The OIF PLL interfaces: the unheralded specifications which support the optical industry

This article reviews the activities of the Physical Link Layer (PLL) Working Group of the Optical Internetworking Forum (OIF). Since its formation the PLL Working Group has been the leader in the development of optical and electrical interfaces. The completed publicly available interface specifications are reviewed. In addition, the current works in the progress of the PLL group are summarized. New work topics include high-speed electrical signaling and protocols (CEI and CEI-P), tunable lasers, and optical internetworking.