Patent ID: 6477864
Filing Date: 2002-11-12
Classification: C01B,C03B,C03C

Abstract:
A method of depositing natural or synthetic silica on an optical fiber preform, in which a substantially cylindrical preform extending in a longitudinal direction is set into rotation about its axis in front of a plasma coming from a heat energy supply source which moves back and forth substantially parallel to the longitudinal direction of the preform, and in which a first feed duct feeds the plasma with grains of natural or synthetic silica, wherein a second feed duct positioned entirely external to the heat energy supply source feeds the plasma with a flourine or chlorine compound mixed with a carrier gas, the grains of natural or synthetic silica and the flourine or chlorine compound both being supplied externally and directly to the plasma at an end of the heat energy supply source, the feed conditions of the two ducts being adjusted to cause alkali or alkaline-earth elements contained in the grains of natural or synthetic silica to react with the flourine or the chlorine of the flourine or chlorine compound, causing flourides or chlorides to be given off in gaseous form.