Performance Investigation of Error-Feedback Noise Shaping in Low-Resolution High-Speed IM/DD and Coherent Transmission Systems

In this paper, we comprehensively investigate the performance of error-feedback noise shaping (EFNS) in low-resolution high-speed intensity-modulation direct-detection (IM/DD) PAM4 and coherent DP-mQAM transmission systems by simulation and experiments. The influence of EFNS parameters and digital to analog converter (DAC) parameters on EFNS performance is first numerically investigated in a low-resolution 56-GBaud 2-km IM/DD PAM4 transmission system. The combination of clipping and EFNS is also numerically evaluated and the impact of overloading is deeply analyzed. For coherent transmission, the EFNS performance is investigated for different modulation formats including QPSK, 16QAM and 64QAM. The optical signal to noise ratio (OSNR) penalties for different modulation formats are evaluated numerically in a low-resolution 56-GBaud 80-km coherent transmission system. Finally, we experimentally demonstrate the EFNS performance in low-resolution 32-GBaud 10-km IM/DD PAM4 and 28-GBaud 80-km coherent DP-64QAM transmission experiments. Extensive numerical and experimental results show that EFNS can effectively mitigate the quantization noise of low-resolution DAC and thus reduce received optical power or OSNR penalty significantly. Although EFNS is a little inferior to DRE at the PNoB of 3, both of them have very similar performance when PNoB
$\geq$
4. Compared with DRE, EFNS has lower computational complexity and no processing latency. In addition, no channel response is required for EFNS.