Development of Rapid Production Process of Optical Fiber

Si和/或Ge的氧化物在燃烧器顶部上方瞬间形成，其中反应物气体通过分子扩散混合。同时，氧化物颗粒的平均粒径在50- 60 nm之间，并随气流的上升而上升，而平均粒径基本不变。根据颗粒和气体在粘附表面附近的速度分布，推导出颗粒的热泳速度为1.0-1.4cm/s，与亚微米级球形颗粒的热泳速度相当。在吸附表面附近，由于气体温度突然降低，气体收缩，颗粒密度增加，颗粒凝聚成亚微米尺寸，Ge含量在1600 K时达到最大值。1750 K时，Ge-O-Si键的数量比1600 K时少，1450 K时，Ge-O-Si和Ge-O-Ge键的数量都减少。考虑到Ge-O-Ge键合据说通过VAD烟灰的后处理而蒸发，期望将火焰温度保持在约1600 K。可以想象，在火焰的影响下，在温度仍然很高的粘接表面，Ge-O-Ge键可能会转变为Ge-O-Si键。这种现象是重要的，也是我们下一个研究的目标之一。总的来说，为了开发光纤的快速生产工艺，有必要尽可能有效地利用热泳，并尽可能多地使Ge-O-Si键合。

Oxides of Si and/or ge were instantaneously formed just above a burner top where reactant gases were mixed by molecular diffusion. Simultaneously, ultra-fine oxide particles were formed with a mean diameter of 50-60nm and were ascending with gas flow without changing the average size. From Velocity distributions of particles and gas near an abhering surface, a thermophoresis velocity of particles was deduced to be 1.0-1.4cm/s, which is corresponding to that of submicron sized spherical particle. In the close vicinity of the abhering surface, hence, it is concluded that the particles are coagulated to submicron size due to the increase of a population density of particles near the surface where the gas temperature suddenly decreases and gas is contracted.Ge content became maximum at 1600K. at 1750K, the amount of Ge-O-Si bonding was less than that at 1600K, and the amounts of both the Ge-O-Si and Ge-O-Ge bondings became less at 1450K. Considering that the Ge-O-Ge bonding is said to be vaporized through the post treatments of VAD soot, it is desirable to keep the flame temperature at around 1600K. It can be imagined that the Ge-O-Ge bonding may be changed to the Ge-O-Si bonding at the abhering surface where temperature is still high under the influence of flame. This phenomenon is important and is one of our next targets of investigation.As a whole, it is necessary for the development of a rapid production process of an optical fiber to effectively use the thermophoresis as far as possible and to make the amount of Ge-O-Si bonding as much as possible.