Non-Additive Effects of Ionizing Radiation and Hydrogen on Optical Fiber Attenuation

Optical fibers having various dopants (pure silica, fluorine, germanium and phosphorous) were consecutively exposed to ionizing radiation (gamma or beta) and hydrogen-rich environments. The attenuation spectra measured before, in-between and after the exposures displayed impacts of the radiation and hydrogen as optical loss factors. Their intermediate and ultimate losses were found to drastically depend upon the dopant type. The fibers with pure silica and fluorine-doped cores behaved as most immune to the applied conditions. The irradiated germanium-doped fibers were found to be much more sensitive to hydrogen than the as drawn fibers, which is explained by development of radiation-induced reactive sites in the fiber, that further promote interactions with hydrogen. In contrast, the irradiated phosphorous-doped fiber displayed a strong hydrogen-induced bleaching at longer wavelengths (>1000 nm), which was attributed to hydrogen reacted at P1 defect sites. A carbon coating present on one of the studied P-doped fibers was shown to prevent the bleaching.