JPS6370201A - Laying method for optical cable - Google Patents

Abstract

PURPOSE:To improve the efficiency of laying construction by measuring and cutting the tension member of an optical fiber to length corresponding to a span, and fitting anchor clamps to both ends and laying the optical fiber. CONSTITUTION:The span of power transmission line steel towers 21A and 21B, and 21B and 21C where the optical cable 14 is laid is accurately measured and the length L of the optical cable required for the laying in consideration of the slacking, elongation, etc., of the optical cable is determined based on the measured value. Then the optical cable is measured by a normal measuring instrument and cut to length L+alpha which is the extra length of both ends than the length L; and the optical cable is measured finely in this state to find the actual length of the optical fiber. The accurate measurement is performed by an optical method and the sheath is removed at both ends to expose the optical fiber and tension member; and both ends of the member are cut so that the length of the tension member is equal to the length L of the optical fiber, the anchor clamps 25A and 25B are fitted to both ends of the tension member 11, and protectors 26A and 26B for protecting the excessive length part of the optical fiber core 12 are fitted, so that the optical fiber is laid by being drawn by a wire 27.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a method for installing an optical cable on a support such as a steel tower.

[Prior art and its problems]

Conventionally, when performing optical communication using overhead power transmission lines,
It is common to construct optical communication lines by storing or wrapping optical fiber cores around overhead ground wires, but recently, high tensile strength non-metallic optical cables have been installed on power transmission towers without using overhead ground wires. It is currently being considered to construct an optical communication line by directly constructing an optical communication line.

The structure of the optical cable in this case is basically as shown in Fig. 4, in which a required number of optical fiber cores 12 are twisted around a high tensile strength, non-metallic tensilan member 11, and a protective layer is placed on top of it. plastic sheath 13
It is coated with.

In order to install such an optical cable 14 between the steel towers, first, the optical cable is extended between the steel towers using a normal method, and then the sheaths at both ends are peeled off to expose the optical fiber core and tension members. The method used is to pull the chisel and perform tension lines. This is because if the optical cable is held from the outside of the sheath using a come-along method or the like for tensioning, an unreasonable external force is applied to the optical fiber, resulting in damage to the optical fiber. For this reason, there is a problem in that it is extremely difficult to adjust the slackness.

In addition, once the slackness has been determined by the tension line, mark the position to attach the tension clamp on the tensilan member, lower it to the ground, reattach the tension clamp at that position, and use the tension clamp again to tighten the tension member. will be carried out. For this reason, there are problems such as it takes a lot of effort, the optical fiber core wire is easily damaged, and the optical cable is wasted.

[Means for solving problems and their effects]

In order to solve the problems of the prior art as described above, the present invention measures the optical cable after precisely measuring the span length of the support (steel tower, utility pole, etc.) on which the optical cable is to be installed. Cut the optical cable so that the tension member has a length corresponding to the above span length, leaving an extra length of optical fiber at both ends, attach a retaining clamp to both ends of the tension member, and then cut the optical fiber at both ends. After the excess length of the fiber core is protected (covered with a protuberance, etc.), the optical cable is extended to the amount of support, and then the optical cable is held in place using clamps at both ends. be.

In this way, the extended optical cable can be strung as is and installed on the supporting object, making the wire tensioning work extremely easy and making the construction work more efficient and labor-saving.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

In FIG. 1, 21A, 21B, and 21C are transmission line towers for installing the optical cable 14 (power transmission lines are not shown). The span lengths of 21C and 21C will be precisely measured, and from the measured values, the length of the optical cable required for installation will be determined, taking into account the slackness and elongation of the optical cable.

Next, the optical cable is measured using an ordinary measuring device, and cut to a length +α that is longer than the above-mentioned length by at least the extra length of the coated optical fibers at both ends.

In this state, the optical cable is precisely measured to determine the actual length of the optical cable.

A suitable method for precisely measuring an optical cable is to optically measure the length of the optical fiber. One of them is a method that utilizes the phase difference between incident light and outgoing light. That is, as shown in FIG. 2, two optical fiber cores 12a and 12b are selected from the optical cable 14, and both optical fiber cores 5Ja2a and 12b are connected at one end side. At the other end of the optical cable 14, the light from the light source 22 is divided into two by a beam brick 23, and one of the two is connected to one optical fiber core 1.
2a, and the other side is manually input to the phase difference detector 24. Furthermore, the phase difference detector 24 has the other optical fiber core 12b.
Input the emitted light from. Then, the detector 24 detects the phase difference between the incident light and the output light, calculates the length of the two optical fibers from the phase difference, and takes one-half of the length as the length of the optical fiber. It is.

Another method is to use TDR to find the length of an optical fiber from the time difference between the light that enters from one end of the optical fiber and the light that travels to the other end and is reflected. There is a way.

The length of the optical fiber core obtained as above is longer than the actual length of the optical cable because the optical fiber core wire is twisted (the optical fiber core wire is twisted around the tension member). . For this reason, the relationship between the length of the optical fiber core wire and the actual length of the optical cable is determined in advance by calculation or sample testing, and the actual length of the optical cable is determined from that relationship.

Once the actual length of the optical cable has been determined in this way, the sheaths at both ends are peeled off to expose the optical fiber and the tension member, and the length of the tension member is the length of the optical cable required for the installation. After cutting both ends of the tension member 11, as shown in FIG.
25B, and protectors 26A and 26B are attached to protect the extra length of the optical fiber core 12. Thereafter, as shown in FIG. 1, one of the retaining clamps 25A is pulled with the wire 27 to extend the optical cable 14, and after the wire is stretched, the retaining clamps 25A and 25B at both ends are secured to the steel towers 21A and 21C. The line is completed.

〔Effect of the invention〕

As explained above, according to the present invention, the tension member of the optical cable is cut to a length corresponding to the span length, and retaining clamps are attached to both ends of the tension member and then erected. This greatly simplifies construction work, making it possible to improve efficiency and save labor. Further, since the excess length of the optical fiber at both ends is protected by a protector or the like, there is no risk of damage during installation, and there is an advantage that the installation work can be carried out easily.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing a method for installing an optical cable according to an embodiment of the present invention, Fig. 2 is an explanatory diagram showing an example of a method for measuring the length of an optical cable, and Fig. 3 is an explanatory diagram showing an example of a method for measuring the length of an optical cable. FIG. 4 is a longitudinal cross-sectional view showing the structure of the optical cable. 11~tension member, 12~optical fiber core, 1
3~Sheath, 14~Optical cable, 21A/21B/21
C ~ Steel tower, 25A/25B ~ Retaining clamp. Figure 1

Claims (1)

[Claims] Measure the optical cable, cut the optical cable so that the tension member has a length corresponding to the pre-measured span length, leaving an extra length of optical fiber at both ends, and cut the optical cable so that the tension member has a length corresponding to the pre-measured span length. A method for installing an optical cable, which comprises installing the optical cable after attaching a retaining clamp and performing a process to protect the excess length of the optical fiber core at both ends.