Fig. 1. Measurement of refractive index change of core based on FP principles. (a) Schematic of experimental setup; (b) shift of transmission spectrum caused by small optical path difference; (c) real measurement of image shift by spectrometer based on As2S3 fiber under light irradiation

Fig. 2. Refractive index change of As2S3 fiber core versus irradiation time for different irradiation powers. (a) 4.5 mW; (b) 8 mW; (c) 13.5 mW; (d) 18.5 mW (insets indicating refractive index changes at irradiation time of 0-10 s)

Fig. 3. Shift of (a) Bragg grating central wavelength and (b) its peak of transmission during exposure

Fig. 4. Transmission spectrum of As2S3 fiber Bragg grating at exposure time of 30 s

Fig. 5. Optical stopping effect of As2S3 fiber under near bandgap light irradiation