The photosensitivity of a low-loss As_2S_3 chalcogenide glass fiber core under 532 nm near-bandgap light irradiation is experimentally investigated.The experimental results show that at the beginning of light irradiation,the photo-induced refractive index change of the fiber core first decreases rapidly towards the negative direction,and then recovers and increases gradually towards the positive direction with the extension of irradiation time.As for these two processes,the time duration and the refraction ...