A low-threshold multiwavelength Brillouin fiber laser with double-frequency spacing based on a small-core fiber

We demonstrate multiwavelength Brillouin fiber lasers (MWBFLs) with double-frequency spacing based on a small-core fiber (SCF) and a standard single-mode fiber (SMF), which have core diameters of 5 and 8.8 μm, respectively. Experimental results show that the SCF-based MWBFL exhibits a higher laser output power and a lower pump threshold. The output powers of the SCF-based MWBFL are > 1.4 times those of the SMF-based MWBFL. Moreover, the threshold power required to generate each channel of the SCF-based MWBFL is 59% that of the SMF-based MWBFL. When the same pump power of 180 mW is injected, the number of laser channels generated for the SCF-based MWBFL is 13, which is twice that generated for the SMF-based MWBFL. In addition, the SCF-based MWBFL exhibits good wavelength tunability from 1535 to 1565 nm and temporal stability over an hour.