Saturable absorbers based on excitonic absorption saturation in quantum well
structures have found extensive application in mode-locked lasers. The
recovery time of such absorbers is limited by the free carrier lifetime to
typicallly a few nanoseconds, making them unsuitable for signal processing
in high bit-rate optical communication systems.
This talk will describe the use of ion-implantation to reduce the carrier
recovery time to a few picoseconds, enabling the devices to be applied to
signal processing problems in optical communication systems such as signal
regeneration and wavelength conversion.
Results will be presented on noise suppression and wavelength conversion in
40 Gb/s sytems and on all-optical regeneration in 10 Gb/s transmission
systems, where the error free (< 10^-9 BER) transmission distance in systems
using standard single mode fibre with 80 km amplifier spacing has been
increased from 2,000 km to over 7,000 km.
Alwyn Seeds received the Ph.D. and D.Sc. degrees from the University of
London. From 1980 to 1983 he was a Staff Member at Lincoln Laboratory,
Massachusetts Institute of Technology, where he worked on GaAs monolithic
millimetre-wave integrated circuits for use in phased-array radar. He
returned to England in 1983 to take up a lectureship in telecommunications
at Queen Mary College, University of London, moving to University College
London in 1986, where he is now Professor of Opto-electronics and Head of
the Opto-electronics and Optical Networks Group. He has published over 200
papers on microwave and opto-electronic devices and their systems
applications and is presenter of the video "Microwave Opto-electronics"
in
the IEEE Emerging Technologies series. His current research interests
include microwave bandwidth tuneable semiconductor lasers, semiconductor
optical modulators, optical control of microwave devices, mode-locked
lasers, optical phase-lock loops, optical frequency synthesis, broadband
radio over fibre access systems, dense WDM networks and non-linear
processing in optical transmission.
Professor Seeds is Chairman of the IEE Photonics Professional Network, a
Fellow of the Royal Academy of Engineering, an IEEE Fellow, a past- Chairman
of the Technical Committee on Microwave Photonics of the IEEE Microwave
Theory and Techniques Society and a member of the Microwave Photonics
Committee of IEEE LEOS. He has served on the programme committees for many
international conferences.