JPH08122594A - Optical fiber cable and its production - Google Patents

Abstract

PURPOSE: To reduce the increase of distortion of optical fibers due to bend, the extent of distortion, and the variance in distortion of fibers and to make the arrangement density extra-high by forming grooves of H group type units so that the spiral direction of these grooves is opposite to the twisting direction of H group type units and making twisting directions of the inner layer and the outer layer opposite to each other. CONSTITUTION: Two kinds of H group type units 30 where the spiral direction of grooves is counterclockwise and H group type units 30 where it is clockwise are prepared, and many units 30 of one kind are twisted together on a concentric circle around a tension member 42 to form the inner layer, and many units 30 of the other kind are twisted together on a concentric circle on the outside of the inner layer to form the outer layer. At this time, the spiral direction of grooves is opposite to the twisting direction. This operation is repeated to put one over another. Since twisting directions of the inner layer and the outer layer are opposite, units 30 in the outer layer don't drop between units 30 in the inner layer. Since the spiral direction of grooves is opposite to the twisting direction, the increase of distortion of optical fibers due to bend of the cable is suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-density multi-fiber optical fiber cable, and more specifically, it can reduce transmission loss in the case of multi-fibers by assembling optical fiber knits in multiple layers. High density multi-fiber optical fiber cable

[0002]

2. Description of the Related Art As a structure of a multi-core optical fiber cable, it is known that, for example, five multi-slot type units are arranged concentrically around a tension member, twisted, and covered with a sheath (Fig. 4). However, with this multi-slot type optical fiber cable,
Since the packaging density of the fiber is low, the outer diameter of the optical fiber cable becomes very large when the number of cores is increased, and as a result, the distortion of the optical fiber due to the bending of the optical fiber cable increases and the transmission loss increases. is there. Therefore, it is difficult to obtain a multi-core cable by stacking and twisting multi-slot type units in multiple layers, and usually the maximum number of core wires is 1000. On the other hand, although not known, a large number of H-groove type units (Japanese Patent Application No. 5-177442).
No.) optical fiber cable has a relatively small transmission loss due to its bending, and can be twisted in multiple layers concentrically around the tension member.
Since the storability of the optical fiber tape is higher than the conventionally known multi-slot type unit, this advantage is utilized to
A high-density optical fiber cable can be easily obtained by overlapping and twisting the groove-type units in a concentric circle around the tension member (hereinafter, although not known, this optical fiber cable will be referred to as “a prerequisite technique”). ")). An optical fiber cable 40 (see FIG. 1, hereinafter the same in this section) according to this prerequisite technique has eight H-groove type units 30 arranged around a center tension member 42, which are twisted together and wound around a holding tape 44. In this case, 16 H-groove type units are arranged on the outer side, and the H-groove type units are twisted together and covered with the pressing tape 44, and then covered with the sheath 46. However, this H groove type unit has a larger groove opening than the unit diameter. Therefore, if the H groove type unit is simply twisted around the tension member, the groove portion of the inner H groove type unit is H
The groove type unit easily falls, and the unit diameter is small and the bending rigidity is also small, so that when the optical fiber cable is bent, a part of the H groove type unit twisted together causes a strong twist and the like, and the optical fiber is stored. It is unavoidable that a large distortion is locally generated in the optical fiber to increase the transmission loss, and that the number of cores is large and the transmission loss varies among the fibers of the same optical fiber tape. For this reason, even if the advantages of the H-groove type unit are utilized, there is a limit to the densification of optical fiber cables by itself, and in the era when high-density multi-fiber optical fiber cables are required in accordance with the increase in demand in the future. I cannot meet your request. In order to maximize the density and multi-core of the optical fiber cable using the H groove type unit, at least the above problem, that is, the groove of the H groove type unit of the inner layer, the H groove type unit of the outer layer It is necessary to solve the problem that the H-groove type unit is strongly twisted when the optical fiber cable is bent and the H-groove type unit is strongly twisted and the optical fiber tape accommodated therein is distorted to increase the transmission loss. .

