Few-mode/single-mode fiber

摘要

The present invention pertains to an optical fiber comprising a transparent core having a maximum refractive index n1 and a radius a surrounded by a layer of transparent cladding material having a refractive index n0 which is less than n1. The refractive indices n1 and n0, the radius a, and the refractive index profile of the core are designed such that: (a) DELTA tau j, the difference between ¦d(Vb)/dV¦j, the normalized delay time of the jth mode and ¦d(Vb)/dV¦0, the normalized delay time of the fundamental mode, is less than about 5 x 10-2 over a wide range of V-values where j is equal to 1 or 2 and represents the highest order mode that propagates with a low loss, 0 represents the fundamental mode, b is the propagation constant and V is the normalized frequency, and (b) the normalized waveguide dispersion Vd2(Vb)/dV2 is about equal to or less than 0.2 at V-values near V1_c, the normalized cutoff frequency of the first higher order mode. A fiber exhibiting characteristics (a) and (b) is capable of providing mode equalized two-mode or three-mode and low dispersion single-mode operation. e