JPS635308A - Optical cable connected section - Google Patents

Abstract

PURPOSE:To use a connected section protecting tube so that occurrence of disconnection in an optical cable in the vicinity of an optical core line connected section can be prevented even if the tube is used under a condition where the temperature change is relatively large, by integrating the end sections of the tube with the sheaths of the cables to one body by heating and setting the length of the optical core line from the heated section to the connected section at >=1.5m. CONSTITUTION:Length of an optical core line 2 from a heated section 2 to an optical core connected section 3 is set at >=1.5m. At the end sections of optical cables 1 to be connected with each other, the Pb sheaths 10 of the cables 1 are removed and the optical core lines 2 are exposed. The exposed core lines 2 are connected with each other by fusion and an optical core connected section 3 is formed. Then the connected section 3 and the loop-like parts of the core lines 2, namely, the excessive length parts of the core lines 2 are put in a connecting box 4. Outside of the connecting box 4 is covered with a Pb protecting tube 5 having an inner diameter which can house the box 4 and both end sections 5a and 5b of the tube 5 are tightly brought into contact with the Pb sheaths 10 of the optical cable and sections 1a and 1b by a diameter reducing work. Then the tightly contacting parts 5a and 5b are heated by a plumber and heat welded sections 6 and 6 are welded to the Pb sheaths 10 and 10 of the optical cables 1 and 1 so as to form a watertight structure.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a connecting portion of an optical cable having a Pb jacket used in the optical communication sector.

[Conventional technology]

To connect an optical cable that has a full Pb jacket, first remove the Pb jacket from the end of the optical cable to be connected to expose the optical core wire.
After aligning and fusion-splicing the ends of the corresponding optical core wires and covering the entire joint with a PB protection tube, both ends of the protection tube are integrated with the Pb jacket of the optical cable by heating to create a watertight structure. ing. In this case, conventionally, the length of the optical core line from the heating section was the above-mentioned optical core line connection distance α8~t, ff1a degree.

[Means for determining the problem to be solved by the invention] The optical cable having the optical fiber connection part and the heating part is used as a composite cable with a ring cable or as an underground cable under conditions where the temperature changes between day and night are relatively large. When used, wire breakage may occur near the connection between the core wires during use.

After examining various causes of this disconnection, we found that when the end of the connection protective tube was heated to integrate it with the optical cable jacket, P
(b) The optical core wire itself in the part where the outer sheath has been removed is heated, and the difference in thermal expansion between the quartz glass and the nylon coating that make up the optical core wire causes distortion in the quartz glass, and this distortion occurs during use. It has been found that the cause of wire breakage is that the temperature change PO heat cycle gradually transmits to the core wire connection part, and tensile stress acts on the quartz glass near the connection part.

Therefore, in order to prevent such disconnection near the optical fiber connection part, it is necessary to make the length of the optical fiber from the heating part to the optical fiber connection area as long as possible.

As described in detail in the Examples, the applicant connected optical cables with several different lengths of the optical core wires, and then conducted a heat cycle test on these connections. In order to prevent this, the length of the optical core wire is required to be at least 15 m, and it has been found that if the length is less than 15 m, disconnection may occur during the heat cycle test, which poses a problem in the reliability of the connection part.

The optical core wire from which the PB outer sheath has been removed is usually made into a loop and housed in a junction box, and the outer side of the optical core wire is further covered with a PB outer sheath. A length of 15 m or more is required, and even if the optical core line is substantially straight, a length of 15 m or more is still required.

Based on the above results, the optical cable connection part of the present invention removes the PB jacket at the end of the optical cable to expose the optical core wires, and fusion splices the optical core wires together to protect the dimensional core wire connection part and the entire connection part. In the optical cable connecting part having a pipe, the end of the protective pipe of the connecting part is integrated with the optical cable jacket by heating, and the length of the optical core wire from the heating part is at least L5m above the optical fiber connection length. It is characterized by:

〔Example〕

Next, embodiments of the present invention will be described in detail with reference to the drawings.

First, FIG. 1 shows the structure of the optical cable connection section of the present invention.

1 is an optical cable, 2 is an optical core wire, 3 is an optical core wire connection section, 4 is a connection box, 5 is a protection tube, and 6 is a heat welding section.

At the end of the optical cable 1, the PBB sheath 1 of the cable 1 is
0 has been removed and the optical core line 2 is exposed.

The exposed optical core wires 2 are fusion-spliced to form an optical fiber connection section 3, and the connection section 5 and the looped optical core wire 2, that is, the extra length, are housed and held in a connection box 4. has been done. The outside of the connection box is covered with a PBB protection tube 5 having an inner diameter that can accommodate the connection box IIi, and both ends 5a and 5b of the protection tube 5 are diameter-reduced to form the optical cable end 1.
It is in close contact with the a1 lb PB shell 10, and the contact portion 5a,
5b is heated by a lead worker, and the heated welded portion 6.6 is welded to the PBB jacket 10, 10 of the optical cable 1.1 to form a watertight structure.

Next, an example of the structure of the optical cable 1 used in the present invention is shown in FIG.

The cable 1 is composed of an FRP tension member 7, an optical core 2, an aramid fiber 8, a polyethylene sheath 9, and a PB jacket l. Further, the optical core wire 2 is composed of a quartz glass 11, a silicon buffer layer 12, and a nylon coating layer 15, as shown in FIG.

In the optical cable connection section described above, the length outside the extra length from the optical core wire 2 exposed at the cable ends 1a and 1b, that is, the heating welding part 6 to the optical fiber connection section 3, is 08 to 2.0 m.
The optical cable connections obtained in this way were subjected to a heat cycle test of 100 cycles at a temperature range of -30°C to 60°C and a repetition rate of 2 cycles/day. We investigated whether there was any disconnection. The results are shown in Table 1.

Table 1 As is clear from Table 1, the optical core line 2 from the heated welding part 6
In the example of the present invention, which has a length of 15 m or more up to the optical fiber connection part, no disconnection was observed even after 3000 wires were subjected to a heat cycle test, and the reliability of the connection part was extremely excellent.

- On the other hand, in the comparative example and the conventional example, in which the length of the optical core wire is shorter than that of the inventive example, 1 to 5 out of 1000 optical core wires were disconnected, and there was a problem in the reliability of the connection part.

〔Effect of the invention〕

゛The present invention is an optical cable connection part characterized in that the length of the optical core wire from the heating welding part at the end of the connection part protection tube is 1.5 m or more to the optical core line contact part, Even when used under conditions where the optical core wire is relatively large, there is no disconnection near the optical fiber connection, and the connection has excellent reliability.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the structure of an optical cable connection section. Second
The figure is a diagram showing the structure of an optical cable, and the second figure is a diagram showing the structure of an optical core wire. DESCRIPTION OF SYMBOLS 1... Optical cable, 2... Optical core line, 5... Optical core line connection part, I... Junction box, 5... Protection tube, 6...
Welding part (heating part), 7... Tension member, 8.
...Aramid fiber, 9...Polyethylene coating, 10
... PB jacket, 11... Quartz glass, 12... Buffer layer, 15... Nylon

Claims (1)

[Claims] In an optical cable connection part that has an optical fiber connection part in which the Pb outer sheath at the end of the optical cable is removed to expose the optical core wires and the optical core wires are fused and spliced together, and a protection tube that protects the entire connection part, the connection part is protected. An optical cable connection part characterized in that the end of the tube is integrated with the optical cable jacket by heating, and the length of the optical core wire from the heating part to the optical fiber connection part is 1.5 m or more.