On the dependence of differential mode delay in few-mode fibers on the number of modes

This paper presents the design of few-mode fibers (FMFs) with low differential mode delay (DMD) over the C-band, considering a refractive index profile with a graded core and a cladding trench. By optimizing the core grading exponent and the dimensioning of the trench, the lowest DMD achievable is obtained for different numbers of linearly polarized (LP) modes. Additionally, considering the concatenation of two FMFs with profiles of the same type but with different parameters values, both profiles are optimized in order to minimize the residual DMD. For both cases, the accumulated DMD increase rate with the number of LP modes is presented, as well as the maximum distance reach for mode-division multiplexing transmission.