JPH0450811A - Optical fiber cable - Google Patents

Abstract

PURPOSE:To prevent crosslinked polyolefin in a working part from being melted even if a continuous work is executed for many hours, and to efficiently obtain a spacer whose characteristic is satisfactory by constituting the spacer of the crosslinked polyolefin excellent in a heat resistance property. CONSTITUTION:A coated optical fiber 2 is twisted into a recessed groove 1a provided along a longitudinal direction on the outer peripheral surface of a spacer 1, and its spacer 1 is formed by crosslinked polyolefin. In such a manner, since the spacer 1 is constituted of the crosslinked polyolefin excellent in a heat resistance property, even if a groove working method excellent in dimension accuracy is used, it does not occur that the crosslinked polyolefin is melted with the heat of a cutting tool caused by a continuous work extending over many hours, and accordingly, it becomes unnecessary to interrupt a cutting work due to cooling. In such a manner, the spacer 1 whose characteristic is satisfactory can be obtained efficiently.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an optical fiber cable that can be manufactured efficiently.

(Prior Art) Conventionally, as illustrated in the drawings, a spacer 1 made of high-density polyethylene has a plurality of grooves 1a spirally formed on its outer circumferential surface, and an optical fiber core is inserted into each groove 1a. An optical fiber cable called a so-called spacer type is known, which has a structure in which an optical fiber 2 is inserted to protect the optical fiber from lateral pressure and to make it easy to identify.

This cable also uses
The center of the spacer 1 is made of high-tensile steel wire, stranded steel wire, or glass fiber reinforced plastic (hereinafter referred to as FRP).

) A tension member 3 consisting of a rod or the like is disposed, and the entire body is further covered with a protective sheath 4 such as a plastic sheath or a laminate sheath.

Conventionally, the concave grooves 1a of the spacer 1 have been formed using two methods: (a) a method in which high-density polyethylene is formed continuously at the same time as extrusion using a rotary die (simultaneous processing method); One of the methods used was to extrude polyethylene into a cylindrical shape and then form it by machining (post-processing method).

However, the dimensional accuracy of the groove is poor in the simultaneous processing method (a), and although the dimensional accuracy is excellent in the post-processing method in The problem was that it required cooling time, which led to poor manufacturing efficiency.

In addition, in this type of spacer type optical fiber cable,
When it is necessary to use a non-metallic material for cable construction, such as when installing the cable in a high magnetic field area, an FRP rod is used as the tension member 3; Generally, a method is used in which fibers are molded into a rod shape using a thermosetting resin such as polyester or epoxy resin as a matrix and cured, and then the outer periphery of the rod is coated with high-density polyethylene by extrusion.

However, in such a method, the rate of thermosetting of the thermosetting resin or the rate of molding of the rod is determined, which causes problems such as poor manufacturing efficiency and high costs.

(Problem to be Solved by the Invention) As described above, in conventional spacer-type optical fiber cables, since the spacer is made of high-density polyethylene, the problem is that it is not possible to manufacture spacers with high dimensional accuracy using an efficient manufacturing method. In addition, in the case of a tension member or an FRP rod, the molding speed of the rod is determined by the curing speed of the thermosetting resin that is the matrix, so there is a problem that efficiency becomes worse.

The present invention has been made in response to these conventional problems, and allows efficient manufacturing of spacers with high dimensional accuracy.
An object of the present invention is to provide an optical fiber cable that can be manufactured efficiently and can reduce manufacturing costs.

[Structure of the Invention (Means for Solving the Problems) The present invention provides a fiber-optic cable formed by twisting optical fiber cores into grooves provided along the length direction on the outer peripheral surface of a spacer. The spacer is characterized by being made of cross-linked polyolefin, and a tension member made of a thermosetting resin composition containing a fibrous reinforcing material is disposed at the center of the spacer.

The crosslinked polyolefin may be chemically crosslinked using a crosslinking agent such as an organic peroxide, crosslinked by electron beam irradiation, or water crosslinked using a conventional method such as silane-modified polyethylene. Crosslinked polyolefins have better heat resistance than uncrosslinked polyolefins such as low density polyethylene.

Examples of the fibrous reinforcing material include glass fiber and carbon fiber, and examples of the thermosetting resin include polyester resin and epoxy resin.

Note that when the fiber-optic cable of the present invention is made into a non-metallic type, a non-conductive material such as glass fiber is used as the fibrous reinforcing material.

(Function) In the optical fiber cable of the present invention, since the spacer is made of cross-linked polyolefin with excellent heat resistance, a groove processing method with excellent dimensional accuracy is used, that is, after manufacturing a rod-shaped spacer made of cross-linked polyolefin, the spacer is made of cross-linked polyolefin with excellent heat resistance. Even if a cutting tool is used to create a concave groove on the outer circumferential surface for inserting the optical fiber, the crosslinked polyolefin will not melt due to the heat generated by the cutting tool during continuous operation over a long period of time. This eliminates the need to interrupt the cutting operation, making it possible to efficiently manufacture spacers with good characteristics.

