Multilongitudinal mode fiber laser for strain measurement

A multilongitudinal mode fiber laser sensor formed by two fiber Bragg gratings and a piece of erbium-doped fiber is first proposed and validated experimentally. When the strain is applied on the sensor, the laser cavity is stretched, which leads to a change of round-trip frequency. Thus the strain can be obtained by measuring the beat frequency of the resonant cavity. The proposed sensor is found to be characterized with simplicity, easy setup, high resolution, low-cost demodulation, and good stability. Experimental results show that the sensor has a sensitivity of −1.1 KHz/μϵ and the root-mean-square deviation of 3.6 μϵ.