FIELD: optical communication facilities; private information transmission. SUBSTANCE: on sending end of fiber-optic communication line auxiliary optical radiation is modulated by information signal, optical radiation being transmitted is generated by mixing modulated working and auxiliary rays; on receiving end of this line separation of masking signal from received optical radiation is followed by generation of inverted masking sync signal synchronized with separated masking sync signal. EFFECT: enhanced quality of information received at high efficiency of its protection against unauthorized access. 1 cl, 2 dwg
