Drawing‐induced defect centers in a fused silica core fiber

The process of fiber drawing has been found to produce defect centers in optical fibers with a silica core of low OH content (Suprasil W‐1), but not in fibers with a silica core of high OH content (Suprasil 1). At least one center gives rise to the drawing‐induced optical absorption, which is identical to the 630‐nm band created by ionizing radiation in bulk samples of Suprasil W‐1. By means of electron‐spin‐resonance techniques, additional drawing‐induced defect centers have been observed; these centers are identical to the radiation‐induced oxygen‐associated hole centers in bulk fused silica.