| 摘要 |
PURPOSE:To obtain the above glass fiber free from the intrusion of bubbles and foreign materials in the interface of the core and the rod, by increasing the pressure at the outer circumference of a tube for clad relative to the gas pressure in the space between the clad tube and the core rod inserted into the tube and drawing the tube and the rod. CONSTITUTION:A glass rod 1 for core is inserted into a glass tube 2 for clad having lower refractive index than the core 1 and the gas pressure at the outer circumference of the tube 2 is adjusted to be higher than the gas pressure in the gap between the tube 2 and the rod 1. The tube 2 and the rod 1 are simultaneously heated with a heater 17 and drawn while keeping the above state to obtain an optical fiber having a core-clad structure. In the above process, the gas pressure in the gap between the tube 2 and the rod 1 is adjusted below atmospheric pressure, especially <=10<-2>Torr and the gas pressure at the outer circumference of the tube 2 is adjusted above atmospheric pressure, especially >=0.2kg/cm<2>. |
