PRODUCTION OF PREFORM FOR FLUORIDE GLASS FIBER AND APPARATUS THEREFOR

摘要

PURPOSE:To produce a large-sized preform for fluoride glass fibers with excellent dimensional accuracy at a low cost, by transferring glass melt chemically treated with a fluorine based gas using carbon crucibles to metal crucibles for producing the preform. CONSTITUTION:A core glass 1 and clad glass 22 are respectively contained in carbon crucibles 3 and 4 in a hermetically sealed vessel 10 for melting glass and melted by a high-frequency coil 5. A fluorine based gas is then introduced from inlets 6 to chemically treat the glasses 1 and 2. A gate valve 17 is then opened to move the above-mentioned crucibles 3 and 4 into a connected hermetically sealed vessel 15 for producing a preform through crucible tongs 18 provided at a horizontal moving rod 19 and transfer the glass melts 1 and 2 to metal double crucibles 11 and 12 with a nozzle for producing a preform. The aimed preform for long fluoride glass fibers having a low loss is then taken out through a common jig 13 for preventing glass melt outflow and taking out glass.