Radiation-Hardened Optical Fibers for High Dosage Space Applications

Abstract

ABSTRACTHydrogen doping of optical fibers has been examined as an approach to increase the radiation hardness of optical fibers for high dosage (107 rad) space applications. A systematic study has been performed on 4 types of optical fibers designed to operate at 1.31 and 1.55 μm and doped with up to 8200 ppm H2. For low dosages, the most significant reductions m radiation-induced losses were obtained with low H2 concentrations (<10 ppm). Spectral loss measurements for hydrogen-doped fibers containing GeO2 show a radiation-induced loss peak at 1.45 μm and a broad absorption band around 0.6–0.8 μm. These bands are not observed in the pure silica-core fibers.Fibers were fabricated to permanently trap 2.7 ppm H2 and the radiation-induced losses in these fibers are 35 to 85% that of the untreated fibers. Experimental data are used to delineate the γ-T-α operating limits which define the maximum gamma radiation (γ) dosages at different temperatures (T) while still meeting a requirement of α<150 dB/km. Among the four fiber types, hydrogen-doped silicacore fibers show the widest operating range and smallest radiation-induced loss for space applications. However, hydrogen-doped fibers with moderately high GeO2-doped core offer the best tradeoff between the bending and radiation-induced losses.