What Are OLT And ONU Devices?

Optical access network is an access network that uses light as the transmission medium, replacing copper wire, to access every household. The optical access network generally consists of three parts: optical line terminal (OLT), optical network unit (ONU), and optical distribution network (ODN), among which OLT and ONU are the core components of the optical access network.

What is OLT?

The full name of OLT is Optical Line Terminal. OLT is an optical line terminal, which is a telecommunications office equipment used to connect fiber optic trunk lines. Its function is equivalent to a switch or router in traditional communication networks, and it is a device that serves as an external network entrance and an internal network entrance and exit. Placed at the office end, the most important execution functions are traffic scheduling, buffer control, and providing user oriented passive fiber optic network interfaces and bandwidth allocation. Simply put, it means implementing two functions: upstream, completing the upstream access of the PON network; For downstream, the obtained data will be sent and distributed to all ONU user terminal devices through the ODN network.

What is ONU?

ONU is the Optical Network Unit. ONU has two functions: selectively receiving broadcasts sent by OLT, and responding to OLT reception if the data needs to be received; Collect and cache the Ethernet data that users need to send, and send the cached data to the OLT end according to the assigned sending window.

The deployment of ONU access methods varies in different FTTx networks, such as FTTC (Fiber To The Curb): ONU is placed in the central data center of the community; FTTB (Fiber To The Building): The ONU is placed in the junction box in the hallway; FTTH (Fiber To The Home): ONU placed in home users.

What is ONT?

ONT is the Optical Network Terminal, the terminal unit of FTTH, commonly known as the "light cat", similar to the xDSL electric cat. ONT is an optical network terminal applied to the end user, while ONU refers to an optical network unit that may have other networks with the end user. ONT is a component of ONU.

What is the relationship between ONU and OLT?

OLT is the management end, ONU is the terminal; The business activation of ONU is issued through OLT, and the two have a master-slave relationship. Multiple ONUs can be mounted through a splitter under one OLT.