Performance Evaluation and Optimization of Receivers for Direct Detection Optical Communication.

Available from UMI in association with The British Library. This thesis is concerned with performance evaluation and optimization of direct detection optical communication systems. It is based on a comprehensive model of a fibre -optic receiver which accounts for the stochastic nature of the signals in a mathematically rigorous manner. Special emphasis is placed on the inclusion of jitter into the receiver description since this impairment is of increasing importance in very high speed communication systems. A tight upper bound on the error probability, the modified Chernoff bound, is employed for performance assessment. Its formulation incorporates timing imperfections either of the received signal or of the extracted clock. A distribution-free bound is derived which is based on jitter range and variance only. Using variational calculus techniques receiver filters are identified which minimize the bound on the error probability, taking into account simultaneously all impairments including jitter and arbitrarily coloured additive noise. The optimum filter impulse responses are obtained as solutions of a differential equation. This approach does not address the problem of filter realizability. However, realizable, low-order filters can be obtained--again on the basis of the modified Chernoff bound --by means of numerical optimization. This approach is particularly attractive because it results in considerable performance advantages over conventionally used filters of the same complexity. The performance of these practical filters is further found to be only marginally inferior to that of the theoretical optimum filter.