High-speed PON solutions: recent evolutions and expected trends [Invited Tutorial]

This tutorial paper presents a survey on several current ongoing research activities about the expected evolution of passive optical networks, focusing on the physical layer (i.e., on the physical media dependent or PMD layer). After the recent public release of the ITU-T G.9804.3 50G-PON standard, there is today ongoing extensive scientific brainstorming on what can be the best optical transmission solutions for the PON “next step,” which will likely be targeting 100G or 200G per wavelength per direction. Elaborating on our OFC2025 tutorial on these topics, we start with a brief overview of the possible IM-DD solutions and their actual limitations for 200G-PON, while the core of the paper discusses the pros and cons of the introduction of advanced modulation formats and coherent detection also in PON, including some hybrid solutions that are currently under investigation in the ITU-T Very High Speed PON initiative. We show that coherent PON can actually reach the 200G per wavelength target, including some spare link budget margin, which can potentially be used for new access architectures. As an example, we present a summary of our recent results on hybrid solutions and on the all-optical convergence between the metro and access segments.