Fig. 1. Diagram of fiber FPI structure. (a) Schematic diagram of fiber FPI structure; (b) optical micrograph of fiber FPI

Fig. 2. Interference spectra of each cavity of the sensor

Fig. 3. Interference spectra of the sensor. (a) Considering all cavities; (b) ignoring FP3; (c) ignoring FP2; (d) ignoring FP1

Fig. 4. Formation of spectral envelope. (a) Spectra of FP1 and FP3; (b) spectrum of cascaded structure

Fig. 5. Interference spectra of single and cascaded cavities at different temperatures. (a) FP1 cavity; (b) FP3 cavity; (c) cascaded double cavities

Fig. 6. Temperature sensitivites of FP1 and FP3 cavities and cascaded double cavities

Fig. 7. Interference spectra and temperature response of the sensor. (a) Interference spectra; (b) temperature response

Fig. 8. PDMS membrane filled double cavities cascaded temperature sensor experimental device

Fig. 9. Interference spectra of cascade double cavity temperature sensors at different temperatures

Fig. 10. Interference spectrum envelope peak change curve with temperature rise and drop