• Fibre-optic cables use light pulses to transmit data and are used for broadband
• But they are sensitive to changes in environmental pressure caused by sound
• This security flaw may let snoopers eavesdrop on confidential conversations

Fibre-optic cables could be used to eavesdrop on people over half a mile away by detecting changes in light that occur when they speak, a new study shows. 

Researchers in China have developed a system that picks up sound at one end of a fibre-optic cable and transmits the audio at the other end. 

But they're sensitive to changes in environmental pressure, which could be caused by acoustic waves, such as sound from someone speaking – a potential security risk.Modern fibre optic cables, which use pulses of light to transmit data, deliver full fibre broadband (file photo)

The new study was conducted by researchers at Tsinghua University, Beijing and published on the pre-print server arXiv. 

'Optical fibre networks are widely deployed all over the world, which not only facilitates data transmission but also provides an opportunity to obtain additional information,' they say in their paper.