JPH0449683B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for connecting self-supporting optical cables, and is particularly suitable for preventing damage to optical cables caused by movement of optical cable cores between connecting parts. This paper relates to a method for connecting self-supporting optical cables.

[Conventional technology]

It is generally known that at the cable end of an optical cable connection, there is a "cable core movement phenomenon" in which the cable core, similar to that of conventional copper communication cables, protrudes or retracts in the axial direction relative to the cable sheath. It is being If the amount of optical cable core movement exceeds the allowable limit for core movement in the junction box, bending stress and tensile stress will be applied to the optical fiber, causing an increase in transmission loss and breakage of the optical fiber. This optical cable is fundamentally different from traditional copper communication cables.In optical cables, small bends in the optical fiber will cause an increase in transmission loss, and static fatigue can cause the optical fiber to crack or in the worst case scenario. rupture occurs before the design life. Therefore, cable core movement is particularly important in the case of optical cables as one of the factors that greatly influences their reliability.

This cable core movement varies depending on the cable structure, and the increase in optical fiber transmission loss depends on the relationship between the amount of cable movement and the junction box structure. The cable core movement phenomenon in self-supporting optical cables is thought to occur from the following three factors.

Sheath contraction (Lp) When manufacturing a cable, processing distortion is applied to the cable sheath, and after the cable is installed, this processing distortion is released and the sheath contracts. Therefore, the cable core protrudes relatively.

Sheath contraction due to slack (Ls) As the cable body and the messenger wire are separated at the connection point, the sheath loses the binding force of the messenger wire and the sheath contracts by the strain equivalent to the binding force of the messenger wire. The cable core protrudes relatively.

Relative movement of the sheath and core due to tension ( _LE ) After the cable is installed, the cable tension changes due to temperature changes, wind pressure loads, etc., and the messenger wire and cable sheath expand and contract accordingly. The cable core, which is connected to the cable core by a finite and relatively weak frictional force, cannot follow this expansion and contraction and slips, causing the sheath and core to pull in or protrude relative to each other.

Among these, the present invention relates to measures against relative movement of the sheath and core due to tension.

It has been revealed that the phenomenon of increased transmission loss in self-supporting optical cables installed overhead has an important relationship with the phenomenon of cable core movement at the optical cable connections, and this phenomenon This is a well-known fact in cables, but in the case of cables, it has a particularly large effect on its reliability.

The structure of self-supporting optical cables was published in 1982.
This is clearly shown in the ``Study of Cable Core Movement Phenomenon of Self-Supporting Overhead Optical Cables'' in the lecture collection of the 2018 IEICE General Conference. The self-supporting optical cable shown in Figure 2 is an example of the SSD type discussed above. The optical cable 10 includes a suspension wire 12, a cable core 13,
It is constituted by a sheath 11 that covers and fixes the hanging wire 12 and cable core 13 together. This hanging wire 12 is usually formed by twisting a plurality of steel wires. Further, the cable core 13 is constructed of a cushioning material, with a steel wire arranged at the center and six optical fiber wires arranged around the steel wire.

Such a self-supporting optical cable 10 is usually in units of 1 km, and has a length of about 40 m as shown in Figure 3.
They are attached to utility poles 30 installed at intervals. An electric wire 40 is installed on this utility pole 30. This self-supporting optical cable 10 is fixed to a utility pole 30, as shown in FIG. 4, except for the portion connected by the connecting portion 20. That is,
An optical cable 10 is divided into a suspension wire 12 and a cable core 13, and the suspension wire 12 is fixed to a utility pole 30 by a mounting band 14, and an earth clamp 15 is attached to the suspension wire 12. A ground wire 16 is connected to this ground clamp 15, and although not shown, the ground wire 16 is grounded. This ground wire 16 is fixed to a utility pole 30 with a stainless steel band 17.

Further, the self-supporting optical cable 10 is connected to the connecting portion 20.
The portion connected by the is fixed to the utility pole 30 as shown in FIG. That is, the suspension wire 12A and the suspension wire 12B are connected to the round simple 22 via the restraining band 23 fixed to the utility pole 30.
connected by. Further, the cable core 13A and the cable core 13B covered by the sheath 11 are connected by a connector 20.
Both ends of this connector 20 are holders 21A and 21B.
The sheath 11 is suspended from the coated hanging wire 12B by a wire. Slacks 25A and 25B are provided at both ends of the connector 20 in the cable core 13A and the cable core 13B.

In such a self-supporting optical cable used for overhead power distribution, when the tension applied to the optical cable increases due to wind or temperature changes and the entire cable is stretched, the frictional force between the cable sheath 11 and the cable core 13 is small. At both ends of the cable, that is, at the connection part, the cable core does not stretch and becomes retracted. At this time, the optical fiber core, which is part of the optical cable core, also moves, and if the amount of movement is large, the optical fiber core may be stretched or bent, increasing transmission loss, and the movement may become even larger. Then, a problem arises in that the optical fiber core wire becomes disconnected.

Therefore, by providing groove slacks approximately 800 mm wide and 400 mm deep at both ends of the self-supporting optical cable connection, as shown in Figure 6, the tension can be reduced.
No need to move the cable core even when the weight increases to 800Kg.
The present inventors have already developed that the thickness can be suppressed to 10 mm or less.

