JPH0766097B2 - Optical fiber core wire bending correction method and its sleeve - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for correcting a curl that remains in an optical fiber core wound in a loop for a long time, and a method for applying heat to the optical fiber core to leave it. The present invention relates to a sleeve that corrects a bent bend.

[Conventional technology and its problems]

First, the extra length of the optical fiber core at the connection point of the optical cable will be described. At the optical cable connection point, it is necessary to allow for the length of the optical fiber to be connected to the optical fiber fusion splicer and the length for reconnection of about 50 to 80 cm. Therefore, the connected optical fiber has an extra length that is twice the above value, and is wound to a diameter of about 8 cm to accommodate it in the optical cable connection box. That is, as shown in FIG. 3, the extra length of the optical fiber core wire 2 is accommodated in the extra length storage sheet 3, which is wound so as to surround the central axis of the optical cable 1. In this state, the bending habit remains in the coating of the optical fiber core wire left for a long time.

At such a connection point, the connection may be made again due to a failure of the optical fiber core or a switching accompanying the route change of the cable. At this time, if there is a bend, the following problems will occur. When the optical fiber is set in the V groove of the optical fiber fusion splicer, the optical fiber does not fit in a predetermined position on the bottom of the V groove, or it takes time to set the optical fiber to fit it. Even if two optical fibers can be set, the axes of both may be displaced. Further, as shown in FIG. 3, when the extra length of the optical fiber core wire 2 after connection is stored in the extra length storage sheet 3, the optical fiber 2 still has a bend. A smooth optical fiber core flow cannot be obtained, and the optical fiber cores cross each other. While suppressing this crossing, the extra length storage sheet 3 is wound so as to wrap around the central axis of the optical cable 1 as shown by the arrow, but this work takes a considerably long time.

On the other hand, as a method of correcting the bending behavior of the optical fiber core wire coating, a method of heating the coating to release the residual stress in the coating is known. However, the appropriate temperature range for this was not clear. Also, as a heat source for this, a dryer, an electric heater, etc. are used, but it is difficult to obtain a constant heating condition and to uniformly heat the entire circumference of the coating, and the curving behavior is corrected uniformly. It was difficult to do. Further, there is a drawback that the above-mentioned heat source for heating the coating must be further prepared. Further, in the conventional method, even if the bending behavior can be corrected, the optical fiber transmission characteristics may be adversely affected.

[Means for solving problems]

 The present invention overcomes the above-mentioned drawbacks of the prior art.

The optical fiber core wire curving correction method according to the present invention keeps the optical fiber core wire with the remaining curving shape straight, while the residual strain due to heat shrinkage above the glass transition point of the core wire coating material affects the transmission characteristics. The bending of the optical fiber is corrected by heating the optical fiber core wire to a temperature range not higher than the temperature at which the bending is not given.

Further, the bend-correcting sleeve of the present invention is composed of an inner tube having an inner diameter that allows the optical fiber core wire to pass therethrough, and an outer tube enclosing the inner tube, and between the inner tube and the outer tube. It has a cavity layer consisting of a closed space. The curved gusset correction sleeve is used as follows. That is, as a heat source for heating the sleeve, the heat shrinkable tube heater used for reinforcing the fusion splicing part during the optical fiber fusion splicing work performed before the bending and bending correction work is diverted and heated. An optical fiber core wire whose bending behavior is to be corrected is passed through the sleeve, and the heat of the optical fiber core wire corrects the bending behavior of the optical fiber core wire. In particular, the bend-correcting sleeve according to the present invention is characterized in that the hollow layer provided between the inner tube and the outer tube has a heat retaining effect.

The heater diverted here is usually used for the purpose described below, and is always used together with the fusion splicer at the time of connection work. That is, the coating near the splicing point is partially removed at the location where the optical fiber is fused by a fusion splicer, and the structure has a weak structure against external force. For this reason, place a stainless steel rod and a hot-melt adhesive along this part,
A heat-shrinkable tube is covered so as to cover these, and these are heated and shrunk by the heater to be integrated and reinforced. FIG. 4 is a basic configuration diagram of the heater, in which the heat-shrinkable tube 4 is heated for a predetermined time by the heater 5 below the heat-shrinkable tube 4.
Shrinks when heated to 120 ° C.

〔Example〕

FIG. 1 is a cross-sectional view showing an embodiment of a curving habit correction sleeve of the present invention. The inner tube 10 has an inner diameter that allows the optical fiber core wire 2 to pass therethrough, and in this embodiment, the inner diameter is 1.2 mm for an optical fiber core wire having an outer diameter of 0.9 mm. Outer tube 1
1 has a cavity layer 12 provided coaxially with respect to the inner pipe 10, and the cavity layer 12 is bent so as to form a closed space and is closed at both ends of a correction sleeve 13. The outer diameter and the length of the curved gusset correction sleeve are set to 6 mm and 65 mm according to the dimensions of the heater in this embodiment, but these dimensions change depending on the heating value of the heater and the heating time, and the internal temperature of the curved gusset correction sleeve Is determined to be a predetermined value.
The curving correction sleeve is placed in contact with the heater of the heater shown in FIG. 4 and heated.

