| 摘要 |
PURPOSE:To obtain the preform capable of uniforming the transmission characteristics of an optical fiber in the longitudinal direction. CONSTITUTION:The temp. of a heating furnace 1 is controlled in accordance with the outside diameter of the built-up body 5 of particulate glass in a dehydration and transparent vitrification treating stage. Before this dehydration and transparent vitrification treatment, information of the outside diameter is obtained at every position in the longitudinal direction of this built-up body 5 of particulate glass. When the built-up body 5 of particulate glass is moved in the heating furnace, the temp. thereof is regulated in accordance with this outside diameter at every position thereof. When the outside diameter is changed, radiation heat is changed and the temp. conditions are made different. Since the temp. is regulated in accordance with the outside diameter so as to correct it, even the built-up body 5 of particulate glass whose outside diameter is fluctuated is treated in the practically uniform temp. conditions. |
