Practical Considerations in Direct Detection Under Tukey Signalling

The deliberate introduction of controlled intersymbol interference (ISI) in Tukey signalling enables the recovery signal amplitude and (in part) phase under direct detection, giving rise to significant data rate improvements compared intensity modulation with detection (IMDD). use an integrate-and-dump detector makes precise waveform shaping unnecessary, thereby equipping scheme a high degree robustness nonlinear distortions introduced by practical modulators. Signal sequences drawn from star quadrature (SQAM) formats admit efficient trellis description that facilitates codebook design low-complexity near maximum-likelihood sequence presence both shot noise thermal noise. Under (though suboptimal) allocation 50% duty cycle between ISI-free ISI-present segments, at symbol 50 Gbaud launch power -10 dBm has maximum theoretically achievable throughput 200 Gb/s (8,4)-SQAM constellation, while IMDD achieves about 145 using PAM-8. Note two mentioned constellations have same number magnitude levels difference is resulting exploiting information complex-valued constellation.