[Problem that the invention seeks to solve]

However, such a conventional slack-equipped device has the disadvantage that the depth of the slack must be increased, making it difficult to adjust dimensions when installing, and that the appearance is poor.

An object of the present invention is to provide a self-supporting optical cable connection method that can prevent cable core movement without increasing the slack depth.

[Means for solving problems]

In order to achieve the above object, the present invention provides a self-supporting optical cable connection method in which two optical cables in which a hanging wire and a cable core are integrally fixed by a sheath are connected using a connector. At least two slacks are provided in the cable core of the optical cable to be connected to both ends within a width of 400 to 800 mm in the direction away from the end of the connector, and the depth of the valley of the slack is approximately equal to the width. 400mm
If the width is approximately 30mm, if the width is approximately 800mm, it will be 50mm.
It is characterized by having a diameter of about mm.

[Effect]

According to the above configuration, even if the self-supporting optical cable expands or contracts due to wind or temperature changes,
The cable core is integrated with the sheath, and movement of the cable core at the connection portion is suppressed, and the cable core is not pulled in or protruded relative to the sheath.

〔Example〕

Examples of the present invention will be described below.

FIG. 1 shows an embodiment of the invention.

In the figure, a self-supporting optical cable 1 is composed of a hanging wire 2 and a cable core 3 that are integrally fixed by a sheath. This cable core 3 is connected by a connector 4. Two cable cores 3 connected at both ends to this connector 4
Two slacks 5 each having a width of 800 mm and a valley approximately 50 mm deep are provided.

In this way, when configured as in this embodiment, conventionally,
The tension is
When the tension reaches 800Kg, the cable core retracts by 5 to 20 mm, but even when the tension applied to the cable core reaches 800Kg, the cable core does not retract.

Now, the amount of movement of the cable core by the conventional slack and the amount of movement of the cable core by the slack of the present invention are calculated by installing an optical cable with a span of 40 m, increasing the tension of the messenger wire (suspension wire), and comparing the amount of movement of the cable core with the slack of the present invention. A comparison of the amount of retraction is shown in Fig. 7. The conventional slack has a width of 800 mm and a depth of d = 0, d = 100 mm, d = 200 mm, d = 300 mm, d
The same figure shows the experimental results when = 400 mm and 5 types.

The present invention type has two slacks within a width of 800 mm, and the experimental results are shown in the same figure when the depth d of each slack was set to two types: d = 120 mm (small) and d = 190 mm (large). .

Figure 7 shows that in the conventional slack, if the depth is set to 300 mm or more, the amount of cable core retraction is reduced.
In contrast, in the case of the present invention (W-shaped large), the weight is 800 kg.
Even when the tension increases, almost no cable core movement occurs.

In this embodiment, two slacks are provided within a width of 800 mm, but the effects of the present invention can be fully exerted as long as there are three or four slacks, or two or more slacks. Further, the width does not need to be 800 mm, and even if the width is 800 mm or more, the effects of the present invention can be fully exhibited. Furthermore, the depth of the slack should be 50mm for a width of 800mm to withstand normal tension, and 50mm for normal installation.
A certain degree is sufficient.

Further, in this embodiment, an example of a width of 800 mm is shown, but this represents an optimum state, and the width does not necessarily have to be 800 mm. The effect can also be fully exerted by providing a plurality of slacks with a width of about 400 mm and a depth of about 30 mm within this width. The number of slacks in this case is determined by the radius of curvature of the cable core when making the slacks. This is because transmission loss occurs depending on the radius of curvature of the cable core.

〔Effect of the invention〕

As described above, according to the present invention, by regulating the slack provided at the connection between the sheath and the cable core, the movement of the cable core can be suppressed within a small tolerance range in a simple manner, and the long-term performance of the optical fiber can be improved. This has the excellent effect of ensuring high reliability.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a block diagram of a self-supporting optical cable, Fig. 3 is a block diagram of a self-supporting optical cable installed on a utility pole, and Fig. 4 is a block diagram showing a self-supporting optical cable installed on a utility pole.
The figure shows the part of the self-supporting optical cable without the connector installed on the utility pole, Figure 5 shows the part of the self-supporting optical cable with the connector installed on the utility pole, and Figure 6 shows the part with the connector installed on the pole. FIG. 7 is a diagram illustrating a conventional cable core connection method provided with a slack, and is a diagram illustrating the characteristics of the cable core retraction amount with respect to the tension of the suspension wire in the conventional example and the present invention. 1... Self-supporting optical cable, 2... Hanging wire, 3
...Cable core, 4...Connector, 5...Slack.

Claims (1)

[Claims] 1. In a self-supporting optical cable connection method that uses a connector to connect two optical cables in which a suspension wire and a cable core are integrally fixed with a sheath,
At least two or more slacks provided in the cable core of the optical cable connected to both ends of the connector are provided within a width of 400 to 800 mm in the direction away from the ends of the connector, and the depth of the valley of the slack is A method for connecting a self-supporting optical cable, characterized in that the width is approximately 30 mm when the width is approximately 400 mm, and approximately 50 mm when the width is approximately 800 mm.