Fig. 1. Schematic of cascade sensor

Fig. 2. Manufacturing process diagrams of cascaded sensors. (a) Diagram of silicon tube corroded by HF solution; (b) diagram of fusion between SMF and NCF with coating; (c) diagram of PI coated NCF end face; (d) diagram of fiber insertion into silicon tube; (e) diagram of FPI and AR structure cascade

Fig. 3. Sensor micrograph and test setup diagram. (a) Micrograph of sensor; (b) experimental test setup diagram

Fig. 4. Vernier effect. (a) Reflectance spectrum; (b) FFT result of interference spectrum

Fig. 5. Relative humidity response characteristics. (a) Envelope of the interference spectra; (b) fitting of envelope displacement curve; (c) transmittance spectra; (d) fitting of non-transmission wavelength displacement curve

Fig. 6. Temperature response characteristics. (a) Envelope of interference spectra; (b) fitting of envelope displacement curve; (c) transmittance spectra; (d) fitting of non-transmission wavelength displacement curve

Fig. 7. Calculation test results. (a) Reflection spectra; (b) transmission spectra

Fig. 8. Stability test results. (a)(c) Characteristic spectral changes; (b)(d) shift of wavelength position

Fig. 9. Reproducibility test results. (a)(b) Humidity repeatability test results; (c)(d) temperature repeatability test results