On the impact of laser´s relaxation oscillation on quadratically detected heterodyned lightwave signals

We consider the performance of quadratically detected heterodyned lightwave signals in the presence of a laser´s relaxation oscillations. Here the limiting form of the channel presents both additive white Gaussian noise (AWGN) of spectral density N₀ and the laser´s phase noise. The widely accepted model for the laser´s phase noise is a Brownian motion giving rise to a Lorentzian line spectrum. However, the actual line shape of semiconductor lasers deviates from this simplified and idealized statistical characterization. The analytical techniques provided here show that this deviation may have a significant impact on the communication-system performance