Next, the temperature characteristics of the curved gusset correction sleeve will be described. The solid line in FIG. 2 shows the center temperature of the curving correction sleeve with respect to the elapsed time from the start of heating the heater 5. The broken line shows the temperature of the heater 5 and the heater energization time is 2 minutes. From the solid line, the temperature of 90 ℃ to 100 ℃ is stopped for 1.5 minutes (2 minutes to 3.
5 minutes) You can see that it is kept. In this sleeve, heat is transferred from the heater heater to the outer tube, the cavity layer, and the inner tube. Due to the heat retaining effect of the cavity layer, the temperature at the center of the sleeve reaches the maximum temperature (97 ° C in 2.5 minutes) after heating is stopped. It can be seen that after that it gradually decreases.

In order to actually correct the bend using this bend correction sleeve, after heating with a heater is stopped, insert a curved optical fiber into the center hole of the sleeve and keep it straight about 3 cm / Move at the speed of seconds. In this embodiment, since the clearance between the inner diameter of the sleeve and the outer diameter of the optical fiber core wire is small (0.3 mm), it was sufficient to simply pass through the center hole of the sleeve. It is more effective to apply tension to the cord to make it straight. By this operation, the coating (nylon) of the optical fiber core wire is heated to a temperature of about 90 ° C., so that the residual stress of the coating is released and the bending can be removed. The extra length of the optical fiber is 1 m as described above.
Since it is as follows, the work of correcting the curving behavior by heating one core once reciprocally takes less than 1 minute and can be completed within the remaining heat time. When we examined the heating temperature of the coating, when the coating was nylon, the temperature was above the glass transition point (about 55 ° C) of nylon and the residual strain due to heat shrinkage did not affect the transmission characteristics (about 150 ° C). Below 80 ° C ~ 110 ° C
It was confirmed that there was an effect within the range of, and more preferably around 90 ° C.

In the present embodiment, the nylon coating has been described as an example, but it goes without saying that the same effect can be obtained even if other thermoplastic resin or ultraviolet curable resin is used as the coating material.

Further, although copper is used as the material of the inner tube and the outer tube in the present embodiment, it is needless to say that other material may be used as long as it has a large heat capacity per unit volume. Further, in the present embodiment, after cutting the optical fiber core wire in the case of the heat shrinkable tube 4 of FIG. 3, the optical fiber core wire is passed through a sleeve, bending work is corrected, and then reconnection is performed for trouble repair or switching. However, in order to shorten the disconnection time of the communication line, the sleeve should be divided in half in the longitudinal direction, the bending should be corrected in the connected state, and then the sleeve should be disconnected and reconnected. It is also possible. In this case, it is necessary to have a structure in which the two half sleeves can be integrated with a hinge or a fitting pin / fitting hole, etc., and to make the contact surface flat to improve heat conduction between the two half sleeves. Is.

[Advantages of the Invention] As described above, the present invention has the following advantages.

1) As a heater for this sleeve, a heater already prepared for a heat shrink tube can be used. Therefore,
This sleeve body has a simple structure and is inexpensive.

2) Due to the heat retaining effect of the cavity layer, the optimum temperature (around 90 ° C) can be maintained for a long time.

3) Only by passing the optical fiber core wire through the center hole of the heated main sleeve, the optical fiber core wire can be uniformly heated, and the bending can be corrected without requiring skill.

4) Since the bending behavior can be easily corrected, the efficiency of subsequent optical fiber connection work and extra long core wire storage work can be improved.

5) The transmission characteristics of the optical fiber after the correction of the bending behavior are not deteriorated.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an optical fiber core wire bending correction sleeve according to the present invention, FIG. 2 is a diagram showing temperature characteristics of the sleeve, and FIG. 3 is a method for treating an extra length of the optical fiber core wire at an optical cable connection point. FIG. FIG. 4 is a basic configuration diagram of a heater for a heat-shrinkable tube, which heats the sleeve according to the present invention. 2 ... Optical fiber core wire, 5 ... Heater, 10 ... Inner tube, 11
…… Outer tube, 12 …… Cavity layer, 13 …… Bending twist correction sleeve.

Claims (2)

[Claims] 1. A temperature which is equal to or higher than the glass transition point of the coating material of the optical fiber and at which the residual strain due to heat shrinkage does not affect the transmission characteristics, while keeping the optical fiber core with the remaining bends straight. A method for correcting the bending behavior of an optical fiber core wire, which comprises correcting the bending behavior by heating the optical fiber core wire to a range. 2. A curved gusset correction sleeve heated by a heater, comprising an inner tube having an inner diameter capable of passing an optical fiber core wire, and an outer tube enclosing the inner tube. A bending-correcting sleeve for an optical fiber core wire, which has a cavity layer formed of a closed space between the outer tube and the inner tube.