Fabrication method of optical fiber preforms

摘要

The method comprises the steps of:- moving a seed rod while rotating said seed rod (2); blowing out a glass raw material gas and a flame forming gas separately from a synthesizing torch (4) to synthesize fine glass particles from said glass raw material gas through hydrolysis by flame or thermal oxidation by a high temperature heat source, said glass particles being blown out and deposited on to one end of said seed rod which moves while rotating, so that a cylindrical porous preform is grown in the direction of said rotation axis of said seed rod; exhausting glass particles not attached on the growing surface of said cylindrical porous preform of said glass particles, gas produced as a result of said hydrolysis or oxidation, non- reacted glass raw material gas and said flame forming gas through at least one exhaust port (9) which is disposed at a distance of 1 mm to 50 mm from the periphery of said cylindrical porous preform formed by the deposition of said glass particles and in the vicinity of a growing surface of said cylindrical porous preform; and heating said cylindrical porous preform at a high temperature to vitrify said cylindrical porous preform into a transparent optical fiber preform.