In order to meet the needs of the development of the 5G fronthaul networks and provide greater bandwidth, in this paper, a four pulse amplitude modulation(PAM4) signal with a downlink rate of 50 Gb/s and an non return to zero(NRZ) signal with an uplink rate of 10 Gb/s are used to constitute a two-way communication system in the reflective semiconductor amplifier(RSOA) based on wavelength division multiplexing passive optical network(WDM-PON) system with an asymmetric transmission architecture as a fronthaul network carrying scheme. The simulation software Optisystem is used to simulate and analyze the WDM-PON system based on RSOA remodulation, and analyzes the transmission performance of the system at different transmit optical power; The performance of the uplink and downlink transmission system is analyzed under the conditions of back-to-back and dispersion compensation. It is proved that WDM-PON with downlink 50 Gb/s PAM4 signal and uplink 10 Gb/s NRZ signal can be used as a fronthaul network carrying scheme.