Optical waveguides – Optical transmission cable – Tightly confined
Patent
1998-04-28
2000-01-04
Palmer, Phan T. H.
Optical waveguides
Optical transmission cable
Tightly confined
385100, 385106, 385112, 385103, G02B 644
Patent
active
060118873
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an optical fiber cable and, in particular, to an optical fiber cable having a reinforcing wire for reinforcement in addition to an optical fiber core wire.
BACKGROUND ART
As is well known, an optical fiber is a fibrous light wave guide made of glass or the like, and has a structure composed of a central portion called a core and a peripheral portion called a clad, wherein the refractive index of the central portion is set greater than that of the peripheral portion for light confinement. The optical fiber has excellent properties, such as a small diameter, a light weight and non-induction.
However, since the optical fiber itself is made of a very brittle material, such as glass, when used as a long-distance communication cable, it is not used by itself. For example, when the optical fiber is used as a submarine cable, since the submarine cable is exposed to a very severe environment, it is necessary to protect the optical fiber from such a severe external force so as to maintain a stable transmission characteristic thereof.
For this reason, the optical fiber is covered with several layers. First, immediately after wire drawing of the optical fiber, a primary cover of plastic or the like is applied. The optical fiber in this state is called an optical fiber wire. The optical fiber wire covered with a buffer layer and a secondary cover is called an optical fiber core wire.
The optical fiber cable comprises at least one optical fiber core wire, a reinforcing wire made of a conductor extending close to the optical fiber core wire and along a longitudinal direction of the optical fiber core wire, and an external covering member containing an insulating material and covering the optical fiber core wire and the reinforcing wire.
FIG. 1 shows an example of a conventional optical fiber cable 10'. The shown optical fiber cable 10' comprises a tension member (for example, made of a copper wire) 11 working as a reinforcing wire at a central portion thereof, twelve optical fiber core wires 13 arranged in symmetry around the tension member 11 via a pipe 12, a buffer layer 14' covering the optical fiber core wires 13, a presser winding 15 covering the buffer layer 14', and an LAP (Laminated Aluminum Polyethelene) sheath 16' provided around the presser winding 15. The LAP sheath 16' has a coating structure in which a polyethylene coat and an aluminum tape at its inner side are unified through bonding so as to have a moisture-proof effect. For the buffer layer 14', silicon resin, for example, is used. The buffer layer 14' and the polyethylene outer jacket of the LAP sheath 16' work as external coating members. Some of the optical fiber core wires 13 may be replaced with intervenient core wires.
FIG. 2 shows another example of a conventional optical fiber cable 20'. The shown optical fiber cable 20' is called a self-supporting optical fiber cable and uses, instead of the tension member 11 shown in FIG. 1, a supporting wire or a suspending wire in which an outer cover 27' covers the circumferences of seven lead wires (for example, made of copper wires) 21. Further, a signal transmission wire is provided apart from the suspending wire or the supporting wire. In the signal transmission wire, seven optical fiber core wires 23 are provided at a central portion thereof, the optical fiber core wires 23 are covered with a buffer layer 24, the buffer layer 24 is covered with an aluminum tape 25, and the aluminum tape 25 is covered with a PE (polyethylene) sheath 26. The signal transmission wire and the lead wires 21 covered with the outer cover 27' are unified in a mutually contacting state by a lashing wire 28. The lead wires 21 work as reinforcing wires, and the outer cover 27', the buffer layer 24 and the PE sheath 26 work as external covering members.
The optical fiber core wires 13 or 23 do not suffer an influence of electromagnetic induction. However, since the reinforcing wires 11 and 21 suffer the influence of the electromagnetic induction, noise may ride on the reinforcin
REFERENCES:
patent: 4160872 (1979-07-01), Lundberg et al.
patent: 5333230 (1994-07-01), Hata et al.
patent: 5390273 (1995-02-01), Rahman et al.
patent: 5448669 (1995-09-01), Dunne
patent: 5761361 (1998-06-01), Pfandl et al.
Kamei Koji
Yoshida Shigeyoshi
Palmer Phan T. H.
Tokin Corporation
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