Research of PAM-4 Modulated WDM-PON Architecture for 5G Millimeter-wave Hybrid Photonics-wireless Interface

In this paper 4-level pulse amplitude modulation (PAM-4) analog radio over fiber (A-RoF) transmission through wavelength division multiplexed passive optical network (WDM-PON)architecture for future broadband fifth-generation (5G/5G+) cellular mobile communication networks is proposed. The goal of future cellular mobile communication infrastructures of the next decade is retaining at least one-third of global market share in Europe regarding future network equipment and support higher spectral efficiency providing ubiquitous access to wider spectrum applications in order to reduce the network energy consumption.An alternative solution that offers a good trade-off between performance and complexity is multi-level signaling formats such as PAM-M, where multiple digital bits are encoded into different signal amplitude levels or symbols. It is a relatively easy and effective way to double the bitrate of data transmission link by the implementation of PAM-4 modulation technique instead of well-known non-return-to-zero on-off-keying (NRZ-OOK). In this paper, we investigated the use of PAM-4 modulation format for A-RoF signals transmission through the passive optical network (PON), which is standardized to NGPON2. In our research, we show the possible A-RoF transmitter implementation into improved fiber-optical line terminals (OLT), enabling to generate PAM-4 modulated signal and perform mm-wave signal transmission over the WDM-PON optical distribution network.