Patent ID: 6802191
Filing Date: 2004-10-12
Classification: C03B

Abstract:
Process for the manufacture of optical fibers comprising:preparing an optical fiber preform, heating the preform to the softening temperature, and drawing an optical fiber from the optical fiber preform wherein the optical fiber preform is produced by steps including:(i) preparing a porous silica body of silica particles, the porous silica body having an inner up-doped region surrounded by an outer shell region, said outer shell region comprising a lower doped region, (ii) heating the porous silica body to a temperature of at least 1100Â° C. in the absence of fluorine for a period sufficient to selectively consolidate the inner up-doped region, (iii) heating the porous silica body in an atmosphere of a fluorine compound to produce a fluorine doped preform region with a refractive index change &Dgr;n, the atmosphere having a partial pressure of fluorine compound that is at least five times greater than the equilibrium partial pressure p expressed by &Dgr;nËœp1/4 and a temperature maintained below 1050Â° C., (iv) reducing the fluorine concentration, and (v) heating the porous silica body at a temperature greater than 1300Â° C., to complete consolidation of the porous silica body.