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Modelling and Design of Components for All-optical Signal Processing

The unavoidable deterioration of optical signals in the fibre due to loss, dispersion, and nonlinearities leads to the distortion of the shape and timing of the signals, which necessitates the so-called 3R: reamplifying, reshaping, retiming of the signal. Currently this is done electronically, but as optical communications progress to ultrahigh bit rates (40 GBit/s in the current generation, 100 and potentially 160+ GBit/s in the next generations) the electronics becomes prohibitively complex and expensive. A considerable amount of research is therefore spent worldwide on all-optical realisation of both 3R and related signal processing tasks such as optical time-division demultiplexing.

Our contribution to this direction has consisted in proposing several constructions of advanced semiconductor optical amplifiers for reshaping and retiming picosecond (10-12s) pulses at bit rates of 40-100 GBit/s. As with short-pulse generators, we proposed, among other approaches, to make use of quantum dot materials which under certain operating conditions promise extremely fast response, ideal for these ultrahigh bit rates. The recently proposed Semiconductor Saturable Absorber Mirror can also be used for this purpose.

The next development in this project will involve modelling and designing hardware for advanced modulation schemes in future optical communications, such as ultrafast pulse-position modulation.

This work was done in collaboration with Dr Boris Ryvkin of the A.F. Ioffe Physico-Technical Institute and Prof Krassimir Panajotov of TONA, Vrije Universiteit Brussel.