Abstract: Dielectric optical waveguides can be made having a core of vitreous silica doped with nitrogen in the form of silicon nitride, and a cladding of pure vitreous silica. Silicon nitride may be present in the core material in quantities varying between .1% to 10% by weight. The silicon nitride doped silica glass can be formed in a boule by passing a mixture of gaseous compounds containing silicon and nitrogen through a induction coupled plasma discharge. The outside of the doped silica boule may be oxidized to reduce the nitrogen content.

Abstract: A particular range of glass compositions in the soda-boro-silicate glass system has been found to be particularly suitable for ultra-low loss dielectric optical waveguides. The composition range is indicated in FIG. 1 of the specification. By preparing such glasses in a reducing atmosphere (0-20% CO in CO.sub.2) and adding about 1% As.sub.2 O.sub.3 to the melt attenuation coefficients due to copper and iron can be minimised. The water content of the glass can be reduced by bubbling dry CO in CO.sub.2 through the molten glass. Glasses containing less than 30% Na.sub.2 O by weight have the lowest losses. Using glasses of this type dielectric optical waveguides having an insertion loss of less than 14 dBKm.sup.-.sup.1 have been made.