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MIMO equalization analysis for SDM transmission over 2km elliptical-core few-mode fiber for datacenter applications

As intra-datacenter networks (DCN) continue to experience exponential traffic growth, techno-economic reasons, such as cabling footprint reduction, are driving increases in the number of data channels per optical fiber. Optical space division multiplexing (SDM), wherein independent data channels are carried over a single fiber through a multiplicity of spatial modes are thus gaining prominence for intra-DCN transmission. In this paper, we present a time and frequency domain MIMO equalization analysis for experimental space division multiplexed (SDM) transmission of LP01 and LP11e modes over 2km of elliptical core few-mode fiber (EC-FMF). For 19Gbaud dual polarization quadrature phase shift keying (DP-QPSK) transmission with coherent detection, we observe polarization mode dispersion (PMD) durations of about 12 and 15 taps at half-baud-rate equalizer tap spacing for LP01 and LP11e modes, respectively. Since modal crosstalk between LP01 and LP11e modes is very low, 2×2 MIMO processing is sufficient for dual-polarization and dual-mode SDM transmission over the EC-FMF. By efficiently enabling channel density gains, the EC-FMF SDM approach can be attractive for next-generation intra-DCN.