84 GBd Faster-Than-Nyquist PAM-4 Transmission using Only Linear Equalizer at Receiver

Based on Tomlinson-Harashima precoding, we demonstrate 84 GBd PAM-4 transmission in an intensity-modulation direct-detection system with 33 GHz brick-wall bandwidth limitation. BER below 7% hard-decision FEC threshold is achieved using only linear equalizer at receiver.