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

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

What is OLT?

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

What is ONU?

ONU is Optical Network Unit. The ONU has two functions: it selectively receives the broadcasts sent by the OLT, and responds to the OLT if it needs to receive the data; it collects and caches the Ethernet data that the user needs to send, and sends it to the OLT according to the assigned sending window. Send this cached data.

Different deployment methods of ONU access in 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 the home user.

What is an ONT?

ONT is Optical Network Terminal, the terminal unit of FTTH, commonly known as “optical modem”, similar to xDSL electric modem. ONT is an optical network terminal, which is used by end users, while ONU refers to an optical network unit, and there may be other networks between it and the end user. ONT is a component of ONU.

What is the relationship between ONU and OLT?

OLT is the management end, and ONU is the terminal; ONU service provisioning is issued through the OLT, and the two have a master-slave relationship. Multiple ONUs can be connected to one OLT through an optical splitter.

What is ODN?

ODN is Optical Distribution Network, which is the physical optical transmission channel between OLT and ONU. Its main function is to complete the two-way transmission of optical signals. It is usually connected by optical fiber cables, optical connectors, optical splitters and installation. The device consists of supporting equipment, the most important component of which is the optical splitter.