Radial effective-index method for the analysis of optical fibers

A novel effective-index method is formulated for solving the scalar wave equation expressed in cylindrical polar coordinates. With this method, the propagation constant for a noncircular fiber can be approximated by that for an equivalent circular fiber with index profile determined by the geometrical shape of the fiber. Numerical results show that the accuracy and applicability of the new method are complementary to those of the conventional effective-index method, which is developed in Cartesian coordinates.