An efficient method for determining the chromatic dispersion characteristics of nonlinear single-mode optical fibers

To determine the dispersion characteristics of nonlinear single-mode optical fibers, the various orders of derivative of the propagation constant with respect to frequency must be calculated. Recent studies have shown that high nonlinearity changes the guided modal field and then modifies the chromatic dispersion characteristics. However, the methods used either were approximate or were based on rigorous formulation but requiring numerical differentiation. A rigorous method that eliminates the need of numerical differentiation entirely is proposed. It is based on a variational finite-element formulation. The propagation constant and the modal field are obtained by solving a set of nonlinear algebraic equations, and this part dominates the computational efforts. The derivatives of the propagation constant can be easily obtained by solving sets of linear algebraic equations. Several examples are examined to show the change of chromatic dispersion characteristics resulting from the change in the modal field under the influence of nonlinearity