gamma-Radiation resistance of aluminum-coated all-silica optical fibers fabricated using different types of silica in the core

Induced loss spectra in four Al-coated large-core optical fibers are measured in the range 380-1000 nm during and after Co-60 gamma irradiation. These fibers had F-doped-silica claddings and synthetic silica core materials produced by different technologies. Measurements were carried out independently in Washington and Moscow using differing techniques but yielding very similar results. The highest radiation resistance is exhibited by two fibers with extremely low OH and Cl contents in their cores, one with a core material containing 0.5 mass % of fluorine, fabricated specially for this study, and one based on KS-4V silica, an original technology developed in Russia. The latter fiber demonstrates a rather flat induced loss spectrum in the visible region at a level of 2-2.5 dB/m for gamma-ray doses of similar to 10 MGy(Si). (C) 1996 American Institute of Physics.