Accuracy of scalar-wave method for evaluation of dispersion in broadband single-mode fibers

The accuracy of scalar-wave analysis for evaluating chromatic dispersion in broadband multiple-clad fibers is investigated. Exact and approximate dispersion characteristics, based on vector-wave and scalar-wave analyses respectively, are calculated and compared for step-index and W-index fibers. It is shown that for W-index fibers, as representative of broadband fibers, the exact and approximate dispersion characteristics agree well for wavelengths well below the cutoff wavelength where more than one mode may be supported by such fibers. However, for wavelengths not far from the cutoff, corresponding to a single-mode regime, the difference between the dispersion values obtained from the exact vector-wave and approximate scalar-wave analyses is no longer very small and should be accounted for in accurately predicting the information capacity/repeater spacing of long-haul and/or high-speed transmission links.