Dynamics of polarization fluctuations in aerial and buried links

The coherent optical systems based on polarization multiplexing deployed in core networks in the last years have generated a renewed interest for the study of polarization effects in fiber optic links [1]. Fluctuations of the state of polarization (SOP) of the optical signal, combined with polarization-dependent loss (PDL) and polarization mode dispersion (PMD), can affect the performance of coherent optical communication systems. The dynamics of the polarization fluctuations can be expected to be strongly dependent on the characteristics of the fiber plant. Some polarization measurement data have already been obtained using coherent transponders or a polarimeter, but on a few links only and mostly over short periods of time [2–6]. Recently, the results of a 22-month SOP activity monitoring on an in-service aerial installation of 750 km have been reported, which provides more insight into the polarization activity in optical ground wire (OPGW) fiber cables [7]. In this paper, we report on a long-term SOP activity monitoring on an experimental metro ring network using a polarimeter and a dual polarized, modulated with dual-polarization quadrature phase-shift keying (DP-QPSK) modem à 100 Gb/s. The temporal and frequency dynamics of the polarization fluctuations and SOP transients observed in the buried fiber plant are presented and compared to those reported in the aerial installation.