Experimental demonstration of adaptive recursive least square frequency-domain equalization for long-distance mode-division multiplexed transmission

We demonstrate experimentally adaptive recursive-least-square frequency-domain equalization (RLS-FDE) for mode-division-multiplexing. The RLS-FDE algorithm improves convergence speed as transmission distance increases. For MDM transmission over a 1,000-km few-mode fiber, the convergence speed was increased by 17.5 times in comparison with LMS-FDE.