Superfast broadband uses fibre optic lines, which allow information to be transmitted in the form of light. Fibre lines are incredibly fast and reliable.
Ofcom and the EU define super fast broadband as connections with download speeds greater than 30Mbps.
Unfortunately it would be incredibly costly to install fibre cables to every home and office. As a result telecoms operators, such as BT and Virgin Media, have preferred to adopt a more cost effective approach by mixing existing (old) cables with the latest fibre optic lines. This is known as FTTC (Fibre-to-the-Cabinet).
The advantage of this method is that related services are usually both significantly cheaper and easier to install because the last part of the connection into properties does not need to be replaced (i.e. the fibre optic cable is taken to a local street cabinet - but no further).
BT requires an existing green cabinet for its FTTC service and will install a new cabinet, with a fibre link back to the exchange, near the existing cabinet. The new cabinet basically houses the ADSL technology from the exchange. Telephone calls go down the copper wire to the exchange in the normal way but data is split off at the fibre cabinet and uses the fibre to the exchange.
As the distance of copper wire from the ASDL equipment and the home is much shorter, much greater broadband speeds can be achieved. Speeds of up to 80Mbps download and 20Mbps upload are the current standard, which could rise to 100Mbps+ in the near future.