PROCESS AND APPARATUS FOR PREPARING SYNTHETIC SILICA GLASS

摘要

The invention relates to the preparation of synthetic quartz glass which is free from OH ions and is prepared by oxidation of a hydrogen-free silicon compound in a hydrogen-free gas stream containing elemental and/or bound oxygen, and deposition of this oxidation product as a glassy material on a heat-resistant substrate. The gas stream is passed through an induction-coupled plasma burner. In order to reduce the refractive index of synthetic quartz glass, a hydrogen-free fluorine compound in vapour form which decomposes at elevated temperature, in particular dichlorodifluoromethane, is passed into the flame of the plasma burner. The plasma burner used has three offset quartz glass tubes arranged concentrically to one another. The fluorine-doped synthetic quartz glass serves as a material for the cladding of optical fibres.