FABRICATION METHOD OF POROUS PREFORM FOR OPTICAL FIBER, AND GLASS PREFORM FABRICATED THEREBY

摘要

A method for manufacturing a porous-glass material for optical fiber performed in a reaction apparatus having a plurality of burners for producing glass particles toward a initial base material and a ventilation mechanism at a position opposed to the plurality of burners, the method comprises the steps of (a) moving the plurality of burners back and forth along a initial base material, (b) depositing the glass particles produced by the flame hydrolysis reaction of the glass raw material around the initial base material, (c) starting the deposition of a next porous-glass material without removing soot stuck to the inside of the chamber after the deposition of the glass particles is completed. Under the above condition, the inside pressure of the chamber is preferably adjusted within the range of -80 Pa<=P_min<=-40 Pa, which is a pressure differential between the inside and outside of the chamber. (Hereinafter referred to a pressure differential between the inside and outside of the apparatus)