An OLT (Optical Line Terminal) is the core device in a Passive Optical Network (PON) — the interface between the core network and the subscriber's optical access network. If you are building a Fiber-to-the-Home (FTTH) or Fiber-to-the-Business (FTTB) network, understanding the OLT is critical for ensuring high-speed, reliable. In the age of fiber-to-the-home (FTTH) and ultra-broadband connectivity, the Optical Line Terminal - or OLT - is one of the most crucial devices powering our high-speed digital world. These devices enable. An optical line termination (OLT), also called an optical line terminal, is a device which serves as the service provider endpoint of a passive optical network.