Slow Light to Speed Up the Net

Aug 13th, 2008
http://news.bbc.co.uk/1/hi/technology/7557280.stm
By: Jason Palmer


Oxford - A huge increase in the speed of the internet could be produced by slowing parts of it down, say researchers.

Applying the brakes could be the 'metamaterials' that may make it possible to create invisibility cloaks.

The net's speed limit comes about not in transporting information, but in routing it to its various destinations.

Metamaterials could replace the bulky and slow electronics that do the routing, paving the way for lightning fast speeds.

Dividing light

High-speed telecommunications routes include fibre-optic cables that span vast distances, carrying different streams of information in different channels—each with its own frequency of light.

As data nears the end of its journey, these frequencies must be separated and sent to their destinations.

The separation is accomplished with bulky equipment that spreads the closely spaced frequencies in the pulses into different detectors.

'The ability to slow the light could be a tremendous force for telecoms.'
- Xiang Zhang

The light must then be converted into electrical signals which are stored, routed, and turned back into optical signals with lasers. The conversion, besides adding significant cost and complexity, also slows down the data transmission.

'It limits the speed of the whole process to the speed of your electronics,' says Dr Chris Stevens from the department of engineering sciences at the University of Oxford.

'The light and the fibres can quite cheerfully sustain a couple of terahertz, but your electronics can't do more than a few gigahertz.'

It is at this point that the metamaterials prove most useful. If the light signals could be slowed sufficiently during the switching process, there would be no need for the electrical conversion step.

Hurry up and wait

The optical properties of metamaterials are accomplished by design—which is why they are touted for use in cloaking—and they can be engineered to deliberately slow light down.

The effect could be used to store light signals, with different delays for different frequencies, in a so-called 'all optical network'.

'The ability to slow the light could be a tremendous force for telecoms that is sure to enhance speed and efficiency,' says Professor Xiang Zhang, the University of California researcher who demonstrated cloaking earlier this week.

The design of the metamaterials gives them their properties

The metamaterials could be engineered to accomplish the frequency spreading step as well, working much like a prism that splits white light into a rainbow.

'With these materials, you could imagine something more like a single chip with the metamaterial handling the routing—all the capability of one of these big filtering systems, but the size of your fingernail,' says Dr Stevens.

Professor Ortwin Hess of the University of Surrey says that the jumps in speed will become increasingly necessary as more people use bandwidth-intensive video-on-demand services such as the BBC iPlayer.

'We're living with what was put into the system before the telecoms bubble burst in 2000,' Prof Hess says. 'There needs to be more clever ideas so that the existing infrastructure can be used in a different way.'