Symbol-Wise Phase Predistortion to Enhance Reach of Optical Pulse Amplitude Modulation with Direct Detection

Chromatic Dispersion (CD) of Standard Single-Mode Fibers (SSMF) is generating a characteristic phase perturbation of propagating pulses, even before these pulses are substantially broadened by CD. This feature is exploited to impress a symbolwise phase predistortion that reduces CD-induced Inter-Symbol Interference (ISI) and, thus, increases transmission distance of pulse-amplitude-modulated optical signals with Direct Detection (DD). In this contribution, theory, numerical simulations, and lab experiments of phase-predistorted PAM4-transmission with DD over non-dispersion-managed transmission links are outlined.