Methods and apparatus for fabricating a lightguide preform

摘要

Undeposited reactants (i.e., soot) passing through a glass substrate tube (12), during the fabrication of a lightguide perform by the Modified Chemical Vapor Deposition (MCVD) process, flow into a reactant exhaust system (50) and are carried therethrough by a uniformly flowing reactant-free gas. The reactants pass through an exhaust tube (52), a reactant collection chamber (54), through a pressure control apparatus (56;114) and into a gas scrubber. The pressure within the exhaust system (50) is maintained substantially constant during the MCVD process by continuously monitoring the pressure therein and adjusting the pressure control apparatus (56;114) accordingly. Additionally, a continuous, uniform flow of soot-free gas is directed into the exhaust system to assist in the removal of the undeposited reactants therefrom.