Abstract: The invention relates to apparatus for supporting a preform manufactured in an installation for manufacturing or building up preforms having supporting cores, said installation including at least rotation means having a horizontal axis of rotation and two mounting points between which the supporting core of the preform to be manufactured or built up is mounted, plasma-torch and material-supply means disposed radially relative to said supporting core and being mounted to move in axial translation relative to and parallel to the supporting core so as to make said preform around said supporting core, said apparatus being wherein it includes controlled support means constituting additional localized abutment points between said mounting points for said preform being manufactured or built up.

Abstract: The invention relates to a method of manufacturing a cylindrical preform for use in making an optical fiber of substantially smaller diameter. The method consists in increasing the diameter of a primary preform by injecting grains onto the surface of the primary preform and in fixing the grains on the surface by means of a heat flow obtained by a plasma torch comprising a tube made of refractory material, and an inductor surrounding the tube. The distance between the inductor and the end of the tube is reduced when the diameter of the preform increases. The temperature of the outside surface is thus increased, thereby enabling preforms to be obtained of larger diameter or with improved efficiency.

Abstract: A method and associated apparatus for increasing the over cladding rate in perform production while maintaining the integrity of the glass quality of the cladding. The method and apparatus are designed to utilize the full capacity of the generator to thereby improve the overall deposition speed without sacrificing the glass quality. In particular, it is estimated that the process of the present invention will increase the deposition speed by approximately 50% and still obtain suitable glass quality. This object is achieved by utilizing two plasma torches, instead of just one, that are driven by the same power generator.

Abstract: The invention relates to apparatus for supporting a preform manufactured in an installation for manufacturing or building up preforms having supporting cores, said installation including at least rotation means having a horizontal axis of rotation and two mounting points between which the supporting core of the preform to be manufactured or built up is mounted, plasma-torch and material-supply means disposed radially relative to said supporting core and being mounted to move in axial translation relative to and parallel to the supporting core so as to make said preform around said supporting core, said apparatus being wherein it includes controlled support means constituting additional localized abutment points between said mounting points for said preform being manufactured or built up.

Abstract: The invention relates to a method of performing surface treatment on a preform manufactured in an installation for manufacturing or building up preforms having supporting cores, the installation including at least rotation means having a horizontal axis of rotation and two mounting points between which the supporting core of the preform to be manufactured or built up is mounted, plasma-torch and material-supply means disposed radially relative to the supporting core and mounted to move in axial translation relative to and parallel to the supporting core so as to make the preform around the supporting core, the preform being manufactured or built up by effecting successive passes with the plasma torch while material is being supplied.