Effects of elevated temperature hydrogen exposure on short-wavelength optical losses and defect concentrations in germanosilicate optical fibers

The relation between short-wavelength optical loss increases and defect concentrations has been examined for a single-mode germanosilicate fibers exposed to H2 at 150–250 °C. The hydrogen-induced loss increases under these conditions appear to be due to the reaction of H2 at Ge–E′ centers, resulting in the formation of —OH and ‘‘GeH’’ defects, the latter of which is responsible for a 650-nm fluorescence. ‘‘GeO’’ defect levels, characterized by fluorescence and optical loss measurements, remain unchanged in these experiments. This indicates that ‘‘GeO’’ defects are not part of the reaction mechanism that lead to short-wavelength loss increase at these temperatures, although they may cause other types of short-wavelength loss increase at higher temperatures.