Autocorrelation of the polarization-dependent loss in fiber routes

We study the spectral properties of polarization-dependent loss (PDL) in fiber routes with multiple spans and amplifiers. In these systems, PDL stems from asmall number of lumped WDM components interconnected by PDL-free fibers, a configuration that is poorly described by the popular model of distributed PDL. We derive transparent and practical analytical expressions for the autocorrelation functions of the PDL vector and of the square PDL magnitude and show that they are strongly affected by the order of the individual PDL elements.