Effective impurity removal from optical fibre preform - by diffusion into layer removed before tube collapsing

摘要

In impurity removal from an optical fibre preform, starting from a preform tube which is purified before collapsing, the novelty comprises (a) applying, onto the preform tube (1), a diffusion layer (2) which takes up impurities (5) by diffusion from the preform tube; (b) removing the layer (2) after inward diffusion of the impurities; and (c) collapsing the preform tube to obtain a preform. ADVANTAGE - Impurities are removed rapidly and extremely effectively even from the body of the tube.