A MASSIVE 25-fold increase in the carrying capacity of fibre-optic cables could result from the work of two teams of researchers at Lucent Technologies and Nippon Telegraph and Telephone (NTT).
Standard fibre-optic transmitters send up to ten billion bits per second by switching a single laser beam on and off. Faster switching is impractical, so the only way to increase the capacity of the cables is to send several signals at once. Fortunately, optical fibres can carry separate signals at different wavelengths without interference.
In the past year, telephone companies have started to install systems that can send four separate signals at different wavelengths. But research at Lucent Technology of Crawford Hill, New Jersey, and NTT of Ibaraki in Japan could increase the number of channels to around a hundred.
A key limit on the number of optical channels comes from the need to amplify the signals after they have ...
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