Alcatel

Alcatel Alsthom Compagnie Generale D'electricite

Jean-Philippe Francois

Michel Hertz

Jean-Florent Campion

Jean-Maxime Saugrain

Christelle Lavallade

Bernard Wurier

Jacques Goudeau

Philippe Oskeritsian

Henri Marc Michaud

Thierry Auvray

Patrick McKenzie

Silica granules made up of mutually agglomerated silica soot particles are treated by placing the granules in a crucible inside a furnace which contains an inert gas mixed with a chlorine-containing compound and in which the temperature lies in the range 1000&deg; C. to 1500&deg; C. According to the invention, a crucible is used that is made of porous graphite firstly to increase the surface area of the crucible through which the chlorine-containing compound diffuses. This gives rise to faster exchange between the granules and the gas for given partial pressure of the chlorine-containing compound, thereby improving purification. Secondly, the difference between the chemical natures of the silicas and the crucible make the two materials inert relative to each other so that the granules do not adhere to the walls of the crucible, thereby making it possible to recover the granules without having to apply any mechanical operation that might contaminate them.

Method and apparatus for treating silica granules using porous graphite crucible

In the fiber-drawing method, a first preform is lowered along a fiber-drawing axis through a fiber-drawing oven so as to be heated and drawn down into an optical fiber, and a second preform is lowered along the fiber-drawing axis through the fiber-drawing oven so as to be heated and drawn down in turn after the first preform has been withdrawn. While the first preform is being drawn down into a fiber, the second preform is heated in a preheating oven disposed adjacent to the fiber-drawing oven so as to raise the second preform to a temperature which is slightly below the fiber-drawing temperature, and the preheated second preform is transferred quickly onto the fiber-drawing axis after the first preform has been withdrawn therefrom. This method contributes to increasing the capacity for producing optical fibers.

Semicontinuous method of drawing fibers from preforms, the method including a preheating step

The fiber-drawing furnace includes a graphite tube positioned vertically, heated by induction, and subjected internally to an inert atmosphere, said tube internally defining a fiber-drawing chamber. In the furnace said graphite tube is a double-walled tube having an inner wall and an outer wall, its inner wall is porous and separates the fiber-drawing chamber from a peripheral chamber defined between the walls and subjected to a flow of inert gas which diffuses through said porous wall into said fiber-drawing chamber. Application to drawing down an optical-fiber preform.

Fiber-drawing furnace for drawing down an optical-fiber preform into an

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Thones, France

Jean-Philippe Francois