JPS58163905A - Optical fiber cable - Google Patents

Abstract

PURPOSE:To make a titled optical fiber cable endurable against lateral pressure, and also to improve its mechanical stability, by placing a tension member in the center, combining an optical fiber core holding spacer and a core forming spacer at each suitable interval, and installing them to said tension member by a prescribed method. CONSTITUTION:A tension member 6 is placed in the center of a cable, a core holding spacer 15 and a core forming spacer 16 are combined suitably, are installed to said tension member at an interval, a core 1 is contained in a core holding groove 15b and a core winding groove 16c of these spacers 15, 16, is wound like a smooth spiral, subsequently, a surplus length part of the core 1 is made by rotating the spacer 16, and subsequently, push-winding 17 is performed, by which an optical fiber cable formed as one body with a cable sheath 18 is obtained. In this way, the cable is endurable against lateral pressure since the surplus length being capable of coping with expansion and contraction, etc. of of the cable is formed, and also there is no possibility that buckling or rupture occurs, therefore, the mechanical stability can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical fiber cable, and more particularly to an optical fiber cable having a structure suitable for providing excellent mechanical stability.

FIG. 1 is a sectional view showing an example of an optical fiber core, which is a main component of an optical fiber cable. As shown in FIG. 1, an optical fiber core wire 1 includes an optical fiber wire (hereinafter simply referred to as a wire) 2 made of glass or quartz, a coating layer 3, a silicone rubber buffer layer 4, and a silicone rubber buffer layer 4. For example, the outer diameter of the wire 2 is 125 μm, and the outer diameter of the optical fiber core 1 is about 1 mm.

FIGS. 2 and 3 are cross-sectional views of conventional optical fiber cables containing the optical fiber core 1 shown in FIG. 1, respectively. In Figures 2 and 3, 6 is a tension member, 7 is a presser winder, 8 is a cable jacket, 9 is a V-shaped spacer, and I
O is a grooved holder, and 11 is a groove in which the optical fiber core 1 is accommodated. By the way, optical fibers have the disadvantage that their transmission characteristics change significantly due to bending (microbending) caused by applied pressure. This is to prevent harmful bending from occurring due to 1o.

Therefore, in the structure shown in Fig. 2, the core wire 1 is protected by the V-shaped spacer 9 and can withstand pressure from the sides, but the cable actually installed has a slope in height and a gap. , vibrations are added, and expansion and contraction fluctuations due to temperature changes overlap, so it is necessary to take sufficient measures against these as well. However, the second
In the structure shown, since the V-shaped spacer 9 and the core wire 1 are not fixed to each other by adhesive or the like, the core wire 1 tends to move longitudinally relative to the spacer 9 under environmental conditions. In addition, since the spacer 9 has a continuous structure in the length direction, there is no play (clearance) in the core wire 1 in the radial direction.
Less is. For this reason, it is difficult to uniformly form a sufficient length of the optical fiber core wire 1 in the length direction for expansion and contraction of the cable. As a result, in an actual long laid line, there is a risk that a portion where harmful bending or tensile stress is applied to the core wire 1 may occur locally. Moreover, this structure has a basic drawback in that it is difficult to analyze movement phenomena due to dynamic environmental factors and formulate concrete measures.

In addition, in the structure shown in FIG. 3, since the optical fiber core 1 lies loosely in the groove 11 of the grooved holder 1o, if there is a guarantee that this state will always be maintained, the transmission characteristics will be No problems will occur. However, it definitely shows excellent characteristics against lateral pressure. However, it is designed to move very easily in the length direction. In addition, since the grooves 11 are provided continuously in a straight line or in a spiral shape in the length direction, there is little clearance in the radial direction of the core wire 1, and the remaining length in the length direction when viewed as a long cable. There are surprisingly few. That is, even in the structure shown in Figure 2,
A drawback is that deterioration in transmission characteristics caused by creep of the core wire 1 cannot be avoided.

