Fig. 1. Structural diagram of NMN

Fig. 2. Field distribution of light propagation in NCF

Fig. 3. Transmission spectra of NMN structures with NCF lengths of 15, 30, and 45 mm

Fig. 4. Transmission spectra of NMN structures with different MMF lengths. (a) 10 mm; (b) 30 mm; (c) 50 mm

Fig. 5. Schematic of sensing mechanism

Fig. 6. Wavelength as a function of concentration of H₂S. Inset shows spectral responses of sensor under various concentrations of H₂S

Fig. 7. Gas selectivity of H₂S sensor

Fig. 8. Response-recovery curve of H₂S sensor