Strain demodulation method based on matched fiber Bragg grating Fabry-Perot interferometer

A novel demodulation method based on matched Fiber Bragg grating Fabry-Perot interferometer (FBG-FPI) for strain measurement is proposed and demonstrated, which combines the advantages of fiber Fabry-Perot interferometry and matched fiber Bragg grating filtering technique. In order to solve the mismatch problem and keep the static working point at the best matching position, the strain and temperature of the matched FBG-FPI are adjusted by a closed-loop control system consisted of the semiconductor refrigeration and piezoelectric ceramic. Meanwhile, the system is immune to the surrounding temperature. Experimental results show that the system can respond to the input signal with the frequency range of 50~800 Hz, is insensitive to the temperature fluctuation, and the strain resolution is up to 0.4 nε/Hz ^1/2. Therefore, this method has a higher practicality for dynamic strain monitoring and vibration measurement.