Effect of oxygen content on defect formation in pure-silica core fibers

There is slight lack of stoichiometry in pure silica glass, which varies according to the synthesis process. The lack of stoichiometry leads to defect formations: The 245 nm absorption band and drawing-induced E’ centers are formed in oxygen-deficient silica, but peroxy radicals and drawing-induced 2 eV band are formed in oxygen-rich silica. The 245 nm band seems to be caused by the Si-Si bonding.