinal sectional view showing one embodiment of the present invention.

As shown in the figure, in this embodiment, a plurality of silicone resin-coated optical fibers 4 are concentrically twisted around the outer periphery of a tension member 3, and a polyimide tape 5 is wrapped around the outer periphery of these. It is composed of

In the composite optical fiber cable for overhead ground wire constructed in this way, the optical fiber core 4 is coated with the polyimide tape 5 which has excellent heat resistance and can be used at temperatures of about 400°C. Even when used as an optical fiber cable for a composite overhead ground wire, which can reach temperatures exceeding 300°C during abnormal conditions, it will not melt, and therefore will not cause micro-bending that would increase optical fiber transmission loss. .

Further, since the polyimide tape 5 can be easily peeled off, workability during connection is also good.

Furthermore, tension member 3 is placed in the center,
Since the tension applied to the cable can be mainly borne by the tension member 3, it is possible to prevent changes in tension due to temperature changes or the like from being applied directly to the optical fiber, thereby increasing the reliability of the cable. In order to further ensure this effect, it is desirable to configure the connection portion of this cable as shown in FIG. 2.

In other words, FIG. 2 schematically shows the connecting part of the overhead ground wire in which the optical fiber cable of this embodiment is combined. The illustrations and explanations for these parts will be omitted.

As shown in the figure, the connection end of the optical fiber cable with the polyimide day 15 removed from the end to expose the tension member 3 and the optical fiber core 4 is inserted into the junction box 6, and the inner surface of the optical fiber cable is inserted into the junction box 6. The polyimide tape 5 is fixed from above with a presser metal fitting 7, and the tension member 3 is similarly fixed to the inner surface of the junction box 6 using a suitable presser metal fitting 8.

Each coated optical fiber 4 is connected by a conventional method, either by omitting illustration or by providing an extra length for each of a plurality of coated optical fibers to be connected thereto. In the figure, 9 is the composite overhead ground wire main body, 1
0 is a cable protection fitting attached to the bottom of the junction box.

By fixing the tension member 3 to the junction box 6 in this way, all the tension applied to the cable can be borne by the tension member 3, so the influence of tension changes on the optical fiber core 4 can be almost completely eliminated. can significantly improve reliability.

[Effects of the Invention] As explained above, according to the composite optical fiber cable for overhead ground wire of the present invention, a tape with a high heat resistance temperature is wound around the outer periphery of the twisted optical fiber core wires, and a tension member is provided at the center. This structure improves heat resistance and workability during connection, and can sufficiently handle changes in tension due to expansion and contraction of the cable without impairing its characteristics.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing a composite overhead ground wire optical fiber cable according to an embodiment of the present invention, FIG. 2 is a view explaining its connection method, and FIG. 3 is a cross-sectional view showing a conventional example. . 3...Tension member 4...
...Optical fiber core 5...Polyimide tape Fig. 1 Fig. 2 Fig. 3

Claims (1)

[Claims] (1) A composite optical fiber cable for an overhead ground wire, characterized in that a plurality of optical fiber cores are twisted around the outer periphery of a tension member, and a polyimide heat-resistant tape is wound around the outer periphery of the twisted optical fibers.