Few-mode/single-mode fiber

TLDR: In this article, an optical fiber comprising a transparent core having a maximum refractive index n 1 and a radius a surrounded by a layer of transparent cladding material has been designed such that the difference between |d(Vb)/dV| j, the normalized delay time of the jth mode, is less than about 5×10 -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

Abstract: The present invention pertains to an optical fiber comprising a transparent core having a maximum refractive index n 1 and a radius a surrounded by a layer of transparent cladding material having a refractive index n 0 which is less than n 1 . The refractive indices n 1 and n 0 , the radius a, and the refractive index profile of the core are designed such that: (a) Δτ 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 5×10 -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 Vd 2 (Vb)/dV 2 is about equal to or less than 0.2 at V-values near V 1 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.