JP2006195100A - Optical cable - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize an optical cable which enables a prescribed excess length to be secured without enlarging the outer diameter of the cable and which has superior post branching performance. <P>SOLUTION: The optical cable is provided with a plurality of cable units (2-7) which are SZ-collected around a tension member (1). Each cable unit has a spacer (20) in which a plurality of SZ grooves (20a-20d) are formed, with coated optical fibers (21a-21d) stored in each SZ groove. Further, in this invention, the cable units are also SZ twisted together. Thus, the coated optical fibers and the cable units are both SZ-collected in two steps, enabling much more long excess length to be secured. As a result, a post branching operation is further facilitated, enabling a required excess length to be secured without enlarging the outer diameter of the optical cable. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical cable, and more particularly, to an optical cable having a sufficient post-branching performance that can sufficiently secure an extra length of an optical fiber core wire during a post-branching operation.

  With the arrival of broadband communications, there is a strong demand for the development of optical cables with excellent post-branching performance. The optical cable is erected or laid and then branched off from the main cable to a connection device installed in each floor of the building, and connected to various devices via the branch cable. As an optical cable excellent in back branching property, an SZ twist spacer type optical fiber cable is widely used. This SZ twisted spacer type optical fiber cable has a spacer in which SZ grooves whose turning directions are alternately reversed along the longitudinal direction of the cable are formed, and each of the SZ grooves has a 4-core or 8-core tape-like light. One or a plurality of fibers are accommodated (see, for example, “Patent Document 1”). In the SZ twist spacer type optical fiber cable in which the tape-like optical fiber is accommodated, the post-branching operation is performed as follows. First, the sheath and the presser winding are peeled off in the middle of the cable, and the tape-shaped optical fiber at the reversal portion in the groove of the spacer is taken out by the extra length. Next, the tape-shaped optical fiber is branched for each optical fiber core, and the necessary optical fiber is taken out and connected to the branch cable. An optical fiber cable in which a single optical fiber is housed in an SZ groove instead of a tape-shaped optical fiber is also known (see, for example, “Patent Document 2”).

Japanese Patent Application Laid-Open No. 10-221577 Japanese Patent Laid-Open No. 63-301911

  In an SZ twisted spacer type optical fiber cable in which a tape-shaped optical fiber is accommodated in an SZ groove, it is necessary to branch the tape-shaped optical fiber into individual optical fiber cores after taking out the necessary tape-shaped optical fiber. There is a disadvantage that the post-branch operation becomes complicated. In addition, it is necessary to find a specific optical fiber of a given tape-shaped optical fiber and connect it to a specified branch cable, and it is often difficult to identify individual optical fibers. The danger of connecting is also pointed out. In addition, there are many cases where only one or two optical fiber cores connected to a branch cable and used for actual data transmission are used. In this case, there is a disadvantage that the remaining unused optical fiber cores are wasted. . Furthermore, in order to secure the extra length necessary for the branch connection, there is a drawback that the outer diameter of the optical cable is increased.

  In an optical cable in which a large number of SZ grooves are formed on the outer periphery of the spacer and a single optical fiber core is accommodated in each SZ groove, for example, when a large number of optical fiber cores such as 24 cores are accommodated, A large number of SZ grooves must be formed at equal intervals on the outer periphery, and there is a disadvantage that the outer diameter of the spacer is increased and the manufacturing cost is increased. In addition, the cable length for stripping the sheath in the middle branching work is limited to about 500 mm, so the outer diameter of the spacer must be set to ensure the extra length required for the rear branching work. It is necessary to increase the size and the manufacturing cost is not only expensive, but also a problem that requires a large space for installation is pointed out.

Therefore, an object of the present invention is to realize an optical cable with improved workability of intermediate branching.
Furthermore, another object of the present invention is to provide an optical cable capable of ensuring a necessary extra length without increasing the outer diameter of the optical cable at the time of intermediate branching.

The optical cable according to the present invention has a spacer formed with a plurality of SZ grooves whose turning directions are alternately reversed along the longitudinal direction of the cable, and optical fiber cores respectively accommodated in the respective SZ grooves, A plurality of cable units having presser windings on the outer periphery of each spacer are provided,
The plurality of cable units are gathered in an SZ twist around the tension member.

