Frequency and Duration of Communication System Outages Resulting From Polarization Mode Dispersion

In this paper, we employ measurements of transponder tolerance to both differential group delay (DGD) and second-order polarization mode dispersion (SOPMD) and of the temporal evolution of DGD and SOPMD in installed transmission systems to predict the influence of PMD on the rate and duration of PMD-induced system outages. An empirical 2-D random-walk model predicts that the outage rate and duration depends solely on the mean fiber DGD. We find that the step size of the random walk is nearly uncorrelated with the instantaneous value of the PMD. We then justify the assumptions of this procedure with a full numerical simulation and employ a biased Markov chain algorithm to generate highly accurate results for system outages where simplified models fail.

I. Introduction

Polarization mode dispersion (PMD) complicates the assessment of network performance because of its time-varying nature. Estimates of PMD-induced outages are often quantified in minutes per year [1]. However, this metric does not provide insight into the frequency or duration of outage events. For example, if one claims an impairment of 53 min a year, does this occur as one yearly event, or a distribution of shorter events? This issue impacts both static point-to-point links, which can accommodate PMD outages with dedicated protection switching, and networks for which the total PMD from transmitter to receiver will depend on routing that normally changes with time. Accommodating the provision of various paths in a network may, therefore, ultimately require adaptive compensation for PMD. However, accurate knowledge of the PMD impairments and dynamics for the possible paths are required in order to prescribe the optimum mitigation technique.