OPTICAL FIBRE MANUFACTURE

摘要

An optical fibre preform with a rare-earth doped core is made by a vapour deposition process upon the bore of a silica substrate tube (10). The source material for the rare-earth doping is contained in a heated chamber (12) formed upstream of the deposition zone. This source material is a chloride prepared in situ in anhydrous form substantially uncontaminated by oxide or oxychloride by heating a mixture of ammonium chloride and the hydrated rare-earth chloride in a current of helium.