| 摘要 |
PURPOSE:To manufacture a long-sized wide-band optical fiber base material by depositing glass films of different refractive indexes on the inner wall of a reaction tube and heating the film to a high temp. in the longitudinal direction of the tube in accordance with a temp. distribution of a predetermined period whenever one layer is deposited to periodically change the refractive index of the film correspondingly to the temp. distribution. CONSTITUTION:Whenever one layer of glass films of a predetermined refractive index is deposited on the inner wall of hollow glass reaction tube 1 toward the center, the dopant GeO2 content of starting material gas is changed so that the result ing base material has an optimum refractive index distribution in the radius direction. At this time, whenever one layer is deposited, the starting material gas is changed over to a carrier gas such as O2 alone, and the deposited film is heated to a temp. equal to or higher than the depositing temp. with moving heating source 4 in the longitudinal direction of tube 1 with a fixed period, e.g., at positions A, B, C, etc. Thus, the dopant GeO2 in glass film 5 is selectively evaporated, and the refractive index depending upon the dopant is changed correspondingly to the heating temp. distribution. |
