ULTRAVIOLET-ABSORPTION STUDIES ON PHOTOSENSITIVE GERMANOSILICATE PREFORMS AND FIBERS

Detailed measurements of the ultraviolet absorption spectra of germanosilicate preforms, multimode and single-mode fibers are presented. Significant differences between the spectra of preforms and fibers are revealed and these differences are thought to be caused by the stresses induced during fiber pulling. Measurements are also presented of the changes in the absorption spectra in single-mode fibers into which reflection gratings have been written using an ultraviolet laser. These results suggest that changes in the absorption between 200 and 600 nm are not responsible for the inferred changes in the refractive index.