Fig. 1. Structure diagram of parallel sensor

Fig. 2. Production process of air cavity and PDMS cavity

Fig. 3. Schematic diagram and microscopic images of the sensor testing device. (a) Experimental testing device schematic diagram; (b) microscopic image of FPI_r1 sensor; (c) microscopic image of FPI_r2 sensor; (d) microscopic image of FPI_s sensor

Fig. 4. Reflection spectra and FFT results of FPI_s and FPI_r. (a) Reflection spectrum of individual FPI_s; (b) reflection spectrum of individual FPI_r1; (c) reflection spectrum of individual FPI_r2; (d) FFT results of a single FPI_s interference spectrum; (e) FFT results of a single FPI_r1 interference spectrum; (f) FFT results of a single FPI_r2 interference spectrum

Fig. 5. Reflection spectra of different cavities in parallel. (a) Reflection spectrum of FPI_s+FPI_r1 parallel structure; (b) reflection spectrum of FPI_s+FPI_r2 parallel structure

Fig. 6. Temperature response characteristics of FPI_s+FPI_r1. (a) FPI_s temperature response characteristics; (b) FPI_s wavelength displacement curve fitting; (c) envelope curves versus temperature; (d) fitting of envelope displacement curves

Fig. 7. Temperature response characteristics of FPI_s+FPI_r2. (a) Envelope curves versus temperature within 32‒34 ℃; (b) envelope displacement curves fitting within 32‒34 ℃; (c) envelope curves versus temperature within 35‒38 ℃; (d) envelope displacement curves fitting within 35‒38 ℃

Fig. 8. Results of stability experiments. (a) Characteristic spectral changes of FPI_s+FPI_r1; (b) wavelength shifts of FPI_s+FPI_r1; (c) characteristic spectral changes of FPI_s+FPI_r2; (d) wavelength shifts of FPI_s+FPI_r2