Electricite De France - Service National

Societe Anonyme Dite: Compagnie Generale D'electricite

Alcatel Fibres Optques

Gilles Barre

Christian Le Sergent

Josiane Ramos

A method of improving the symmetry of a cylindrical silica tube to be used in making a preform having a circular outside surface eccentric to a circular inside surface thereby providing a varying tube thickness throughout the circumference of the tube which includes the following steps. The first step is locating a longitudinal generator line of the cylindrical tube at a greatest thickness of the tube at a given circumferential point on the tube, and while preventing the tube from rotating, etching in at least one pass the inside of the tube with a gas capable of decomposing silica, while heating the outside of the tube along that longitudinal generator line.

Method of improving the geometrical shape of a tube used for making a

A mist is formed by an ultrasonic generator (5) from a liquid solution containing a dopant, and the mist is inserted into the tube blank to be doped (4) by means of a flexible pipe (2) in order to deposit microdrops on the inside surface of said tube blank. The flexible pipe is withdrawn progressively so that deposition takes place along the entire length of the tube blank. The deposit is dried and a new layer of glass is deposited thereon. The dopant from the deposit is heat diffused into the glass of the tube blank and of the new layer of glass. The invention is particularly applicable to fabricaitng rare-earth-doped silica preforms for the purpose of drawing optical fibers that can be used to constitute lasers or sensors.

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Saint Michel Sur Orge, France

Gilles Barre