How does fibre optic broadband work?

Fibre optics


I’m trying to find out more about switching broadband but I don’t understand all the jargon. How does fibre optic broadband work? And which is better - fibre-to-the-cabinet (FTTC) or fibre-to-the-home (FTTH)?


Our expert says...

Fibre optic broadband, as you probably know, is superfast and has enough bandwidth to get loads of gadgets online at once. It's good stuff.

The majority of UK broadband providers have fibre packages, but with some of the jargon the industry uses, it can get confusing when you try to figure out exactly what they're offering.

How does fibre work?

Fibre optic broadband is all in the cables.

The kind that deliver fibre optic broadband do indeed consist of fibre optics - yes, exactly like those cool hippy lamps. They're tiny tubes, each about as thick as a human hair, reflective on the inside. They transfer data by sending a ray of light through the tube, which bounces off the inner walls to travel along the cable. The speed of light is generally thought of as being quite fast, meaning data can travel pretty quickly this way. And because the cables are so thin, a load can be bunched together to get lots of data to lots of people at once.

Broadband that isn't fibre optic is known as ADSL (asymmetric digital subscriber line). Data is instead sent through the traditional copper phone lines all the way from the exchange.


The most common setup for fibre broadband is fibre-to-the-cabinet, or FTTC. It involves fibre optic cables running from the BT exchange to the cabinet on your street, which then connects to your home via the ol' copper phone line.

That means data can zoom from the exchange to your street super quickly, but it's a little slower from the street to your home. Luckily, the distance from the street to your home is way, way shorter than the distance from the exchange to the street - so for most tasks you'll hardly notice the difference.

Still, if the distance between the cabinet and your home - also known as "the last mile" - is quite far, expect your broadband speeds to be slower. This is especially likely in rural areas where properties are far apart.

Providers that offer FTTC connections include BT (, Sky (, TalkTalk (, Plusnet (, and EE (

Virgin Media (, on the other hand, works a little differently. It runs its own fibre network, and then connects your home to the local cabinet with coaxial cables. These are still made of copper but they're more resilient to interference than traditional phone lines, making them a lot faster. That's how Virgin Media can offer broadband speeds up to 200Mb.

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Take that copper line in the last mile and make it a fibre optic cable instead. This makes it a fibre-to-the-home (FTTH) setup, in which the entire line from the BT exchange to your building is fibre optic. That makes it alotfaster and way more reliable.

But FTTH comes with its own problems. For one thing, installing it in the first place can be disruptive to your property, and it takes longer and costs more money to install. As a result, very few providers offer it - BT only usually does so in special circumstances in certain areas where it's already available.

One provider that does offer FTTH is Hyperoptic ( Because it's fibre the whole way, it can offer lickety-split speeds of up to 1Gb with totally unlimited downloads.

The downside is that Hyperoptic isn't available everywhere. It's only found in select buildings, usually apartment blocks, that would particularly benefit from it. This is because of all that pesky disruption it takes to install - it makes more sense to connect an entire building full of residents than just one house.

Which is better?

FTTH is the fastest and most reliable connection of the two by a long way, but it's not widely available and can cost a bomb.

FTTC, meanwhile, is widespread and more affordable, and gives you greater choice over which provider you choose, but it's a little bit slower.

The average home should be more than fine with a FTTC package. Download speeds up to 76Mb are impressive, and Virgin Media's Vivid Broadband up to 200Mb even more so. That said, some homes can really benefit from the amazing speeds of FTTH broadband - if you run an online business from home, or have a big household of very heavy users, for example. 

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