As a modification of the structure shown in FIG. 2, the width of the entrance of the groove 11 is 1
It has also been considered to make the outer diameter of the optical fiber core slightly smaller than the outer diameter of the optical fiber core 1 to prevent the stored core wire 1 from escaping, or to grip the stored core wire 1 by applying an appropriate clamping force. . However, the former does not provide a measure against creep in the length direction, and the latter continuously pinches the core wire 1, so the core wire 1 is also forced to expand and contract as the cable expands and contracts, which also causes mechanical problems in terms of transmission. There are even more problems with the characteristics. This phenomenon is
This occurs because the gripping and fixing of the core wire 1 and the necessary extra length cannot be reliably formed over the entire length of the cable for an appropriate unit length. As a countermeasure against this problem, there is a structure in which a tension member such as a steel wire is placed in the center of the structure shown in FIG. However, the limit for materials that can be used as tension members is to secure an elongation of about 0.5 to 2 inches.

By the way, when tension is applied to the long cable, it may be considered that the tension member elongates each part cumulatively over the entire length. On the other hand, the optical fiber core 1 housed and held in a11 is different from the holder 10 due to the rigidity of the core 1, the way it is wound, the way it is twisted, and the difference between the materials (between the holder 10 and Friction between nylon jackets (5),
The coefficient of friction between each part of the core wire 1 and the holder IO is distributed in slightly different ways depending on the topography of the cable installation and the social and natural environment of the cable installation location. That is, a phenomenon occurs in which the optical fiber 1 is subjected to tension in some parts and buckling force in certain parts.

This can cause harmful microbending in long installed lines, which is difficult to detect in short cable production lengths, but has been experienced and is a problem on real lines.

Furthermore, in the structure shown in FIG. 3, as a method of preventing creep of the core wire 1, it is also possible to fix the holder 10 and the core wire 1 by pouring adhesive into the grooves 11 at appropriate intervals. However, even if creep of core wire 1 could be prevented by this, the extra length of the core that can be taken between the fixing points would be insufficient, and the cable could become unstable due to cable elongation or significant temperature expansion and contraction. The danger of becoming is not resolved.

The following has since been proposed as a method to solve the above-mentioned problem. That is, as shown in FIG. 4, the optical fiber core 1 is housed in a plastic pipe 12, and the pipe 12 is heated at a certain interval to provide a blocking portion 13, and the core wire 1 is closed with the pipe 12. The extra length part 14 of the core wire 1 is held fixed at the part 13, and the extra length part 14 of the core wire 1 is held between the closed part 13.
This is a method of forming. The problem with this method is that first, the pipe 12 is formed while creating an extra length in an empty space, and then the pipe 12 is closed. It is also possible to consider a manufacturing method in which the pipe 12 is formed and closed on the core wire 1 with an extra length formed in advance, but in either case, there are manufacturing difficulties. Secondly, in this structure, the extra length is taken in the radial direction with the axis of the pipe 12 as a reference, so the extra length securing rate is small, and in actual cable design, the limit is about 0.1 to 0.2 inches at most. be. Third, since there is no tension member, it is not suitable for long cable installations.

FIG. 5 shows a partially improved structure of FIG. 4. That is, by arranging the tension member +6 at the center, it has a structure that can withstand long length installation. In this case, since the tension member 6 is provided, it becomes easy to form the spiral shape of the core wire 1, which has the advantage of improving manufacturability. By the way, when heating the plastic pipe 12 to form the closed portion 13, it is necessary that both the tension member 6 and the core wire 1 be located approximately at the center of the pipe 12. However, if the core wire 1 is wound around the tension member 6 as shown, the excess length of the core wire will be insufficient.

In the end, the structure shown in FIG. 5 can be manufactured only when the extra length of the core wire is extremely small relative to the tension member 6, and the mechanical stability becomes unstable and insufficient. It has shortcomings.

In order to compensate for these drawbacks, a structure shown in FIG. 6 has been proposed. This is different from the structure shown in FIG. 4 in that the tension member 6 is provided outside the cable. This type of configuration is applied in general communication cables. The defects in this structure (), except for the tension member 6, are as already described with reference to FIG. Although V-shaped cables like this one are suitable for overhead installation, they have the disadvantage that they cannot be used as underground cables.

The optical fiber cable having the structure shown in Figs. 4 to 6 was originally conceived by gripping and fixing the core wires 1 at predetermined intervals in order to withstand side pressure. 13) The aim was to provide a necessary and sufficient extra length of core wire in between, and although this goal is correct, it has not yet reached the point where the required conditions are fully satisfied.

As mentioned above, none of the cables having the structures shown in FIGS. 2 to 6 fully satisfy the required conditions.

