PROCESS FOR PRODUCING GLASS PREFORM

摘要

A process for producing a glass preform, in which thermal processing of core ingot is facilitated and there is obtained a glass preform having a low content of OH causing an increase of transmission loss and excelling in optical characteristics. The process is characterized in that glass microparticles are deposited in the axial direction so as to produce a porous glass preform having a core portion loaded with a dopant and a clad layer (inner clad layer) provided around the core portion and having a refractive index lower than that of the core portion; the porous glass preform is converted to transparent glass, thereby obtaining a core ingot; the core ingot is heated and oriented in the axial direction in an electric furnace to thereby obtain a core rod; and an outer clad layer is provided around the core rod.