JPS5922006A - Manufacture of optical fiber cable - Google Patents

Abstract

PURPOSE:To cancel the elongation of optical fiber units due to tensile force in bundling and to prevent deterioration in strength, by giving the sheath pipe of the optical fiber units a contraction stress previously, and releasing the contraction stress and generating a contraction strain during the process of bundling the units. CONSTITUTION:An Al tape 22 is wound longitudinally around an optical fiber core 21 and they are sheathed with the sheathing pipe 12 made of polyethylene. In this case, when the external diameter of the die of a polyethylene extruder is phi1 and the external diameter of the drawn pipe 23 is phi2, the drawing rate shown by an equation is controlled to form an optical fiber unit 1 which is given the contraction stress. This unit 1 is bent by rolls 11, 12- alternately in two ways repeatedly until the stress generated in said contraction is released. Then, plural units 1 are bundled to manufacture an optical fiber cable. Thus, the elongation due to the tensile force in the bundling is canceled by the contraction strain to prevent the deterioration in strength and the shortening of the life of the cable due to the residual elongation strain.

Description

[Detailed description of the invention] This invention is directed to a method of manufacturing a six-fiber cable.

Fiber-filled cables are made by gathering multiple optical fiber units at a gathering point, so when assembled into each unit, 1 (
Tension will be added. By the way, some optical fiber units (K) have a structure in which a plurality of optical fiber cores are gathered together in the shape of a round bar or tape without a tension member, and covered with an outer jacket such as a polyethylene pipe. When using optical fiber units that do not have a tension member with such a structure, if tension is applied during assembly as described above, elongation strain will be applied to the outer sheath of each unit and the optical fiber core, causing the cable to deteriorate. The strain remains inside the product, deteriorating its strength and shortening its lifespan. Conventionally, when making original fiber cables from optical fiber units that do not have such tension members, the fibers are assembled with as low a tension as possible, but there is a limit to how low the tension can be. It was not possible to lower υ to a certain degree, and therefore the problems of deterioration of strength and shortening of life could not be solved.

This invention prevents residual elongation strain by shrinking the optical fiber unit in advance in the longitudinal direction and returning it to its original state with a back tensile run during assembly.
It is an object of the present invention to provide a method for manufacturing an optical fiber cable that does not cause problems such as a decrease in strength and a shortened service life.

An embodiment of the present invention will be described below with reference to the drawings. First, shrinkage stress is applied to the jacket pipe of the optical fiber unit. For example, when a synthetic resin pipe is formed by pipe extrusion, shrinkage stress can be generated by controlling the drawdown rate. Here, the withdrawal rate refers to (' 1) x 100 (%), where the outer diameter of the die of the extruder is ψl, and the outer diameter when the synthetic resin is drawn down from this die is φ2φ1-. To be. FIG. 1 shows the measurement results of the relationship between the drawdown rate and the shrinkage stress when the ξ-ib is formed by extrusion using polyethylene as the synthetic resin. Therefore, by such a forming method, shrinkage stress can be applied to the jacket pipe of the original fiber unit.

Next, the stress of the material having such shrinkage stress is released, and the material is caused to shrink in the longitudinal direction. An analogy for this is bending a pipe repeatedly. As shown in Fig. 2, the optical fiber unit 1 is repeatedly bent back and forth while being held between rollers 11, 12, 13, 14. I tested the distortion to see if it made me cry.

FIG. 3 shows the test results when a polyethylene pipe and an aluminum laminate pipe (described later) were used as the pipes.

This process of stress release and contraction is performed during the process of assembling a plurality of optical fiber units. The relationship between the tension at the time of assembly and the amount of elongation of the unit is shown in Figure 4, so
The amount of elongation is calculated from the actual pack tension as shown in Figure 4, and a stress release/shrinkage process is performed during the assembly process so that a contraction commensurate with this amount of elongation is applied and these are canceled out. It is.

To explain one specific example, it is assumed that optical fiber units having an outer sheath made of aluminum laminate pipes having a structure as shown in FIG. 5 are assembled by an assembly machine with a pack tension of 4KF. In this case, since the tension is 4Ky, the fourth
From the figure, an elongation amount of 0.2% can be read. In other words, if you try to assemble them using this aggregator, each unit will try to grow by 0.2%. Therefore, a stress release/shrinkage process is performed during this assembly process so that a contraction corresponding to this amount of elongation occurs. As shown in FIG. 5, this optical fiber unit has an aluminum tape 22 longitudinally wrapped around an optical fiber core 21, and the wrap is further covered with a polyethylene web 23. Outer diameter of polyethylene pipe 23: 1d 4.5 mm
.

The inner diameter of the aluminum tape 22 is 3.5 mm, and the rollers 11, 12 and 30 mm in diameter of the optical fiber unit having the outer sheath of this aluminum laminate pipe.
The shrinkage strain for the number of reciprocating bending is measured as shown in Fig. 3 (see Fig. 2), so from this Fig. 3, we can calculate the shrinkage of 0.2% by 2 reciprocating and half the number of bending. I know that I can give. Therefore, during the assembly process, the rollers 11, 12. If we place five pieces of ... and bend this original fiber unit two and a half times to give it a shrinkage of 0.2%, this will offset the 02% elongation due to the pack tension during assembly mentioned above. can do.

As described above with respect to the embodiments, according to the method for manufacturing an optical fiber cable of the present invention, the jacket pipe of the optical fiber unit is given shrinkage stress in advance, and during the assembly process of the optical fiber unit, The above-mentioned process of releasing the shrinkage stress and generating shrinkage strain is included in step 9, so that the elongation due to the tension during assembly is offset by this shrinkage strain, so the elongation strain due to the tension during assembly remains and the strength is increased. Deterioration and shortened lifespan can be prevented.

[Brief explanation of drawings]

Fig. 1 is a graph showing the measurement results of the relationship between the drawdown rate and shrinkage stress of a polyethylene pipe, Fig. 2 is a schematic diagram of an apparatus that performs a step of generating shrinkage strain by stress release according to an embodiment, and Fig. 3 is a graph showing the measurement results of the relationship between the number of reciprocating bends and shrinkage strain, Figure 4 is a graph showing the relationship between tension and elongation, and Figure 5 is a graph showing the structure of an optical fiber unit with an outer jacket made of aluminum laminate pipe. FIG. 1... Optical fiber unit 11.12.13, 14.15... Roller 21...
Optical fiber core 22... Aluminum tape 23... Polyethylene pipe Applicant Nippon Telegraph and Telephone Public Corporation Fujikura Electric Wire Co., Ltd. Bu@”&.

Claims (1)

[Claims] (1+ In the method of manufacturing a fiber optic cable by assembling multiple optical fiber units, the outer sheath of the optical fiber unit) The process of releasing the shrinkage stress of the outer sheath and ξ-wave to create a shrinkage strain is carried out during the forearm assembly step 1 (insertion, and the elongation of the original fiber unit due to the tension at the time of assembly is caused by the shrinkage strain 1). A method for manufacturing an optical fiber cable, characterized in that the optical fiber cable is offset.