A novel and accurate method for analysis of single-mode dispersion-shifted and dispersion-flattened fiber directional coupler

Employing the simple series expression for fundamental mode based on Chebyshev technique, we present a simple but accurate analysis of coupling characteristics of identical single-mode dispersion-shifted trapezoidal and dispersion-flattened graded W and step W fibers directional couplers. Analytical expressions of the relevant parameters are formulated and the concerned calculations require simple and little computations. We show that our formulations on coupling characteristics of such type of fibers directional couplers provide excellent results.