| 摘要 |
PURPOSE:To improve strength by replacing air in a jacket tube with a halogen- containing inert gas, heating the jacket tube and a glass rod or glass preform, further making negative pressure in the tube, heating and drawing the glass rod or glass preform. CONSTITUTION:A fluoride glass rod comprising Zr/F4/BaF2/LaF3/AlF3 in the molar ratio of 62/30/4/4 is made into primary preform 8, which is inserted into a jacket tube 7 of fluoride to give secondary preform. The secondary preform is introduced into a core tube 5 of furnace and the secondary preform is heated at about 270 deg.C for about three hours by a drawing furnace 6 while sending a halogen-containing gas such as mixed gas of F2/Ar=10%/90% from a gas inlet pipe 1 to the furnace. Then the preform is heated to about 350 deg.C while adjusting a main body 3 of supporting tube to negative pressure by a gas exhaust pipe 2 and the secondary preform is drawn. On the other hand, an inert gas is introduced from a nozzle 9 to the core tube 5 of furnace, the drawn optical fiber 11 is dried to give optical fiber of fluoride having excellent strength. |