  In the present invention, the SZ twisted structure is adopted for both the spacer for housing the optical fiber core and the cable unit including the spacer. Therefore, the extra length when the post-branching process is performed is the SZ groove formed in the spacer. A total surplus length corresponding to the surplus length and the surplus length of the cable unit that is SZ-twisted is obtained. As a result, the extra length of the length necessary for branch connection can be secured without increasing the outer diameter of the optical cable. In other words, when a large number of SZ grooves are formed in a single spacer and an optical fiber core is accommodated, the extra length is formed only in the surface area of the cable outer periphery where the SZ grooves are formed. In order to ensure a sufficient extra length, it is necessary to increase the outer diameter of the spacer. On the other hand, in the optical cable of the present invention, since the SZ groove structure is formed in the spacer and the cable unit has an SZ twist assembly structure, an extra length is also formed in the internal space of the cable. The necessary extra length can be secured without becoming large, and as a result, even if the length of the cable that is operated by peeling the sheath is relatively short, a sufficient extra length can be secured and the manufacturing cost of the optical cable can be reduced. it can.

In the preferred embodiment of the optical cable according to the present invention, when the reversal pitch of the SZ grooves formed in the spacer is P1, and the reversal pitch of the cable unit assembled by SZ is P2, the reversal pitches P1 and P2 are formula,
1.0 ≦ P2 / P1 ≦ 1.65
It is characterized by setting to satisfy.

The SZ inversion pitch of the spacer in which the SZ groove is formed needs to be set to about 200 mm in consideration of the bending characteristics of the unit and cable, the optimum inversion angle, and the productivity of the unit assembly process. On the other hand, a cable unit using a spacer in which an SZ groove having an outer diameter of 3.5 mmφ, an SZ twist reversal pitch of about 200 mm, and an SZ twist reversal angle of about 270 ° is formed, and a 0.25 mmφ optical fiber core. When the cable length to be exposed by peeling the sheath in the intermediate branching operation is 500 mm, the take-out length of the optical fiber core wire (maximum separation distance from the slack core wire to the cable axis line) was 6.3 mm. . However, the extra length required for the intermediate branch connection (the above-mentioned extraction length of the optical fiber core wire) is 20 to 40 mm in consideration of workability, and the extra length obtained by the unit is not sufficient. Therefore, in the present invention, a set of units is also SZ twisted to secure a necessary extra length. If six units are prepared and the reversal angle is about 270 °, the reversal pitch of the SZ twist set of the unit for securing a takeout length of 20 to 40 mm is about 140 to 330 mm. On the other hand, if the reversal pitch of the unit is smaller than the reversal pitch of the SZ grooves formed in the spacer, the optical fiber core wire may be distorted. It is necessary to set the pitch to be equal to or greater than the inversion pitch. Considering these matters, it is necessary to set the inversion pitch of the SZ twist set to 200 to 330 mm. Therefore, when the reversal pitch of the SZ grooves formed in the spacer is P1, and the reversal pitch of the cable unit assembled in the SZ twist is P2, these reversal pitches are expressed by the following equation:
1 ≦ P2 / P1 ≦ 1.65
It is desirable to satisfy.

A preferred embodiment of the optical cable according to the present invention has a formula in which the reversal pitch P1 of the SZ groove formed in the spacer and the reversal pitch P2 of the SZ twisted cable unit are expressed by the following equation:
1.25 ≦ P2 / P1 ≦ 1.65
Set to satisfy.
When the length of the cable exposed by peeling off the sheath in the intermediate branching operation is set to 500 mm, it has been experimentally confirmed that the workability is greatly improved when the twisting pitch is inverted twice or more in this 500 mm cable length. It was. Accordingly, it is desirable to set the preferred reversal pitch of the SZ twist set to 250 mm or less, and the reversal pitches P1 and P2 are set so as to satisfy the formula 1.25 ≦ P2 / P1 ≦ 1.65.

  In the preferred embodiment of the optical cable according to the present invention, different colored displays are formed on the presser winding of the cable unit, and different colored displays are also formed on the single optical fiber cores housed in the spacer. It is characterized by being. In this example, since the colored display for identification is formed for both the optical fiber core and the cable unit, the workability of selecting the required optical fiber core from a large number of optical fiber cores is greatly improved. It is possible to eliminate the problem of erroneous connection during branching work.

  In the present invention, since the SZ twisted structure is adopted for both the spacer for housing the optical fiber core wire and the set of spacers, the inner space of the cable can be used effectively and a sufficient length is secured. As a result, the workability of the intermediate branch connection is greatly improved.

  1 and 2 show an example of an optical cable according to the present invention. FIG. 1 is a cross-sectional view taken along a plane orthogonal to the cable axis, and FIG. 2 is a perspective view showing a sheath peeled off. The optical cable according to the present invention has a tension member 1, and six cable units 2 to 7 are assembled around the tension member 1 by SZ twist. Therefore, in the six cable units, the turning direction is alternately reversed periodically along the longitudinal direction of the cable. The outer periphery of the set of six cable units is pressed and wound with the upper winding tape 8, and the outer periphery is covered with the sheath 9. Two tear strings 10 a and 10 b are disposed between the upper winding tape 8 and the sheath 9. The inversion angle of the SZ twist set of the cable units 2 to 7 is set to about 270 °.

