| 摘要 |
PURPOSE:To obtain desired heat zone suitable for each parent material for optical fiber by providing a shielding tube which forms an annular slit between an annular heater and a furnace core pipe concentrically with the furnace core pipe to between the annular heater and the furnace core pipe. CONSTITUTION:In a wire drawing furnace for optical fiber, an electric resistant annular heater 3 is installed to the middle part of a case 2 to which a furnace core pipe 1 is attached. A parent material 4 for optical fiber is fed from the top end of the furnace core pipe along the axis of the pipe 1 to the inside of the cylindrical furnace core pipe 1. The tip end of the parent material 4 for optical fiber is melted by keeping the middle part of the furnace core pipe 1 at ca. 2,000 deg.C with a heater 3, and optical fiber 5 is drawn. A shielding pipe 6 provided with an annular slit 7 having a specified length in the axial direction is provided to this wire drawing furnace between the heater 3 and the furnace core pipe 1. Therefore, the radiated heat from the carbon heater 3 is isolated by the shielding pipe 6, and a desired heat zone DELTA is formed in the inside furnace core pipe 1 by the radiated heat through an annular slit 7 having a specified breadth. |
