Experimental and Theoretical Research of Brillouin Gain Spectrum With Three Peaks in a LEAF

Investigating the Brillouin gain spectrum (BGS) is crucial for various applications, including distributed sensors and optical notch filters. In this letter, we both experimentally and theoretically study excitation mechanisms of the BGS, featuring three Brillouin gain peaks (BGPs), within a large effective area fiber (LEAF). We investigate the properties of the BGS, as the injected laser power is increased, including Stokes power, linewidth, and frequency. The findings reveal that the change in Stokes power and linewidth shows the predominance of only the main BGP, with the other BGPs fading away upon surpassing the stimulated Brillouin scattering threshold (SBST). Moreover, we find that the second BGP exhibits dual frequency states, with relative frequencies of ~73.54 MHz or ~195.81 MHz.