Articles
Who
Researchers on the EU-funded Phasors project, led by the University of Southampton’s Opto-electronics Research Centre (ORC), have developed a data transmission system that could improve the capacity and efficiency of fibre-optic communications.
Technology
Data transmission through optical networks is limited by interference called phase noise – rapid, short-term, random fluctuations in the phase of a signal – and “cross talk” where signals simultaneously circulating through the network at different wavelengths affect each other. Both types of interference affect the quality of the signal and result in data transmission errors.
Researchers have developed the first practical phase sensitive amplifier and phase regenerator for high-speed binary phase-encoded signals. The device eliminates the phase noise directly without the need for conversion to an electronic signal, which would inevitably slow the speeds achievable.
The regenerator takes an incoming noisy data signal and restores its quality by reducing the build-up of phase noise and any amplitude noise. Professor David Richardson, ORC deputy director, said: “This is an important first step towards the practical implementation of all-optical signal processing of phase-encoded signals, which are being exploited commercially because of their improved data-carrying capacity relative to conventional amplitude coding schemes.
“Our regenerator can clean noise from incoming data signals and should allow for systems of extended physical length and capacity.
To achieve this result, a major goal of the Phasors project has required significant advances in both optical fibre and semiconductor laser technology.”
Application
Optical data is sent as a sequence of bits coded in the amplitude of a light beam, a system that was simple and practical but inefficient in its use of bandwidth. Until recent years, this was not a problem given the enormous data-carrying capacity of an optical fibre. However, the introduction of bandwidth-hungry video applications such as YouTube and the continued growth of the internet have led to increasing interest in finding more efficient data-signalling formats – in particular, schemes that code data in the phase rather than amplitude of an optical beam.
The Phasors project, which started in 2008, was tasked with developing new technology and components to substantially improve transmission capacity and energy efficiency of optical communication networks. Richardson said: “This device and associated component technology will have significant applications across a range of disciplines beyond telecommunications – including optical sensing and metrology, as well as many other basic test and measurement applications in science and engineering.”