How to distinguish OLT, ONU, ODN, ONT?

An optical access network is an access network that uses light as the transmission medium instead of copper wire for access to all homes. Optical access network is generally composed of optical network unit OLT, optical network unit ONU and optical distribution network ODN, among which OLT and ONU are the core components of optical access network.

What is OLT?

OLT stands for Optical Line Terminal and Optical Line Terminal. Olts are local devices for optical network units and telecommunications that are used to connect fiber optic trunk lines. As a switch or router in a traditional communication network. Equipment at external entrances and exits. Networks and internal networks. The most important executive functions located in the central office are traffic scheduling, buffer control, and user-facing passive optical network interfaces and bandwidth allocation. Simply put, it has two functions. Uplink access to the PON network is complete. When below, the retrieved data is sent and distributed over the ODN network to all ONU user terminal devices.

What is an ONU?

An ONU is an optical network unit. The ONU has two functions. It selectively receives broadcasts sent by the OLT and responds to the OLT if it needs to receive data. It collects the Ethernet data that the user needs to send, caches it, and sends it to the OLT accordingly. The allocated send window sends cached data.

In The FTTx network, The ONU access mode is different. For example, Fiber To The Curb (FTTC) : ONU is located in the center of the cell, and Fiber To the Building (FTTB) : ONU is located at the intersection. Corridor Box; FTTH (Fiber To The Building: To The Home) : The ONU is placed in the home user.

What is ONT?

ONT is FTTH terminal unit, optical network terminal, commonly known as "optical modem". This is similar to an xDSL electrical modem. ONT is the optical network terminal applied to the end user, ONU is the optical network unit, and there may be other networks between ONT and the end user. ONT is a component of ONU.

What is the relationship between ONU and OLT?

The OLT is the management terminal and the ONU is the terminal. ONU service activation is issued through the OLT and is in a master-slave relationship. Multiple ONUs can be connected to a single OLT via a separator.

What is ODN?

ODN is an optical distribution network and an optical distribution network, and ODN is an FTTH optical cable network based on PON equipment. This is the physical channel for optical transmission between the OLT and the ONU. Its main function is to complete the bidirectional transmission of optical signals. It usually consists of optical cable, optical connector, optical splitter and support equipment for installation. Connect these devices. The most important component is the beam splitter.

From the functional point of view, the ODN can be divided into four parts: the feeder cable subsystem, the distribution cable subsystem, the home line cable subsystem and the optical fiber terminal subsystem from the office end to the user side.