Optimized power coupling for enhanced wavelength switching in Brillouin-Raman fiber lasers

In this paper, we propose a new configuration of switchable wavelength Brillouin Raman Fiber Laser (BRFL) using a simple approach of power coupling. Various power coupling ratios were tested during the experiment, and the combination of a 50/50 coupler and an 80/20 coupler was identified as the most effective for achieving optimal switchable wavelength spacing. When the Raman pump power exceeded 1550 mW, a single Brillouin wavelength spacing was consistently observed. The BRFL achieved a maximum of 441 lines at single spacing (SS) and 213 lines at double spacing (DS). Additionally, the system exhibited remarkable flatness, with the SS achieving a 6 dB flatness and the DS achieving an impressive 1.6 dB flatness. These results underscore the effectiveness of the proposed power coupling method, offering a simple yet powerful solution for switchable multiwavelength BRFL systems.