Structural parameter dependence of differential mode delay in dual-step index core based 2LP-mode fiber

This study investigates a structure for minimizing Rayleigh scattering loss and differential mode delay (DMD) in a dual-step index 2LP-mode fiber which is composed of a pure silica center core, F-doped outer core and F-doped cladding. The optimum structure with DMD = 0 ns/km shows a Rayleigh scattering loss reduction of 13 % compared to that of the 2LP-mode fiber with a graded-index (GI) GeO2-doped glass core. We examined the effect of structural change on the DMD with the optimum structure and found that the structural change in the radial direction strongly affects the DMD. A radial structure change of less than 2.3 % is required to achieve low DMD in a dual-step index 2LP-mode fiber.