Abstract: Glass fiber optical-waveguides consisting of a metal oxide-silicate glass core and silica cladding are produced according to the invention by means of a metal evaporation technique. An evacuated fused silica tube containing an evaporated metal deposit is heated to temperatures sufficient to form a uniform metal silicide layer on its inner surface. This layer is then oxidized and reacted with the silica tubing at elevated temperatures to form a metal oxide-silica glass layer. The tube is then collapsed to give a solid rod preform with a metal oxide-silica glass core. Fibers drawn from such preforms exhibit a graded refractive index profile and low loss. The details of the fabrication technique are described, and a representative loss spectrum is presented.