Photo-Annealing Effects on Gamma Radiation Induced Attenuation in Erbium Doped Fibers and the Sources Using 532-nm and 976-nm Lasers

Two erbium doped fibers (EDFs) with different radiation sensitivities were used in the photo-annealing tests, and their photo-annealing efficiencies were compared by using 532-nm and 976-nm lasers. For both EDFs, the 532-nm laser with 10 mW showed better efficiency than 976-nm laser with 290 mW. The radiation induced attenuation (RIA) could nearly be diminished in the wavelength range from 900 nm to 1700 nm by the photo-annealing of 532-nm laser. The half-time of recovery was 5.6 seconds by using 532-nm laser, and was about 40 minutes by using 976-nm laser whose annealing rate was similar to that of purely thermal annealing at about 330°C. For γ-irradiation tests of superfluorescent fiber sources (SFSs) exposed to a dose rate of 129.2 krad/hr, the rate of output power loss could be reduced by the 976-nm pump laser, but the output power loss could not be recovered. A most radiation-tolerant case was an SFS with 2.8-meter EDF#1 co-pumped by both the 532 nm and the 976 nm lasers. The output power loss could be recovered with a rate of 0.009 dB/min.