Single-Pixel IQ Monitor via Computational Coherent Reception with Widely Linear Phase Retrieval

For in-service and in-field monitoring of frequency-dependent IQ imbalance in optical IQ modulators, we propose a low-complexity IQ monitor using a single photodetector based on phase retrieval. The feasibility of the proposed single-pixel IQ monitor was demonstrated experimentally with a 63.25-Gbaud 16QAM signal.