Fig. 1. Schematic diagram of cascaded FPI+FBG temperature sensor

Fig. 2. Simulated temperature responses of CFPIs based on single air cavity, glass-cavity, and cascaded cavities. (a) Single air cavity; (b) glass-cavity; (c) cascaded cavities

Fig. 3. BPM simulation diagram of the SMF-HCF-SMF structure

Fig. 4. Relationship between temperature sensitivity and parameter M

Fig. 5. Simulation of heat transfer on aluminum alloy substrates

Fig. 6. Simulation of thermal expansion of aluminum alloy substrates

Fig. 7. Diagram of sensor fabrication process

Fig. 8. Microscope pictures of the fiber optic sensing section

Fig. 9. Sensor calibration diagram

Fig. 10. Reflectance spectrogram of the sensor

Fig. 11. Temperature fit curves for FBG and cascaded FPI. (a) FBG; (b) cascaded FPI

Fig. 12. Temperature repeatability error box line diagrams for FBG and cascaded FPI. (a) FBG; (b) cascaded FPI

Fig. 13. Relationship between sensor response time and sensor time constant

Fig. 14. Comparison of ordinary FBG and post-interference FBG reflection spectra