Optical fiber fabrication

Claim 1

A process for fabrication of an optical fiber transmission line comprising a core section and a cladding, wherein the cladding has an index of refraction of a value lower than the maximum index of the core for energy of the wavelength to be transmitted comprising: introducing a moving stream of a vapor mixture including at least one compound glass-forming precursor together with an oxidizing medium into a tube while heating the tube so as to react the said mixture and produce a glassy deposit on the inner surface of the tube, characterized in that the heating of tube and contents are by a moving hot zone produced by a correspondingly moving heat source external to the tube, and in that temperature within the hot zone, composition of the vapor mixture, and rate of introduction of the vapor mixture are maintained at values such that at least a part of the reaction takes place within the gaseous mixture at a position spaced from the inner walls of the said tube thereby producing a suspension of oxidic reaction product particulate material, which deposits on the inner surface of the tube and in that said particulate material is consolidated to produce said glassy deposit on the inner surface of the tube.