The role of fluorine-doped cladding in radiation-induced absorption of silica optical fibers

Radiation-induced absorption spectra and radial distribution of nonbridging oxygen over the fiber core are compared in fibers and preform slices fabricated under different technological regimes with high- and low-hydroxyl silicas in the core. The radiation-induced nonbridging oxygen concentration is found to peak at the core-cladding interface. Fiber perform fabrication and fiber drawing processes are found to have different influence on its value in fibers with low- and high-hydroxyl silicas in the core. The precursors of nonbridging oxygen near the core-cladding interface are argued to arise at the stage of preform fabrication at least in the case of high-hydroxyl fibers. Their concentration decreases with increasing the fluorine concentration in the cladding. In the case of low-hydroxyl silica fibers the increase of the radiation-induced nonbridging oxygen concentration at the core periphery is argued to have a different nature as compared to high-hydroxyl silica fibers.