Energy-efficient PON with sleep-mode ONU: progress, challenges, and solutions

Energy usage in our networks is increasing rapidly; and to conserve energy, progress has been made in designing energy-efficient passive optical networks, which are being widely deployed for broadband access. Among the various energy-saving techniques, enabling sleep mode in optical network units is a very promising approach. However, the slow transition of power from active mode to sleep mode in an optical network unit, and the relatively large recovery and synchronization time needed during the wakeup process are challenges that need to be addressed. In this regard, we propose a service-level-agreement-based scheduling scheme for passive optical networks in which the optical line terminal can adjust the sleep time and the optical network unit can quit sleep mode for sending high-priority packets. The trade-off in energy savings vs. delay performance is evaluated using simulations under practical power consumption settings.