Introduction of optical access network OLT, ONU, ODN, ONT?

Introduction of optical access network OLT, ONU, ODN, ONT?

Optical access network is an access network with light as the transmission medium, instead of copper wires, it is used to access each family. Optical access network. The optical access network generally consists of three parts: the optical line terminal OLT. The optical network unit ONU, and the optical distribution network ODN, among which the OLT and the 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 central office equipment for 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 executive functions are traffic scheduling, buffer control, and providing user-oriented passive optical network interfaces and allocating bandwidth. To put it simply, it implements two functions: for the upstream, the upstream access to the PON network is completed; for the downstream, the acquired data is sent and distributed to all ONU user terminal devices through the ODN network.

What is ONU?
ONU is Optical Network Unit optical network unit. The ONU has two functions: it selectively receives the broadcast sent by the OLT, and if it needs to receive the data, it needs to respond to the OLT; it collects and caches the Ethernetdata that the user needs to send, and sends it to the OLT according to the allocated sending window. Send the cached data.
The access methods of ONUs in different deployments of FTTx networks are also different. For example, FTTC (Fiber To The Curb): the ONU is placed in the central computer room of the community; FTTB (Fiber To The Building): the ONU is placed in the junction box of the corridor;  FTTH ( Fiber To The Building)  To The Home): The ONU is placed in the home user.

What is ONT?
ONT is the Optical Network Terminal, the most terminal unit of FTTH, commonly known as "optical cat", similar to the electric cat of xDSL. ONT is an optical network terminal, which is applied to end users, while ONU refers to an optical network unit, and there may be other networks between it and end users. 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 service provisioning of the ONU is delivered through the OLT, and the two are in a master-slave relationship. Under one OLT, multiple ONUs can be connected through the optical.
What is ODN?
ODN is Optical Distribution Network, optical distribution network; ODN is FTTH optical cable network based on PON equipment. It is the optical transmission physical channel between the OLT and OLT Its main function is to complete the bidirectional transmission of optical of It is usually composed of optical fiber cables, optical connectors, optical splitters, and supporting equipment for installing and connecting these devices. The most important component is a beam splitter.
Regarding function, ODN can be divided into four parts: feeder optical cable subsystem, distribution, optical cable subsystem, household optical cable subsystem, and optical fiber terminal subsystem from the central office end to the user end.

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