Modified chemical vapor deposition of an optical fiber using an rf plasma

A process for fabrication of a glass fiber optical 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 vapor mixture including at least one compound glass-forming precursor together with an oxidizing medium into a tube;
• heating the tube by means of a moving hot zone so as to react the said mixture and produce a glassy deposit on the inner surface of the tube, said hot zone produced by a correspondingly moving heat source external to the tube, the temperature within the hot zone, composition of the vapor mixture, and rate of introduction of the mixture, 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 whereby the particulate material while traveling downstream comes to rest on the inner surface of the tube, and is fused to form a continuous glassy deposit within a region which extends from a position within the said hot zone;
• the invention characterized in that the moving hot zone is an rf plasma and the moving external heat source is an rf source.