AN X-RAY-ABSORPTION STUDY OF DOPED SILICATE GLASS, FIBER OPTIC PREFORMS

Optical fibre preforms, which have their germanosilicate core regions doped with small quantities of the rare-earth element erbium, have bee n studied using Extended X-ray Absorption Fine Structure Spectroscopy (EXAFS) at the germanium K absorption edge. These studies were perform ed using a circular X-ray beam of 100 mu m diameter, allowing informat ion to be gathered as a radial function of position across the core re gion of the preform. This positioning was accomplished by means of a m otorized pinhole collimator and sample stage developed for use on the focused X-ray beamline 8.1, at the SRS, Daresbury Laboratory, UK. The EXAFS results are consistent with the germanium sites coordinated to s urrounding oxygen atoms at a mean distance of 0.17 nm. Absorption maps of the rare-earth and germanium distribution across the core region o f the preforms have also been obtained, showing a correlation between the distributions of the two atom types.