Credit: © 2007 Nature Photonics

The demand for optical communication is rapidly increasing. However, when optical systems transfer large amounts of data, the signal quality may degrade because of dispersion effects and noise. For this reason, scientists such as Alexander Gaeta and co-workers at Cornell University in the US are making use of nanotechnology in high-speed regeneration devices that clean up optical signals1.

Previous attempts at optical signal regeneration have had limited bandwidth or require long lengths of optic fibres. To overcome these obstacles, Gaeta and co-workers have taken advantage of a special type of light interaction called four-wave mixing. The researchers constructed a 'nanowaveguide' consisting of a silicon nanowire encased in silicon oxide. Four-wave mixing was induced by inserting a damaged input signal alongside either a continuous wave or an optical clock pulse. At the output end of the nanowire, the converted signal was selected using a band-pass filter.

The continuous wave improved the digital signal resolution — the difference between '1's and '0's — while the clock pulse reduced jitters in the signal timing. Both processes improved the general shape of the signal. Therefore, a combination of these regeneration schemes could greatly improve signal quality at the receiving end of a long-haul optic-fibre transmission.