JPH031853Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Field of Application] This invention relates to an optical fiber composite overhead wire such as an optical fiber composite overhead ground wire.

[Prior art and its problems]

Conventionally, a structure as shown in FIG. 2 has been known as an optical fiber composite overhead line. In this optical fiber composite overhead line, the optical fiber assembly 1 is substantially integrated with the protection pipe 2 in the protection pipe 2 made of aluminum or the like. This protection pipe 2 is housed in a state where relative movement is suppressed.
A metal stranded wire layer 3 is formed by twisting together a plurality of metal stranded wires such as aluminum-coated steel wires on the outside of the wire.

By the way, when such an overhead wire is extended or connected, the following elongation occurs in the overhead wire.

[1] Initial elongation of wire 0.01-0.02% [2] Wire extension elongation 0.03% [3] Rotational elongation of wire 0.05% [4] Elastic elongation during tensioning approximately 0.1% Such elongation is protected by optical fiber assembly 1 Since it has a substantially integral structure with the pipe 2, initial stress (tensile stress) is generated in each optical fiber of the optical fiber assembly 1 as it is. Naturally, when such stress occurs on an optical fiber, its transmission characteristics are adversely affected.
This will lead to an increase in transmission loss, and in the long run will lead to breakage of the optical fiber.

For this reason, a structure different from that shown in FIG. 2 has been proposed, that is, a structure in which the protective pipe 2 and the optical fiber assembly 1 are not integrated.

For example, as seen in Japanese Utility Model Application Publication No. 55-181204, a structure in which an optical fiber assembly is housed loosely in a protective pipe, that is, with a gap between the two, has been proposed. There is. Hereinafter, a structure in which such an optical fiber assembly is loosely housed within a protection pipe will be referred to as a loose type, and the optical fiber assembly 1 and protection pipe 2 as shown in FIG. The one with a one-piece structure is called a tight type.

In this loose type optical fiber composite overhead line, a gap is formed between the protective pipe and the optical fiber assembly housed inside, so the tensile force applied to the metal strand layer and the protective pipe is no longer applied. It will not be transmitted to the optical fiber assembly,
The above-mentioned disadvantage, ie the occurrence of terminal stress on the optical fiber assembly, is thus avoided.

However, such a loose type optical fiber composite overhead line has the following disadvantages when it is installed and used.

That is, there is a problem in that a local bend (microbend) occurs in a part of the optical fiber assembly due to repeated temperature changes. This is because there is generally a large difference in linear expansion coefficient between the metal stranded wire layer and the optical fiber assembly, and the optical fiber assembly housed in the protection pipe has a metal stranded wire layer in its own longitudinal and radial direction. and due to the possibility of movement relative to the protective pipe. In other words,
When the sag of the overhead wire increases or decreases due to changes in the ambient temperature (air temperature) of the installed line, relative movement occurs between the optical fiber assembly and the metal stranded wire layer and protection pipe existing around it, often causing the line to deteriorate. The optical fiber assembly and the protection pipe come into strong contact with each other at some point in the longitudinal direction. Since the frictional resistance is significantly increased at the points where these two contact each other strongly compared to other points, even if the overhead wire slackness is restored to its original state, the optical fiber assembly and the surrounding metal stranded wire layer and the protective pipe The two may not completely return to the same relative positional relationship as before, and may remain misaligned with each other. In other words, in such a situation, the tension in the optical fiber assembly is no longer uniform over the entire length of the line, creating areas where the tension is stronger than average, and areas where it is loosened and sagging.
This slack portion that occurs in a part of the optical fiber assembly may eventually develop into a local bend with a large curvature due to repeated changes in slackness.
The local bending that occurs in this way significantly impedes the transmission characteristics of the optical fiber assembly, and in the worst case, buckles the optical fiber core wire or optical fiber bare wire that is the transmission body of the optical fiber assembly. It will cause damage.

The drawbacks seen with the loose type do not occur in the tight type shown in Figure 2, however, with such a tight type, it is difficult to carry out overhead wire extension work as described above. In this case, there is a problem in that initial stress (tensile stress) is generated in the optical fiber assembly.

[The problem that the idea attempts to solve]

Therefore, the problem with this invention is that in a tight-type optical fiber composite overhead line, external forces such as pulling force generated on the stranded part of the overhead line during wire extension and overhead line work can cause damage to the optical fiber assembly. The purpose is to provide a structure that does not act on the system.

