Optical waveguides – With splice
Patent
1996-06-21
1997-07-15
Ngo, John
Optical waveguides
With splice
65501, 65433, 65407, 385147, 359900, G02B 636
Patent
active
056490402
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND
The present invention relates to a method and a device for splicing an aged optical silica fiber to another fiber, e.g. to a new optical fiber for repair purposes.
It is well-known that optical fibers based on silica corrodes in a humid environment. Further, substantially all optical fibers which are installed for ordinary telecommunication in national networks are exposed to moisture to a larger or smaller extent. Naturally, the surface of a silica fiber is in particular exposed to corrosion attacks. The attacks cause that the tensile strength of the fiber is reduced and that the fiber gets more brittle. The deterioration of the mechanical characteristics of fibers is a large problem when repairing e.g. a fiber which is installed below ground level and has been cut off in some digging operation. Installed, aged fiber can be so brittle that it may be difficult to handle it and it can even be impossible to splice the fiber to other fibers. Up to now, for failures such as breaks or ruptures of old fibers, it has often been necessary to replace whole fiber lengths which is naturally very costly.
It has been observed previously that the rupture and tensile strength of glass fibers and wave guides can be increased by heating the fibers or waveguides to temperatures in the vicinity of the softening temperature, see the German patent applications made available to the public DE-A1 28 17 651 for Siemens AG and DE-A1 40 41 150 for kabelmetal electro GmhH. The methods and devices disclosed are conceived to be used on ordinary fibers, before the practical use thereof.
SUMMARY
It is an object of the invention to provide a method and device by means of which an aged optical silica fiber can be given improved properties in order to splice the fiber to another optical fiber.
This object is achieved by the invention, the characteristics of which are set out in the appended claims.
For improving mechanical properties of a segment of an aged optical fiber to allow the handling thereof which is required for a splicing process, the segment is heated to a high temperature near the softening temperature or the melt temperature of the glass material in the fiber. Hereby, the corrosion attacks resulting from a moist environment can be "healed", i.e. microcracks, resulting from the moisture, are melted together by the heat.
The heating power can be provided from a light beam of a laser. The light beam is focused over a cross section of the optical fiber and this heated cross-sectional area is made to be displaced along a segment of the fiber. The light beam power and the displacement velocity are chosen so that the temperature on the surface of the fiber achieves a temperature near the melt temperature. Practically it is visible by the fact that the surface of the fiber gets a "smooth" or "shiny" appearance.
Other possibilities for the heating is e.g. heating in a gas flame, by means of a heating spiral element (resistive heat element) or by means of an electric arc of the type used for a melt-fusioning in splicing optical glass fibers.
Thus the steps for splicing an aged optical fiber to another optical fiber generally comprise that first the polymer protective sleeve on the aged fiber is removed over a segment of the fiber for exposing the surface of the fiber cladding which is supposed to be of some glass or silica material. The surface of at least a portion of the segment of the aged fiber, where the cladding is exposed, is then heated to a high temperature in the vicinity of or essentially the melt temperature of the material in the fiber cladding. In particular the temperature may be chosen to such a high value that the surface of the silica fiber melts somewhat during the heating. The fiber is cut off at a place within the segment to produce an end surface, which is then spliced as an ordinary optical fiber to another one, that is this end surface is placed adjacent to an end surface of another optical fiber and these end surfaces are coupled optically to each other, by e.g. welding the fiber ends to each oth
REFERENCES:
patent: 4045198 (1977-08-01), Rau et al.
patent: 4304582 (1981-12-01), Aussenegg et al.
patent: 4810054 (1989-03-01), Shinbori et al.
patent: 5061265 (1991-10-01), Abela et al.
patent: 5566262 (1996-10-01), Yamane et al.
Johansson Magnus
Ljungqvist Goran
Stensland Leif
Ngo John
Telefonaktiebolaget LM Ericsson
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