High-Resolution Static Strain Sensor Based on Random Fiber Laser and Beat Frequency Interrogation

We proposed a high-resolution static strain sensor using random fiber lasers (RFLs) and the sweep-beat frequency interrogation technique. An RFL with 3-dB linewidth of 548 Hz and frequency jitter of ~±70 kHz is established by random distributed gratings and a high-precision π-phase shifted fiber Bragg grating (π-FBG) ring mirror. Two RFLs act as probes and are interrogated by frequency-swept laser. One RFL is used for strain sensing, the other is used for compensating temperature and frequency shift of swept laser. By using sweep-beat frequency demodulation, a static strain resolution of 196 pico-strain (pε) is obtained in 160 s. To the best of our knowledge, this is the first time that RFLs have been used in static strain sensing based on sweep beat-frequency interrogation.