System for transformation of radiant flux as a delivery system with modification of the flux diameter was considered. That can be used with most efficiency in modelling radiators and simulators for electro-optical test facility where there is necessity of modulation of collimated radiant flux with considerable diameter D1 and little angular convergence or divergence 2(alpha) . This system consists of consecutively installed coaxes reflecting concentrator with tapered angle 2(beta) and cylindrical hollow fiber of diameter D2, at first; two mirror truncated cones formed in meridian section angular mirror with angular basis (beta) , at second. These two mirror cones carried out the recollimation of radiant flux for obtaining the starting angular convergence (divergence) 2(alpha) . Formulas for determining geometrical dimensions of this delivery system depending on concentration rate C both angles (alpha) and (beta) are adduced. One attends those energy losses for this transformation of radiant flux were not more than 2 - 3%. Focon-fiber configuration of proposed delivery system has been presented.