Abstract: The present invention provides an installation for fabricating or overcladding an optical fiber preform, which installation includes an inductive torch for producing a plasma from a plasma generating gas and material feed means and is characterized in that said plasma generating gas is a mixture of a first gas chosen from diatomic gases and mixtures of at least two gases and argon in a proportion by volume from 0.5% to 10%.

Abstract: The present invention provides an installation for fabricating or overcladding an optical fiber preform, which installation includes an inductive torch for producing a plasma from a plasma generating gas and material feed means and is characterized in that said plasma generating gas is a mixture of a first gas chosen from diatomic gases and mixtures of at least two gases and argon in a proportion by volume from 0.5% to 10%.

Abstract: The method is designed to be implemented in an installation provided with means enabling a preform held between two points by supporting end-pieces to be rotated and to be moved in translation. Heater means for heating the preform by means of a plasma torch are associated with material supply means, so as to enable the preform to be manufactured in layers. Preform/torch relative displacements, with or without material being supplied, lead either to a new layer of material being deposited on the preform, or to the most recent layer deposited being glazed. Said method interposes a one-ended reduction in layer length, starting from one of the intermediate layers, while a succession of concentric layers are being deposited on the preform in a manner such that the lengths of the layers are progressively reduced so that the preform tapers towards it ends. The one-ended reduction leads to a limitation of the thickness of a determined segment at the level of the layer deposited immediately prior to the reduction.

Abstract: The invention relates to the field of processes for manufacturing optical fiber preforms. This is a process for manufacturing optical fiber preforms that includes a step of drawing the preform with a draw ratio that remains constant for the same preform and may vary from one preform to another depending on their respective mean diameters so as to reduce the variation in mean diameter between preforms or else a process for manufacturing optical fiber preforms that includes a step of compressing the preform with a compression ratio that remains constant for the same preform and may vary from one preform to another depending on their respective mean diameter so as to reduce the variation in mean diameter between preforms.

Abstract: A method of manufacturing an optical fiber preform (3) comprising: forming at least one silica-based outer deposition layer (23) by depositing silica on a primary preform (24) constituted by a bar mainly comprising silica and including a silica-based outer peripheral portion (22), the method being characterized in that the viscosity of the outer deposition layer (23) is adjusted to be substantially identical to the viscosity of the outer peripheral portion (22) of the primary preform (24) by adding to the silica, over a substantial portion of the outer deposition layer (23), at least one compound selected from the group formed by the following compounds: CaF2, MgF2, AlF3, B2O3, and Al2O3.

Abstract: A device for producing spherical silica grains includes a cylinder having its axis inclined to the horizontal and an inside wall made from a material that is significantly softer than silica. The cylinder has an entry chute for non-spherical silica grains and an exit chute for spherical cylinder grains. A rotary member is rotated at high speed by a drive shaft having its axis coincident with the axis of the cylinder. The rotary member includes at least one paddle vertically aligned with the entry chute so that silica grains entering via the entry chute are thrown by the paddle against the inside wall of the cylinder and follow a path most of which is against the wall before leaving via the exit chute.

Abstract: A method for producing spherical silica grains using a cylinder having its axis inclined to the horizontal and having an inside wall made from a material that is significantly softer than silica. The cylinder has an entry chute for non-spherical silica grains and an exit chute for spherical cylinder grains. According to the method, a rotary member is rotated at high speed by a drive shaft having its axis coincident with the axis of the cylinder. The rotary member includes at least one paddle vertically aligned with the entry chute so that silica grains entering via the entry chute are thrown by the paddle against the inside wall of the cylinder and follow a path most of which is against the wall before leaving via the exit chute. As a result, the silica graining have a spherical shape.