Polarization dynamics of a fibre Fabry-Perot laser with feedback

Experimental results on the low-frequency polarization dynamics of a free-running Nd-doped optical fibre laser and a fibre laser with derivative feedback are presented. It is found that the power spectrum of each polarization mode reveals three relaxation peaks. Using the combined (negative and positive) derivative feedback it is possible to suppress noise in the region of the in-phase relaxation oscillations and to excite noise in the region of one of the two antiphase relaxation oscillations. The model developed of a class B laser with two orthogonal elliptically polarized modes is checked and explains the main experimental features of relaxation oscillation peaks.