JPS5910905A - Production of optical cable - Google Patents

Abstract

PURPOSE:To prevent the generation of waving in an optical cable core even if the sheath thereof contracts and to prevent the increase in the transmission loss thereof by applying the tension larger than the frictional force generated between the core and the sheath on the optical cable core. CONSTITUTION:The tension larger than the frictional force generated between an optical cable core 1 and a plastic sheath 2 when the sheath 2 shrinks is applied on the core 1 in the stage of applying the sheath 2 thereon. The tension is generated by applying the brake on the core 1 with a core supply device thereby applying back tension on the core 1. Then, the sheath 2 shrinks and even if the laminated tape 3 in one body with the sheath is shrunk, the core 1 is held tense; therefore, the generation of waving in the sheath 2 is obviated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a method of manufacturing an optical cable.

Optical cables are constructed by extruding a plastic sheath over an optical cable core such as an optical fiber core, an optical fiber core wire, or a cable unit combining these. However, since the plastic sheath contracts in the radial and longitudinal directions during the cooling process after extrusion, the optical cable core 1 generates undulations within the sheath 2, as shown in FIG. For this reason, the transmission loss of the optical cable core increases due to interference with the inner surface of the sheath, especially when the optical cable core consists of multiple optical fibers gathered around a central tensile strength line. Since it is sandwiched between the central tensile strength wire and the sheath and is subjected to lateral pressure, it has the disadvantage of significantly increasing transmission loss.

An object of the present invention is to provide a method of manufacturing an optical cable that can prevent an increase in transmission loss by preventing waviness from occurring in the optical cable core even when the sheath contracts.

Embodiments of the present invention will be described in detail with reference to the drawings.
The figure schematically shows the method of the present invention, in which an optical cable core 1 is supplied from a core feeder 10, and a laminate tape 3 supplied from a tape feeder 12 is longitudinally attached to the optical cable core 1 by a longitudinal attacher 14. As shown in FIG. 2, the optical cable core 1 includes a plurality of optical fiber core wires twisted together on a central tensile strength line 4, and a polypropylene yarn (7) M
It is formed by pressing and winding a plastic tape 7 covered with a Y (=j layer 6).The laminate tape 3 is formed by applying a plastic thin film layer of polyethylene on an aluminum tape, and this plastic thin film layer is It is placed vertically on the outside.

The optical cable core 1 to which the laminate tape 3 is longitudinally attached in this way is covered with a polyethylene plastic sheath by extrusion in an extruder 16 to form the optical cable 8 shown in FIG. This optical cable 8 passes through a cooling water tank 8 to cool the plastic sheath 2, and is taken by a take-off machine 22.

In the method of the present invention, in the process of applying the plastic sheath 2, a tension greater than the frictional force generated between the core 1 and the sheath 2 when the plastic sheath 2 contracts is applied to the optical cable core 1. This tension is generated by applying a brake to the optical cable core 1 at core supply i 1.0 and applying back tension to the core 1. In this way, even if the plastic sheath 2 contracts and the laminate tape 3 integrated with the sheath contracts, the optical cable core 1 remains taut and no undulations occur within the sheath 2.

In addition, although the case where the optical cable core 1 is a cable unit was shown in the said Example, the optical cable core 1 may be an optical fiber raw wire or an optical fiber core wire. Further, in the above embodiment, the plastic sheath 2 was coated by extrusion after the laminate tape 3 was vertically applied onto the optical cable core 1, but the plastic sheath 2 may be directly extruded and coated onto the optical cable core 1.

According to the present invention, even if the plastic sheath shrinks as described above, the optical cable core does not undulate within the sheath, so the transmission loss of the optical cable does not increase.

[Brief explanation of drawings]

Fig. 1 is a longitudinal cross-sectional view of an optical cable manufactured by a conventional method, Fig. 2 is a cross-sectional view of an example of an optical cable manufactured by an uninvented method, and Fig. 3 is a schematic system diagram showing an uninvented method. It is. 1---Polarized cable core, 2---Plastic sheath, 8---Polarized cable, 1 (1------
Core feeding machine, 16----- Extruder, 18-- Cooling water tank.

Claims (3)

[Claims] (1) A method for manufacturing an optical cable in which an optical cable core is coated with a plastic sheath by extrusion, the method comprising applying a tension to the optical cable core that is greater than the frictional force generated between the core and the sheath. . (2) The optical cable manufacturing method according to claim 1, wherein the tension is generated by a brake applied to the core feeder. (3) The optical cable manufacturing method according to claim 1 or 2, wherein the optical cable core is a bare optical fiber or a cored optical fiber. (4) The optical cable core is a plurality of bare optical fibers. Alternatively, the method for manufacturing an optical cable according to claim 1 or 2, which is a cable unit in which optical fiber core wires are assembled.