METHOD FOR EXTERNALLY DEPOSITING DOPED SILICA ON AN OPTICAL FIBRE PREFORM

摘要

The invention concerns a method for making an optical fibre (15) preform (3), consisting in forming at least one external silica-based layer (23) by depositing silica on a primary preform (24), consisting of a bar comprising mainly silica and comprising an external peripheral silica-based part (22). The invention is characterised in that it consists in adjusting the external deposit layer (23) viscosity so that it is substantially identical to the primary preform (24) external peripheral part (22) viscosity by adding to the silica, for a substantial part of the external deposit (23), at least a doping agent selected in the group formed by the following compounds: CaF2, MgF2, AlF2, B2O and Al2O3.