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Sunday, November 14, 1999 Published at 23:14 GMT


Optic fibre world records broken

In the future optic fibres could carry millions of phone calls at once

Bell Laboratories believe they have broken two world records in the use of optical fibres to transmit information.

The huge increases in the use of mobile telephones and the internet mean that technical innovations such as these are crucial if information gridlock is to be avoided.

Firstly, the scientists crammed 160 billion bits (gigabits) per second down 300 kilometres of optical fibre using only one wavelength, or colour, of light.

And, in a separate development, they have used 1,022 different colours of light to send simultaneous signals down a single optic fibre.

Speed of light

Transmitting information using optical fibres means delivery at the speed of light. But laying optical fibres means digging up roads which is expensive.

This is why a great deal of effort is going into trying to get the maximum speed and capacity from the fibres which are laid.

The first record promises to increase speed. "This experiment represents the world's first practical 160-gigabit system," said Alastair Glass, director of the Bell Labs Photonics Research Lab.

"Like today's commercial systems, it uses a semiconductor-based transmitter. Multiplying 160 gigabits over additional wavelengths, we expect to be able to scale up to many trillions of bits a second in the foreseeable future."

Chasing the rainbow

The second record increases to 1,022 the number of different colours of light that can be used as separate channels to send different signals down the same optical fibre.

Today's commercial optical systems combine up to 100 colours on an optical fibre.

The team used a single ultra-high-speed laser to generate signals over all 1,022 wavelengths, instead of using a separate laser for each.

Wayne Knox, also of Bell Labs, the research arm of Lucent Technologies, said "Transmitters with high channel counts and minimal hardware are attractive for such applications."

Calling the tune

Last month, Marconi Communications announced that an optical switch would be available from summer 2000. At the moment, when telephone calls or internet traffic need to be switched from one optic fibres to another, they first have to be converted into electrical signals.

But Marconi's optical switch uses a tunable laser to switch the traffic whilst retaining the signal as light.

They claim the technology will allow the number of simultaneous calls that can be carried using 32 colours on a fibre to be increased from 30,000 to millions.

"Growth in the Internet and the use of mobile phones for example, is phenomenal," said Mike Parton, Chief Executive Officer of Marconi Communications.

"The world needs the new optical technology now being developed but until now it has been restricted by the lack of the ability to accurately tune the lasers that sort out the channels which send these enormous amounts of traffic down the optical fibre cables."

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