| 摘要 |
<p>PROBLEM TO BE SOLVED: To prevent the fall of an optical fiber preform without giving rise to a great difference in the external diameter in a longitudinal direction even of the optical fiber preform having large dimensions and without producing an unvitrified part in a vitrified part. SOLUTION: According to the position of the vitrified part of a porous soot body 58 of the optical fiber preform 50 corresponding to the vitrification region existing within an electric heater 124 within a furnace tube 122, i.e., according to whether the porous soot body 58 is a bottom end 72, an intermediate section 70 or a top end 74, a controller 16 controls at least one of any among the vitrification temperature by the electric heater 124, the moving speed of the vitrification region and the optical fiber preform 50 and the flow rate of the gas supplied into the furnace tube 122.</p> |
