Development of Rapid Production Process of Optical Fiber

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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.