Low-resolution Kramers-Kronig detection system with error-feedback noise shaping

In this paper, we investigated the effects of error-feedback noise shaping (EFNS) on a low-resolution Kramers-Kronig (KK) detection system for the first time. Both 16-ary quadrature amplitude modulation (16-QAM) and 64-ary quadrature amplitude modulation (64-QAM) were considered in the experiment. The carrier tone was added on the transmitter side using the virtual carrier-assisted single sideband (VCA-SSB) method to meet the minimum phase (MP) condition. Under the MP condition, KK detection only needs the intensity of the optical signal to be detected by one photodiode (PD) to retrieve the phase information. However, the virtual carrier tone increases the carrier-to-signal power ratio (CSPR), which results in a high peak-to-average power ratio (PAPR) at the transmitter, causing an increase in quantization noise. To mitigate quantization noise in the low-resolution KK detection system, EFNS was applied. The application of EFNS increased the optimal CSPR of the KK detection system and improved receiver sensitivity. Using a 4-bit DAC and the EFNS, 80 km transmission was achieved in the 60-Gbit/s 64-QAM KK detection system.