FIELD: fiber-optic communications; secret data exchange among computers. SUBSTANCE: system has transmitter and receiver interconnected through optical cable; transmitter has information source whose output is connected to input of first optoelectronic transducer; it also has beam input unit, and its monitoring signal source as well as second optoelectronic transducer are replaced by dual-channel optical reflectometer operating on two wavelengths; it also has resolver, program-controlled trigger-pulse shaping unit and optical generator; reflectometer digital output is connected to input of resolver one of whose outputs is connected to reflectometer control input and other output, to input of trigger-pulse shaping unit of optical generator whose optical output is coupled with third input of optical signal input unit. Appropriate changes are introduced in reflectometer and resolver design. EFFECT: improved reliability of system preventing unauthorized access, effect of ionizing radiation or mechanical impact. 3 cl, 4 dwg
