| 摘要 |
PURPOSE:To attain a prescribed stable flow rate of a raw material gas from the start in the case of moving a burner to the starting end of a forward path and starting the supply of the raw material gas, to stabilize the deposition state of glass soot even near the starting end of the forward path and to minimize the defect at the end of an optical fiber preform. CONSTITUTION:The speeds of three burners 1,2,3 in the return path Q are set to be about 2 times those in the forward path P. The circulation timing of the burners is adjusted in such a manner as to position a burner (e.g. the burner 2) at the starting point of the forward path P when the other burner (e.g. 3) reaches the end of the forward path P. The raw material gas is supplied through two lines 14A and 14B. When a burner reaches the end of the forward path, the raw material supplying line supplying the raw material gas to the burner is switched to supply the raw material gas to a burner positioned at the starting point of the forward path by automatic shut-off valves V1A to V3A and V1B to V3B. |
