A METHOD FOR PREPARING A PRIMARY PREFORM BY ETCHING AND COLLAPSING A DEPOSITED TUBE

摘要

The present invention relates to a method for preparing a primary preform by etching and collapsing a deposited tube, the method comprising the steps of * mounting a deposited tube on a lathe and introducing the deposited tube into a central aperture of a furnace mounted on the lathe wherein the furnace and the deposited tube are movable in axial direction with respect to each other; * creating within the furnace a hot zone that moves in translation back and forth over the length of the tube during one or more cycles wherein: - during at least one cycle at least part of the outside of the deposited tube is etched by supplying a fluorine-containing etching gas to an annular region between the outer surface of the deposited tube and the central aperture of the furnace; and - during at least one cycle the deposited tube is collapsed; in order to obtain a primary preform. The present invention moreover leads to a preform and optical fibers obtained therefrom.