How to distinguish optical access network OLT, ONU, ODN, ONT

An optical access network is an access network that uses light as a transmission medium, replacing copper wires, and is used to access each home. An optical access network generally consists of three parts: an optical line terminal OLT, an optical network unit ONU, and an optical distribution network ODN, in which the core components of the OLT and ONU optical access network.

What is OLT?

The full name of OLT is Optical Line Terminal, optical line terminal. OLT is an optical line terminal, and is the central office equipment of telecommunications. It is used to connect optical fiber trunks. It functions as a switch or router in a traditional communication network. It is a device for the entrance of the external network and the entrance and exit of the internal network. Placed at the central office, the most important execution functions are traffic scheduling, buffer control, and providing user-oriented passive optical network interfaces and allocating bandwidth. In simple terms, it implements two functions: upstream, it completes the upstream access of the PON network; and downstream, it sends the acquired data to all ONU user terminal equipment through the ODN network.

What is ONU?

ONU is the Optical Network Unit. The ONU has two functions: Selectively receive the broadcast sent by the OLT, and receive the response to the OLT if the data needs to be received; collect and cache the Ethernet data that the user needs to send, and send it to the OLT according to the allocated sending window Send the cached data.

The deployment methods of ONUs in different FTTx networks are also different. For example, FTTC (Fiber To The Curb): ONU is placed in the central computer room of the community; FTTB (Fiber To The Building): ONU is placed in the junction box of the corridor; FTTH (Fiber To The Home): ONU is placed in home users.

What is ONT?

ONT is the Optical Network Terminal, the most terminal unit of FTTH, commonly known as “optical cat”, similar to xDSL electric cat. ONT is an optical network terminal and is used for end users. ONU refers to an optical network unit. There may be other networks between it and the end user. ONT is an integral part of ONU.

What is the relationship between ONU and OLT?

The OLT is the management end, and the ONU is the terminal; the ONU service provisioning is delivered through the OLT, and the two are in a master-slave relationship. Multiple ONUs can be hung through a splitter under an OLT.

What is ODN?

ODN is Optical Distribution Network, which is the physical channel of optical transmission between OLT and ONU. The main function is to complete the bidirectional transmission of optical signals. Usually these are connected by fiber optic cables, optical connectors, optical splitters, and installation. The supporting equipment of the device is composed of optical splitters.