Abstract: An optical fiber waveguide resistant to ionizing radiation having a glass core of predetermined refractive index surrounded by glass cladding having a lower predetermined refractive index. The glass core and glass cladding are each composed of high purity silica incorporating gallium as a constituent. The gallium is present in the form of Ga.sub.2 O.sub.3 in a concentration of about 0.01 to 0.15 mole percent ratio to the silica. The glass of the optical waveguide can further include phosphorus in the form of P.sub.2 O.sub.5 as an additional constituent in the amount of from about 5 to 16 mole percent ratio to the total amount of all constituents.The waveguide of the invention is preferably manufactured by using GaCl.sub.3 in combination with an internal vapor phase process to produce a silica soot (16) containing Ga.sub.2 O.sub.3 on the interior surface of a high purity silica tube (10). The soot is then consolidated and the tube collapsed to form a substantially voidless solid rod preform of high purity SiO.

Abstract: Metal-coated optical fibers are often employed in high temperature optical communications applications. However, such optical fibers have been found to evidence a substantial decrease in optical transmission as a function of increased temperature. Optical fibers having a temperature-insensitive optical transmission are obtained by annealing a metal-coated optical fiber at a temperature at which optical transmission is substantially the same as that observed at room temperature. Aluminum-coated optical fibers annealed at 560.degree. C. evidence an optical transmission independent of temperature between about -200.degree. C. and at least about 560.degree. C.