JPH11194250A - Optical fiber cable for branching and branching method of optical fiber cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the optical fiber cable for branching which can improve the efficiency of branching operation and is small in material cost and fitting cost and suitable to a low-cost prefabricated branch cable. SOLUTION: Plural optical fiber cords 2 for branching are led out of an optical fiber cable formed by stranding optical fiber cords 2 around a tension member 1 and leading out the optical fiber cords 2 for branching from the optical fiber which winds them with a pressure winding tape 3, a connector 4 is fitted atop of the lead-out part 2a, which is covered with a tubular protection member 5, constituting the optical fiber cable for branching. Then the connector 4 atop of the lead-out part 2a is exposed through the protection member 5 and the optical fiber cord 2 is connected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a branch optical fiber cable and a method of branching an optical fiber cable, and more particularly to a branch optical fiber cable and a method of branching an optical fiber cable suitable for prefabricated branching.

[0002]

2. Description of the Related Art A prefabricated branch cable is composed of an aggregate of a plurality of communication lines. The prefabricated branch cable is laid in advance in a condominium or other apartment complex, and if necessary, the communication line is branched off in the middle thereof. The line is supplied to the subscriber.
Conventionally, prefabricated branch cables for communication used in condominiums and other condominiums consist of metal communication lines,
For example, a metal twisted cord, a coaxial cord, or the like is used. However, a prefabricated branch cable using an optical fiber is conceivable for application to broadband information transmission in the future.

Since the performance of an optical fiber cable may deteriorate due to external stress, a plastic sheath is usually provided on an aggregate of a plurality of optical fiber cords, and the sheath is protected by the sheath. It is said. For this reason, at the time of branching, the sheath must first be peeled off, which lowers the work efficiency of branching and increases the processing cost. To make the sheath easy to peel off,
The constituent material of the sheath is limited. For example, as a method of branching an optical fiber cable, there is a method using a closure. When a closure is used, a space for installing the closure is required for each branch point, and the material cost increases. Further, site work such as installation of a closure at a branch point is required.

[0004] On the other hand, the sheath at the branch point of the optical fiber cable is removed in advance, and a cylindrical branch protective case slightly larger than the outer shape of the optical fiber cable is covered on the exposed portion of the optical fiber cord. It is also conceivable to lay things. In this case, at the time of branching, the optical fiber cord can be directly taken out from the branch protection case and branched. With this configuration, the installation space is smaller than when the closure is provided, and the on-site work can be reduced. However, since the optical fiber cord has low bending characteristics, it is necessary to attach a part for protecting the optical fiber cord so that the optical fiber cord taken out of the branch protection case is not bent excessively and deteriorated. Therefore, after all, on-site work is required, and further, not only a branch protection case but also other new parts are required, so that the material cost and the mounting cost are increased, and it is difficult to improve the work efficiency and cost.

[0005]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a branch optical fiber cable and an optical fiber which can improve the operation efficiency of branching, reduce material costs and mounting costs, and are suitable for low-cost prefabricated branch cables. It is an object to provide a method of branching a cable.

[0006]

According to a first aspect of the present invention, a plurality of optical fiber cords are twisted on a tension member, and a holding cord is wound thereon. An optical fiber cable for branching is drawn out of the optical fiber cable thus formed, and a tube-shaped protective member is covered on a lead-out portion of the optical fiber cord. According to a second aspect of the present invention, a plurality of optical fiber cords are twisted on a tension member, and an optical fiber cable for branching is pulled out from an optical fiber cable having a holding cord wound thereon. A protective member in the form of a tube, and connecting the optical fiber cord for branching by exposing the tip of the drawer from the protective member.

[0007]

FIG. 1 is a sectional view showing an example of an optical fiber cable used for an optical fiber cable for branching according to the present invention, and FIGS. 2 to 5 are optical fiber cables for branching using the optical fiber cable shown in FIG. Are sequentially shown as an example. In the figure, reference numeral 1 denotes a tension member 1, on which twelve optical fiber cords 2 are twisted, and on which a holding cord 3 is wound in a direction opposite to the twisting direction of the optical fiber cord 2. ing.

