In the report the parameterization of few-photon light sources is discussed. This question relates to a new area of research in quantum optics -the development of methods for characterizing optical components and devices used in optical quantum technologies that are supposed to be used in industry. Apart from, the recent results in this field obtained in the Laboratory of Experimental Quantum Optics and Nanophotonics of M.V.Lomonosov Moscow State University are briefly presented At present, optical quantum technologies are emerging from the walls of laboratories and, as a result, issues of parameterization of quantum optics devices are become relevant. In 2016, the European Telecommunications Standards Institute (ETSI) issued the first preliminary standard [1] which established the rules for characterizing the optical components of quantum key distribution systems. Activity in this direction over the past 3 years has increased significantly. New specialized organizations and expert groups have emerged whose purpose is to develop preliminary standards for optical components and quantum optics devices. Obviously, the existing methods for characterizing classical light sources are insufficient to characterize quantum light sources. In [1] and in subsequent documents, the first procedures for characterizing pseudo-single-photon-sources are provided. But the proposed characterization methods are limited to measuring the Granger's α-parameter and characterizing the quantum states of the generated light themselves remains open, although this is a key challenge for quantum optics [2].Over the past 3 years, our laboratory has been developing methods for characterizing quantum optics devices. The work is carried out in 3 directions: 1) the development and characterization of quasi-single-photon SPR sources using quantum tomography, 2) the characterization of few-photon sources by the photon counting method, and 3) the development and characterization of photon counters using standardless methods. The schemes of a double-crystal SPR generators were developed which are not subject to the negative influence of the Migdall effect on the degree of entanglement of the states of generated photon pairs [3]. The method and the prototype of the device for certification of such sources has been proposed [4]. The effectiveness of certification was analyzed using various criteria of entanglement. The choice fell on the application of the parameter of proximity of quantum states -fidelity ( ). It was shown that when using such sources, F adequately characterizes the error of the distribution of the quantum cryptographic key,