Lucent pushes back theoretical limits of fibre optics

Boffins see the light

Boffins at Lucent Technologies' Bell Labs have discovered that optic fibre cables can transmit 10 times more information than was previously thought possible.

The research, which is to appear in today's edition of the Science journal Nature, mean that it might (at least in theory) be possible to send 100 terabits of information per second (Tbps), the equivalent of 20 billion one page emails, down a single strand of fibre optic.

Lab results had previously pointed to an upper limit on transmission speed of 10Tbps, with the fastest commercial systems achieving 2Tbps.

During the research, Bell Labs scientists looked at systems that use wavelength division multiplexing and estimated how fast information could be transmitted.

If too little power is used a signal would be swamped by noise but cranking up the power results in interference with other signals. Determining the best way to balance these requirements is a challenge even for the brightest minds in physics.

The interest in the work by Lucent is that boffins have figured a much more elegant technique of sending ultra-high speed transmissions without excessive noise or interference.

Alastair Glass, chief technical officer of Lucent's Optical Networking Group, told Reuters "this says that we are still a long way from the fundamental limits in current commercial systems, and it's still uncertain when optical systems will be able to approach theoretical limits."

Predicting how fast information might be transmitted over glass fibre is important in planning capital intensive cable laying operations. If advances in transmission techniques can be expected to result in the possibility of sending more traffic down a single strand in five years time it's useful to know that when laying cable to meet projected bandwidth requirements.

Reuters reports that network operators spent about $90 million over the last four years laying fibre-optic networks in the US. Of an estimated 39 million miles of glass fibre laid in America only about five per cent of the cable is 'lit', that is equipped with the repeaters and terminal equipment needed to transmit information.

Such estimates have resulted in concern over a broadband glut that has troubled telecom investors, and (arguably) had a negative effect on the market as a whole. ®

External Links

Reuters: Lucent Finds Theoretical Outer-Limits of Fibre
Nature - not updated with Lucent research yet

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