Numerical analysis of low-order modes in thermally diffused expanded core (TEC) fibers

Optical intensity distributions, cut off frequencies and propagation constants for the low-order modes of Thermally-Diffused Expanded Core (TEC) Fibers are demonstrated by numerical analysis based on Galerkin's method. A set of orthogonal Laguerre-Gauss functions is used to calculate the spectral dependence of effective indices and mode fields of LP-modes. Results are compared with and shown to be accurately approximated by those obtained by an one-parameter variational method.