Photos: Inside BT's world of innovation

One problem BT found with the deployment of its fibre-based next-generation network is that, unlike an electricity-conducting copper infrastructure, individuals strands of fibre are impossible to identify by traditional means. So BT asked its engineers to develop a fibre-optic sensor that can do just that. The result identifies fibres by noise detection, with sensitivity to half a millionth of a metre.

Thirty of the patented devices are currently deployed in the field by BT Wholesale, but the company is also now talking to utility companies about using the technology to do things like detecting leaks in water pipes.

But further uses continue to pop up. BT has experimented, in conjunction with Rolls Royce, with using fibre wrapped in copper as a long, thin, makeshift microphone for pinpointing flaws in jet engines — the technology is simple and hardy enough for use in such extreme environments, where the noise generated by jet engines tends to destroy conventional microphones.