Fig. 1. Schematic diagram of gas pressure sensing probe

Fig. 2. Detection structure of gas pressure sensing probe

Fig. 3. Preparation process of sensing probe. (a) Fusion splicing of SMF to HCF; (b) fixed-length cutting of HCF; (c) fusion splicing of HCF to PCF; (d) fixed-length cutting of PCF

Fig. 4. Microscope images of optical fibers after welding and PCF cross section photograph. (a) Fusion splicing result of SMF and HCF; (b) fusion splicing result of HCF and PCF; (c) PCF cross section photograph

Fig. 5. Side views of gas pressure sensing probes. (a) 1#; (b) 2#; (c) 3#; (d) 4#

Fig. 6. Schematic diagram of gas pressure sensing system

Fig. 7. Schematic diagram of gas pressure sensing device

Fig. 8. Output spectra and FFT results. (a) Interference spectra of sensing probes 1#‒4#; (b) FFT results of final spectrum of sensing probe 4#; (c) filtered spectra of sensing probe 4# at different gas pressures

Fig. 9. Linear fitting curves of gas pressure versus wavelength. (a) 4#; (b) 1# and 2#

Fig. 10. Reversibility test results of sensor probes. (a) 3#; (b) 4#

Fig. 11. Temperature test results of sensor probe 4#. (a) Spectra at different temperatures; (b) linear fitting curve of temperature versus dip wavelength