Tunable multiwavelength Brillouin-Erbium fiber laser with a polarization-maintaining fiber Sagnac loop filter

We demonstrate the generation of 12-wavelength comb with 14.5-nm tunable range in the Brillouin-Erbium fiber laser. This is achieved through tuning the gain profile of Erbium-doped fiber by a Sagnac loop filter with 18-cm polarization-maintaining fiber, in conjunction with modifying the wavelength of Brillouin pump. The experiment also demonstrates that the tunable range is closely equal to the 3-dB bandwidth of Sagnac loop filter due to its periodic transmission profile. Meanwhile, the effect of the 980-nm pump on the tunable multiwavelength generation is investigated. The power of 980-nm pump has a great effect on the wavelength number and the output power of the generated multiwavelength comb, but little on the tunable range. This technique may be applicable to multiwavelength operation lasers with a large tunable range.