A technique for measuring atmospheric extinction of light, or visibility, from the backscattered signal of a modulated cw laser is presented. The extinction coefficient is contained in the amplitude and phase of the return signal and can be extracted in several ways from certain amplitude and/or phase measurements. No assumption about a relationship between the extinction coefficient and backscattering coefficient need be made.
G. T. Schappert, "Technique for Measuring Visibility," Appl. Opt. 10, 2325-2328 (1971)