Optimization of time and frequency allocations in a TFDMA PON with diverse user conditions and diversified rate targets.

Active research is being conducted for beyond-100G passive optical networks (PONs) to cover contemporary society's ever-increasing information rate demand. In this context, time-frequency-division multiple access (TFDMA) PON can potentially extend the coverage of the current time-division multiple access (TDMA) scheme in a diversified user network. In this Letter, we study the time and frequency allocations in a TFDMA PON based on digital subcarrier multiplexing (DSCM), where the users' channels exhibit frequency-dependent performance and disparity. We also consider the possibility that the users target different information rates. We provide a formal proof that the TFDMA approach yields a diversity gain over the traditional TDMA scheme and verify the effectiveness of our allocation method by calculating the diversity gain for a 200G-class intensity-modulation direct-detection (IM-DD) system.