What is the maximum speed of fibre optic cable?

As the world becomes increasingly more connected, the need for reliable, faster fibre optic transmission speed remains paramount.

12/06/2026 - 02:00 AM

The Gigabit Britain rollout is currently underway. Since April 2026, around 90.5% of UK premises can now access gigabit-capable broadband, and the latest government target set out in the 2025 Spending Review is to reach 99% or premises by 2032.

“Gigabit Broadband” is defined as any technology that can deliver download speeds of at least 1 gigabit per second (Gbps). 1 Gbps is equal to 1000 Mbps. At 1 Gbps an entire HD film can be downloaded in under a minute. To put it into context, here’s how fibre optic compares in terms of internet download speeds:

Fibre optic: up to 10Gbps (at a data transfer rate of up to 10 billion bits per second)
Copper cable: 25-300 Mbps (at a data transfer rate of up to 300 million bits per second)
DSL: 0.5-75 Mbps
Satellite: 5-25 Mbps

A full-fibre connection can also deliver very low latency, meaning there’s less delay in the time it takes from sending a request and receiving a response.

However, it is important to note that the broadband speed can still vary depending on a number of factors, including location and the type of fibre connection in the area, such as fibre to the cabinet (FTTC), fibre to the premises (FTTP), etc.

Full fibre broadband (Fibre-to-the-Premises or Home FTTP/FTTH) offers a full fibre optic cable connection from the local exchange to each premise. This is the most reliable broadband technology available.

What technologies can deliver Gigabit Broadband?

image showing abstract fibre optic lines over a city

FTTP provides full fibre optic cable all the way from the nearest exchange point to the local roadside cabinet, achieving speeds from 40 Mbps to 1 Gbps.

High-speed cable broadband (DOCSIS3.1) Cable broadband uses a combination of fibre optic cables and legacy co-axial cables (used for cable TV). It is more susceptible to local congestion compared to full fibre networks.

Future 5G networks should also be able to support gigabit speeds, but this will be a challenge in rural areas, given the need for 5G antennas to be very close together and for them to be connected back to a core internet network (“backhaul”) with lots of fibre optic cable.

How fast can fibre optic go?

abstract image of fibre cables going around the world

Full fibre broadband is now available to over 90% of UK premises, with business users able to access speeds of up to 10Gbps and residential gigabit connections of 1Gbps now widely available across the country.

In theory, high-speed cable broadband (D3.1) can reach downstream speeds of 10Gbps and upstream speeds of 2Gbps but only in ideal conditions and it’s doubtful it can be consistently achieved in a commercial rollout.

5G networks can theoretically reach speeds of 10–50 Gbps, with the UK making significant progress since the early rollout of 5G. However, consistent gigabit 5G at scale, particularly outside urban areas, remains a work in progress. More importantly, every 5G mast depends on fibre optic cable to carry traffic back to the core network. That means the continued rollout of full fibre infrastructure is fundamental in revealing the full potential of 5G.

However, the transmission speed of fibre cable is set to go much faster. Prysmian, together with Nokia Bell Labs and the National Institute of Information and Communications Technology (NICT) managed to achieve a world record data transmission speed of 1 Petrabit per second (equal to 1,000,000 Gigabits) over an optical fibre with standard dimensions.

Since then, the record has been surpassed. In May 2025, researchers at the National Institute of Information and Communications Technology (NICT) and Sumitomo Electric achieved 1.02 petabits per second over 1,808 kilometres using a 19-core fibre with standard cladding dimensions.

This was achieved by combining highly spectral efficient wideband optical transmission with a fibre guiding 15 spatial modes, and the use of specific mode multiplexers. As a result, the transmission speed was 1.7 times faster (for multi-mode fibre) and 5.7 times faster (for single-mode fibre) than the previous record of 0.4 Pbps.

So even though it’s possible for data transmission to travel at breath-taking speeds, it may not be available for home broadband for a long while.

What factors affect fibre optic speed?

Prysmian products help speed fibre roll-out

Several factors can affect fibre optic cable transmission speed:

Bandwidth: This refers to the capacity of an internet connection that is shared by all users in a particular area. High usage by neighbours streaming films, attending Zoom meetings, or playing video games can reduce the available bandwidth and slow down internet speed for others.

Network congestion: During peak usage hours, more people are competing for the data, which can cause problems with bandwidth usage, leading to high latency. This means it will take longer for a particular amount of data to travel from one server to another. For internet users, it will take longer for a website to load, make online purchases, or watch a video.

Quality of equipment: The type and even the age of devices used can also have an impact. For example, types of hardware, network interface card (NIC), operating systems, and web browsers can all affect fibre optic speeds.

Single-mode vs multi-mode fibre: It is important to consider the type of fibre installed. Single-mode fibre is smaller in diameter but offers higher performance over longer distances. This is because there are lower internal reflections, which results in faster signals and a lower chance of signal loss. Multi-mode fibre has a larger diameter and experiences more internal reflections. This means the signal is slower and can only travel short distances.

What are the limitations of fibre optic?

Fibre offers higher bandwidth, faster speeds, longer transmission distances, and immunity to interference, but it is more expensive, fragile, and requires specialised installation. When installing fibre, extra care must be taken so that it is not twisted or bent too tightly. Copper is easier and cheaper to install, which makes it more suitable for shorter distances and less demanding applications, however, it has lower bandwidth, higher attenuation, and is susceptible to interference.

Prysmian Fibre Optic Cable: Linking the future

As demand for full fibre continues to rise, the transmission speed for fibre cable is continuing to increase, and Prysmian is constantly developing cable solutions that meet these evolving network demands.

From fibre optic and copper cables, to connectivity components and accessories; Prysmian is helping to link communities, continents and countries faster and more efficiently than ever before.

Our global presence, combined with our experts’ regional knowledge, means we’re uniquely placed to support the needs of every customer: from manufacturing high-performance and cost-effective data cables within tight lead times, to offering specialised network solutions which enable high-speed connectivity in the core network, within datacentres, or at the edge.

Find out more about the Prysmian Fibre Optic project range.