Optical diagnostics is the most effective method for non-invasive monitoring of tissue condition during non-ablative infrared laser exposure. In this work, laser radiation with a wavelength of 1560 nm and a power of 1-3 W was used to create microscopic zones of thermal damage in rabbit skin. The dynamics of the intensity of diffusely reflected and diffusely transmitted laser radiation from the sample were recorded using an integrating sphere. After laser exposure, the completeness of collagen denaturation in the irradiated area was assessed by the resistance of the tissue to the proteolytic enzyme treatment. A comparison of the optical characteristics dynamics of the sample and the degree of collagen denaturation allowed us to establish a correlation between the onset of collagen denaturation and changes in optical parameters: by reducing diffuse light transmission and increasing diffuse reflection. The time of the output of the diffuse transmission signal to a stationary level clearly correlates with the complete denaturation of collagen throughout the entire depth of the skin sample. Monitoring the dynamics of light transmission and reflection makes it possible to quickly and effectively adjust the geometric and energy parameters of laser radiation, which ensures the achievement of targeted local coagulation with minimal risk of overheating of surrounding tissues Keywords: IR laser irradiation, skin, diffuse transmission, diffuse transmission, collagen denaturation.