A power manager for a passive optical network, including a network statistics collector, for collecting data regarding traffic in a passive optical network (PON) including a plurality of optical network units (ONUs) on the downstream side of the PON, wherein each ONU can be in at least a sleep state and an active state, and wherein the PON transmits data in packets of data frames, a buffer for storing downstream data frames for each ONU while the ONU is in the sleep state, an activity detector for processing the data collected by the network statistics collector to generate indicators of activity levels for each ONU, and a protocol manager including a plurality of state machines for the respective plurality of ONUs, wherein each state machine governs state transition of its respective ONU to the sleep state when the activity detector indicates a low activity level for the ONU, and to the active state when the activity detector indicates a high level of activity for the ONU.