Fig. 1. Experimental setup and measuring principle. (a) Schematic of experimental setup for measuring the photorefractive index change of chalcogenide optical fiber by applying tension along the axial direction; (b) displacement of oscillogram measured by OSA when light irradiates chalcogenide optical fiber for calculating the photorefractive index change

Fig. 2. Dependence of the photorefractive index change Δn of As₂S₃ fiber core on the illumination time under the light irradiation power of 10 mW. (a) Without tension; (b) with tension of 0.490 N

Fig. 3. Dependence of the photorefractive index change Δn of As₂S₃ fiber core on the illumination time under the light irradiation power of 13 mW. (a) Without tension; (b) with tension of 0.490 N

Fig. 4. Dependence of the photorefractive index change Δn of As₂S₃ fiber core on the illumination time under the light irradiation power of 11 mW. (a) With tension of 0.274 N; (b) with tension of 0.353 N

Fig. 5. End face photos of tapered As₂S₃ glass fiber with small diameter. (a) Without coupling light; (b) with coupling light (end coupling, the central wavelength of 1550 nm)

Fig. 6. Characterization of written Bragg grating without tension. (a) Dependence of the depth of Bragg transmission peak on exposure time; (b) transmission spectrum of Bragg grating with exposure time of 80 s

Fig. 7. Characterization of written Bragg grating with tension of 0.196 N. (a) Dependence of the depth of Bragg transmission peak on exposure time; (b) transmission spectrum of Bragg grating with exposure time of 80 s