US Patent 7366389 Multistep index optical fiber

A multi step index optical fiber includes at least two concentrically arranged core portions, each having constant refractive index. The refractive indices of the core portions decrease toward the outer periphery of the optical fiber. The refractive indices of the core portions are set such that differences ΔN between refractive indices of adjacent core portions are uniform, and the distribution of the refractive indices approximates a G power distribution. Thereby, bandwidths on the order of several GHz/l00 m can be realized.