Method and apparatus for producing a glass preform for optical fibres

摘要

A method and an apparatus for producing a glass preform for an optical fibre having a uniform J ratio (see below) by adjusting the weight of glass particles to be deposited on a starting glass rod (1). The method uses an OVD method by which glass particles are successively deposited on an external cylindrical surface of a starting glass rod (1) to create a growing soot layer (3) thereon and the soot layer (3) is then vitrified into a transparent glassy body, characterized in that the glass particle deposition is conducted by adjusting an amount of glass particles to be deposited based on data of J ratio fluctuations (where the J ratio is a ratio of an outer diameter of a glass preform to an outer diameter of a starting glass rod) of a previously produced glass preform in its longitudinal direction so that the glass preform to be produced can attain a uniform J ratio in its longitudinal direction.