Clipping noise effects on the performance of digital baseband signal in lightwave hybrid digital and analogue transmission systems

Accurate modelling of the clipping effects in lightwave hybrid SCM carrier and digital baseband transmission systems is presented using newly derived formulae. Unlike the cases of bandpass transmission, the PDF of clipping noise in the baseband receiver is found to be asymmetrical. Numerical simulation is described for a system with a 140 Mb/s baseband channel and 33 microwave FM video channels. Results show that clipping noise can have a serious impact on the baseband transmission of digital signals, although its influence on analogue signals is moderate. It is also shown that the decision level may be adjusted to give an optimum BER in the presence of clipping noise.