Frequency-Division Multiplexing Sensing System Based on Multilongitudinal Mode Fiber Lasers and Beat Frequency Demodulation

A five-channel frequency-division multiplexing (FDM) fiber laser sensor array based on multilongitudinal mode fiber lasers (MLMFLs) and beat frequency demodulation was proposed. Detailed theoretical analysis of the FDM principle was also described. The potential application of the MLMFL-based FDM for strain measurement was further experimentally studied. The strain sensitivity of -0.92 kHz/με at 1183.52 MHz is consistent with the theoretical calculation. The proposed FDM sensing system only needs one detector and one general frequency analyzer for monitoring all sensors. This all-electrical demodulation improves the stability of the fiber sensor and greatly decreases the cost of sensors. It offers a competitive technology for large-scale monitoring field.