Process for the manufacture of a preform for optical fibres, particularly a preform of large diameter

• Main Authors: FAUCHE, REMI, JOLLY, JACQUES, CAMPION, JEAN-FLORENT
• Format: Patent
• Language: English; French; German
• Published: 11.09.2002
• Edition: 7
• Subjects: CHEMISTRY; GLASS; MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES; METALLURGY; MINERAL OR SLAG WOOL

An optical fiber preform overcladding process, comprising intermediate unilateral layer length reduction to obtain reduced material thickness on one of the preform holder tips and a limited preform length, is new. An optical fiber preform is produced by subjecting a preform (1'), held horizontally at its ends between two mounting point support tips (6a, b), to axial rotation and repeated displacement relative to a plasma torch and an associated a material feeder deposition of a new material layer on the preform or smoothing of the last deposited layer being carried out during the relative preform/torch displacements. Unilateral layer length reduction of one of the intermediate layers is carried out in one of the passes, during the deposition of a sequence of concentric material layers of respective lengths which are progressively reduced progressive reduction of the displacement length so that the thickness of deposited material, which covers the preform and parts the tips, is reduced regularly towards the ends. The unilateral layer length reduction leads to a reduced material thickness, determined by the layer deposited prior to the unilateral layer length reduction, on one of the tips and on a preform zone of limited length.