JPS6343441Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical fiber cable spacer for safely housing and protecting the optical fiber against various external forces.

Optical fiber cables for communication, which accommodate a large number of optical fibers, differ from conventional cables made up of copper wire pairs.In order to prevent deterioration of the transmission characteristics and mechanical properties of the optical fibers, fiber optic cables for communications accommodate a large number of optical fibers. Special structural design is required for various external forces such as In particular, it is important to arrange a tensile strength member against the tension applied to the cable and to prevent the optical fiber from breaking due to thermal expansion/contraction strain of the material. An effective structure for optical cables that meets these requirements is a structure in which an optical fiber is loosely accommodated in a spacer. In this case, it goes without saying that the characteristics of the spacer are extremely important.

A conventional spacer has a cross-sectional structure as shown in FIG. 1, the tensile strength member 12 is made of steel wire, and the space forming member 11 is made of a polymeric material such as PE. However, although steel wire has a high Young's modulus, its coefficient of thermal expansion is about 30 times higher than that of optical fiber, and PE also has a coefficient of thermal expansion 15 times that of steel, so the thermal expansion and contraction of the entire spacer increases.
For this reason, the design of the fiber housing structure becomes complicated, and in order to ensure long-term reliability, it is necessary to overestimate the safety factor against thermal expansion and contraction distortion and over-design, which reduces the applicability of the cable. There is a problem that economicization is hindered as well as being restricted.

The present invention eliminates the conventional drawbacks and provides an optical fiber cable spacer in which a tensile strength member is closely disposed inside the center of a space forming body having a plurality of groove spaces on the periphery for loosely accommodating optical fibers.
The tensile strength body is formed of a wire made of a polymeric material having a high modulus of elasticity and a coefficient of thermal expansion, or a wire made of the polymeric material and a wire made of a metal material containing iron as a main component are formed in close contact with each other. The absolute value of the sum of the values of (Young's modulus x cross-sectional area x coefficient of thermal expansion) of both the spacer forming body divided by the sum of the values of (Young's modulus x cross-sectional area) of both is 10 ^-6 or less. The purpose is to have comprehensively sufficient tensile strength properties and to have a coefficient of thermal expansion comparable to that of optical fiber.

The present invention will be explained based on the drawings.

2 to 5 show cross-sectional views of embodiments of the present invention.

1 is a spacer, 11 is a space forming body, 13 is a space, 14, 15, 16 is a tensile strength body made of polymer wire, and 17, 18 is a tensile strength body made of steel wire. First, FIG. 2 shows the basic configuration of the present invention. The space forming body 11 has a groove space 13 on its periphery for loosely accommodating the optical fiber, and includes a tensile strength body 14 in its inner center. Here, the space forming body uses a polymeric material such as PE as in the past, but the tensile strength body uses a wire made of a polymeric material that has a high modulus of elasticity and a negative coefficient of thermal expansion. It is.

When two materials are closely integrated in this way, if the Young's modulus, cross-sectional area, and thermal expansion coefficient of each material are E ₁ , S ₁ , α ₁ , E ₂ , S ₂ , and α ₂ , then
It is known that the overall coefficient of thermal expansion αe is αe=E ₁ S ₁ α ₁ +E ₂ S ₂ α ₂ /E ₁ S ₁ +E ₂ S ₂ . The present invention utilizes this principle and attempts to set αe to a minute value comparable to that of an optical fiber by combining positive and negative values of the thermal expansion coefficients of two types of materials. That is, by appropriately selecting E ₂ S ₂ α ₂ of the polymer wire tensile strength member 14 with respect to E ₁ S ₁ α ₁ of the space forming member 11, (E ₁ S ₁ α ₁ +
E ₂ S ₂ α ₂ ) is set to a required minute value.

As a polymeric material that satisfies this condition, a material obtained by stretching a normal thermoplastic resin at a high magnification can be used. Stretched polymer materials often have a negative coefficient of thermal expansion at high magnifications, and it is easy to select materials suitable for the present invention from among materials that have been used in practice.

Normal PE has a Young's modulus of about 0.7 GPa and a thermal expansion coefficient of about 180×10 ^-6 , so if the Young's modulus of a stretched polymer material is 50 GPa and the thermal expansion coefficient is -4×10 ^-6 , then the stretched polymer material By setting the cross-sectional area of the material to 4/10 of the cross-sectional area of the PE space forming body, it is possible to suppress the coefficient of thermal expansion of the entire spacer to 10 ^-6 or less.

3 to 5 show examples in which steel wire rods are used in combination as the tensile strength member. By combining and closely arranging steel wire rods having a high Young's modulus of about 200 GPa in this way, the elastic modulus of the polymer tensile strength body 14 can be supplemented and tensile strength design can be facilitated. In particular, if a steel material such as nickel steel (Invar), which has a coefficient of thermal expansion of about 1×10 ^-6 , is used, the design for the coefficient of thermal expansion can also be made easier.

The above steel material also has the effect of compensating for the drawbacks of the polymer tensile strength material. Polymer materials have a remarkable creep property, and have the possibility of being stretched completely when tension is constantly applied. However, according to the configuration shown in FIGS. 3 to 5,
Steel materials that exhibit almost no creep function effectively to prevent creep in polymeric materials. In addition,
In the above configuration, if the tensile strength member is made into a composite tensile strength member by combining a polymer tensile strength member and a steel wire as described above, the total cross-sectional area can be made smaller than 4/10. The composite tensile strength member can be applied when the diameter of the space forming member is large to produce an effect.

As explained above, according to the configuration of the present invention,
Thermal expansion and contraction of the space forming body of the optical cable can be suppressed to a minute amount, comparable to that of fiber glass, and the design conditions for the optical fiber accommodation structure can be greatly eased. The cable structure can be simplified, dramatically improving manufacturability. This brings about effects such as improving performance, reducing the cost of optical fiber cables, and expanding applicability.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a conventional spacer, Figure 2~
FIG. 5 shows a cross-sectional view of an embodiment of the invention. 1: Spacer, 11: Space forming body, 12:
Steel wire tensile strength body, 13: Space, 14, 15, 1
6: Polymer wire tensile strength body, 17, 18: Steel wire tensile strength body.

Claims (1)

[Claims for Utility Model Registration] 1. A spacer for an optical fiber cable in which a tensile strength member is closely disposed inside the center of a space forming body having a plurality of groove spaces for loosely accommodating optical fibers at the periphery, wherein the tensile strength member is At least 1 with a high modulus of elasticity and a negative coefficient of thermal expansion
A spacer for optical fiber cable, characterized by being composed of two tensile strength members. 2 Utility Model Registration In the optical fiber cable spacer according to claim 1, the sum of the values of (Young's modulus x cross-sectional area x coefficient of thermal expansion) of both the tensile strength body and the space forming body is calculated as (Young's modulus of both). The absolute value of the value divided by the sum of the values of
10 ^-6 or less. 3 Utility Model Registration Scope of Claims 1. The spacer for optical fiber cables according to claim 1, wherein the tensile strength body is made of a wire made of a polymeric material having a high modulus of elasticity and a negative coefficient of thermal expansion, and iron as a main component. It is formed by closely adhering metal wire rods.