There has been a decade long history of groundbreaking work on Common Electrical Interface (CEI) Implementation Agreements within the Optical Internetworking Forum (OIF). While the first edition of CEI specifications was dedicated to 6 Gb/s and 11 Gb/s serial electrical interfaces, later revisions address a range of applications encompassing 20 Gb/s to 28 Gb/s rates involving various classes of reach, with recent initiatives targeted at doubling these rates. This paper discusses the evolution of OIF CEI specification development, including the impacts of critical elements such as channel models, signaling schemes, and the power consumption of the required Serdes designs. It provides an overview of current active work areas that are focusing upon 28 Gb/s and 56 Gb/s serial electrical interfaces and their relevance to some of the latest 100G to 400G line card and system developments. Finally, it offers a projection of ongoing OIF work regarding the Next Generation Interconnect (NGI) framework project, which is starting to define a transition path from electrical to optical intra-system interconnects for even higher serial data rates and longer reaches. © 2013 Alcatel-Lucent.