Stokes-Space Analysis of Modal Dispersion of SDM Fibers with Mode-Dependent Loss: Theory and Experiments

Signal propagation in Space-Division Multiplexed (SDM) systems in the linear regime is dominated by the effects of modal dispersion (MD) and mode-dependent loss (MDL). While multiple models have been proposed for characterizing these phenomena separately or to study the effect of MD on MDL, the effect of MDL on the system MD has never been analyzed. In this article, we report such an analysis, where the inclusion of MDL is accounted for by introducing a complex MD vector $ec{ au }$. We show that the signal delay spread, quantified by the duration of the intensity impulse response function, is not affected by the presence of MDL, and its functional dependence on $ec{ au }$ remains the same as in the absence of MDL (in which case $ec{ au }$ is a real-valued vector). The model, which represents SDM systems operating in the regime of strong coupling between modes, is validated by comparison with experimental data.