Method for making preforms for optical fibres.

摘要

According to the invention a hollow silica rod (14) is formed on a mandrel by an external deposition method employing a plasma torch, the mandrel is removed and a vitreous coating (34) intended for the subsequent formation of the fibre core, is deposited onto the inner face of the rod. The deposition is obtained by means of a plasma column (28) formed in the rod by virtue of an ultrahigh-frequency coupler (18) capable of injecting a progressive surface wave into the plasma column.
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