In addition, in the case where a tension member made of a thermosetting resin composition containing a fibrous reinforcing material such as FRP is placed in the center of the spacer, during manufacturing, the thermosetting resin is Since curing can be completed, the production rate is no longer limited by the curing rate of the thermosetting resin, improving manufacturing efficiency, and the adhesive force between the tension member and the spacer is increased, resulting in the above-mentioned This further facilitates groove machining when performed using post-processing methods such as this.

Furthermore, in a cable constructed using a petroleum-based water sealant to provide a waterproof effect, the properties of the cable are not impaired because the cross-linked polyolefin is resistant to the petroleum-based water sealant.

(Example) Examples of the present invention will be described below.

Example 1 A water-crosslinkable silane-modified high-density polyethylene composition was extrusion coated on the outer periphery of a tension member made of a monotonous wire with an outer diameter of 2.0 mm so that the outer diameter was 8.0 mm.
Crosslinking was carried out for 24 hours in steam at a temperature of 0.degree. C. (degree of crosslinking was 69% in terms of gel fraction). Next, four grooves (width 1.5 og) were cut on the outer circumferential surface using a cutting machine equipped with a cutting tool.

A spiral groove with a depth of 1.4 mm was formed.

Even though this groove machining continued for more than 12,000 m, no melting of the part machined by the cutting machine was observed. Thereafter, optical fiber cores were twisted into each groove of the spacer by a conventional method, and a sheath was then provided around the outer periphery to produce an optical fiber cable as shown in the drawings.

Example 2.3 Instead of a water-crosslinkable silane-modified high-density polyethylene composition, organic peroxide 1,7PHI? (Example 2) or a low-density polyethylene composition that can be crosslinked by electron beam irradiation (Example 2)
Optical fiber cables were produced in the same manner as in Example 1, except that Example 3) was used and crosslinked under conditions suitable for each. The degree of crosslinking of each low density polyethylene in Example 2.3 was 87% and 72% in terms of gel fraction, respectively.

In these Examples, as in Example 1, continuous 12
No melting was observed in the machined portion even after continuous groove machining exceeding 1,000 m.

For comparison, when high-density polyethylene, which has been commonly used in the past, was used as the material for forming the spacer, melting occurred due to groove processing at 8000 m.

Example 4 Glass fibers were pultruded into a rod shape with a circular cross section of 2.0 mm in outer diameter using polyester resin as a matrix, and a water-crosslinkable silane-modified high-density polyethylene composition with an outer diameter of 5.6 mm was placed around the outer periphery of the rod. The polyester resin of the glass fiber matrix was cured by extrusion coating and crosslinking in steam at 80° C. for 8 hours. After that, a cutting machine equipped with a cutting tool was used to create four spiral grooves (width 1, 3 m + *, depth 1.3 mm) on the outer circumferential surface. Processing was easy due to the strong adhesion with the polyethylene, and no melting of the crosslinked polyethylene was observed during processing even at a distance of over 12,000 m.

After this, the optical fiber core wires are twisted into each concave groove of the spacer.
Next, a sheath was provided around the outer periphery to produce an optical fiber cable.

[Effects of the Invention] As is clear from the above examples, according to the optical fiber cable of the present invention, since the spacer is made of crosslinked polyolefin with excellent heat resistance, it is difficult to form grooves on the outer peripheral surface of the spacer. The method performed in the post-process prevents the crosslinked polyolefin in the processed area from melting even after continuous operation for a long time, making it possible to efficiently produce spacers with good characteristics.

In addition, spacers in which a tension member made of a thermosetting resin composition containing a fibrous reinforcing material such as FRP is arranged at the center of the spacer can be manufactured without the production speed being limited by the curing speed of the thermosetting resin. Therefore, manufacturing efficiency can be improved, and the adhesive force between the tension member and the spacer can also be increased.

Furthermore, since the crosslinked polyolefin has resistance to petroleum water sealants, the properties of the spacer will not be impaired even if the spacer is of a waterproof type using such petroleum water sealants.

[Brief explanation of drawings]

The drawing is a cross-sectional view showing an example of the structure of a spacer type optical fiber cable. 1・・・・・・・・・・・・Spacer 1a・・・・・・Concave groove

Claims (2)

[Claims] (1) An optical fiber cable formed by twisting optical fiber cores into grooves provided along the length direction on the outer circumferential surface of a spacer, wherein the spacer is made of crosslinked polyolefin. cable. (2) The optical fiber cable according to claim 1, wherein a tension member made of a thermosetting resin composition containing a fibrous reinforcing material is disposed at the center of the spacer.