Patent ID: 7092611
Filing Date: 2006-08-15
Classification: C03B

Abstract:
1. A method for manufacturing a bar-shaped preform, which method comprises the following steps: i) supplying one or more reactive gases which comprise an amount of fluor compound, which may or may not be doped, to the interior of a substrate tube, ii) carrying out a deposition reaction of gases from step i) in said substrate tube so as to obtain one or more glass layers on the interior of the substrate tube, and iii) contracting the substrate tube from step ii) while heating said tube so as to obtain the massive, bar-shaped preform, wherein the amount of fluor compound that is supplied to the interior of the substrate tube in accordance with step i) is increased by a value of at least 10% at the end of the deposition of glass layers on the inner side of the substrate tube in accordance with step ii), after which the substrate tube is subjected to a heat treatment under conditions such that diffusion of the additionally incorporated fluor from the deposited glass layers will occur.