Design of ultra-dispersion flattened M-type few-mode fiber for weakly-coupled mode division multiplexing transmission

Abstract

In this work, we present an ultra-dispersion flattened few-mode (UDF-FMF) fiber design that can support ten linearly polarized modes in the C-band. The proposed fiber has an M-type refractive index profile with 13.5% GeO2 doped original core, and fused silica cladding. A high-index ring is inserted in the cladding, to increase the number of modes with low mode coupling. A trench in the cladding and a depression in the original core are added to manage the chromatic dispersion parameter and to reduce the bending loss. The fiber exhibits non-zero dispersion at 1.55 µm for the fundamental LP01 mode to satisfy the ITU-G.655 standard and yields a minimum dispersion flatness of ~0.18 ps/nm/km over the C-band for the first time according to our knowledge. The modal characteristics of the UDF M-type FMF have been systematically analyzed through the finite element method-based COMSOL software. The fiber parameters and the dopants concentration are systematically chosen through simulations to guide ten LP modes with large mode separation (max∆neff≅5×10−3), optical loss in the range of 10-10 to 10-12, minimum differential mode delay of 0.09ps/m, nonlinear coefficient lower than 2 × 10-3 km−1 W−1, and large effective mode-area of 385 µm2 across the C-band. We believe the proposed fiber design can be a potential contender for new-generation optical communication using mode-division multiplexing.