What is an optical network terminal (ONT)? - Neos Networks

What is an optical network terminal (ONT)?

What is an optical network terminal (ONT)?

An optical network terminal is a device that connects a customer’s premises to an optical network. Learn all about ONTs, how they work, and why they’re a critical link in the “last mile” of fibre networks.

What is an optical network terminal (ONT)?

An optical network terminal (ONT) is a device that serves as the endpoint of an optical network, connecting users to the network. It’s typically used in fibre-to-the-premises (FTTP) or fibre-to-the-home (FTTH) networks to deliver ultrafast connectivity to your business or home.

Commonly known as a “fibre box”, an ONT is installed inside or outside your building as the interface between the optical fibre infrastructure and your premises.

Example of an optical network terminal (ONT)

Openreach optical network terminal


How does an ONT work?

In fibre optic networks, your network service provider transmits data as pulses of light. An ONT processes this light as follows:

  1. The ONT converts the light into electrical signals using an optical interface. It corrects errors and prepares the data for transmission over your business or home local area network (LAN).
  2. The ONT transmits the data via one or more Ethernet ports to a router, computer or other connected devices, delivering internet access to your end users.
  3. In reverse, the ONT converts data your users generate into optical signals and transmits them to the internet over the fibre optic network.

In short, an ONT is a gateway for two-way communication between your premises, the fibre network and the internet beyond.

What is the difference between an OLT and an ONT?

An optical line terminal (OLT) and an optical network terminal (ONT) are both critical components in an FTTP passive optical network (PON), but they play different roles.

ONTs and OLTs in a passive optical network (PON)

Low latency network


An OLT (1) is located at the network service provider's central office or point of presence (PoP). It aggregates and distributes data to many customers, connecting to multiple ONTs via passive optical splitters (2).

In contrast, an ONT (3) is situated at the customer’s business or home and converts optical signals into electrical signals usable by devices like routers, computers, and printers. An ONT is installed in each customer’s premises, from individual businesses and homes to office and apartment buildings.

Both OLTs and ONTs process and distribute data upstream and downstream between backbone networks and end users.

Types of optical network terminals

ONTs vary in size and purpose, ranging from single-user units for individual businesses or households to multi-user devices for office buildings or apartments. They also come in compact, indoor models and larger, weatherproof units for outdoor installation.

In addition to their basic functionality, some ONTs have built-in routers and support for features like Wi-Fi or Voice over Internet Protocol (VoIP) for voice calls. Business-oriented ONTs may also incorporate advanced security features and enhanced Quality of Service (QoS) settings.

Designed to work with PONs, ONTs may support various PON standards, like EPON, GPON or XGS-PON. However, active optical networks may use a different type of optical network unit.

What are the benefits of ONTs and PONs?

ONTs and passive optical networks (PONs) offer several advantages over traditional, copper-based access networks, including:

  • High speed: Fibre optic cables support significantly higher data transmission than copper cables.
  • High bandwidth: Fibre connections offer higher bandwidth, which is ideal for streaming, online gaming and high-definition video conferencing.
  • Reliability: Fibre cables are less prone to interference or loss of signal over long distances.
  • Low latency: Fibre networks have lower latency compared to copper-based networks.
  • Low cost: PONs are more energy-efficient over long distances than copper-based networks.

To sum up, ONTs are a vital component of PONs, the “last mile” providing ultrafast connectivity to businesses and homes across Britain.

As UK companies look to invest in digital infrastructure to meet the growing demands of AI, 5G and IoT, network service providers are using PONs to give businesses the high-capacity networking they need.

Networking solutions for your business

At Neos Networks, we’re helping businesses nationwide build their digital futures with a range of networking solutions, from Business Ethernet, including Ethernet over FTTP, and Dedicated Internet Access to Optical Wavelengths and Dark Fibre.

If you’re looking to boost your connectivity to grow your business, get in touch.


We’ll be happy to help you supercharge your network for the future.

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