| 摘要 |
PURPOSE:To suppress the lowering of the strength of an optical fiber due to SiC and power consumption at the time of drawing an optical fiber preform in a dawing furnace by specifying the difference between the inner diameter of a preform heating element and the outer diameter of the preform. CONSTITUTION:A drawing furnace 1 consisting of an annular carbon, for example, and having a heater around the furnace core tube 2 acting as an optical fiber heating element is used. The core tube 2 is arranged coaxially with the preform 4, the lower periphery of the perform 4 is heated and melted, and the preform is drawn from the molten part to obtain an optical fiber 13. In this method, the difference between the inner diameter of the core tube 2 and outer diameter of the preform 4 is controlled to 6-26mm. The minimum difference is determined in consideration of the bending, etc., of the preform 4, and the maximum difference is determined from the screening average persistent length of the fiber 13. Consequently, the objective is achieved without excessively raising the temp. of the core tube 2 and without increasing the power consumption. |
