“…Driven by such cutting-edge applications as 5G, Internet of Things (IoT), streaming Internet video, and cloud computing, demands for the bandwidth performance of optical access networks are growing continuously. 1,2 Due to its unparalleled advantages of low cost, compact footprint, and low power consumption, intensity modulation/direct detection (IM/DD) is regarded as an ideal choice for the actual application scenario, which is able to boost the transmission rate up to 100 Gb/s or even more. 3 A series of advanced modulation formats based on IM/DD have been extensively applied, such as, discrete multi-tone (DMT) modulation, 4,5 carrier-less amplitude/phase (CAP) modulation, 6 and pulse amplitude modulation (PAM).…”