Details of Grant 

EPSRC Reference:	GR/J09215/01
Title:	MULTIGIGABIT/S MULTIPLEXING AND MULTIPLE ACCESS SYSTEMS USING COHERENCE PROPERTIES OF PICOSECOND PULSES.
Principal Investigator:	Jackson, Professor D
Other Investigators:
Researcher Co-Investigators:
Project Partners:
Department:	Sch of Physical Sciences
Organisation:	University of Kent
Scheme:	Standard Research (Pre-FEC)
Starts:	17 November 1993	Ends:	16 February 1997	Value (£):	140,502
EPSRC Research Topic Classifications:	Digital Signal Processing
EPSRC Industrial Sector Classifications:
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Panel History:
Summary on Grant Application Form
The project is conveniently divided into 4 main objectives:1. research into optical coherence coding techniques to establish the theoretical performance and test these predictions experimentally; 2. demonstration of point to point transmission (through an optical fibre waveguide) to reconstruct or reject an encoded pulse with a passive decoder based on (i) optical coherence coding exploiting frequency domain pseudo random phase codes and (ii) the pulse to pulse coherence of mode locked lasers; 3. performance assessment of multigigabit/s multiplexing and multiple access systems;4. evaluation of possible practical implementations of the demonstrated concepts.Progress:The research undertaken in this project builds on a previous SERC/MoD grant, GR/G16939. Under the auspices of GR/J09215 we have successfully demonstrated the concept of a secure, reconfigurable CDMA communications system based upon the modification of the optical coherence properties of a laser diode combined with a spectrally encoding phase mask. The phase mask was designed to generate a 15 bit pseudo random M sequence code. The optical source is a gain switched Fabry-Perot laser diode. The action of gain switching produces a pulse of <20ps with a considerably broadened spectral content when compared with the laser operating C.W. The output from the source is then injected into an unbalanced interferometer (the encoder) with a phase mask in 1 arm, the encoder imbalance being governed by the temporal coherence of the source. This pulse can then only be reconstructed by injecting it into a second interferometer (the receiver) which has the same path imbalance and a phase mask with the same random phase sequence as the encoder . The system can then be reconfigured by changing the phase mask in the encoder. Theory related to these concepts has also been developed. Four papers associated with these concepts have been published during 1994/5. A detailed paper describes our original research on communications systems based upon coherent correlation. We have also studied the possibilities of using the inherent delaying properties of highly-birefringent fibre to produce encoders and matching decoders. A paper describing the work is currently in preparation. We next plan to exploit the unique coherence properties of 'Mode Locked Lasers' (MLL) for reconfigurable encoders, to enable random addressing of interferometric receivers with different path imbalances. This work will be undertaken in collaboration with Dr. Raman Kashyap at BTRL who has developed a ruggedized MLL. Originally we planned to build the MLL with components supplied by BT; however, despite the fact that we will now have to make a financial contribution to BT for the components, this will be more than offset by the considerable saving in research time.
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Organisation Website:	http://www.kent.ac.uk