Using such an optical fiber cable 10, first, as shown in FIG. 2, the optical fiber cord 2 to be branched is cut out from the middle and pulled out. Next, as shown in FIG. 3, the coating layer at the tip of the lead portion 2a of the optical fiber cord 2 is removed, and the connector 4 is attached. Further, as shown in FIG. 4, a protective member 5 in the form of a tube is put over the entire drawer 2a from the tip of the drawer 2a. The protection member 5 has, for example, a bellows-like elastic portion 5a on the base 2b side of the drawer portion 2a. Further, a fixing member 6 is provided around the base 2b of the drawer 2a (the portion in contact with the presser string 3) and around the main body of the optical fiber cable 10, and the protective member 5 is attached to the main body of the optical fiber cable 10. Fix the optical fiber cable for branching.

Such a branching optical fiber cable is laid in an apartment house or the like, and branching is performed when needed. That is, when the elastic part 5a is contracted at the site, the tip of the protective member 5 moves to the base 2b side, and the connector 4
(The tip of the drawer 2a) is exposed. Then, the connector 4 is connected to another optical fiber cord or the like via an adapter, and the contracted expansion / contraction portion 5a is returned to cover the connector 4 whose connection has been completed, thereby completing the branching operation. As described above, since the branching optical fiber cord 2 is drawn out in advance and the connector 4 is attached, the on-site work is extremely small.

In this example, the tension member 1 is made of a steel wire or the like. The size of the tension member 1 can be appropriately changed according to the size of the optical fiber cord 2, the number of cores of the optical fiber cable 10, and the like.

The optical fiber cord 2 is composed of an ordinary bare optical fiber having an outer diameter of 125 μm made of quartz glass and coated with a plastic made of a silicone resin, an ultraviolet curable resin, or the like. above,
In addition, a coating layer made of nylon or the like is formed with a plurality of tensile strength members such as aramid fibers vertically attached, and has an outer diameter of about 1 mm.

One function of the presser cord 3 is to keep the twist of the optical fiber cord 2 stable. In addition, the use of the holding cord 3 having a certain outside diameter can protect the optical fiber cord 2. In other words, since the presser cord 3 has a certain thickness, even when it is suspended in vertical laying peculiar to the branching optical fiber cable, or when it is dragged at the time of construction, the presser cord is not attached to the external wall or the ground. 3 are in contact with each other and absorb external stress. For this reason, the optical fiber cord 2 is hardly affected by external stress, and the required mechanical characteristics can be obtained even when the sheath is not provided.

The connector 4 comprises a ferrule for housing the bare optical fiber portion from which the coating layer at the tip of the lead portion 2a has been removed, and a plug for housing and holding the ferrule and the coating layer portion following the bare optical fiber portion. It is normal. Further, the connector 4 can be attached on site. In this case, the optical fiber cord 2 for branching is pulled out from the optical fiber cable 10 without attaching the connector 4, the protection member 5 is covered on the lead portion 2 a, and the product is fixed with the fixing member 6 to obtain a product.

The protective member 5 prevents the drawer 2a from being bent more than necessary and the performance thereof does not deteriorate. Therefore, it is preferable that the protection member 5 be covered over a range including the base 2b of the drawer 2a to the connector 4. The protection member 5 is connected to the drawer 2.
a must be strong enough to support a. Therefore, the protection member 5 is preferably made of plastic or the like.

Further, since the protection member 5 of this example has the expansion and contraction portion 5a, when branching or the like, the protection member 5 is kept covered on the base 2b side of the drawer portion 2a, and the tip side of the drawer portion 2a. Can be easily exposed for the required length.

As the protective member 5, a spiral tube, a half tube, or the like can be used. The spiral tube is configured such that, for example, a tape is wound obliquely around the drawer 2a to form the tubular protection member 5, and is formed in a direction opposite to the direction in which the tape is first wound from the tip side of the drawer 2a. By unwinding, the tip of the drawer 2a can be exposed.

The half-split tube is such that the tube can be divided into two along its length.
For example, a tube divided in advance may be covered with the drawer portion 2a and fixed from the outside with a string or tape, or an ordinary tube may be intermittently cut into a position to be divided later. At the time of branching, the tip of the half-split tube is divided into
Can be exposed.

In order to improve the operability of covering the drawer 2a with the tubular protective member 5 and to improve the adhesion between the drawer 2a and the protective member 5 at the time of manufacturing the optical fiber cable for branching at a factory or the like. Alternatively, a cold shrink tube may be used. The room-temperature shrinkable tube is a tube in which a rubber tube is expanded and held in a cylindrical plastic guide having a large outer diameter, and is removed from the plastic guide and shrunk when necessary. Therefore, when the protection member 5 is put on the drawer 2a at a factory or the like and the plastic guide of the protection member 5 is removed, the protection member 5 contracts and the outer surface of the drawer 2a and the inner wall of the protection member 5 come into close contact with each other. In this way, the drawer 2 located inside the protection member 5
a is held more stably.

