FIELD: technical physics. SUBSTANCE: optical amplifier includes first optical detection fiber meant for reception of multiply reflected light formed inside device to cut off backward light propagation and for detection of detection beam of input stage with usage of multiply reflected light, first lens to collimate input optical signal, first polarizer to split collimated input optical signal to vertically and horizontally polarized light rays, rotator of polarized light to shift phases of rays of split input optical signal, second polarizer to concentrate split rays of input optical phase-shifted signal, second lens to collimate input optical signal from output of second polarizer to input optical fibre, output optical fiber intended for transmission of output optical signal, second optical detection fiber for detection of backward propagating light reflected from output optical fiber and input inside device to cut off backward light propagation. EFFECT: exclusion of necessity of usage of optical distributor with special coating. 21 cl, 5 dwg
