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

摘要

A method for measuring non-circularity at the core portion of an optical fiber parent material (1) comprising a relative outside diameter value distribution measuring step for obtaining the relative outside diameter value distribution at the core portion in the longitudinal direction of the optical fiber parent material (1) by moving the optical fiber parent material (1) in the direction parallel with the central axis while irradiating the optical fiber parent material (1) immersed into matching oil (3) with light from a direction orthogonal to the central axis at the core portion and recording a variation in width of transmitted light through the core portion out of the above light in association with the moving amount of the optical fiber parent material (1), a relative outside diameter value distribution storing step for performing the relative outside diameter value distribution measuring step every time when the optical fiber parent material (1) is rotated about the central axis up to a predetermined rotational angle and recording a plurality of relative outside diameter value distributions associated with the rotational angle, and a non-circularity calculation step for calculating a plurality of non-circularities at the core portion in the longitudinal direction of the optical fiber parent material (1) based on the plurality of relative outside diameter value distributions stored in the relative outside diameter value distribution storing step.