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.

在本文中，N级脉冲幅度调制（PAM- N）和M级正交幅度调制（M）的理论误码率（BER）-QAM) 已经在不同场景下进行了研究和比较，包括 (i) 带直接检测的强度调制 (IM/DD) 和带检测的场调制 (FMD)（包括相干检测和带直接检测的单边带调制 (SSB) -DD))，以及 (ii) 具有相干检测和 SSB-DD 的 QAM。考虑到符号间距和信噪比（SNR）之间的关系，我们提供了数学BER方程，包括光信噪比（OSNR）和载波信号功率比（CSPR），特别是用于 PAM 信号。为了验证我们对 SSB 系统的理论表达式的有效性，在统一的光学系统平台上使用 Kramers-Kronig (KK) 接收器实现了 224-Gb/s SSB-PAM4/16QAM 信号的传输。