An extremely simple procedure is given for estimating the mean intensity of each component of a twocomponent optical field from measurements of the number of photocounts recorded over counting intervals of T sec duration spaced τ sec apart. The only a priori knowledge required about each component is the functional form of the first- and second-order coherence functions and an order of magnitude estimate of their coherence times.
F. Davidson and R. S. Iyer, "Estimation of Optical Field Mean Intensities from Photocount Correlations," Appl. Opt. 13, 2171-2176 (1974)