| 摘要 |
PURPOSE:To manufacture an optical fiber having a refractive index distribution coefficient which changes periodically in the longitudinal direction by controlling the dopant concn. of a glass layer and the distribution of refractive index by utilizing the fact that the reaction efficiency of halide as glass starting material with O2 and vapor pressure of the reaction product oxide are changed by the heating temp. CONSTITUTION:SiCl4 as principal starting material for core glass, GeCl4 as a refractive index controlling dopant, POCl3 as a lowering dopant of the vitrifying temp. and 02 are continuously fed into reaction tube 9 and heated with oxyhydrogen burner 11 to induce the oxidation reaction of the halide and 02 in a high temp. region 10. At this time, by periodically changing the heating temp., the vapor pressure of the resulting oxide is controlled to periodically change the dopant concn. of a glass layer deposited. As a result, the value of the refractive index distribution coefficient also changes periodically in the longitudinal direction. Such a core glass layer is deposited predetermined times, and after carrying out a stage 9 for collapsing hollow parts of the glan fiber and a drawing stage, a product optical fiber is obtd. |
