Nondestructive measurement of axially nonsymmetric refractive-index distribution of optical fibre preforms

A nondestructive computer-aided measurement of the arbitrary two-dimensional refractive-index distribution of an optical fibre preform is described. The angle of refraction of rays in the preform is measured by an optical set-up which features the use of a triangular mask for converting the angle of rays to their displacement. The index distribution is computed from the information on these refraction angles.