A fast and accurate method for numerical modelling of a cross-phase-mo
dulated (XPM) fibre laser is introduced. The method can handle variati
ons in the laser parameters and deal with detuning and loss in the las
er, and is suitable for optimizing the performance of XPM lasers. For
a given modulation pulse width, it is shown in numerical examples that
the quality of signal pulses depends on the repetition rate of the ex
ternal modulation and the length of the modulation path.