/spl gamma/-radiation-induced absorption in pure-silica-core fibers in the visible spectral region: the effect of H/sub 2/-loading

/spl gamma/-radiation-induced absorption in the visible spectral region is studied in H/sub 2/-loaded and untreated optical fibers with high-OH low-Cl KU core and low-OH low-Cl KS-4V core. H/sub 2/-loading is found to suppress the low-dosage transient absorption band centered at 670 nm in KS-4V fibers. After irradiation to 1.7 MGy(Si), H/sub 2/-loaded fibers show losses many times lower than the untreated fibers. H/sub 2/-loaded and irradiated fibers are found to retain very high radiation resistance under subsequent irradiations even in the absence of molecular hydrogen. It is concluded that H/sub 2/-loading followed by pre-irradiation can be used as an efficient radiation hardening technique for pure-silica optical fibers.