Light speed

An ultra-fast laser built in the

has clocked up a data transmission rate of 1.36 terabits per second, in a breakthrough that could lead to a huge increase in the speed of broadband connections to homes and businesses.

The laser, which has been developed as part of the ultra-fast photonics collaboration project, is the forerunner of network technology that is expected to be widely available in 10 years’ time.

It was built by researchers at St Andrews University. Dr Tom Brown, a member of the St Andrews computer sciences team, said: ‘We have had to deliver a femtosecond laser with a pulse rate that was four times more than anything delivered previously. We believe it’s the highest repetition rate of any sub-100 femtosecond laser.’

The researchers argue that such devices will reach speeds of up to 100 terabits per second when ultrafast photonics technology matures. The maximum speed of existing digital subscriber line (DSL) networks is 100Gbits per second.

Targets set by governments around the world to boost broadband speeds will only be met by such ultra-fast photonic networks. The Japanese government, for example, recently set a target of achieving a rate of 1Gbit per second to every Japanese home by 2010.

According to the researchers, the average Japanese town will need to be supplied with 10–100 terabits/sec of data to meet this ambitious target.

Rather than bring applications to the lab to test the laser’s speed, the laser has been made sufficiently portable to be transported anywhere in the back of a car. Earlier femtosecond lasers have been heavy boxes of around 6ft x 3ft or heavier, while the new laser is the size of a shoebox.

The next step for researchers will be to test the laser over a long distance by shining it down an optical fibre from St Andrews to the University of Essex.

Researchers at Essex are developing network technologies that use lasers to increase both download and upload speeds. Commercial partners, including Alcatel, Bookham Technology, Nortel Networks and Sharp Laboratories, are also assessing the laser for use in computer networks.

Researchers in other sections of the Interdisciplinary Research Collaboration (IRC) are developing the laser for use in different disciplines, said Brown. ‘We are doing a lot of work on laser-based medicine.’

The researchers can manipulate light using superprisms in far smaller spaces than previously possible. The best photonic crystal devices produced so far are just 30 micrometres in diameter.

The IRC will leave the development of commercial systems to the IT companies, said Brown. ‘We are not working on processors themselves here — we are working on the technologies underpinning those systems.

‘We can’t compete with Intel, but we can provide the underlying technology.’