To provide a method for producing a preform ingot having excellent eccentricity ratio of core part and capable of obtaining an optical fiber excellent in connection loss and eccentricity of core part by spinning at a low cost.
This method for producing an optical fiber preform ingot 1 comprising piling up soot on the starting core member, glassifying by dehydrating and sintering, thereafter cylindrically grinding the surface while rotating, characterized in that the radius of the master ingot is measured with an outer shape measuring device for each 90° or 180° of rotation in advance to the grinding, the position of rotating axis of the cylindrical grinder 4 is obtained by calculation based on the measured values, and the outer circumference of the preform ingot 1 is finished by grinding based on the calculated value.
SHIMADA TADAKATSU
HIRASAWA HIDEO