[Means to solve the problem]

This problem can be solved by using a tight-type optical fiber composite overhead line in which an optical fiber assembly is housed in a protection pipe so as to be substantially integrated with the protection pipe, and in which a lubricant layer is provided on the outside of the protection pipe. This can be solved by providing a layer of twisted metal wires.

[Effect]

The tensile force applied to the metal strand layer is blocked by the lubricant layer and is not transmitted to the protective pipe and the optical fiber assembly therein.

〔Example〕

Hereinafter, the optical fiber composite overhead line of this invention will be explained in detail with reference to the drawings.

FIG. 1 shows an embodiment of this invention, and its overall configuration is of a tight type that is substantially the same as the conventional optical fiber composite overhead line shown in FIG. This invention has a unique structure in that a lubricant layer 4 is provided between the protective pipe 2 housing the optical fiber assembly 1 and the metal stranded wire layer 3 on the outside thereof.

This lubricant layer 4 prevents the stress (tensile stress) corresponding to the elongation of the metal stranded wire layer 3 from reaching the protective pipe 2 and the optical fiber assembly 1 housed within the protective pipe 2. It functions as a barrier layer that blocks stress, and fatty acid-based grease, for example, is used for this.
In order to provide the above-mentioned lubricant layer 4 between the protective pipe 2 and the metal stranded wire layer 3, for example, the protective pipe 2 containing the optical fiber assembly 1 is lubricated with high-temperature melting type fatty acid grease. The lubricant is applied to the surface of the protective pipe 2 by passing it through a melting tank, and then passing through a die to form a lubricant layer 4 of a predetermined thickness. A plurality of metal wires such as aluminum-coated steel wires are twisted together on the lubricant layer 4 by running the wire at a predetermined speed to form the metal twisted wire layer 3.

According to the optical fiber composite overhead line having the above structure, the metal strand layer 3 and the protection pipe 2 are relatively easy to slide, so even if the metal strand layer 3 is stretched during wire extension or tensioning, , the force at the time of the elongation does not act on the optical fiber assembly 1, and does not adversely affect the optical fibers.

In addition, in the case of such optical fiber composite overhead lines, after installation, large currents flow due to lightning strikes, ground faults, etc., and this causes the metal stranded wire layer 2 to It may be heated to about 400℃, but in such cases, with the configuration of this invention,
Since most of the heat generated during the heating is consumed by melting, combustion, sublimation, etc. of the lubricant layer 4, the heat transferred to the optical fiber assembly 1 via the protection pipe 2 is small, and Therefore, it is possible to prevent thermal damage to the optical fiber assembly 1 and the protection pipe 2.

Note that the above lubricant layer 4 is formed by providing the metal stranded wire layer 4 on the protective pipe 2, and then applying the metal stranded wire layer 4 to the protective pipe 2.
The lubricant may be formed in such a way that the lubricant permeates inside through the interlacing gaps. In addition, protection pipe 2
The metal strand layer 3 is not limited to a seamless tubular shape, but may be, for example, a plurality of divided bodies having a truncated fan-shaped cross section combined into a pipe shape as a whole. It is not limited to one layer, but a plurality of layers may be provided, and the strands may also be strands of irregular cross section other than round strands.

[Effect of idea]

As explained above, according to this invention, in a tight type optical fiber composite overhead line, a lubricant layer is interposed between the metal stranded wire layer and the protective pipe, so that the metal stranded wire layer can be removed during wire extension and overhead line. Even if the wire undergoes initial elongation, wire elongation, wire rotational elongation, and elastic elongation during tensioning, the force at the beginning of the elongation is not transmitted to the protection pipe, and therefore the optical fiber in the protection pipe It is possible to effectively prevent stress (tensile stress) corresponding to the elongation from being applied to the aggregate. Moreover, it does not have the above-mentioned drawbacks found in loose type optical fiber composite overhead lines. In addition, when heat is generated due to lightning strikes or short circuit accidents, the lubricant layer absorbs this heat.
Damage to the protection pipe and the optical fiber assembly due to the heat described above can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing an example of an optical fiber composite overhead line of this invention, and FIG. 2 is a schematic cross-sectional view showing a conventional optical fiber composite overhead line. 1... Optical fiber assembly, 2... Protection pipe,
3...Metal twisted wire layer, 4...Lubricant layer.

Claims (1)

[Scope of utility model registration request] An optical fiber assembly is housed within the protective pipe,
The optical fiber assembly is substantially integrated with the protection pipe so that relative movement with the protection pipe is prevented, and a metal stranded wire layer is provided on the outside of the protection pipe with a lubricant layer interposed therebetween. An optical fiber composite overhead line characterized by being provided with.