Shin-Etsu Chemical Co., Ltd.

Kazuhiro Hamaguchi

Hideo Hirasawa

Hiroyuki Koide

Masami Terashima

An improvement is proposed in the process for the preparation of a porous silica glass preform as a precursor of optical fibers by the VAD method, in which fine silica particles produced by the flame hydrolysis of a silicon-containing compound are deposited on the lower end of a seed rod suspended at the lower end of a suspender rod rotated by a carriage in a vertical tubular reactor furnace to grow in the vertical direction. Instead of taking the fully grown porous preform out of the tubular furnace by pulling up as suspended on the suspender rod as is undertaken in the prior art, the seed rod is temporarily held by clamping with a holding device with disconnection from the suspender rod and the porous preform and seed rod are pulled up by a separate vertical driving device so that the overall height of the apparatus can be greatly decreased contributing to a reduction of the manufacturing cost of optical fibers of silica glass.

Method for pulling-up a porous silica glass preform

An improvement is proposed in the apparatus and method for the preparation of a transparent silica glass preform as a precursor of optical fibers by sintering and vitrifying a porous silica glass preform in a sintering furnace as vertically suspended at the lower end of a suspender rod rotated by a carriage. Different from the conventional process in which the porous preform is lowered into the sintering furnace and the transparent preform after vitrification is pulled up out of the furnace as suspended at the lower end of the suspender rod throughout, a separate vertical driving device is provided along with a horizontal driving device for the carriage so that the effective up-and-down stroke of the carriage can be greatly reduced and the apparatus as a whole can be by far more compact contributing to the reduction of the manufacturing costs of the optical fibers of silica glass.

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Gunma, Japan

Kazuhiro Hamaguchi