248 nm induced vacuum UV spectral changes in optical fibre preform cores: support for a colour centre model of photosensitivity

Abstract

UV (248 nm) induced changes in the UV spectrum (165–300 nm) of optical fibre preform cores have been measured which can account for refractive index changes observed on writing Bragg gratings in optical fibres. The changes are thermally reversed at 900°C. A fibre grating has been thermally erased and rewritten with no significant change in fibre photosensitivity.