Fig. 1. Schematic diagram of the parallel double FPI sensor

Fig. 2. Schematic of the SFPI structure fabrication process

Fig. 3. Simulation of cavity length drift. (a) Reference FPI; (b) sensing FPI; (c) parallel FPI

Fig. 4. Simulation of cavity length drift. (a) Reference FPI; (b) sensing FPI; (c) parallel FPI

Fig. 5. Schematic of experimental setup for strain measurement

Fig. 6. Measurement spectra. (a) Reflection spectra of single FPI; (b) reflection spectra of parallel structure

Fig. 7. Strain response of single SFPI. (a) Reflection spectrum; (b) fitting line

Fig. 8. Response of the parallel FPI sensor 1 to strain. (a) Reflection spectrum; (b) fitting line

Fig. 9. Response of the parallel FPI sensor 2 to strain. (a) Reflection spectrum; (b) fitting line

Fig. 10. Temperature response of single SFPI. (a) Reflection spectrum; (b) fitting line

Fig. 11. Response of the parallel FPI sensor 1 to temperature. (a) Reflection spectrum; (b) fitting line

Fig. 12. Response of the parallel FPI sensor 2 to temperature. (a) Reflection spectrum; (b) fitting line

Fig. 13. Repeatability and stability test of the sensor 1. (a) Repeatability test; (b) stability test

Fig. 14. Repeatability and stability test of the sensor 2. (a) Repeatability test; (b) stability test