The interest towards passive control of the light polarization through nonlinear effects has been stimulated by recent works: in particular a polarization pulling effect has been obtained by means of stimulated Brillouin scattering. Here we investigate the condition for obtaining polarization pulling by exploiting the stimulated Raman scattering, which is most suitable for optical communications thanks to its large gain bandwidth. The role of the polarization-dependent Raman amplification and of the random fiber birefringence is clarified by theoretical considerations and numerical simulations starting from the vector theory of the Raman effect in optical fiber. Experiments carried out with a 1571-nm signal and high-power 1486-nm pump evidence the Raman-induced polarization pulling.

Temperature measures on overhead power lines are shown thanks to a Raman-based fiber optic distributed sensor. Monitoring performance on optical ground wires is compared to typical electric measurement in field. A large number of measurement cycles are performed over multiple days under various weather conditions. Monitoring performance on phase conductors is also evaluated and compared to electric measurement in realistic environment simulating solar irradiation and natural wind ventilation both on unloaded and loaded conductors.

The dependence of propagation performance on the signal baud-rate is investigated by simulations for WDM PDM-16QAM systems operating at a spectral efficiency of 4 b/s/Hz. We take into account the case of transmission over uncompensated links, both for standard single-mode fiber and non-zero dispersion-shifted fiber. Three baud-rates are tested: 16.25, 32.5 and 65 Gbaud, including overhead for soft-decision FEC. Hence, we compare the performance limited by the nonlinear impairments in case of 100, 200 and 400 Gb/s data rate transmission, respectively. We demonstrate that the trade-off between higher OSNR margin and nonlinear transmission penalty favors transmission at lower baud-rate (16.25 Gbaud) and narrower channel spacing (25 GHz), among the three different simulated baud-rates.

No abstract