Predicting first-order PMD outage rates on long-haul optical fiber links using measured and modeled temporal and spectral DGD data

Polarization-mode dispersion (PMD) is a major impairment for high bit rate systems resulting in pulse broadening and distortion and thus leading to system performance degradation. Given the stochastic nature of PMD, it is extremely important to characterize PMD and perform system outage analysis to gain a better understanding of its impact on network reliability. The objective of this research work is to develop a numerical model that would accurately model the temporal and spectral PMD characteristics on buried long-haul optical fiber links and use the model to predict first-order PMD outage rates and also study how the outage rates vary with link length.; To achieve the above objective, a three-fold approach was followed. First, the first-order outage rate expression given by Caponi et al. [1] was simplified to a closed-form expression that depends only on two parameters. Second, the existing numerical model for PMD was enhanced by adding the temporal component to it and the model was validated by replicating the PMD characteristics observed through measurements on several buried fiber links. Third, the enhanced model was used to simulate the PMD characteristics on long-haul optical fiber links of different lengths and using the simulated data and the simplified first-order outage rate expression outage rates were predicted on long-haul links and the variation of outage rates with link length was studied.; From the analysis of measured differential-group delay (DGD), it was determined empirically that DGD time derivative (Deltatau' ) has a Laplacian PDF and this led to the simplified first-order outage rate expression which showed that the outage rates are inversely proportional to the Laplacian parameter (alpha). The enhanced numerical model was able to replicate all of the major PMD characteristics observed from measurements. A simulation study of the long-haul links showed that the Laplacian parameter is inversely related to the link length and that the outage rates increase monotonically with the link length provided the receiver DGD threshold is greater than the link mean DGD. This important finding will have a great impact on the network design of all the major carriers that are pushing for high-speed, all-optical, ultra long-haul optical fiber links. The above finding implies that realizing such links requires sophisticated PMD mitigation strategies to ensure network reliability.