DEVICE FOR MANUFACTURING POROUS PREFORM FOR OPTICAL FIBER

摘要

PROBLEM TO BE SOLVED: To reduce adhesion and deposition of excess glass fine particles on an inwall of a reaction vessel and thereby to suppress or eliminate generation of crystals or bubbles in a preform after verification. SOLUTION: A target 6 is put down in the reaction vessel 1, a lower end of the target 6 is exposed to flames from burners 7, 8 in the reaction vessel 1 and the glass fine particles synthesized in the flames are deposited on the top end of the target 6 to manufacture a porous preform for an optical fiber. The size of the reaction vessel 1 is so made that the shortest distance from the top end position of the preform 9 to a bottom inwall of the reaction vessel 1 at the time of manufacturing the preform 9 and the shortest distance from an outer peripheral surface of the preform 9 to the inwall of the reaction vessl 1 facing thereto are at least 1.5 times the outside diameter of the preform 9.