The amplification of small signals was investigated both experimentally and theoretically. The theoretical
analysis was provided in terms of unsaturated regime. It is shown, that it is necessary to take into account the temporal
shapes of interacting waves. When pump pulse duration is of the order of hupersound phonons lifetime, the Stokes
pulse has duration in two times lower then pump. It is necessary to have time delay between input Stokes pulse and
pumping pulse of the order of life time of hupersound phonons to have amplification maximum. Energy amplification
~ 2•10<sup>9</sup> was obtained experimentally when the energy of input signal was about 10<sup>-11</sup> J.
The affect of the active medium SBS - amplifier parameters on SBS threshold is investigated. The universality
of expression for a threshold increment of amplification, valid in a big range of change of parameters is shown. The
threshold increment of amplification in the light guide in which spontaneous noise can amplify in big solid angle is
experimentally confirmed. Experiments on SBS amplification in the light guide of small signal images are carried out.
Amplification coefficient ~10<sup>6</sup> is obtained without essential change of picture quality.