Abstract

In estimation of propagation characteristics for singlemode fibers, the refractive index profile plays an important role. Several measurement methods such as the exit radiation pattern method (ERP)[1] and the near field intensity method (NFI)[2] have been recently developed with a relatively high spatial resolution. Both methods, however, require complicated features: cumbersome computation, with inverse Hankel transformation and correction of dynamic range in the case of ERP; numerical derivations and smoothing for noise reduction in the case of NFI. In this study, we present a new processing technique for calculation of the refractive index profile in single-mode fibers. This technique makes use of hybrid optical processing with a spatial filter (a radially inhomogeneous transparent filter) and two lenses, creating the Hankel transformation and the inverse transformation. This method allows real time monitoring of the profile and permits significantly less computational time as compared to that of conventional computer methods.

© 1989 Optical Society of America