Optical waveguides – Optical transmission cable
Patent
1995-12-04
1997-09-23
Lee, John D.
Optical waveguides
Optical transmission cable
264 128, 385112, G02B 644
Patent
active
056713126
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a cable having fine conductors, in particular optical fibers, and also to a method and to apparatus for making a cable having fine conductors.
BACKGROUND OF THE INVENTION
Document FR-A-2 665 266 discloses an optical fiber cable comprising a series of optical fiber modules, each optical fiber module being enclosed in a supporting sheath that is disposed in contact with the optical fibers so as to surround them in such a manner as to achieve mechanical coupling between the fibers. Such a cable is particularly compact, but it nevertheless leaves interstices between the zones of contact between the optical fibers and those between the fibers and the supporting sheaths, and as a result the cables are not leakproof longitudinally, i.e. if an end of a cable of the above type is immersed in water, then water penetrates progressively along the inside of the cable with all the drawbacks that that can cause. The same applies to a cable having fine electrical conductors, e.g. each having a diameter of less than 0.5 mm and each covered in a primary sheath, with conductors being grouped together in one or more modules each enclosed in its own supporting sheath.
It is also known that to make a cable that is leakproof longitudinally, it is conventional to place grease between the insulated conductors, which grease is chemically inert relative to the primary sheaths of the conductors and that has viscosity that is sufficiently high to oppose penetration by water. In particular, it is common to use silicone greases having viscosity of 200,000 cPo. Such greases are highly satisfactory from the point of view of longitudinal sealing, but when an end of the cable is to be stripped for connection to equipment or to another cable, it becomes necessary to eliminate the grease. Grease elimination can be achieved by using a solvent, but that gives rise to manipulations during which the fine conductors such as optical fibers run the risk of being damaged.
SUMMARY OF THE INVENTION
According to the invention, the fine conductors of a cable of the type described in document FR-A-2 665 266 are coated in an oil having viscosity lying in the range 100 cPo to 5,000 cPo, and preferably in the range 1,000 cPo to 4,000 cPo.
Thus, unexpectedly, an oil of this type having viscosity that is much less than that of the greases normally used does not run out from the end of a cable when the cable is cut, and as a result it provides longitudinal sealing for the cable even though it can be eliminated when stripping the end of the cable merely by wiping the fine conductors with absorbent paper, thus considerably facilitating the operations of making a connection to a cable of the invention.
In another aspect, the invention relates to a method and to apparatus for making a fine conductor cable obtained by extruding a supporting sheath around a group of fine conductors, each of which is covered in a primary sheath, the fine Conductors being coated in an oil of viscosity lying in the range 100 cPo to 5,000 cPo, and preferably in the range 1,000 cPo to 4,000 cPo, by means of an applicator member such as a felt pad associated with an oil feed member and located upstream from the extrusion head.
BRIEF DESCRIPTION OF THE DRAWINGS
Other characteristics and advantages of the invention appear further from reading the following description of a particular and non-limiting embodiment of the invention described with reference to the accompanying drawing, in which:
FIG. 1 is a fragmentary section view on a greatly enlarged scale through an optical fiber cable of the invention; and
FIG. 2 is a diagram of a device for making an optical fiber cable of the invention.
DESCRIPTION OF PREFERRED EMBODIMENTS
With reference to FIG. 1, the cable of the invention comprises, in a manner known per se in particular from document FR-A-2 665 266, a series of fine conductors, e.g. optical fibers 1, each of which fibers is covered in a primary sheath 2. The optical fibers 1 are collected together in modules 3 that may contain some variable
REFERENCES:
patent: 4370023 (1983-01-01), Lange et al.
patent: 4464013 (1984-08-01), Sabia
patent: 4840454 (1989-06-01), Mayr
patent: 5155789 (1992-10-01), Le Noane et al.
patent: 5224192 (1993-06-01), Wagman
patent: 5276757 (1994-01-01), Levy et al.
Lee John D.
Societe Industrielle de Liaisons Electriques
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