High bandwidth processing of optical or electronic signals is often restricted by the achievable bandwidth of electronic processors. Photonics is an expanding area of our research, in which photons replace electrons in order to process signals at much higher rates than is possible with electronics alone, thus avoiding the so-called electronic bottleneck. One interest is in using the coherence properties of light and passive optical waveguides to encode and decode information on an optical fibre communications link. These techniques may form the basis for transparent optical multiple access for future high-bit rate local area networks or intra- and inter-computer links.
They also have intrinsic high-security properties which may make them attractive for private optical networks on public systems and may have application to optical ranging. Another activity takes a different approach to replace electronics with optics and optoelectronics to increase the performance of an instrument for processing primarily electronic signals. A multi-channel digital correlator is used to extract frequency information from a signal by analysing it in the time domain. It is used in a vast number of fields such as spectroscopy of photons in light scattering and in astronomy, laser Doppler velocimetry and spread-spectrum radar and microwave and RF communications. By replacing the electronic delays with networks of optical fibres and electronic logic gates with an optoelectronic hybrid equivalent, much higher speed correlators can be constructed than ever before.
Funding in these areas came from the EPSRC and the Paul Fund (Royal Society).
Prof. D.A. Jackson
Dr. C.N. Pannell
Dr. B Wacogne