Mid-term stability of a fiber ring laser with a wavelength-tunable Fabry-Perot filter

Mid-term (I - 1000s) stability of the travelling-wave Er-doped fiber ring laser has been experimentally studied as a function of laser parameters: the pump power, the doped fiber length and type, the total laser cavity length, polarization control, and the exit coupler ratio. In all cases the total cavity length over ten meters resulted in a multi-wave length generation with the comb central wavelength, defined by a 1.12 GHz-band tunable Fabry-Perot filter with a 3.1 THz free spectral range. We have found that the key parameters defining the laser stability are the cavity length and the out-coupling ratio, while the polarization control seems not very important for our multi-wavelength regime. Output power variations are less than 0.02 dB on a 10 min interval were obtained.