This tutorial paper provides an overview of studies and works to address the power saving issue in the optical access network (OAN), which typically comprises passive optical networks (PONs) and Ethernet aggregators (EAs). First, it describes techniques to reduce the power consumption of the optical network unit in each subscriber's home. It outlines methods standardized in ITU-T such as “dozing” and “cyclic sleep,” as well as elucidating other techniques. Next, power saving at the optical line terminal (OLT)/EA side is focused. The energy-aware operation of link aggregation and its application to OAN are described to decrease power consumed by the EAs used with time-division multiaccess (TDMA) PONs. Finally, a selective OLT sleep technique is introduced for the next-generation wavelength division multiplexing (WDM)-TDMA PON with wavelength routing technologies.