| 摘要 |
PURPOSE:To obtain an optical fiber of high accuracy, by detecting the flow rate of an inert gas and controlling the flow rate so as to always provide a constant value in drawing a wire of an optical fiber while blowing the inert gas from a blow-off of a diffuser into a furnace core tube. CONSTITUTION:A furnace core tube 2 having a heating element 3 is provided in a furnace body 1 and a diffuser 5 is mounted on the upper part of the furnace core tube 2. Wire drawing of a preform 10 is carried out while blowing an inert gas from blow-off ports 8 of the diffuser 5 into the furnace core tube 2 to produce an optical fiber (10a). In the process, a change in flow rate of the inert gas descending in the furnace core tube 2 is detected as a change in current value by a flow rate detector 11. The flow rate is controlled so as to provide a constant current value by a flow rate controller 12 to always control the flow rate of the inert gas to a constant value. Thereby the flow rate of the inert gas is controlled to the constant value without causing a change in the outside diameter of the optical fiber (10a) even if the outside diameter of the preform 10 is changed. |
