METHOD FOR PRODUCING GLASS PREFORM FOR OPTICAL FIBER

摘要

A method for producing a glass preform for use in the fabrication of an optical fiber comprises the steps of forming a glass soot preform from a glass-forming raw material, optionally heating the soot preform under a reduced pressure at a temperature at which the soot preform is not vitrified, heating the soot preform in an atmosphere comprising at least one fluorine-containing compound under a reduced pressure or a pressure not lower than atmospheric pressure, if the soot preform has been heated under the reduced pressure in the previous step, or under a reduced pressure, if the soot preform has not been heated in the previous step, and vitrifying the fluorine-added preform for a sufficient time to vitrify it. In this way a glass preform having substantially no bubbles therein and containing a sufficient amount of fluorine can be produced.