Effect of four-wave mixing on the loss budget of four-channel multiplexing NG-PON systems

Abstract

In this study, the loss budget for adopting non-return-to-zero (NRZ) and four-level pulse amplitude modulation (PAM4) in next-generation passive optical networks (NG-PONs) was investigated by simulation and experiment. Through simulation, the signals are distorted by four-wave mixing (FWM) when the zero-dispersion wavelength locates in the middle of the channels. For 25-Gb/s NRZ, a maximal loss budget of approximately 32.5\u2009dB is obtained. For 50-Gb/s PAM4, the bit error rate cannot reach 1\u2009×\u200910−3. While, the impact becomes negligible whens the zero-dispersion wavelength stays away from the middle of the channels, and the loss budget is 36 and 25.7\u2009dB for NRZ and PAM4 systems. Therefore, at least a 32.5-dB loss budget ise obtained in a 4\u2009×\u200925G NRZ system. While, the loss budget cannot reach the basic requirement of 29\u2009dB in the 4×50G PAM4 system. The experimental resultso verify this conclusion.