WDM design issues with highly correlated PMD spectra of buried optical cables

Repeated PMD measurements on a buried optical cable have been performed and the full statistical analysis of the measured DGD spectra vs. time lead to two important conclusions. First, the DGD spectra measured at 24 hours intervals present strong correlations. While the DGD statistics seems to follow the Maxwellian distribution (at least for DGD values from two to three times the average value), this behavior supports the hypothesis of an upper limit for the DGD of a buried optical link, i.e., a "truncated Maxwellian" rather than "pure Maxwellian" DGD distribution. Then, based on the experimental data, we calculated the mean outage rate and the mean outage time, providing important information for an accurate evaluation of the system availability.