Patent ID: 7854157

Claim:
A method of elongating optical fiber base material comprising: heating and softening a base material ingot in a heating means; drawing said ingot with a pair of pinch rollers; and elongating the ingot to make base material rod including a smaller diameter than said ingot, wherein a roller groove of said pinch rollers includes one of a curvature radius which is greater than the outer diameter of said base material rod and a V-shaped roller groove with a cross section including straight lines formed on each surface of said pinch rollers comprised of metal, wherein the facing roller grooves respectively formed on the surfaces of a pair of said pinch rollers nip and draw said base material rod, and wherein a position of the pinch rollers and a position of a mounting part of the base material ingot are adjusted, respectively in two perpendicular axial directions in a plane perpendicular to a central axis of the heating means such that the straight lines, connecting the central axis of the heating means with a groove center of the roller grooves respectively formed on each surface of the pair of pinch rollers, are parallel to a traveling direction of the base material ingot fed into the heating means.