Radiation resistivity in silica optical fibers

Hydrogen treatment of optical fiber waveguides with pure silica cores and boron, fluorine codoped silica claddings was found to effectively reduce the y-ray induced loss increases in visible wavelength region. Germanium-doped core fibers free from metal impurities had good resistance against y-rays. The induced losses were shown to be dependent on the dose rate, a similar behavior to that of pure silica core fibers. Metal impurities such as phosphorus or alkalis added to germanium doped silica core were found to change the glass structure significantly, producing the precursors of a defect center related to the y-ray-induced loss and increasing sensitivity to y-irradiation