Future Evolutions of Fronthauling Architectures over Passive Optical Networks

We overview the expected evolution of 5 G and 6 G functional split (FS)-based fronthauling architectures over Passive Optical Networks (PON), with a specific focus on physical layer considerations. We start by analyzing the expected bit rate, latency, and bit error rate requirements for different advanced fronthauling architectures. Then, we prosecute by showing that these requirements will likely need a technological jump in PON from current direct detection to coherent detection that can lead to several enhancements and performance increments. In turn, this will require new digital twin models for the PON transmission physical layer, which will be reviewed in the last part of the paper.