Equalizer complexity for 6-LP mode 112 Gbit/s m-ary DP-QAM space division multiplexed transmission in strongly coupled Few-Mode-Fibers

We have quantified equalizer complexity for transmitting dual-polarized 6-LP modes (LP₀₁, LP_11a, LP_11b, LP_21a, LP_21b and LP₀₂) of 112 Gbit/s m-ary QAM (m=4, 16, 32, 64, 256) single carrier signals over 20 km step-index few-mode fiber. The transmitted signals are strongly coupled and recovered using 12×12 multiple-input multiple-output (MIMO) adaptive digital signal processing (DSP). Time domain equalization (TDE) is realized to implement the linear adaptive MIMO module that is implemented in blind mode using conventional constant-modulus-algorithm (CMA) for finite impulse response (FIR) adaptive filter continuous update. Moreover, the benefit of employing hard-decision (HD) and soft-decision (SD) FEC for higher order QAM variants are also discussed.