Geslin, Serge; (2000) Influence of laser diode nonlinearities on fibre optic systems supporting direct-sequence code division multiple access signals. Doctoral thesis (Ph.D.), University College London (United Kingdom).

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Abstract

This thesis is concerned with the study of the impact of Laser Diode nonlinearities on Direct-Sequence Code Division Multiple Access (CDMA) based fibre-radio systems. CDMA is a promising technique for radio access for future cellular mobile and personal communication systems. The aim of the third generation systems is the integration of all mobile systems into one universal system. In this context, the use of fibre-optic feeders as the remoting infrastructure in microcellular networks has been proposed for CDMA systems. The presence of a nonlinear device, such as a laser diode, in such systems leads to the generation of intermodulation products, which consequently affect the system performance and ultimately restrain the maximum number of users the system can serve. In the case of a pure CDMA system, the laser diode nonlinearities are well described by a third-order polynomial without memory. This method enables the assessment of the implication of unequal power transmission of mobile users using the derived bit-error-rate. Finally, in order to increase the system capacity, a hybrid SubCarrier Multiplexing (SCM)/CDMA system is proposed. The Volterra series method of nonlinear system theory is then presented and applied to SCM systems to investigate the performance of different system configurations.

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