| 摘要 |
PURPOSE:To prolong a life of furnace by heating an optical fiber preform to be put in a furnace core tube by a heater arranged in the circumference of the tube, feeding a dehydrating agent-containing gas to the preform and continuously applying a torsional moment to the furnace core tube. CONSTITUTION:An optical fiber preform 6 is put in a furnace core tube 2 arranged at the central part of main body 1 of a dehydrating and sintering furnace, a dehydrating agent and a He gas are fed from a He gas feed opening 21 to the furnace core tube 2 in a heated state by a heater 3 and the preform is dehydrated and made into transparent glass. The viscosity of the heated part of the furnace core tube 2 is reduced by heating by the heater 3 and the heated part tends to swell outside by difference in pressure between pressure in the interior of the furnace core tube and the main body 1 of the furnace. Since force in the revolving direction is always applied to a plate 71 by a torsion providing device 7 attached to the lower part of the furnace core tube 2 and inward force acts, the furnace core tube 2 is prevented from swelling outside and life of the furnace core tube 2 can be prolonged. |
