Method for the fabrication of fluoride glass single mode optical fibers with flowing of an etchant through the fiber preform
 Fluoride glass optical fibers are fabricated by minimizing the number of high-temperature operations. A tube comprising an external layer of a first fluoride glass of composition suitable to form the cladding of the fiber and an internal layer of a second fluoride glass of composition suitable to form the core of the fiber is prepared by a conventional rotational casting technique. Then, the internal layer is thinned by means of chemical etching at ambient temperature until the attainment of a ratio between the volumes of the two layers that corresponds to the ratio between the core and cladding diameters required for a single mode fiber, and the resulting tube is drawn. 
Cselt-Centro Studi E Laboratori Telecomunicazioni S.P.A.
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inventional additional inventional inventional
Giuseppe Marco
Cocito Braglia