Experimental research on an L-band multi-wavelength erbium-doped fiber laser based on a cascaded Sagnac loop and M-Z filters

In this paper, we proposed and experimentally demonstrated an L-band multi-wavelength erbium-doped fiber (EDF) laser with a cascaded Sagnac loop, M-Z interferometer filters and a non-linear optical loop mirror (NOLM). The NOLM acted as the intensity-dependent transmissivity; it can effectively alleviate the mode competition and beating caused by homogeneous broadening. The transfer characteristic of the Sagnac loop was investigated firstly and got the optimized parameters. Then the laser output spectrum with different kinds of filters in the cavity was experimentally tested when the pump power was fixed at 450 mW. The experimental results showed that the EDF laser with the cascaded filters in the cavity had a better performance, such as a better flat lasing bandwidth within 3 dB, higher side-modesuppression ratio and more comb lines generated. The peak power fluctuation was less than 0.35 dB within a 30 min monitor time.