Abstract: Wavelength-division multiplexing passive optical network (WDM-PON) is considered as a mainstream solution for 5G fronthaul transmission system to cope with the rapidly increasing demand of bandwidth. However, nonlinearity effects, especially the fourwave mixing (FWM) effect in WDM-PON systems will impair system performances in the transmission distance and channel capacity. In this paper, the influence of FWM effect on multi-wavelength system with 25 Gb·s^-1 ·λ^-1 non-return-to-zero (NRZ) signal over 25 km standard single-mode fiber (SSMF) transmission is explored by experiment and simulation. Study results show that in a 200 GHz spaced 12-channel system, the bit error rate (BER) of all channels, except for the first and last channels, cannot reach the threshold 1.0× 10^-3 of forward error correction (FEC). This implies that FWM crosstalk should be given full consideration while making wavelength plans for 5G fronthaul system, including the wavelength distribution and channel spacing selection.

Key words: 5G fronthaul, wavelength-division multiplexing passive optical network (WDMPON), nonlinear effects, four-wave mixing