Small-signal analysis for nonlinear and dispersive optical fibres, and its application to design of dispersion supported transmission systems with optical dispersion compensation

The exact general analytical solution of the small-signal analysis for nonlinear and dispersive optical fibre is derived and discussed. Exact solutions in case of particular situations are also presented, and compared with other authors´ results. An approximated solution obtained from the physical description of fibre nonlinearity effect on the small-signal conversions is derived, numerically compared with the general solution, and shown to be less accurate for larger fibre nonlinearity effect, larger modulation frequencies and/or fibre dispersion. It is shown quantitatively that, at low-medium frequencies and for moderate optical powers at fibre input, the fibre nonlinearity affects the intensity modulation fibre transfer function (IM-FTF) primarily through the IM-IM conversion. Furthermore, it is shown that the fibre nonlinearity can provide perfect compensation of IM-FTF distortion in case of an external modulator with positive chirp parameter. The performance of various optical dispersion compensation (DC) configurations in dispersion supported transmission systems is compared and discussed using the IM-FTF, from the viewpoint of amplitude and delay distortion and bandwidth available. It is shown that under- and post-optical DC leads to an equalised IM-FTF with smaller amplitude and delay distortions and larger bandwidth