Binary faster than Nyquist optical transmission via non-uniform power allocation

Recently, faster-than-Nyquist (FTN) signaling (or also sub-Nyquist filtering) has been proposed as a means to increase the spectral efficiency of the next generation long-haul optical fiber transmission systems. In the high spectral efficiency regime, however, the severe intersymbol interference (ISI) inherent to the FTN signaling poses a significant challenge in implementing a practical FTN system. In this work, we propose to use non-uniform power allocation at the optical FTN transmitter and establish its optimality in the achievable capacity. Consequently, we utilize the non-uniform power allocation to design a low-complexity FTN receiver that can operate close to the channel capacity limit. Presented simulation results also illustrate that the proposed optical FTN signaling transceiver with non-uniform power allocation allows supporting very high spectral efficiencies.