Long-Term Observation of PMD and SOP on Installed Fiber Routes

We present 18 months of field observations on the state-of-polarization (SOP) and polarization-mode dispersion (PMD) on three routes monitored using deployed coherent 40 Gb/s transponders. Two fiber paths were monitored on each of three different routes, ranging from 30 km with one amplified span to 273 km with seven amplified spans. In general, the changes in SOP and PMD were slow, with the autocorrelation half-width-half-maxima ranging from 1.3 to 4.1 days for the differential-group-delay and from 0.18 to 1.7 days for the SOP. We observed the largest correlation of active periods between fiber paths sharing the same cable and weak correlation with fiber paths sharing an office. With over 10,000 hours of measurements spanning an 18-month period, we believe this to be the most extensive study published on the polarization behavior of buried fiber.