Frequency demodulation of an inhomogeneous medium multi-longitudinal mode fiber laser and its sensing application

Dispersion characteristic could be a significant factor, which impacts the beat frequency of Multi-longitudinal mode fiber laser (MMFL). In this paper, the mechanism of beat frequency generation in inhomogeneous medium Multi-longitudinal mode fiber laser is discussed. Compared with cavity length-dependent fiber laser sensing system, the proposed model uses a several-millimeter-Fiber-Bragg-Grating (FBG) as the sensing head, which features both high sensitivity and compact size. We designed an experiment to exhibit possible sensing application based on the proposed theory as well.