MIMO-Based Crosstalk Suppression in Spatially Multiplexed 3$\,\times \,$56-Gb/s PDM-QPSK Signals for Strongly Coupled Three-Core Fiber

We experimentally demonstrate simultaneous transmission of three spatially multiplexed 56-Gb/s polarization-division-multiplex quadrature phase-shift keying (PDM-QPSK) channels over 24 km of a strongly coupled three-core fiber. The resulting crosstalk of about -4 dB is almost completely removed by coherent multiple-input multiple-output (MIMO) processing.