Optical Losses in As-Prepared and Gamma-Irradiated Microstructured Silica-Core Optical Fibers

Abstract

The optical loss spectra of as-prepared and gamma-irradiated microstructured multimode fibers with KU-1 silica cores are analyzed. Experimental evidence is presented that leakage losses in such fibers can be prevented by producing, in their cladding, two layers of channels separated by thin glass walls. The strong absorption at 630 nm in the radiation-induced loss spectra of the fibers is shown to arise from nonbridging oxygen. The mechanisms underlying the formation of precursors to this color center are discussed, and the possible approaches to suppressing the 630-nm absorption are outlined.