PON Network: Understanding ODN ,OLT, ONU OR ONT

Active optical networks (AON) and passive optical networks (PON) are the two major systems that make FTTH broadband connections possible.

PON network does not require electrical power to send signal to customers

The PON Network will be introduced in this article, which mainly involves the basic components and related technology including OLT, ONT OR ONU, and ODN.

What is a PON Network?

A passive optical network (PON) is a cabling system that uses optical fibers and optical splitters to deliver services to multiple access points. A PON system can be fiber-to-the-curb (FTTC), fiber-to-the-building (FTTB) or fiber-to-the-home (FTTH).

In contrast to AON, multiple customers are connected to a single transceiver by means of a branching tree of fibers and passive splitter/combiner units, operating entirely in the optical domain and without power in a PON architecture.

A PON system consists of optical line termination (OLT) at the communication provider’s end and a number of optical network units (ONUs) at the user’s end. The term “passive” simply means that there are no power requirements while the network is up and running.

PON Structure and Components

In Passive Optical Network (PON) system, there are an optical line terminal (OLT) at the service provider’s central office and a number of optical network units (ONUs) or optical network terminals (ONTs) near end users, as well as the optical splitter (SPL). In addition, the optical distribution network (ODN) is also used during the transmission between OLT and ONU/ONT

• Optical Line Terminal (OLT)

An optical line termination (OLT), is a device which serves as the service provider endpoint of a passive optical network. It provides two main functions:

1.to perform conversion between the electrical signals used by the service provider’s equipment and the fiber optic signals used by the passive optical network.

2.to coordinate the multiplexing between the conversion devices on the other end of that network (called either optical network terminals or optical network units).

• Optical Network Unit (ONU) / Optical Network Terminal (ONT)

ONU converts optical signals transmitted via fibers to electrical signals. These electrical signals are then sent to individual subscribers. Actually, ONT is the same as ONU in essence. Both of they are refer to the consumer end equipment in an optical fiber to the home (FTTH) communication link. But if you want to get technical, there is one difference and that is that ONT is an ITU-T term, whereas ONU is an IEEE term. ITU-T and IEEE are two different telecommunication standards.

On a fiber network, the ONT/ONU is located at your home. The purpose of this device is to use optical fiber to connect to the passive optical network (PON) and communicate with your Internet service provider to get an Internet connection.

• Optical Distribution Network (ODN)

ODN, an integral part of the PON system, provides the optical transmission medium for the physical connection of the ONUs to the OLTs as below

Feeder Cable ➡️ FDT ➡️ Distribution Cable ➡️ FAT ➡️ Drop Cable

–Fiber distribution terminal (FDT)

Used in FTTH networks to connect feeder cables and distribution cables. The Cabinet can be used to fixed and protect optical cables, terminate and splice fibers, distribute and dispatch fibers.

–Fiber access terminal (FAT)

Is a Sub-Cabinet That Recieve the Signal from FDT Through Distribution Cable to Split and distribute using Drop Cable to the Customers.

Access terminal Box (ATB)

Is used to connect drop cables and ONU devices. It is installed on indoor walls to provide fiber sockets, supports fusion splicing, mechanical splicing, and FA connectors.