Optical investigation such as infrared (IR) absorption and Raman spectra are efficient methods for obtaining information on the local structure of the disordered material, especially when the composition is varied. In this paper are reported the optical absorption and Raman spectra of chalcogenide glasses (As₄S₃Se₃)_1-xSn_x (x=0÷0.1) and amorphous thin films as deposited, illuminated and heat treated. For ternary As₄S₃Se₃ chalcogenide glasses the absorption bands of S-H (Se-H) and H₂O located at ν=5190 cm^-1 and ν=3617 cm^-1, characteristic for vitreous As₂S₃ are essentially reduced respectively. The Raman spectra of chalcogenide glasses and thermally deposited amorphous (As₄S₃Se₃)_1-xSn_x thin films consist of two broad bands located at around ν=236 cm^-1 and ν=345 cm^-1, which corresponds to the symmetric stretching vibration modes of AsSe₃/₂ and AsS₃/₂ pyramids, respectively. Tin impurities didn't change the shape of Raman spectra, but shift the both bands to low frequency region. The light exposure of amorphous (As₄S₃Se₃)_1-xSn_x thin films shifts the main maximums of Raman spectra toward the lower frequencies region and decreases the picks intensities.