  The cable units 2 to 7 are composed of SZ twist spacer type optical fiber cables, and these six cable units have the same structure. Each cable unit, that is, an SZ twist spacer type optical fiber cable, has a spacer 20 made of thermoplastic resin, for example, and the spacer 20 has four SZ grooves 20a, 20b, 20c and 20d at equal intervals along the circumferential direction. Form. Single optical fiber core wires 21a to 21d are accommodated in the SZ grooves 20a to 20d, respectively. These optical fiber cores 21a to 21d can be displayed in different colors so that the selection of the optical fiber cores can be prevented when making a post-branch connection. A presser winding 22 is provided on the outer periphery of the spacer 20 to prevent the optical fiber core wire from jumping out of the SZ groove. In this example, a colored display is formed on the presser winding 22 for each cable unit, and the colored display of each presser winding 22 is made different from each other. As a result, the cable unit can be accurately identified when the intermediate branch connection process is performed, and the inconvenience of erroneous connection can be eliminated.

  Considering the bending characteristics of the cable unit, the optimal reversal angle, and the productivity of the unit assembly process, the reversal pitch of the SZ grooves formed in the spacer 20 is optimally 200 mm. The inversion angle of the SZ groove formed in the spacer 20 is set to about 270 °. Further, the inversion pitch of the SZ set of the unit needs to be equal to or more than the inversion pitch of the SZ groove formed in the unit from the viewpoint of preventing undesired distortion in the optical fiber core wire.

  FIG. 3 is a diagram for explaining an operation when the branch cable is connected to the optical cable according to the present invention after the branch cable. When branching backward, remove the upper winding tape and the sheath 9 by a predetermined length from the branch connection part, expose the SZ twist set of the cable unit, and select the required cable unit based on the color indication of each cable unit. Pull out. Next, the presser winding of the taken-out cable unit is removed over a predetermined length, and the optical fiber core wire to be branched and connected is identified and taken out based on the colored display formed on the optical fiber core wire. The taken optical fiber core is cut, connected to a connection closure, and connected to a branch cable via the closure. In this example, since both the cable unit and the optical fiber core are colored, the workability of identifying a designated optical fiber core from a large number of optical fiber cores is greatly improved.

  In the middle branch connection, the optimum cable length for stripping the sheath and the upper winding tape is 500 mm. The sheath is removed over the cable length of 500 mm to ensure a takeout length of 20-40 mm. Then, the SZ groove formed in the unit and the reversal pitch of the SZ set of the unit are set so that the reversal is performed twice or more over the length of 500 mm from which the sheath is removed. In order to satisfy this condition, it is desirable to set the reversal pitch of the SZ set of units to 500 ÷ 2 = 250 mm or less. As a condition that satisfies the above-mentioned conditions, if the reversal pitch of the SZ grooves to be formed as a unit is P1, and the reversal pitch of the SZ set of units is P2, each reversal pitch is set so as to satisfy the formula 1.25 ≦ P2 / P1. It is desirable to set.

  The present invention is not limited to the above-described embodiments, and various modifications and changes can be made. For example, in the above-described embodiment, a four-core spacer type optical fiber cable is used as the cable unit, and six cable units are assembled in SZ. However, optical fibers having various numbers of cores such as a two-core tape core and various types are used. A cable unit having a number of cores can be used.

It is sectional drawing which shows an example of the optical cable by this invention. It is a perspective view which removes and shows a sheath partially. It is a diagram for demonstrating the operation | work of a branch connection.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tension member 2-7 Cable unit 8 Top wound tape 9 Sheath 10a, 10b Tear string 20 Spacer 20a-20d SZ groove | channel 21a-21d Optical fiber core wire 22 Presser winding

Claims (2)

A spacer having a plurality of SZ grooves whose turning directions are alternately reversed along the longitudinal direction of the cable, and an optical fiber core wire respectively accommodated in each SZ groove, and are held on the outer periphery of each spacer. Comprising a plurality of cable units with windings;
An optical cable, wherein the plurality of cable units are gathered in an SZ twist around a tension member. The optical cable according to claim 1, wherein when the reversal pitch of the SZ groove formed in the spacer is P1, and the reversal pitch of the cable unit assembled in the SZ is P2, the reversal pitches P1 and P2 are ,formula,
1 ≦ P2 / P1 ≦ 1.65
An optical cable characterized by being set to satisfy