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Details of Grant 

EPSRC Reference: GR/J12406/01
Principal Investigator: O'Mahony, Professor M
Other Investigators:
Siddiqui, Dr S
Researcher Co-Investigators:
Project Partners:
Department: Computing and Electronic Systems1
Organisation: University of Essex
Scheme: Standard Research (Pre-FEC)
Starts: 01 October 1993 Ends: 31 December 1996 Value (£): 117,635
EPSRC Research Topic Classifications:
Networks & Distributed Systems Optical Communications
EPSRC Industrial Sector Classifications:
Related Grants:
Panel History:  
Summary on Grant Application Form
1. To study theoretically and experimentally the impact on network design of wavelength convertors.2. To establish the design rules for optimising network performance with the constraint of a fixed number of wavelengths.3. To demonstrate a low dimensional network using convertors to validate theory and allow conclusions to be drawn for large scale networks.Progress:This project is associated with a separate grant to the University of Bath, who have the responsibility of studying wavelength convertor devices and supplying device characteristics for system and network modelling by the University of Essex. Since the project started work at Essex has progressed on three fronts following the objectives above. Experimental, theory and simulation have been used to understand the system effects of cascading optical convertors, e.g. how many can be cascaded and what are their transmission characteristics. Characteristics of components from Bath have been incorporated into a Comdisco simulator package to allow validation of the analysis. A signal to noise model of channels passing through a series of alternate wavelength convertors and transmission links has been developed. This model was applied to two types of wavelength convertors in which the presence of a modulated optical signal 'gates'the output of a CW optical signal. The first type was based on gain saturation in a semiconductor laser amplifier (SLA). It was found that this device reduces the extinction ratio of the signal and leads to a limit of traversal of 5 or less convertors. The second was based on a nonlinear optical loop mirror convertor. This is an interferometric convertor and it was found that it is possible to improve the extinction ratio of the signal and inhibit noise for certain operating conditions. This leads to a situation where many convertors could be cascaded. In the laboratory an SLA convertor has been established and measurements taken to validate theory. This project has also tied up to another ESPRC project (GR/H82907) and demonstrated how analogue TV signals in a multiwavelength system can be wavelength switched. Progress has been considerable in the second objective and a network simulator now allows network performance to be assessed as a function of the incorporation of wavelength convertors. One difficulty is that there are many possible network applications and the advantages of using convertors would seem to depend very much on topology. This area of work is now of great interest worldwide. The simulator is now also being used to define the demonstrator (objective 3), which will probably be a multiwavelength ring network. This is currently under discussion. There are three publications associated with the project to date and another has been submitted. The latest paper accepted is : M.E. Bray and M.J. O'Mahony, 'Cascaded Optical Wavelength Convertors', for presentation at OFC '95, 26 February to 3 March 1995, San Diego, USA.
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Organisation Website: http://www.sx.ac.uk