Theoretical analysis of PAM-N and M-QAM BER computation with single-sideband signal

Abstract

In this paper, the theoretical bit error rate (BER) of N-level pulse amplitude modulation (PAM-N) and M-ary quadrature amplitude modulation (M-QAM) have been studied and compared under different scenarios, including (i) PAM with intensity modulation with direct detection (IM/DD) and field modulation with detection (FMD) (including coherent detection and single-sideband modulation with direct detection (SSB-DD)), and (ii) QAM with coherent detection and SSB-DD. Considering the relationship between the symbol spacing and signal-to-noise ratio (SNR), we provide the mathematical BER equations, including the optical signal-to-noise ratio (OSNR) and carrier-to-signal power ratio (CSPR), especially for PAM signals. To verify the validity of our theoretical expressions for SSB systems, transmissions with 224-Gb/s SSB-PAM4/16QAM signals using the Kramers-Kronig (KK) receiver were implemented on a unified optical system platform. The simulation results agreed well with theoretical calculations both in back-to-back (BtB) and 120-km transmission scenarios, which showed that the BER evaluation methods can serve as a theoretical guidance and system assessment criteria for SSB scenarios.