| 摘要 |
PURPOSE:To produce the subject preform having reduced transmission loss, by providing a clad of specific F-containing SiO2 glass and a jacket layer consisting of pure SiO2 on the outer periphery of F-containing SiO2 glass. CONSTITUTION:Pure SiO2 fine particulate porous body of high purity is subjected to dehydration treatment at 1000-1100 deg.C in a reducing atmosphere and then heated at 1000-1600 deg.C in an atmosphere containing 0.0001-0.1% fluorine compound, fluorinated and transprentized to provide a glass transparent body having 0.01-0.05% specific refractive index difference as compared with that of pure quartz for a core. The resultant transparent body is then heated and drawn at 1800-2000 deg.C in an electric furnace to afford a glass rod for the core, which is subsequently inserted into a clad, consisting of F-containing SiO2 and having a lower refractive index than that of the core, fused and integrated to provide a core.clad composite. A jacket layer consisting of pure SiO2 is then formed on the outer periphery of the composite, dehydrated and transparentized. |