[0003]

DISCLOSURE OF THE INVENTION The present invention is based on the prerequisite technique. When the H groove type unit of the outer layer falls between the grooves of the H groove type unit of the inner layer or when the optical fiber cable is bent, the H groove type unit is formed. It is to suppress as much as possible the local distortion of the optical fiber tape due to strong twisting.

[0004]

[Means for Solving the Problems] The measures taken for solving the above problems are constituted by the following elements. (A) Reversing the spiral direction of the groove of the H groove type unit and the twisting direction of the H groove type unit, and (b) reversing the twisting direction of the outer layer to the twisting direction of the inner layer.

[0005]

[Operation] Two types of H-groove type units are prepared: an H-groove type unit whose groove spiral direction is counterclockwise and an H-groove unit whose groove spiral direction is clockwise. A mold unit is concentrically twisted around a tension member to form an inner layer, and a large number of other types of H-groove type units are concentrically overlapped outside the inner layer and twisted to form an outer layer. By repeating this operation in sequence, the H-groove type units are superposed in a concentric circle around the tension member and twisted to form an ultrahigh-density optical fiber cable. First, since the twisting directions of the inner layer and the outer layer are opposite to each other, the H groove type unit of the outer layer does not fall between the H groove type units of the inner layer. Furthermore, the spiral direction of the groove of the H groove type unit and H
Since the twisting direction of the groove type unit is opposite, when the optical fiber cable is bent, the H groove type unit is twisted in the direction in which the spiral of the groove is unwound. Therefore, the bending causes the twist of the H-groove type unit to be tightened, which tends to increase the strain of the optical fiber, while the unwinding of the groove spiral cancels out the increasing tendency of the strain of the optical fiber. As a result, the twist of the H-groove type unit is tightened, so that the strain increase of the optical fiber can be suppressed. Therefore, in the optical fiber cable in which the H-groove type unit is superposed and twisted, an increase in transmission loss of the optical fiber due to the bending of the cable can be suppressed as much as possible. Further, the greater the twist of the H-groove type unit, the greater the variation of the transmission loss between fibers of the same optical fiber tape, and the more the tape width becomes wider as the number of cores increases, this tendency becomes more remarkable. As described above, when the optical fiber cable is bent, the H-groove type unit is twisted in the direction in which the groove is unwound. Therefore, the twisting of the H-groove type unit due to the bending of the optical fiber cable is small, and therefore, The increase in the variation of the transmission loss between the optical fibers is suppressed.

[0006]

