Abstract:A switchable and tunable multi-wavelength Brillouin erbium-doped fiber laser (MWBEFL) is designed and experimentally demonstrated. A Sagnac loop filter is employed as the switcher to obtain the double Brillouin frequency shift (BFS) of 0.172nm (~20GHz) and the quadruple BFS of 0.35nm (~40GHz). The working principles of the proposed laser are theoretically analyzed. The gain in the laser cavity is hybrid gain, which is provided by stimulated Brillouin scattering (SBS) and erbium-doped fiber (EDF). In addition, the 10km single mode fiber (SMF) is not only used as a Brillouin frequency shifter but also provides a certain degree of random distributed feedback. The experimental results show that up to 9 Stokes lines with a wavelength interval of 0.172nm can be obtained. The optical signal-to-noise ratio (OSNR) is greater than 33 dB. The utilization of 980nm pump power and Brillouin pump (BP) power has enhanced the spectral bandwidth of multi-wavelength generation. By adjusting the BP wavelength to investigate the tunability of the fiber laser, the output of 2-5 laser channels can be realized corresponding to 20 nm wavelength range. This approach is simple and can be employed for the microwave generation of other frequency ranges subject to the filtering shift of the Sagnac loop.