| 摘要 |
PROBLEM TO BE SOLVED: To obtain a preformed material improved in yield by introducing clean air into a vessel and conducting a control so that the difference between the maximum and the minimum values of the surface temperature of a glass fine particle body come to a specified level at a specific position of the body. SOLUTION: First, a stock gas such as SiCl4 , fuel gas such as H2 or O2 , inert gas such as N2 are fed to a gas feeder 6 and injected through a multiply tubular burner 5 into a reaction vessel 8 to form a glass fine particle deposit 2. Secondly, the temperature distribution around the deposit 2 is determined by a thermometer 7 and, in response to a command from a CPU 9 into which temperature distribution data have been inputted in advance, the clean excess air flow via a suction port 3a through a filter and the gas inflow from the gas feeder 6 are controlled. Subsequently, the difference between the maximum and minimum values of the surface temperature of the deposit 2 is controlled so as to come to >=60 deg.C below a position where the surface temperature of the deposit 2 presents the maximum value and within the range with a diameter being 50% of that of the deposit 2, thus obtaining the objective bubble-free preformed material for optical fibers in high yield. |
