Process and device for manufacturing optical fibre preforms

摘要

Production of preform for making an optical fiber involves increasing the diameter of a primary preform (10) by injection (24) of grains on its surface and fixing the grains using a plasma torch comprising a refractory material tube (16) and an inductor (22) around the tube. The distance between the end of the tube and the inductor is decreased when the diameter of the preform increases. The axis of the preform is moved away from the inductor which remains fixed when the diameter of the preform increases. The distance between the end of the plasma torch tube and the external surface of the preform is maintained approximately constant when the diameter of the preform increases. An Independent claim is given for a device used to implement the above process. The device has a unit for displacing the plasma torch tube (16) along its axis (26) with respect to the fixed inductor (22). An isolation screen (42) separates the inductor (22) from the space in which the plasma is formed. An injector (24) is provided for spattering the grains onto the surface of the primary preform (10).