By Karthik Sundaresan, CableLabs; Zhensheng (Steve) Jia, Ph.D., CableLabs; Kevin Noll, Vecima
Passive Optical Network (PON) is a fiber-optic telecommunications network that uses point-to-multipoint architecture to provide high-speed data, voice, and video services to subscribers. PON is the dominant solution to provide broadband services using fiber to the premises (FTTP). Operators look to expand access to more people and geographically remote areas in a cost-effective method. There is a need for new PON technology with higher capacities and longer reach and CableLabs has launched the Coherent PON (CPON) project to future-proof operator networks and deliver 100Gbps over PON (with coherent optical technology). Adapting existing standards to this new CPON technology is an advantageous approach. This needs an investigation of existing standards, to understand how to scale them to the speeds and capacities of CPON, which is the main goal of this paper. EPON (Ethernet Passive Optical Network) and GPON (Gigabit Passive Optical Network) are two main PON technologies and cable operators are deploying both. While these PON technologies share similar architecture and topology they differ in many ways. This paper discusses the similarities and differences for the latest version of these technologies (ITU-T [GPON-G.HSP] and IEEE [Nx25G-EPON]). The focus will be on understanding the different layers of each technology and discussing the functional equivalence between the two and areas where they differ from each other. Reusing technology layers from existing standards saves development time. Also, reusing many of the components of ASIC/silicon design implementations will reduce the cost of this new CPON solution. This paper highlights different factors of the existing GPON and EPON technologies that will need to be modified to reach these goals. This analysis includes a study of aspects such as the framing sublayer, fundamental line rates, effective data rates, FEC encoding/decoding, upstream scheduling/granting mechanisms, channel bonding, and provisioning etc. This paper aims to give an understanding of the current technologies and how those could be scaled to meet 100Gbps and beyond with CPON.