| 摘要 |
PURPOSE:To ensure the viscosity of the neck-down part of a base material for an optical fiber necessary for the strength of the fiber while keeping a heater at a relatively low temp. when the base material is drawn in a furnace filled with an inert gas by preheating the inert gas to be introduced into the furnace. CONSTITUTION:A heating chamber provided with a carbon heater 3 is enclosed with a heat insulating material 4, and an inert gas such as N2 is introduced from an inert gas inlet 5 and discharged from an outlet 6 through the heating chamber. The quantity of heat absorbed from the heater surface is in proportion to the product of the flow rate of the inert gas and the temp. difference between the heater surface and the inert gas. The inert gas is preheated with a preheater 8, so the surface temp. of the heater 3 can be dropped, thereby reducing the consumption of electric power and prolonging the life of the heater. |
