BT Infinity fibre-optic broadband: Not infinite in any sense of the word

BT is bringing high-speed Internet access to the home, under the frustratingly misleading brand name 'Infinity'. Offering initial speeds of up to 40Mbps, it uses fibre-optic cable to pump the Web from the telephone exchange to your local 'cabinet' -- those green boxes that you see on street corners. From the cabinet, the Internet will be freshly piped to your home using a special kind of DSL known as VDSL (Very high bit-rate Digital Subscriber Line).

VDSL has the potential to achieve very high speeds over short copper runs -- up to 100Mbps. So, where there is a fibre cabinet near your house, you should get speeds of up to 60Mbps. BT has plans to increase Infinity's 40Mbps where the cable run is short enough. Its upstream bandwidth is also impressive, at up to 10Mbps.

To access Infinity, customers will need a BT phone line, which costs about £12 a month. The service comes in two flavours. The first, most basic pack offers 40Mbps download and 2Mbps upload speeds. There's also a cap of 20GB when you take this option. You get a BT Infinity Home Hub included, but there's a sign-up fee of £50 and an 18-month commitment.

The second pack offers the same 40Mbps download speeds, but ups the upstream to 10Mbps. There's no download cap on this pack, and the activation fee is waived. The cheaper Option 1 costs £20 a month, with the unlimited Option 2 jumping to £25 a month, also for 18 months minimum.

We find the 20GB limit on Option 1 pretty amusing, given that you could munch though it in little more than an hour going full-tilt at 40Mbps. Even the 'unlimited' option isn't without the vague threat of a cap of some kind, warning that a fair-use policy applies. We don't know what that means for downloads, but expect trouble if you leave a BitTorrent client running constantly pumping terabytes of data out each month.

So what if you're using a non-BT ISP and don't want to swap to BT? At the moment, you have no choice: it's BT or nothing. Reseller options will become available at some point, so your favourite ISP should soon be able to sell you 40Mbps broadband. For LLU providers such as Be and Sky, there's the option for them to carry on offering their services independent of BT's equipment. This is managed differently in the exchange, but for the end user, the process will be transparent.

Using fibre to the cabinet is not a new idea -- cable companies around the world have been using this system for a long time. The difference between BT and the UK's major cable provider, Virgin, is how the signal is sent from the cabinet to your home. Where BT is using a DSL variant, Virgin uses a system called DOCIS to move both broadband and TV signals to the customer's home. In theory, there is more potential bandwidth in the Virgin system, but this capacity is shared with TV channels, so don't expect 300Mbps broadband any time soon. 

For those interested, BT has a phone line checker that will tell you if you're able to get the Infinity service in your area. BT suggests that some 40 per cent of the UK population will be able to get this new service by the end of the year. Our own research indicates that, of our self-selecting sample, some 93 per cent of respondents wouldn't be able to access Infinity. So far, the name seems a pretty empty promise.