Laser Diode-Induced Photobleaching at Low Temperatures in Co-60 Irradiated Fibers

Laser diode (820 nm)-induced photobleaching effects have been studied primarily at -55° C in a variety of fibers including polymer clad pure silica core, fluorosilicate clad pure silica core, and doped core fibers which were exposed to Co-60 irradiation with and without simultaneous CW laser light passing through the fibers. Thermal and laser-induced recovery at -55° C following irradiation was also examined. Those fiber parameters which were found to affect the extent of photobleaching were dopant content in the core, especially phosphorus, OH concentration in the core, and saturation of induced attenuation. The optimum fiber which shows minimal attenuation after irradiation and photobleaching is one that has an undoped core with high OH content.