In Passive Optical Network (PON), which usually uses intensity modulated signals to convey information fiber nonlinearities are enhanced due to high input and pump powers, short channel spacing, high bit rates, high
number of channels, etc. This paper proposes an optimization algorithm applied to PON based on wavelength
division multiplexing (WDM) ring. The optimization consists in setting up initial powers and frequencies, based
on Multiobjective Genetic Algorithm (MGA) therefore fiber nonlinearities in the intensity modulated WDM
channels are minimized. The MGA searches for the best channel spacing and initial powers so that the overall
induced intensity distortion is minimized. The fiber nonlinearities are analyzed by the Volterra Series Transfer
Function (VSTF) method that calculates the induced intensity distortion in each channel. The performance of the
network is measured in terms of the eye diagram, which shows an improvement of 6 dB in the best optimization
case.