JPH0341924B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement in a method for manufacturing an optical fiber composite overhead ground wire.

[Conventional technology and problems]

Optical fiber composite overhead ground wire, in which optical fiber is housed inside the overhead ground wire, is an attempt to construct a communication line by attaching it alongside an ultra-high voltage power transmission line, taking advantage of the fact that optical fiber is not susceptible to electromagnetic effects. Yes, because it eliminates the need to construct a separate communication line,
It has come into widespread practical use in recent years.

That is, FIGS. 1 and 2 are cross-sectional views showing an example of such an optical fiber composite overhead ground wire, and FIG. It is of a spacer type in which strands 5 are twisted around the outer periphery of an optical fiber unit that houses an optical fiber 3 therein.
Here is an example of a hollow type in which the fibers 5 are twisted around the outer circumference of an optical fiber unit housed in the storage chamber 2 of the pipe 1 with the optical fiber 3 simply preformed without using any special support as described above. This is what is shown.

In the optical fiber composite overhead ground wire constructed as described above, a particular problem is the large difference in mechanical properties between the single ground wire and the optical fiber. In other words, the ground wire itself is made of conductive metal, so it has great mechanical strength and elongation, but optical fiber has glass and plastic as its main constituent materials, so its mechanical strength is much lower. It also has low elongation properties.
Since such composite components are installed under considerable overhead wire tension and are further exposed to wind pressure loads and loads due to ice and snow accumulation, it is necessary to take some countermeasures.

For this reason, consideration has been given to giving the optical fiber housed inside an extra length or forming it into a spiral shape so that even if a large load is applied to the strands, no direct load is applied to the optical fiber. However, there are some cases where this is not necessarily sufficient.

[Purpose of the invention]

In view of the above-mentioned circumstances, the present invention provides a method for producing an optical fiber composite overhead ground wire that eliminates the risk of a large load being applied to the optical fiber after connecting the optical fiber composite overhead ground wire. It is intended to provide a method.

[Summary of the invention]

That is, the gist of the present invention is that after a first step of twisting strands at a first pitch around the outer periphery of an optical fiber unit containing optical fibers, a twisting pitch smaller than the twisting pitch in the first step is performed. This method is characterized by the provision of a second step of twisting the ground wire so that It's in what I tried to do.

〔Example〕

This will be explained below using examples.

In general, the method for manufacturing an optical fiber composite overhead ground wire is to manufacture an optical fiber unit in which, for example, an optical fiber 3 is housed in an aluminum pipe 1 as described above, and to attach an element made of aluminum or an aluminum alloy to the outer periphery of the optical fiber unit. Usually, wires 5 or strands 5 made of aluminum-coated steel wires such as those shown in FIG. 1 are twisted together, such as aluminum-coated steel wires formed by coating a steel core 5a with an aluminum coating layer 5b. In this case, as already explained, the optical fiber 3 in the pipe 1 is configured to have some extra length, but the extra length of the optical fiber is in the expected state when the stranded wire is manufactured. The reality is that it is not always clear whether this is the case or not.

The present invention provides a method for manufacturing an optical fiber that can reliably secure such extra length, and after twisting the optical fiber composite overhead ground wire as described above, further The ground wire is given a twist in the twisting direction so that the twist pitch is small.

As mentioned above, by applying the twist, the overall length of the ground wire is reduced, but this reduction is directly transmitted to pipe 1, and pipe 1 is also reduced in size, and the internal optical fiber has an excess of that amount. Extra length occurs.

Now, assuming that the twist pitch after twisting is p ₁ , the twist pitch during the first twist is p ₂ , and the core diameter of the twisted wire is d, the amount of reduction is as follows.

In the optical fiber composite overhead ground wire having the configuration shown in FIG. 1, a case will be considered in which the length of the ground wire is reduced by the twisting described above. At first, the extra length only increases and there is no particular change in the transmission characteristics of the optical fiber, but when the amount of reduction in length exceeds a certain value, the optical fiber becomes microbend due to the excessive reduction, and the optical fiber becomes This appears as a transmission loss. This condition clearly indicates excessive twisting. In other words, if the twist is within the microbend generation limit, even if the overhead ground wire is stretched due to the tension of the overhead wire after the overhead wire is connected, the optical fiber will still have sufficient extra length. There is no risk of unexpected abnormal tension occurring.

Now, an optical fiber composite overhead ground wire is manufactured by manufacturing an optical fiber unit in a 5.2φ aluminum pipe through a spacer as shown in Figure 1, and twisting 3.2φ wires around the outer circumference of the optical fiber unit. Let us consider the case where the p 1 is manufactured so that p ₁ =120 mm due to 0.2% reduction. The initial twist pitch p ₂ to achieve such a pitch is 125.91 mm, and the ground wire twisted with such p ₂ pitch is 0.391 mm.
By twisting the twist in the twisting direction by turns/m,
The pitch p ₁ = 120 mm, which allowed the entire ground line to be reduced by 0.2%. However, as a result of experiments, 3
Times/6.65m=0.451 times/m. Therefore, the above
It can be seen that the twist to obtain a pitch of p ₁ is a twist that can achieve a sufficient reduction of the ground wire without causing transmission loss in the optical fiber. By adding the above twist, even when the overhead wire is under tension, the ground wire retains static strain of about 0.2% compared to the conventional method without twisting. Therefore, it becomes possible to operate the overhead line in a state where abnormal tension is completely prevented from being generated in the optical fiber.

Note that the twisting described above also causes twisting of the optical fiber unit, but since the behavior occurs near the center, its influence can be ignored without any problem.

Furthermore, when twisting the strands into an optical fiber unit, they may be twisted directly, but the strands should first be twisted into a solid body such as a steel wire to give the strands a sufficient twist. A twisted wire method may be adopted in which the fibers are then untwisted and replaced with an optical fiber unit.

〔Effect of the invention〕

As described above, according to the method for manufacturing an optical fiber composite overhead ground wire according to the present invention, in addition to the extra length that can be secured by ordinary twisted wires, an additional extra length is secured for the optical fiber inside the ground wire. It is possible to avoid, with a sufficient safety factor, the abnormal tension that might be applied to the optical fiber in the case of normal manufacturing methods, and today, when optical fiber composite overhead ground wires are being implemented in earnest, This is a timely proposal that should be highly praised.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an example of a spacer type optical fiber composite overhead ground wire, and FIG. 2 is a sectional view showing an example of a hollow type optical fiber composite overhead ground wire. 2... Storage room, 3... Optical fiber, 5... Element wire.

Claims (1)

[Scope of Claims] 1. Strand the strands at a first pitch around the outer periphery of an optical fiber unit that holds optical fibers in an internal storage chamber, and then twist a second wire with a twist pitch smaller than the first twist pitch. A method for manufacturing an optical fiber composite overhead ground wire by twisting in the twisting direction so that the twist pitch is as follows. 2. Claim 1, wherein the reduction in the length of the ground wire caused by the tightening of the twist by the second twist pitch is close to the limit value of the increase in transmission loss of the optical fiber deformed thereby. Manufacturing method described.