In addition, place the tension member in the center of the cable,
The method of wrapping the core with a pipe and making use of the space formed by the two to maximize the extra length is to wrap the core wires along the inner surface of the pipe to approximately the same diameter and at an appropriate pitch that takes into account the transmission characteristics. It is a good idea to wind the wire in a spiral shape, but as mentioned above, if the pipe is closed, it becomes difficult to integrate the tension member, the core wire, and the pipe in manufacturing. To avoid this, two options are to increase or decrease the winding diameter of the core wire at predetermined intervals and block the pipe at the small diameter section, but if you do this, the transmission characteristics will be the same at the small diameter section. This results in deterioration and cannot necessarily be achieved satisfactorily.

The present invention has been made in view of the above, and its purpose is to withstand external lateral pressure and to prevent buckling or breakage of the optical fiber core due to movement during long installation or repair. The purpose of the present invention is to provide an optical fiber cable with excellent mechanical stability.

The feature of the present invention is that a tension member is placed in the center,
A spacer for gripping the optical fiber core and a spacer for forming the shape of the optical fiber core are attached to this tension member at appropriate intervals and in an appropriate combination, and the optical fiber is inserted into the groove carved on the surface of each spacer. The core wire is housed, the spacer for gripping the core grips and fixes the core wire marked -F, the spacer for forming the core wire shape holds the shape of the core wire into a spiral shape, and the spacer for forming the core wire shape holds the core wire into a spiral shape. After securing the extra length of the core wire in the radial direction by rotating the spacer by a predetermined angle, press and wind the outer periphery of both spacers to form a cable core, and then apply the cable core to this cable core. The point is that it is structured as follows.

The present invention will be illustrated in FIGS. 7 to 9 below.
This will be explained in detail using FIGS. 0 to 12.

FIG. 7 is a partial vertical sectional view showing an embodiment of the optical fiber cable of the present invention. In FIG. 7, 1 is an optical fiber core wire (only one is shown in the figure), 6 is a tension member made of a single or stranded steel wire or FRP wire placed at the center of the cable, and 15 is a core fiber. Spacers 16 for gripping the wire are spacers for forming the shape of the core wire. In the figure, spacers 15 and 16 are attached alternately to the tension member 6 at predetermined intervals, and both spacers 15 and 16 are made of material U rubber, plastic, or It consists of a combination of these. 1
Reference numeral 7 denotes a presser wrap made of rubber or plastic tape that presses down the outer periphery of the spacers 15 and 16, and 18 is a cable sheath made of metal purve such as copper or aluminum.

FIG. 8 is a plan view showing an embodiment of the core wire gripping spacer 15 shown in FIG. 7. 15a is for a tension saw/member for attaching the spacer 15 to the tension member 6;
15b The spacer 15 has a linear or spiral wire gripping groove carved on its outer periphery, and is configured to grip the optical fiber core 1 with an appropriate pressure to prevent it from slipping.

FIG. 9 is a plan view showing an embodiment of the core wire shape forming spacer 16 shown in FIG. 7. 16a is tension member 6
This is a groove for the tension member into which the spacer 16 is attached, and is configured to be looser than the groove for the tension member 15a of the spacer 15 for gripping the core wire. 16
b is a rotation protrusion used when rotating the spacer 16 in the circumferential direction, 16c is a groove for winding the core wire, 16d is a core wire extra*#RMa-c, groove 6°, 16dUx-knee v16
.

It is engraved in a spiral shape on the outer periphery.

Next, a method for manufacturing an optical fiber cable according to the present invention will be explained. First, the core wire gripping spacer 15 is attached to the tension member 6 from the side. In this case, $15 for tension member a Katenoyon member 6
Since the spacer 15 is constructed so that it does not move easily when the spacer 15 is attached to the spacer 15, it remains in a fixed state.

Next, the core wire shape forming spacer 16 is attached to the tension member 6. In this case, it is attached so that the spacer 15 is at a predetermined interval and the spacers 15 and 16 are positioned alternately.

Note that, at this time, the spacers 15 and 16 do not have to be arranged alternately, but may be combined so that two spacers 16 are provided between the spacers 15. This combination is appropriately selected in consideration of the requirements of the cable, etc. Thereafter, the mounting of the spacers 15 and 16 is repeated one after another. Next, the optical fiber 1 is housed in the fiber gripping groove 15b1 of the spacer 15, 16 through the groove 16cVc6. Note that although the grooves 15b and 16c have a spiral shape, the pinch value is selected to be an appropriate value based on the cable bending requirements and the like. FIG. 10 shows a cross section of the spacer 15 for gripping the optical fiber cable in this state, and FIG. 11 shows a cross section of the spacer 16 for forming the fiber shape. Note that in FIGS. 10 and 11, the same parts as in FIGS. 7 to 9 are indicated by the same reference numerals.

