Fig. 1. Schematic of temperature sensor based on hybrid cascade configuration of SI and FPI

Fig. 2. Ordinary vernier effect. (a) Interference spectrum of FPI; (b) interference spectrum of SI; (c) cascaded interference spectrum of FPI and SI

Fig. 3. 1^st order harmonic vernier effect. (a) Interference spectrum of FPI; (b) interference spectrum of SI; (c) cascaded interference spectrum of FPI and SI

Fig. 4. 2^nd order harmonic vernier effect. (a) Interference spectrum of FPI; (b) interference spectrum of SI; (c) cascaded interference spectrum of FPI and SI

Fig. 5. Variation of interference spectra of FPI and SI when temperature is increased from T₀ to T₀+0.5 ℃. (a) Interference spectra of FPI; (b) interference spectra of SI, D⁰=58.10 cm; (c) interference spectra of SI, D¹=97.80 cm; (d) interference spectra of SI, D²=146.70 cm

Fig. 6. Cascaded interference changes of FPI and SI when temperature is increased from T₀ to T₀+0.5 ℃. (a) 0^th order vernier effect; (b) 1^st order vernier effect; (c) 2^nd order vernier effect

Fig. 7. Displacement spectrograms for single FPI and SIs. (a) FPI; (b) SI with D⁰ of 590.0 mm; (c) SI with D¹ of 970.0 mm; (d) SI with D² of 1450.0 mm

Fig. 8. Spectral shifts of cascaded SI and FPI. (a) Spectrogram of ordinary vernier effect; (b) displacement spectrogram of 1^st order harmonic envelope; (c) displacement spectrogram of 2^nd order harmonic envelope

Fig. 9. Wavelength versus temperature (dot is data and line is fitted curve). (a) Peak wavelength of SI interference spectrum versus temperature; (b) peak/intersection wavelength of interference spectrum envelope versus temperature