Optimized, stabilized and narrow linewidth CW-Erbium fibre ring laser

This paper reports the experimental characterization of a ring configuration erbium-doped fibre laser operating in continuous wave (CW). The output power stability and the linewidth as a function of the cavity parameters were investigated. The fibre laser cavity includes two filters namely, a fibre Bragg grating (FBG) and a fibre Fabry-Perot (FP) tunable filter. Without altering the basic cavity configuration, the study focused on the optimization of key parameters of the fibre laser cavity namely, the erbium-doped fibre length, the pump power, the output coupling ratio and the erbium ion concentration. We have demonstrated that the output power, as well as the power stability of the fibre laser, increased as the output coupling ratio. The maximum power fluctuation of the output power was 7.52 %, corresponding to 0.24 dB and was obtained for a 10 % output coupling. Power stability of 0.71 % and 0.8 % were demonstrated for 80 % and 90 % coupling ratios, respectively. To improve the power stability, we introduced a 2 m unpumped erbium-doped fibre laser into the fibre laser cavity. A stable fibre laser with a linewidth of 10 kHz was obtained during a measurement period of 120 min.