Experimental study of a tunable fiber ring laser stability

We have experimentally studied the mid-term (1-1000 s) stability of a traveling-wave unidirectional Erbium-doped fiber (EDF) ring laser as a function of the pump power, doped fiber length and type, total laser cavity length, polarization control and exit coupler ratio. The laser operated in a multi-wavelength regime with the central wavelength defined by a 1.12 GHz-band tunable Fabry-Pérot filter (FPF) with a 3.1 THz free spectral range (FSR). We have found that the key parameters defining the laser stability are the cavity length and the out-coupling ratio, while the polarization control has little influence on the multi-wavelength regime. In the optimal configuration, we obtained output power variations below 0.02 dB of a total power of about 1.5 mW in a 10 min interval.