DFB fiber laser static strain sensor based on beat frequency interrogation with a reference fiber laser locked to a FBG resonator

We report on a high-resolution static strain sensor developed with distributed feedback (DFB) fiber laser. A reference FBG resonator is used for temperature compensation. Locking another independent fiber laser to the resonator using the Pound-Drever-Hall technique results in a strain power spectral density better than S-s(f) = (4.6 x 10(-21)) epsilon(2)/Hz in the frequency range from 1 Hz to 1 kHz, corresponding to a minimum dynamic strain resolution of 67.8 p epsilon/root Hz. This frequency stabilized fiber laser is proposed to interrogate the sensing DFB fiber laser by the beat frequency principle. As a reasonable DFB fiber laser setup is realized, a narrow beat frequency line-width of 3.23 kHz and a high beat frequency stability of 0.036 MHz in 15 minutes are obtained in the laboratory test, corresponding to a minimum static strain resolution of 270 p epsilon. This is the first time that a sub-0.5 n epsilon level for static strain measurement using DFB fiber laser is demonstrated. (C) 2016 Optical Society of America