The digital coherent optical receiver, with optimized oversampling, allows reaching extremely large sensitivity, in the range of −93 dBm, or below. The key factors enabling such high sensitivity are the coherent photon enhancement operated by the coherent mixing with the LO power and the enhancement of the input SNR operated by the optimized cross-correlation process. Besides this excellent result, there is one question that should arise spontaneously: how much of the weak optical power flux is still recognizable as a continuous electromagnetic flux? This question raises the need for investigating the quantum nature of the light flux, and how the unpredictable nature of the light detection mechanism through the photon absorption process impacts on the probability of detection of the CMCW LiDAR.