A recent scientific discovery has revealed that pulses of light can be sent down tunnels in the air – known as ‘air waveguides’ – to transmit data without losing the signal, or changing its form. So far, however, the breakthrough has been demonstrated only in a very low range.
The scientific fact that light can be used to transport information over very large distances without loss or distortion of signal has played a major part in the Internet connections that today criss-cross our planet. Before the advent of fibre optics, light waves carrying information were passed through conduits which allowed the signal to degrade en route. Subsequently, the manufacture of fibre optical cable enabled the light waves to be reflected back from the glass walls, producing a much more robust signal. Now a team led by Professor Howard Milchberg at the University of Maryland may be about to take this approach to the next level by using laser pulses to guide light signals through a sort of ‘tube’ made out of thin air. Once developed and perfected, this approach could enable information signals to be sent in situations where it is physically impossible to lay fibre optic cable.
Lasers pulses to guide light waves
The photons which make up light waves tend to disperse in air. However, Howard Milchberg’s revolutionary idea is to use four laser pulses to create a low-density ‘tube’ in thin air within which the photons can be captured and hence the beam of light carrying an information signal can be guided. Scientists are calling this method of steering light waves an ‘air waveguide’. This approach could mean that information signals can still be carried by light waves even without any form of physical tube or spliced fibres to guide it. So far experiments have shown that the information signal arrives at a destination one metre away 50% stronger than if simply beamed through normal-consistency air.
Implementation still has a long way to go
The immediate challenge for the Maryland team is to extend the distance at which this new technique can work. Explains Howard Milchberg: “What we’re focusing on at the moment is trying to minimise the level of lightwave dispersion into the atmosphere.” For the purposes of telecommunications this means endeavouring to maintain robust coded signals as we are able to do nowadays with optical fibre. Professor Milchberg remains cautious, pointing out that “we’d need to be able to set up air waveguides across several thousand kilometres distance and it’s not at all clear whether that’s going to be possible.” The fact is that optical fibre enables us to cover distances that even the strongest laser beams would have difficulty reaching. So those who see in this early-stage discovery a revolutionary breakthrough in Internet access will need to temper their enthusiasm a while yet. The Maryland University team has not yet begun to work on encoding information in the ‘guided’ light waves, which still looks a complex task.