Analysis of mode field radius calculated from single-mode fiber far-field radiation patterns

We have investigated the angular range and mesh size required to calculate accurate mode field radii (MFR) from single-mode fiber far-field radiation patterns using the inverse Hankel transform. A computer aided fiber modeling program was used to calculate near-field mode distributions for both step-index and triangular index fibers at 1.55 μm. These distributions were then transformed to the far-field and used as input "data" for the inverse transform studies. Experimental far-field data measured on fibers similar to those modeled were also used. We find that the MFR is insensitive to mesh sizes less than 0.6° but the range of far-field data required depends upon the fiber design and the criteria used to determine the MFR. This study provides guidelines for calculating accurate MFR from experimental data when using the Hankel transform.