The acousto-optic modulator as an element of the radio and optical signal processing system is considered. The transparency function of the acousto-optic modulator is established and a procedure for its linearization is proposed. A new generalized superposition principle for the transparency function of a pair of acousto-optic modulators, which located close to each other, is introduced. In the framework of computer simulation, the diffraction divergence of acoustic waves in the non-dissipative and dissipative mediums of acousto-optic interaction is investigated. The criterion of difference of diffracted field from rectangle consists in the increase of plane figure radius of inertia, which describing a one-dimensional diffraction acoustic field, from the radius of inertia of rectangle, which describes a non-diffracted field.