Next, the rotation protrusion 16b of the core wire shape forming spacer 16
Using a stick or the like, push in the spacer 1 from the side.
Rotate 6. 12 is a cross-sectional view corresponding to FIG. 11 when the spacer 16 is rotated so that θ-=45°.
As shown in the figure. That is, since the core wire 1 is maintained at its original position by the front and rear core wire gripping spacers 15, the core wire 1 is held at the core shape forming spacer 16 as shown in the figure.
moves from the core wire winding a16c to the core wire extra length forming groove 16d, and as a result, the difference in height between the bottom of the core wire extra length forming groove 16d and the core wire l is secured as the extra length. become.

Next, press winding 17 is performed on the spacers 15 and 16 to create a cable core, and the outer periphery of the cable core is covered with a cable north 18 made of a metal pipe, which is integrated by squeeze molding to form an optical fiber cable as shown in FIG. complete. In addition, when the cable requires a corrosion function, a plastic coating is applied on the cable sheath 18,
Additionally, if the strength is insufficient, add wire sheathing or the like on top of the plastic coating.

According to the embodiment of the present invention described above, a tension member 6 is arranged at the center of the cable, and a spacer 15 for gripping the cable and a spacer 16 for forming the cable shape are appropriately combined with the tension member 6 and spaced apart from each other. Fit these spacers 15.16
The core wire gripping groove 15b, the core wire winding is in the groove 16c.
The storage 1-1 is wound in a smooth spiral shape, then the spacer 16 is rotated to create an extra length of the core wire 1, and the cable sheath 18 is integrated after being wrapped with a presser 17. Since it is an optical fiber cable, there is a sufficient extra length between the fixed point of the core wire 1 and the fixed point and 0 to accommodate the expansion, contraction and bending of the ear cable. There is no fear that the optical fiber core l will move and buckle or break during installation or repair, and it can be made to have excellent mechanical stability.

In addition, if there is no need to consider conditions such as extremely severe external pressure or vertical installation, a plastic north similar to that of a general communication cable may be used instead of the cable north 18 made of a metal pipe as described in 2. , this does not cause any practical problems.

As explained below-4-, according to the present invention, the optical fiber core can withstand external lateral pressure, there is no risk of buckling or breaking due to movement of the optical fiber core wire during long installation or repair, and mechanical This has the effect of making it highly stable.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view showing an example of an optical fiber core wire, Figures 2-
Figure 6 is an explanatory diagram of the structure of a conventional optical fiber cable, Figure 7
The figure is a partial vertical sectional view showing an embodiment of the optical fiber cable of the present invention, FIG. 8 is a plan view showing an embodiment of the spacer for gripping the core wire of FIG. A plan view showing an example of a spacer for forming a core wire shape, FIG.
FIG. 12 is a detailed explanatory diagram for explaining the structure of the optical fiber cable according to the present invention. DESCRIPTION OF SYMBOLS 1... Optical fiber core wire, 6... Tension member, 15... Spacer for grasping the core wire, 15a... Groove for tension member, 15b...
... Core wire gripping groove, 16... Spacer for forming the core wire shape, 16a...
...Tension member groove, 16b...
Rotating protrusion, 16c... Groove for winding the core wire, 16d... Groove for forming extra length of the core wire, 17...
Presser winding, 18... Cable sheath 0, ';if Kokusai 2 n ;f''5 m!

Claims (1)

[Claims] 1. A tenon member placed at the center, and spacers for gripping the optical fiber core and spacers for forming the shape of the optical fiber core, which are attached to the tenon member at appropriate intervals and in appropriate combinations; The spacers are stored in grooves carved on the outer periphery of each spacer, are gripped and fixed by the spacer for gripping the core, are held in shape by the spacer for forming the shape of the core, and are held at a predetermined angle by the spacer for forming the shape of the core. An optical fiber core wire whose extra length is ensured in the radial direction by rotating, a presser winding that presses the core wire against the outer periphery of both spacers, and a cable sheath M-shaped around the outer periphery of the presser winder. An optical fiber cable characterized by: