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. It provides two main functions: to perform conversion between the electrical signals used by the service provider's equipment and the fiber optic signals used by the passive optical network.to coordinate the multiplexing between the conversion. FeaturesOLTs include the following features: • A downstream frame processing means for receiving and churning an cell to generate a downstream frame, and converting a parallel dat. Most vendors integrate an entire fiber optic management system for ISPs to manage OLTs as well as client ONTs and as such are not interoperable. • • BT-PON.