This chapter discusses the motivations and challenges of Coherent PON in access with the research progresses. When the technical performance of coherent optics vs. alternative technologies proves superior, the economics often determine whether to deploy coherent optics. While many use cases in the access network exist, scenarios requiring a high bandwidth will highlight the technical and economic superiority of coherent optics, i.e., well economically coherent optics scales with higher capacity applications. Intensity-modulation and direct-detection (IM-DD) is a common digital optical technology deployed by cable operators. Coherent optics addresses the inefficiencies of IM-DD with DWDM and provides greater technical performance. An economic analysis using an actual North American cable node considers a similar use case of optical aggregation in a DAA. The aggregation links can be provided by P2P Coherent Optics today and may evolve into P2MP Coherent Optics in the near future.