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 H-2 at 150-250-degrees-C. The hydrogen-induced loss increases under these conditions appear to be due to the reaction of H-2 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.