Coupling characteristics of step index holey fiber

Coupling characteristics of dual-core step index holey fiber couplers are analyzed by a vectorial beam propagation method in conjunction with the finite element method. Here we considered the two cores to be separated by a distance d. The proposed structure exhibits a very simple geometry, and each fiber that composes the coupler is obtained through the inclusion of a very small air radius hole at the core of one conventional step index fiber. The introduction of the small air hole produces an ultra-flattened chromatic dispersion in the fiber.