MANUFACTURE OF OPTICAL FIBRE PREFORMS

摘要

In a method of manufacturing optical fibre preforms by causing a chemical reaction to take place in a gaseous reaction mixture (5) so as to form a coating (19) on a glass substrate (1) wherein the reaction is promoted by the production of a plasma in the mixture by means of a microwave cavity (12) powered by a microwave generator (15) and conductive tube (16) positioned around the reaction tube system, it has been found that if the conductive tube is made of metal, metal ions diffuse through to the substrate and contaminate it. Therefore, the conductive tube according to the invention is made of graphite.