New optical signal processing to satisfy power-hungry, high-speed networks

The project is part of the European Union Framework 7 PHASORS project which completed earlier this year.

In a paper entitled: Multilevel quantization of optical phase in a novel coherent parametric mixer architecture, which will be published in Nature Photonics on October 9, a team of researchers led by Professor David Richardson at the University of Southampton's Optoelectronics Research Centre (ORC), describes a simple and reconfigurable device created to automatically tune the phase property of ultrafast light signals. This phase quantization function is analogous to the way electronic circuits can adjust electrical signals to ensure their voltage matches the discrete set of values required for digital computing.

According to Professor Richardson at the ORC, this is a significant breakthrough because their new device allows an unprecedented level of control and flexibility in processing light using light, functionality required now that ultra-high speed optical signals can be found everywhere from communication links between microprocessor cores in next generation supercomputers to the sub-sea fibre links spanning continents.

"Today parametric mixers are routinely used for laser wavelength conversion, spectroscopy, interferometry and optical amplification," said Mr Joseph Kakande a PhD student at ORC who undertook most of the research "Conventional parametric mixers when operated in a phase sensitive fashion have for many decades been known to have a two-level response. We have now managed to achieve a multilevel phase response which means that we have demonstrated for the first time, a device that squeezes the classical characteristics of its input light to more than two phase levels."

As an example, the team has already used the device to remove noise picked up by a signal in during transmission in optical fibre at over 100 Gbit/s. In principle, this can be done even faster, at speeds hundreds of times greater than could be done using electronics, and crucially, using less power. The researchers envisage many as yet unknown deployment opportunities, given that controlling the phase of light also finds use in applications spanning enabling ultrasensitive interferometers in the hunt for gravitational waves to facilitating the probing of the inner workings of cells.