World's longest laser poised to improve data transmission

Juan Diego Ania-Castañón and his colleagues have transformed an optical fibre 75 kilometres long into a laser that can transmit light signals with no loss of power.  

In existing optical fibre networks light signals lose about 5 per cent of their power for every kilometre they travel. This means that signals have to be amplified, adding to the cost and complexity of networks. And the amplification process also amplifies background noise, meaning that eventually the signal is drowned out.

The advance depends on the Raman effect, a natural phenomenon that affects light passing through a material. Lasers are used to inject light at each end of the fibre, causing the fibre’s atoms to give out more energy and emit photons of a longer wavelength.

These photons are reflected back into the fibre by special mirrors at each end of the optical link. The fibre then stores a stable, uniform amount of laser light that travels with the signals and strengthens them, enabling them to move through the fibre at full power without suffering any loss, and thus removing the need to amplify the signals.

“Lossless transmission of data has always been a dream goal in the world of communications. The development of a simple method to implement nearly ideal links between receiver and sender paves the way to important advances in long-distance telecommunications,” said Ania-Castañón.