What is OLT? OLT Functions

Optical Network Unit (ONT) converts optical signals transmitted via fiber to electrical signals. These electrical signals are then sent to individual subscribers. In general, there is a distance or other access network between ONU and end user's \premises. Furthermore, ONU can send, aggregate and groom different types of data coming from the customer and send it upstream to the OLT. Grooming is the process that optimises and reorganises the data stream so it would be delivered more efficiently. OLT supports bandwidth allocation that allows making smooth delivery of data float to the OLT, that usually arrives in bursts from the customer. ONU could be connected by various methods and cable types, like twisted-pair copper wire, coaxial cable, optical fiber or Wi-Fi.
FTTH
Actually, ONU is the same as ONT in essence. ONT is an ITU-T term, whereas ONU is an IEEE term. They both refer to the user side equipment in GEPON system. But in practice, there is a little difference between ONT and ONU according to their location. ONT is generally on customer premises.

There are different types of ONT available providing different interfaces like:
- Digital Video
- Analog Video
- Ethernet port
- ATM interface