Method for Etching a Primary Preform

摘要

The present invention relates in a first aspect to a method for etching a primary preform or core rod. The present invention moreover relates in a second aspect to the etched primary preform thus obtained and moreover to a final preform and optical fibers obtained therefrom and to a method of preparing optical fibers therefrom.

主权项

1. A method for etching a primary preform, the method comprising the steps of:
introducing the primary preform having an outer diameter ODPP into the central cavity of a hollow etching tube having an outer diameter ODET and an inner diameter IDET such that 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 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.