Southampton, England--Researchers at the University of Southampton have developed a phase-encoded optical-data-transmission system that directly eliminates phase noise and could substantially improve the transmission capacity and energy efficiency of the world's optical-communications networks.
Traditionally optical data has been sent via binary modulation of the light's amplitude, an approach that was simple and practical but inefficient in its use of bandwidth. Until recent years, this wasn't a problem given the enormous data-carrying capacity of an optical fiber. However, the introduction of bandwidth-hungry video applications (YouTube and the like) and internet growth in general have led to increasing interest in finding more-efficient data-encoding formats--in particular, phase rather than amplitude encoding.
But transmission of data through wavelength-division-multiplexed (WDM) optical networks is currently limited by phase noise from optical amplifiers and crosstalk induced by interaction of a signal with the many other WDM signals at different wavelengths.
No optical-to-electronic conversion needed
Now, researchers working on the European-Union-funded FP7 Phasors project, led by the University of Southampton's Optoelectronics Research Centre (ORC), have announced a major advance in the potential elimination of this interference.1 They have developed the first practical phase-sensitive amplifier and phase regenerator for high-speed binary phase-encoded signals. This device, unlike others developed in the past, eliminates the phase noise directly without the need for conversion to an electronic signal, which would inevitably slow the speeds achievable.
The device takes an incoming noisy data signal and restores its quality by reducing the buildup of phase noise and amplitude noise at the same time.
"Our regenerator can clean noise from incoming data signals and should allow for systems of extended physical length and capacity," said ORC deputy director and Phasors director, professor David Richardson. "Achieving this result, a major goal of the Phasors project, has required significant advances in both optical fibre and semiconductor laser technology across the consortium. We believe this device and associated component technology will have significant applications across a range of disciplines beyond telecommunications--including optical sensing, metrology, as well as many other basic test and measurement applications in science and engineering."
The project combines the expertise of research teams from the ORC, Chalmers University of Technology (Sweden), The Tyndall National Institute at University College Cork (Ireland), the National and Kapodestrian University of Athens (Greece), and industrial partners Onefive GmbH (Switzerland), Eblana Photonics (Ireland), and OFS (Denmark).
1. Radan Slavík et al., Nature Photonics, published online: 05 September 2010 | doi:10.1038/nphoton.2010.203
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