Abstract
A new method for evaluating the performance of optical transmission systems is proposed, that plots the Q-factor on a contour map as a function of transmission power and fibre dispersion. For a given group velocity dispersion (GVD), the power margin at a given Q-factor is obtained immediately. A comparison of the soliton, RZ pulse at zero GVD and NRZ pulse reveals that the dispersion-allocated soliton has the largest margin.