MOMENT CHARACTERIZATION OF PHASE NOISE IN COHERENT OPTICAL-SYSTEMS

The statistical characterization of the phase noise introduced by semiconductor laser in coherent optical transmission systems is a key problem in the system performance evaluation. Particular attention has been paid to the probability density function of the phase noise filtered by an integrate-and-dump filter, but no exact analytical result has been obtained. In this paper we consider the moment characterization of the complex random process. z(t) = integral-0/1 e(i-theta(tau)) d-tau (where theta(t) is a Wiener-Levy process), which represents the mathematical model for the filtered phase noise. In particular we find an analytical closed form expression of the joint moments of the real and imaginary parts of ZETA(t), as well as of the even moments of its modulus. In the evaluation both stationary and nonstationary cases are considered. Then the use of the moments for the computation of probability densities through orthogonal polynomial series expansion and maximum entropy approach is considered in application examples.