PRODUCTION OF POROUS PREFORM FOR OPTICAL FIBER

摘要

PURPOSE:To easily produce a porous preform having small diameter, by ejecting an inert gas from nozzles placed at both sides of a raw material gas ejection nozzle in the production of a porous glass preform for optical fiber using a vapor axial deposition process, thereby separating the raw material gas stream. CONSTITUTION:Inert gas ejection nozzles 16, 17 are placed close to both sides of a raw material gas ejection nozzles 12 of a core synthesizing burner. An oxyhydrogen flame is formed by hydrogen ejected from a hydrogen gas ejection nozzle 14 and oxygen ejected from an oxygen gas ejection nozzle 15 and a raw material gas ejected from a raw material gas ejection nozzle 12 is introduced into the flame and reacted to form glass soot. In the material gas ejection nozzle 12 is separated from the flame by the inert gas streams ejected from the nozzles 16, 17 and only a part of the raw material gas stream is made to react in the oxyhydrogen flame to form a thin stream of glass soot, which is deposited on a starting member to obtain a porous preform for optical fiber having small diameter.