Method for producing glass preform for optical fiber containing fluorine in cladding

Abstract From the Canadian patent

Abstract:, The invention provides a method for producing a glass preform for an optical fiber comprising a core and a cladding containing fluorine. The method involves forming a porous glass layer of substantially pure quartz on an outer surface of a fused glass rod consisting of a central portion of substantially pure quartz and a peripheral portion of quartz glass containing fluorine and heating a, composite of the fused glass rod and the porous glass layer in an atmosphere containing fluorine to add fluorine to the porous glass layer and to make it transparent. By this method, the contamination of the glass with hydroxyl groups can be prevented and the light transmission characteristics …