On the detection, modeling, and mitigation of anomalous QoT fluctuations in optical networks

Monitoring data from deployed backbone networks shows that many lightpaths present large fluctuations of their quality of transmission (QoT), beyond 1 dB in range. In this paper, we investigate the hypothesis that the evidenced fluctuations stem from anomalies in polarization-dependent loss (PDL), equivalent to one large PDL element. We eventually propose and experimentally test a closed-loop automation designed to stabilize the QoT at a maximal level for lightpaths impaired by such a PDL anomaly.