FIELD: fiber-optic data cables.
SUBSTANCE: to determine value of local introduced losses in fiber-optic data cable line, in case of which in current portion of line occurred or is possible a covert removal of data through side surface of optic fiber, by reversed dispersion method a reflection gram of losses in fiber-optic data cable line dependent on its length is received, which is used to find portions with local introduced losses, on which value of losses is measured and distance from start of line to portion with introduced losses. Maximal allowed value of losses is determined from formulae: for common fiber-optic data cable 
for systems with quantum noises 
where Wthr is a threshold of sensitivity of capture receiver with signal/noise relation equal to 1; Q - maximally allowed signal/noise relation for capture receiver, providing for impossibility of data interception; Kn - transfer coefficient, showing which portion of radiation lost in fiber-optic data cable line is received at input pole of interception receiver; Wn - power of optical signal at input pole of fiber-optic data cable receiver, providing for required transmission quality; α - value of introduced losses in fiber-optic data cable line average for a portion (L-1); L - fiber-optic data cable line length; l - distance from transmitter to place with measured value of locally introduced losses; e - electron charge; B - frequencies band of transmitted data signals; In - special integral value; S transfer characteristic of fiber-optic data cable receiver photo-detector. Measured value of losses is compared to calculated maximally allowed value, portions with increased side radiation are detected while measured value surpasses maximally allowed value.
EFFECT: higher security level.
1 dwg
