Partial- and Joint-MIMO Processing Schemes for Space Division Multiplexed Transmission Over Different Multi-Mode Fibers

We experimentally study simplified multiple-input multiple-output (MIMO) processing schemes to support high-capacity space division multiplexed transmission over multiple multi-mode fibers (MMFs) with different mode counts. We exploit the mode selectivity of multi-mode fibers (MMFs) and components to implement a mode group (MG)-based transmission, and MIMO processing. We evaluate various transmission scenarios involving both a 15-mode MMF, and a 6-mode MMF, using different combinations of adjacent and non-adjacent MGs. For signal detection and recovery, we employ simplified MIMO processing approaches to reduce the complexity of the digital signal processing (DSP). We show enhanced flexibility compared to our recent work, demonstrating data recovery even in transmission scenarios with propagation of adjacent MGs, and high uncompensated inter-MG crosstalk. We achieve throughput from 70 Tb/s to 165 Tb/s by transmitting polarization-multiplexed 16-QAM signals across the C-band. We show that the transmission penalty due to uncompensated inter-MG crosstalk is limited to 1.1 bit/symbol. We also show a significant DSP simplification in all considered scenarios, with a total MIMO tap reduction between 52\% and 66\% compared to conventional full-MIMO processing. Our results demonstrate the capability of simplified MIMO schemes to support high-capacity transmission over heterogeneous MMFs in SDM networks.