METHOD FOR MEASURING NON-CIRCULARITY AT CORE PORTION OF OPTICAL FIBER PARENT MATERIAL

摘要

A method for measuring non-circularity of a core portion of an optical fiber base material 1 includes a distribution measuring step of (i) moving the optical fiber base material 1 in a direction parallel to a central axis of the core portion while light is irradiated, in a direction perpendicular to the central axis, to the optical fiber base material 1 which is immersed in the matching oil 3, and (ii) recording a variation in a width of a portion of the irradiated light which transmits through the core portion in association with a moved distance of the optical fiber base material 1, thereby measuring a distribution of relative values of an outer diameter of the core portion in terms of a longitudinal direction of the optical fiber base material 1, a distribution storing step of performing the distribution measuring step each time the optical fiber base material 1 is rotated about the central axis by a predetermined angle, thereby recording a plurality of distributions of the relative values of the outer diameter of the core portion each of which is associated with the predetermined angle, and a non-circularity calculating step of calculating a plurality of values, in terms of the longitudinal direction of the optical fiber base material 1, each indicating non-circularity of the core portion, based on the plurality of distributions of the relative values of the outer diameter stored in the distribution storing step.