Abstract

The index of refraction profiles of depressed cladding MCVD single-mode fibers have been found to differ significantly from the profile of their preforms,¹ perhaps due to the difference in the thermal history between the fiber and preform. To study this effect, a preform was subjected to varying heating cycles, and its refractive index was measured after each cycle using a laser beam refraction technique.² Step-index profile parameters are found as an area-weighted fit to the index of refraction measured in the core and an unweighted fit to the index in the inner 80 % of the cladding. This is illustrated in Fig. 1. Averaging over the left and right sides and over two orthogonal angular orientations helps improve repeatability.

© 1984 Optical Society of America