Cryan, R.A., Unwin, Rodney T., Massarella, Alistair J. and Sibley, Martin J.N. (1990) Digital PPM employing temporal solitons. IEE Colloquium on Non-Linear Effects in Fibre Communications. 14/1-14/5.

The authors propose that advantage be taken of the fibre nonlinearity such that the digital PPM pulse becomes a temporal soliton. The maximum achievable bit rate of such a system is compared with that of PCM. Under ideal conditions (no fluctuations of the input soliton pulse width) digital PPM can be used to achieve a higher bit-rate. However, in a practical situation fluctuations of the input soliton pulse width are translated to variations in the soliton pulse position. This has a severe effect on the error probability of digital PPM, and in this situation PCM offers greater immunity