  A flexible and efficient method for fully vectorial modal analysis of 3D
dielectric optical waveguides with arbitrary 2D cross-sections is proposed. The
technique is based on expansion of each modal component in some a priori
defined functions defined on one coordinate axis times some unknown
coefficient-functions, defined on the other axis. By applying a variational
restriction procedure the unknown coefficient-functions are determined,
resulting in an optimum approximation of the true vectorial mode profile. This
technique can be related to both Effective Index and Mode Matching methods. A
couple of examples illustrate the performance of the method.
