Digital anisochronous pulse time modulation techniques.

Digital anisochronous pulse time modulation (PTM) techniques are alternative schemes for transmission of signals over optical fibre communication links. Modulation is simple and low cost and has the ability to trade performance with bandwidth overhead. Pulse interval width code modulation (PIWCM) and pulse interval code modulation (PICM) belong to the category of schemes where the former offers built in frame synchronisation capability and the latter offers improved receiver sensitivity.This thesis is concerned with analysis, design, simulation and physical implementation of PIWCM and PICM for a single channel system. Original mathematical expressions are given for code characteristics, transmission capacity and power spectral density for both schemes, which explain the the anisochronous nature of the code formats. A simulation model based upon Matlab has been developed for both schemes to assist the development of the implementation process. Analytical and simulated results are presented along with the evaluation of error sources and their impact upon the system performance. The PIWCM and PICM modulators/demodulators are formulated around analogue-to-digital converters and purpose designed Moore state machines, in order to generate the code formats and timing information needed to synchronise transmitter and receiver modules. Depending on source connection, the system is capable of transmitting PCM coded parallel binary information or directly sampled analogue message signals.A complete system operating at 1 Mb/s has been designed, constructed and analysed. The results obtained are in close agreement with predicted and simulated data, indicating the potential of such schemes for wide-band transmission.