I. Introduction
With the rapid development of the 5G era and the deployment of novel modern technologies, the traffic demand of communication networks increases dramatically [1], and numerous researches related to optical communication technologies have been derived accordingly. Next-generation passive optical networks (PONs), characterized by high flexibility, low power consumption, and high bandwidth, have attracted attention and are widely used in practice [2]–[4]. Orthogonal Frequency Division Multiplexing (OFDM) technology has the advantages of strong dispersion resistance, high spectral efficiency, and flexible modulation format [5]–[8], which is considered as the one of the effective solutions to realize PON.