| 摘要 |
PURPOSE:To prepare an optical fiber with good shape and optical property by a method wherein a crusible having a U-shaped tube portion is used between a glass melting portion and a spinning nozzle portion and a predetermined pressure applied from a nozzle leading end portion is removed during spinning. CONSTITUTION:A stock glass material 11 for a core and a stock glass material 12 for a clad are respectively inserted into a melting portion 2, 3, and temp. of a heating furnace 1 is adjusted in a condition applying pressure P from an air sending pipe 7 to melt respective glass material 11, 12. The pressure P is adjusted to a pressure such that molten glass is not flowed out from a U-shaped pipe 4, 5. Thereby, when stock glass materials 11, 12 are molten, a temp. of a furnace 1 is lowered to a spinning temp. as well as a portion of a nozzle 6 is heated to a spinning temp. by a heating furnace 8 and, at the same time, a condition removing an air sending pipe 7 as a pressurizing means is made and an optical fiber is spun. |
