We report simultaneous transmission of six spatial and polarization modes, each carrying 40 Gb/s quadrature-phase-shift-keyed channels over 96 km of a low-differential group delay few-mode fiber. The channels are successfully recovered by offline DSP based on coherent detection and multiple-input multiple-output processing. A penalty of <1.2 dB is achieved by using 6 × 6 feed-forward equalizers with 120 taps each. The 6 × 6 impulse-response matrix fully characterizing the few-mode fiber is presented, revealing the coupling characteristics between the modes. The results are obtained using mode multiplexers based on phase plates with a mode selectivity of >28 dB.
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