Fig. 1. Experimental setup diagram of ring FBG displacement sensor

Fig. 2. Structural diagram of strain gauge

Fig. 3. Beat frequency generation theory

Fig. 4. Spectra of sensor. (a) Beat signal of spectrometer output; (b) beat signal of adjacent longitudinal modes

Fig. 5. Drift spectrum diagram of beat frequency signal under different displacements

Fig. 6. Relationship between beat frequency and strain gauge displacement of adjacent longitudinal modes

Fig. 7. Measured result of sensor stability