For the purpose of attenuation coefficient measurement in seawater under stimulated condition to lidar, an experiment optical path was built. Through selection different line width as 90MHz and 30GHz of Brillouin line width, seawater attenuation coefficient was surveyed under the two distinct condition. The effection to lidar attenuation character in seawater by stimulated Brillouin scattering was discussed. The research results show some strong nonlinear optical course will occur, such as stimulated Brillouin scattering, stimulated thermal scattering and stimulated Raman scattering, when lidar power exceeds the certain threshold value. Then the decay of light in seawater will be sharply changed. Now the attenuation coefficient will never be a constant. The theoretic analysis was programmed to this phenomenon. The average attenuation coefficient formula was deduced. And the academic calculation curve of lidar damping in seawater was obtained. Data of theoretic analysis is consistent with the actual experimental results.
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