Optical network unit (ONU) is the user side equipment in the GEPON (Gigabit Ethernet Passive Optical Network) systems. Optical network unit is used with OLT and provides the users with many kinds of broadband services such as VoIP, HDTV, and videoconferences. Optical network unit is economic and high efficient equipment and play an important role in the FTTx fiber optic network.

GEPON system is a telecom grade FTTx broadband access equipment mainly for telecom operator and large corporate users with the characteristic of high integration, flexible application, high stableness, easy management, flexible extend and buildup of the network, as well as providing QoS function. Optical network unit converts the fiber optic signal into the electric signal at the user side and enables reliable fiber optic Ethernet services to business and residential users through fiber-based network infrastructure.