APPARATUS FOR PRODUCING FLUORINE-CONTAINING GLASS

摘要

PURPOSE:To produce a fluorine-containing glass having controlled composition and free from bubbles, by heating and clarifying a porous glass at a high temperature in a fluorine-containing atmosphere using a furnace separately furnished with a furnace for fluorination and a furnace for clarification along the moving direction of the porous glass. CONSTITUTION:A porous glass 1 which is an aggregate of glass soot is attached to a rotatable and vertically movable shaft 2 and is lowered in a quartz core tube 6 in an electric furnace 3 under rotation while supplying a gaseous mixture of SiF4 and He through a gas inlet port 7 into the core tube 6. In the course of the lowering operation, the porous glass 1 is heated at about 1,300 deg.C with a heater 4 to effect the absorption of F into the porous glass and to form a bubble-free glass. The heat-treated glass is heated at about 1,650 deg.C with a heater 5 having a length of about 1/3 of the length of the heater 4 to clarify the F- doped glass. A glass composition having precisely controlled F-content suitable for optical fiber preform can be produced by this process.