Flatness Investigation of Multiwavelength SOA Random Fiber Laser Based on Sagnac Loop Mirror

We investigated the lasing performance of multiwavelength random fiber laser (MWRFL) at different single-mode fibers (SMFs). The main investigation is based on 700 m SMF with the presence of highly nonlinear fiber (HNLF) and polarizer as the current of the SOA is set to the maximum which is at 900 mA. With the assistance of the nonlinear polarization rotation (NPR) effect, two simultaneous multiwavelength spectra are generated, centered at 1575 nm and 1603 nm with multiwavelength bandwidth of 12 nm and 5 nm and 60 and 27 lines within 3 dB of bandwidth, respectively. The next investigations are based on 10 km and 300 m of SMF and without HNLF and polarizer from the setup, resulting in increased fluctuations and instability when a shorter 8-m of polarization-maintained fiber (PMF) is used. When the PMF length is changed to 42 m, the flatness is improved. The combination of specific fiber types with lengths such as SMF, PMF, and HNLF along with the polarizer influences the lasing lines and stability for the output of MWRFL.