Process for improving the transmission characteristics of optical fibers drawn from preforms made by the MCVD technique
AssigneeCSELT - Centro Studi e Laboratori Telecomunicazioni S.p.A.
InventorsEros Modone, Giacomo Roba
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Abstract
In order to improve the transmission characteristics of optical fibers drawn from the preforms manufactured by vapor deposition of silica on an inner wall surface of a supporting tube of glass, the tube is subjected to a two-stage heat treatment with deuterium whereby OH.sup.- groups at least on the inner tube surface are isotopically replaced by OD.sup.- groups. This pretreatment can be carried out in the same apparatus which is subsequently used for producing the preform.
Claims5
A process for improving the transmission characteristics of optical fibers drawn from preforms which are produced by vapor deposition of silica on an inner wall surface of a supporting tube of silica glass,
- comprising the step of subjecting at least said inner wall surface of the supporting tube to a pretreatment with deuterium at elevated temperatures and for a period sufficient to isotopically replace a significant number of hydrogen atoms in the tube material close to said inner wall surface with deuterium atoms, said inner wall surface being maintained in contact with gaseous deuterium at a relatively low elevated temperature for inducing deuterium adsorption by the tube wall in a first treatment stage followed by a sharp temperature increase in a second treatment stage for promoting the substitution of hydrogen by deuterium in the tube material.
Dependencies are inferred from the claim text.