[Test Example] This test is a comparative example of the structure shown in FIG. 1 (the optical fiber cable of the base technology: the former) and the present invention (the latter).
The optical fiber cable of the first embodiment is bent at a radius of curvature of 500 mm (= bending diameter of 1000 mm), and the strain of the fibers (fiber 1 and fiber 2) at both ends of the optical fiber tape in that state is optically measured. It was measured by the Thereby, the correlation between the strains of the fiber 1 and the fiber 2 which is the layer core radius of the optical fiber unit, and the correlation between the width of the optical fiber tape (the distance between the fiber 1 and the fiber 2) and the strain between the fiber 1 and the fiber 2 are grasped. . The former measurement result is shown in FIG. 2 (1) and FIG. 3 (1), and the latter measurement result is shown in FIG.
This is as shown in (2) and FIG. 3 (2). In addition,
The H-groove type unit of the optical fiber cable used for the former test is 10 16-core tape (fiber wire diameter 180μ
It is the one in which m) is internally laid into two layers.
The latter test is an optical fiber cable similar to the former test, in which the strains of the symmetric fibers 1 and 2 are optically measured. The comparative example is fiber 1
Then, the strain is 0.17% at a layer core radius of 10.5 mm,
The layer core radius increases to 0.33% when the layer core radius is 18 mm, and in the fiber 2, the strain increases from 0.3% when the layer core radius is 10.5 mm to 0.45% when the layer core radius is 18 mm [Fig. 2 (1)]. reference]. On the other hand, in the example, the fiber 1 has a strain of about 0.01% at a layer core radius of 10.5 mm and a layer core radius of 1%.
It becomes 0.05% at 8 mm, and in the fiber 2, the strain is 0.15% at the layer core radius of 10.5 mm, and the layer core radius is 18 m.
It becomes 0.20% in m. As described above, in the comparative example, the strains of the fiber 1 and the fiber 2 are remarkably increased due to the increase of the layer core radius, and both fibers 1 and 2 are increased due to the increase of the layer core radius.
The difference in the magnitude of the distortion of 2 is also remarkable. On the other hand, in the embodiment, the absolute values of strains of the fibers 1 and 2 are small,
The difference in strain magnitude between both fibers is extremely small, and the difference in strain magnitude at a layer core radius of 18 mm is 32% of that in the comparative example. Further, in the comparative example, the strain increases in fiber 1 from 0.17% at a tape width of 2.1 mm to 0.30% at a tape width of 4.2 mm, and in fiber 2, the strain increases at a tape width of 2.1 mm. 0.21% to 0.2 mm for tape width 4.2 mm.
Increase to 49%. On the other hand, in the embodiment, the fiber 1
Then, the strain is almost 0.04% when the tape width is 2.1 mm and 0.04% when the tape width is 4.2 mm.
Then, the distortion increases from 0.10% when the tape width is 2.1 mm to 0.24% when the tape width is 4.2 mm. As described above, in the comparative example, the strains of the fibers 1 and 2 remarkably increase due to the increase in the tape width, and the difference in strain magnitude between the fibers 1 and 2 remarkably increases due to the increase in the tape width. On the other hand, in the example, the absolute values of strains of the fiber 1 and the fiber 2 are small, and the difference in strain magnitude between both fibers is extremely small, and the difference in strain magnitude at the tape width of 4.2 mm is compared. 35% of the example. From the above test results, in the embodiment of the present invention, the absolute value of the strain of the optical fiber due to the bending of the optical fiber cable in which the H groove type units are twisted in multiple layers is small, and the variation of the strain between the fibers is small. It is clear that the variation in the strain of the fiber due to the increase in the radius of the layer core and the variation in the strain of the fiber due to the increase in the tape width can both be suppressed to about 1/3 of the comparative example.

[0007]

[Effect] The invention which has solved the problems of the present invention is not yet known. Therefore, the solution to the problem described above and the solution to the problem in the base technology is the greatest effect peculiar to the present invention. That is, according to the present invention, in an optical fiber cable in which H-groove type units are twisted in a concentric circle, the distortion of the optical fiber due to the bending of the optical fiber cable is increased, the magnitude of the distortion, and the variation between the fibers are significantly reduced. This makes it possible to dramatically increase the density of an optical fiber cable in which H-groove type units are twisted together. Further, since the means for that is to devise a combination of the spiral direction of the spiral groove of the H groove type unit and the twisting direction when twisting the H groove type unit, the application of the present invention is very simple, Further, the increase in the manufacturing cost of the optical fiber cable due to this is extremely small. This is a great advantage of the present invention.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of the present invention.

FIG. 2 is a graph showing a test result of a fiber strain test on an optical fiber cable of (1) the base technology.
(2) It is a graph which shows the test result of the fiber strain test about the optical fiber cable of an Example.

FIG. 3 is a graph showing a test result of a fiber strain test for an optical fiber cable of (1) the base technology.
(2) It is a graph which shows the test result of the fiber strain test about the optical fiber cable of an Example.

FIG. 4 is a cross-sectional view of a conventionally known high-density optical fiber cable.

[Explanation of symbols]

 30 ... H groove type unit 40 ... Optical fiber cable 42 ... Center tension member 44 ... Holding tape 46 ... Sheath

Claims (2)

[Claims] 1. In an optical fiber cable in which H groove type units are arranged in a concentric circle and twisted in multiple, the spiral direction of the groove of the H groove type unit and the twist direction of the H groove type unit are opposite directions, An optical fiber cable in which the twist direction of the outer layer is opposite to the twist direction of the inner layer. 2. An H-groove type unit in which the spiral direction of the groove is the right direction is arranged on a concentric circle and twisted into a left-hand twist,
A method of manufacturing an optical fiber cable in which an H-groove type unit having a spiral direction of a groove on the outside is arranged on a concentric circle and is twisted into a right twist.