Influence of Hydrogen on the Radiation-Induced Attenuation of Ge-doped Optical Fibers

The radiation-induced attenuation (RIA) levels and kinetics depend on several parameters, including silica-based optical fiber composition, operation wavelengths and pre-irradiation treatments. We studied in this work how the X-ray RIA in the visible and near-Infrared domains, up to a total ionizing dose of 100 kGy(SiO ₂ ), of a standard telecom Ge-doped fiber, changes when this optical fiber is subjected to different pre-irradiation treatments such as an H ₂ -loading, with or without an additional thermal treatment at 50°C. The performed systematic study, at room temperature, allows to better characterize the influence of the presence of either molecular H ₂ or bonded atomic hydrogen on the generation and bleaching mechanisms of radiation induced point defects. Our results show that, if the hydrogen can passivate point defects at lower doses (< a few kGy), it globally negatively impacts the visible and near-IR RIA at doses larger than few kGy. This hardening solution can then not be employed for this class of optical fibers.