Optical waveguides – Optical transmission cable – Loose tube type
Patent
1989-07-06
1992-02-11
Lee, John D.
Optical waveguides
Optical transmission cable
Loose tube type
385112, 385113, G02B 644
Patent
active
050871102
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical fiber cable and more particularly to an optical fiber cable which realizes a reduction in size of a core loading material having a spiral groove to accommodate on optical fiber core and a method for manufacturing an optical fiber cable to accurately accommodate the optical fiber core to the spiral groove thereof.
2. Description of the Related Art
A cross-sectional view of an optical fiber cable of the prior art is shown in FIG. 1. In FIG. 1, an optical fiber core 1, which is formed by providing an optical fiber line consisting of a clad glass having the refractive index lower than that of a core glass and a silicon rubber layer covering the outside of the clad glass to the circumference of the core glass used as an optical transmission path and moreover covering and protecting outside of the fiber line with an outer sheath of a synthetic resin such as NYLON (trademark), polyethylene or polycarbonate, is set to about 0.5 mm to 0.9 mm in its outer diameter. This optical fiber core 1 is necessary to be protected from tension, side pressure or bending. In case several optical fiber cores 1 are bundled into a cable constitution, as shown in FIG. 2, such optical fiber cores are housed in the recessed grooves formed at the external circumference of the core loading material 3 made of molded synthetic resin such as NYLON, polycarbonate or other suitable material formed on the circumference of a tension member 2 which is preferably a steel wire or a fiber reinforcing synthetic resin rod material (FRP) coaxial with the core loading material. The recessed grooves are formed as spiral grooves 4 in the longitudinal direction. In FIG. 1 and FIG. 2, a total of eight (8) grooves are formed and an optical fiber core 1 is provided in three of the grooves. The number of optical fiber cores 1 and spiral grooves 4 may be set adequately. The external circumference of core loading material 3 housing the optical fiber cores 1 within the spiral grooves 4 is wound spirally in several layers by a tape 5 made of a synthetic resin such as NYLON and polyester and the external circumference is then covered with an outer sheath 6 made of synthetic resin such as vinyl chloride or polyurethane in order to protect the interior from environmental and mechanical influence. An optical fiber cable 7 is thus formed.
However, according to the optical fiber cable 7 of the prior art, a synthetic resin mold is formed by extrusion molding in order to constitute the spiral grooves 4 to accommodate optical fiber cores 1, resulting a problem that it is necessary to provide a large diameter, high tension member at the center in order to give strength to overcome the tension when it is laid to such mold. Thus, the outer diamond of optical fiber cable 7 becomes large as a result and thereby the weight per unit of length becomes heavier.
In addition, the prior art also has a problem that since the bottom part of spiral groove 4 is formed as a square shape for the convenience of manufacture, adequate clearance to the adjacent spiral groove 4 is necessary. The outer diameter of optical fiber cable 7 thus becomes large because the external pressure to be applied on the optical fiber core 1 is prevented by providing a margin to the spiral groove 4 for the optical fiber core 1.
The prior method of manufacturing optical fiber cable 7 will be explained with reference to FIG. 3. A long length core loading material 3 comprising therein a tension member 2 is wound around a cylindrical core loading material supply reel 8 having disk type edges at both ends. The end part of the core material 3 is released therefrom, transferred and moved linearly and is wound up by a take up reel 9 in the other side. In the linear part of core loading material 3 between the core loading material supply reel 8 and takeup reel 9, an optical fiber core loading apparatus 10 is disposed, along with a tape winding apparatus 11 which winds the tape around the core loading material loading optica
REFERENCES:
patent: 4154049 (1979-05-01), King et al.
patent: 4781434 (1988-11-01), Kitagawa et al.
patent: 4787702 (1988-11-01), Khalil
International Application No. PCT/JP89/00130, filed Feb. 9, 1989 and English translation of amended claims.
Inagaki Shinya
Sasaki Kazuya
Yoshizawa Sakae
Barns Stephen W.
Fujitsu Ltd.
Lee John D.
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