Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Patent
1997-10-30
1999-11-23
Truong, Duc
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
525902, 525928, 525929, 4284235, 385123, 385128, C08G 7310
Patent
active
059902671
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an optical fiber, to an optical fiber ribbon, and to a method of manufacturing them.
In well-known manner, an optical fiber is designed to transmit lightwaves and is constituted by an optical core, made of a silica-based material, surrounded by optical cladding, likewise made of a silica-based material. The optical core is designed to guide the majority of the lightwaves transmitted by the optical fiber. These two elements (the optical core and cladding) constitute the optical portion of the fiber, also referred to as the "bare" optical fiber. This portion is very sensitive to external disturbances, which can give rise to damage to its transmission properties, and thus to degraded operation of the optical fiber.
In order to protect the bare fiber against external disturbances, it is well known to cover the optical cladding in a protective layer of plastics material, referred to as a "primary" covering. It is optionally possible to have other protective layers over the primary covering, and more particularly a second protective layer referred to as a "secondary" covering, together with an identification layer which is usually colored.
The solution presently used for making protective layers consists in covering the optical cladding in thermosetting resin (i.e. a resin which hardens by cross-linking on being heated), e.g. a resin that is capable of being cross-linked under the effect of ultraviolet radiation. The ultraviolet radiation serves to provide the heat necessary for the cross-linking reaction (in practice a temperature of about 200.degree. C. is necessary for cross-linking purposes).
Also in known manner, an optical fiber ribbon is an assembly comprising a plurality of optical fibers that are bare or covered in one or more layers for protective or identification purposes, the fibers being disposed side by side and parallel to one another, substantially in a common plane, said fibers being held together by means of a common matrix of plastics material, which also serves to protect the fibers against external disturbances. The common matrix is constituted by a thermosetting resin, e.g. a resin capable of cross-linking under the effect of ultraviolet radiation.
In order to cover an optical fiber in a covering layer of thermosetting resin, or indeed to make the protective matrix of an optical fiber ribbon out of such a resin, the body that is to be treated (i.e. the fiber or the set of fibers) is caused to run through a coating die containing the resin in the non-crosslinked state, i.e. in the still-liquid state, and then to run through apparatus suitable for supplying thereto the energy which is required (in the form of heat) for causing cross-linking to take place.
Such apparatus must include complex heater means, and in particular, for a resin that is suitable for being cross-linked under the effect of ultraviolet radiation, it must include ultraviolet lamps associated with matching reflectors for the purpose of focusing the radiation on the body to be treated. In addition, it is necessary under such circumstances to provide means that prevent the infrared radiation which is emitted together with the ultraviolet radiation from reaching the body that is to be treated, since the infrared radiation runs the risk of heating the body excessively, thereby degrading its mechanical and optical properties.
Such apparatus is complex, and consequently quite expensive.
In addition, it requires continuous maintenance, and that also is expensive.
The object of the present invention is thus to provided an optical fiber and an optical fiber ribbon which can be manufactured without requiring the use of equipment that is expensive to purchase or that is expensive to maintain.
To this end, the present invention provides an optical fiber comprising an optical core for guiding the majority of lightwaves transmitted by said fiber, the core being surrounded by optical cladding, itself surrounded by a protective covering of plastics material, the fiber being characterized in that said plasti
REFERENCES:
patent: 3435003 (1969-03-01), Craven et al.
patent: 3872057 (1975-03-01), Pazos
Patent Abstracts of Japan, vol. 11, No. 267 (C-443), Aug. 28, 1987 corresponding to JP-A-62 068809 (NTTC) Mar. 28, 1987.
Alcatel Cable
Truong Duc
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