This paper considers principles of construction and methods of analysis of electro-optical probing and characterization of the Brillouin gain contour, based on using the methods of poly-harmonic probing radiation and estimation of the parameters by evaluation of envelopes of its beating frequencies at stages of searching the center frequency, the maximum gain and the width of the contour determination, as the basic characteristics of measuring conversion of temperature and strain tension/compression in a single-mode optical fiber. The purpose is to improve the metrological, technical and economic characteristics of electro-optical systems of this type.