Roll‐Off Factor Influences and Power Loading Analysis of OFDM for Performance Improvement in 50G‐PON

ABSTRACT According to ITU‐T G.9804.3 (09/2021), the implementation of nonreturn‐to‐zero (NRZ) coding is recommended over orthogonal frequency division multiplexing (OFDM) with power loading in commercial 50G‐PON access networks. This preference is primarily motivated by cost‐effectiveness and backward compatibility with existing 1G GPON and 10G XG(S)‐PON infrastructures. Nevertheless, OFDM in combination with square‐root raised‐cosine (RRC) filtering is widely recognized for its high spectral efficiency, robustness against linear dispersion impairments, and mitigation of intersymbol interference, making it a strong candidate as an optional technology for future 50G/100G‐PON systems. Therefore, this study explores the potential performance improvements in commercial 50G‐PON by adopting OFDM and raised‐cosine filtering schemes. Results indicate that, to achieve a target symbol error rate (SER) of 10 −3 at the optical network unit (ONU), the required launch power at the optical line terminal (OLT) can be reduced by 3 dBm using Gaussian filters and by 6.5 dBm with RRC filters. Moreover, employing RRC filters at the optimal launch power of 7 dBm improves the SER by 4 orders of magnitude. Additionally, a 4‐dB power redundancy is achieved in the optical distribution network (ODN). The power loading strategy effectively ensures uniform performance across OFDM subcarriers, with an optimal roll‐off factor of 0.2.