A method for etching a primary preform and the etched primary preform thus obtained.

摘要

The invention relates to a method for etching a primary preform, comprising: * introducing the primary preform into the central cavity of a hollow etching tube such that in angular direction a part of the outer surface of the primary preform contacts a part of the inner surface of the etching tube, thereby forming an open region between a remaining part of the outer surface of the primary preform and a remaining part of the inner surface of the etching tube; * mounting the etching tube with the primary preform inserted in its central longitudinal cavity on a lathe and introducing the etching tube into a central aperture of an applicator mounted on the lathe wherein the applicator and the etching tube are moved in axial direction with respect to each other; * rotating the etching tube around its axis thereby causing a counter rotation of the primary preform within the etching tube; and * coupling electromagnetic radiation into the applicator and creating within a part of the etching tube that is surrounded by the applicator a plasma that moves in translation back and forth over the length of the etching tube during one or more passes wherein during at least a part of at least one pass the outside of the primary preform is etched by supplying a fluorine-containing etching gas to the open region in order to obtain an etched primary preform. The invention relates to a preform and optical fibers obtained therefrom.