FIELD: optics. SUBSTANCE: multistep optical valve of light amplifier has two inlet and two outlet holes to cut off backward flux of transmitted light when incident incoming light enters first inlet hole and when outgoing light enters second inlet hole. Pumping source generates light used to amplify faint incoming light. Modulator with wave length division modulates light generated by pumping source and light transmitted through multistep optical valve. Optical fibre amplifies light from modulator and emits amplified light through first hole of multistep optical valve. EFFECT: diminished dimensions and reduced manufacturing cost of light amplifier. 6 cl, 7 dwg
