Radiation-induced absorption and luminescence in specially hardened large-core silica optical fibers

Abstract

Radiation-induced absorption and luminescence are measured in the visible spectral region in H/sub 2/-loaded and as-drawn fibers with KU and KS-4V silicas in the core in the process of /spl gamma/-irradiation (/sup 60/Co-source). The induced absorption in H/sub 2/-loaded fibers is shown to be much lower than in as-drawn fibers, at least up to 1.2 MGy. A 'blue' band prevails in the luminescence spectra of all the fibers. Its intensity is greater in a KS-4V fiber than in a KU fiber. It is also somewhat greater in H/sub 2/-loaded fibers than in unloaded ones, The luminescence lifetime in a KU fiber has been measured under excitation with a pulsed reactor to be 100 /spl mu/s at /spl lambda/=488 nm and 60 /spl mu/s at /spl lambda/=633 nm. It is concluded that the 'blue' radioluminescence cannot be attributed either to relaxation of the oxygen-deficient center or to Cerenkov emission. A fabrication technology of radiation-hardened H/sub 2/-containing fibers with a hermetic aluminum coating is reported. Such fibers appear to be the best candidates for various applications in radiation environments.