Team looks for fibre-optic cables to transmit more info

Scientists in London are attempting to increase the amount of information that can be transmitted in fibre-optic cables to meet increasing demand.

A team of researchers at University College London (UCL) is using novel techniques to increase the amount of data that can be sent via fibre-optic cables as part of a five-year EPSRC project worth £4.75m.

Prof Polina Bayvel, project leader from UCL’s Optical Networks Group, told The Engineer: ‘There’s currently billions of kilometres of fibres that have been installed around the world and if one could get additional capacity out of that infrastructure it would be extremely valuable.’

Bayvel explained that the UCL team is aiming to achieve the highest data-transmission capacities ever recorded, which exceed 100 petabytes per kilometre. More specifically, the team is aiming to achieve the highest data-transmission rate that is theoretically possible, known as the ‘Shannon limit’.

Bayvel believes it is possible to send more data through optical fibres by exploiting the various properties of the light pulses that carry the information. She hopes that by using advanced modulation techniques, coding techniques and digital signal-processing techniques, they will be able to attain the Shannon limit.

Traditionally, digital information has been processed and sent through fibre-optic cables via two domains, ‘on’ or ‘off’.

‘But it’s possible to use other dimensions of the signal,’ said Bayvel. ‘It’s possible to use optical power, phase, polarisation and wavelength as these four domains can be interpreted by the latest detectors.’

According to Bayvel, the amount of data transmitted each year is increasing by 40 per cent and 99 per cent of all data is carried via optical fibres. However, she claims that the current rate of progress in fibre-optic capacity is only increasing by 20 per cent.

‘So by 2020 we will have run out of capacity,’ she said.

The impact of such an event could be wide ranging. ‘If we run out of capacity then data would have to be rationed to the consumer or prices would have to be put up,’ said Bayvel. ‘If we run out of capacity then any kind of economic growth will stagnate because the internet is a significant part of the economy and growing.’