SINGLE MODE OPTICAL FIBRE AND METHOD OF MAKING IT

摘要

Single mode optical fibre for operation in the wavelength range 1.5 to 1.7 microns is made by depositing a cladding glass layer (51) and then a core glass layer (52) upon the bore of a silica substrate tube (50). The bore of the coated tube is then collapsed to form a solid cross-section optical fibre preform. The cladding glass has an index matching that of silica and either contains no oxide of phosphorus or the minimal amount to proved a low enough deposition temperature and high enough deposition rate to provide an acceptably low diffusion of hydroxyl groups from the material of the substrate tube. Optionally the deposition of the cladding may be preceded by the deposition of a diffusion barrier layer which may contain a higher proportion of oxide of phosphorus.