Dispersion studies of a single-mode triangular-index fiber with a trench by the vector mode analysis

A Runge-Kutta procedure was used for investigating the dispersion characteristics of single-mode triangular-index fibers with a trench in the cladding. Numerical results on the total dispersion, its sensitivities to the core radius, wavelength, index difference variations, and its influence on the fiber's bandwidth-length product are presented. Some interesting features, due to the presence of a trench, are pointed out. One salient feature is the appearance of dispersion flattening over a certain wavelength range near 1.55 microm for b/a = 2 and c/a > 2.7 (a = core radius, b = inner trench radius, c = outer trench radius) where the total dispersion is low, yielding a bandwidth-length product as high as 10(4) GHz . km. The presence of a trench has not been investigated previously.