Perspectives on and the road towards 100 Gb/s TDM PON with intensity-modulation and direct-detection

Abstract

We assess the status of current generation 25G and 50G time division multiplexed passive optical network (TDM PON) technologies based on leveraging the cost efficiencies of the Ethernet intra-datacenter ecosystem. As a first step towards 100G TDM PON, we predict the real-world impact of a flexible modulation enhancement to 50G PON, whereby four-level pulse amplitude modulation (PAM4) symbols can be transmitted at the same symbol rate as 50 Gb/s PAM2, but only where excess margins permit. We find that sufficient margins are likely to exist to allow for a majority of future 50G PON optical network units to operate at 100 Gb/s PAM4. Next, we look at the options for a 100G PON capable of supporting the full loss budget and reach requirements. There is no technical risk if coherent technology is adopted, but intensity-modulation and direct-detection (IM-DD) will provide lower complexity, lower cost, and lower power dissipation. We evaluate this option and conclude that by following IM-DD Ethernet optics to 100 GBd, single wavelength IM-DD will continue to be feasible for 100G PON and will be a strong contender for the next generation of PON after 50 Gb/s.