Furnace for heating glass preform for optical fiber and method for producing glass preform

摘要

A heating furnace for heating a porous preform made of fine particles of quartz base glass for an optical fiber in an atmosphere comprising a fluorine-containing atmosphere to add fluorine to the preform and to vitrify the preform to produce a glass preform for an optical fiber, which comprises a heater and a muffle tube positioned inside the heater to separate a heating atmosphere from the heater. The muffle tube comprises a middle part having at least an inner layer made of highly pure carbon and an upper and a lower part made of a heat and corrosion resistant material having a low gas permeability wherein the parts are detachably connected.