High-speed PAM-4 Signal Transmissions with Directly Modulated Lasers for the Next-Generation Passive Optical Networks

The nonlinear behavior of a directly modulated laser (DML) is a major obstacle to realize the next-generation optical access networks. In this paper, we report an experimental demonstration of 54-Gbit/s optically amplified PAM-4 signal transmission with a power budget of about 35 dB over a 25-km single-mode fiber link by using a nonlinear Volterra equalizer in a DML-based passive optical access network. Furthermore, we compare the performance of the system under various transmission environments using different equalization and learning techniques.