In a passive optical network (PON), the device that terminates the optical local loop at the edge of the network. In a telco PON, the OLT is housed in the central office (CO). In a CATV PON, the OLT is housed in the headend. The OLT can either generate downstream optical signals on its own, or can pass optical signals from the optical backbone through a collocated optical crossconnect or multiplexer. The OLT also receives upstream signals from the optical network terminals (ONTs) at the customer premises and optical network units (ONUs) in remote nodes. See also backbone, CATV, CO, cross-connect, downstream, headend, local loop, multiplexer, OLT, ONU, PON, telco, and upstream.