A method and system for determining a photon statistics of a light source using an unbalanced beam-splitter is disclosed. The method includes collecting data for photon counts for a first output path and a second output path by a first detector and a second detector, respectively, for a first time period, a first power level, and a first characteristic and collecting data for photon counts for the first output path and the second output path by the first detector and the second detector, respectively, for a second time period, a second power level, and a second characteristic; and processing outputs of the first and the second detector to determine the photon statistics.