This paper proposes a novel power-saving mechanism for the 10 Gbit/s Ethernet passive optical network (10G-EPON) systems that are currently being discussed in IEEE 802.3av. The proposed power-saving mechanism includes a sleep control function and an adaptive link rate (ALR) control function. The sleep control function switches the modes of optical network units (ONUs), i.e. active and sleep modes, depending on the presence or absence of traffic. The ALR control function switches the link rate between the optical line terminal (OLT) and an ONU, i.e. 1 Gbit/s or 10 Gbit/s, depending on the quantity of traffic. The proposed hybrid mechanism offers effective power management of ONUs on the basis of the traffic conditions. The proposed hybrid mechanism is validated by some numerical simulations.