The fixing member 6 is provided in order to prevent the drawer 2a located near the end of the protection member 5 from being bent or the like. It is fixed to. The fixing member 6 is, for example, in the form of a tape, and is formed of plastic such as polyethylene, cloth such as nonwoven fabric, or paper such as kraft paper. The width is the drawer 2
a and the protection member 5 can be held, and are not particularly limited as long as they do not hinder the branching operation.

The branching optical fiber cable of the above example is
Since the optical fiber cable 10 having no sheath can be used, there is no need to remove the sheath, and the efficiency of branching can be improved. Further, since the protective member 5 is covered on the lead portion 2a of the optical fiber cord 2, it is possible to prevent the drawer portion 2a from being bent more than necessary and the performance thereof from being deteriorated. Protective member 5
Since they are inexpensive and easy to install as compared with closures and the like, material costs and installation costs can be reduced.
Further, the protection member 5 can be configured so that the tip of the drawer 2a can be easily exposed, and does not hinder the connection work of the optical fiber cord 2 at the time of branching. In this branch optical fiber cable, a branch optical fiber cord 2 is drawn out in advance, and a connector 4
The work is very little on site because the is installed.

The optical fiber cable 10 can be laid in an apartment house or the like in a state where the optical fiber cord 2 is not pulled out, and the work shown in FIGS. 2 to 5 can be performed on site. Although such a method involves on-site work, the branch point can be set arbitrarily. In addition, the material cost, the mounting cost, and the like can be kept low, and the effect of not requiring a space as compared with the case of using a closure or the like is the same.

[0022]

As described above, in the present invention,
Since the optical fiber cable has no sheath,
The branching work efficiency can be improved. In addition, the protective member placed over the lead-out portion of the optical fiber cord can prevent the optical fiber cord from being bent more than necessary and from deteriorating its performance. Further, this protective member is excellent in space efficiency and can reduce material costs and mounting costs as compared with conventionally used components such as closures. With these effects, the cost of the branch optical fiber cable and the method of branching the optical fiber cable can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of an optical fiber cable used in the present invention.

FIG. 2 is a plan view showing a state where an optical fiber cord is pulled out from the optical fiber cable shown in FIG.

FIG. 3 is a plan view showing a state where a connector is attached to a leading end of a drawer of the optical fiber cord shown in FIG. 2;

FIG. 4 is a partial cross-sectional view showing a state in which a protective member is placed over a drawer to which the connector shown in FIG. 3 is attached.

5 is a plan view showing a state in which the base of the drawer portion covered with the protection member shown in FIG. 4 is fixed using a fixing member.

[Explanation of symbols]

1 ... tension member, 2 ... optical fiber cord, 2a ...
Drawer section, 3 ... wrapping cord, 5 ... protective member, 5a ...
Telescopic part, 10 ... optical fiber cable.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yukihiro Hamada 2899 Tahara, Oita City, Oita Prefecture Nishi Nippon Electric Wire & Cable Co., Ltd. 72) Inventor Akio Mogi 1440, Musaki, Sakura City, Chiba Prefecture Inside Fujikura Sakura Factory (72) Inventor Tatsuya Omori 1440, Misaki, Sakura City, Chiba Prefecture Inside Fujikura Sakura Factory, Inc. (72) Koichiro Watanabe Chiba Prefecture 1440, Misaki, Sakura City, Sakura Plant, Fujikura Co., Ltd. (72) Inventor Suehiro Miyamoto, 1440, Misaki, Sakura City, Chiba Prefecture, Sakura Plant, Fujikura Co., Ltd.

Claims (2)

[Claims] A plurality of optical fiber cords are twisted on a tension member, and an optical fiber cord for branching is pulled out from an optical fiber cable having a holding cord wound thereon. A tube-shaped protective member is placed over the lead portion of the optical fiber cable. 2. A plurality of optical fiber cords are twisted on a tension member, and an optical fiber cord for branching is pulled out from an optical fiber cable having a holding cord wound thereon. A method for branching an optical fiber cable, comprising covering a tubular protective member, and exposing the leading end of the drawer from the protective member to connect a branch optical fiber cord.