In a passive optical network (PON), the device that terminates the optical circuit in a remote network node in a fiber-to-the-curb (FTTC) or fiber-to-the-neighborhood (FTTN) scenario. The ONU serves as a media converter, interfacing the fiber circuit to embedded copper in the form of unshielded twisted pair (UTP) in a telco network and coaxial cable in a CATV network.The ONU physically is positioned between the optical line terminal (OLT) at the network edge and the optical network terminal (ONT) at the customer premises. See also CATV, circuit, coaxial cable, FTTC, FTTN, media converter, node, OLT, ONT, PON, telco, and UTP.