METHOD OF DETECTION OF RADIATION COUPLING FROM LATERAL SURFACE OF OPTICAL FIBRE Russian patent published in 2009 - IPC H04B10/08 

FIELD: information technologies.

SUBSTANCE: invention can be used for detection of infringement of working capacity of the protected fiber-optical systems of information transfer (FOTS) of the limited access and as a way of the constant control of a fiber-optical line of transfer (FOTL) from leak on the optical channel. In the way, consisting in reception, detecting of optical signals from the fiber-optical communication line, strengthening, integration and analogue-digital transformation of the received analogue electric signals which in the digital form are compared to control value in such a manner that in case of decrease in amplitude of a signal below control value on the set size the alarm signal is formed. The new thing is that through each quantity of readout N, making a cycle set by the timer, average selective value, for example, in j cycle (1) which is remembered and used in the subsequent cycles for calculation of a control signal under the formula (2) is calculated, and each i size of a control signal is compared to the threshold value in advance set and written down in memory calculated under formula Φ_n=lg Λ_n+0.5Q₂N, (3) where Λ_n - the set threshold relation of credibility; Q - the set relation of amplitude of the signal called by loss of radiation in a fiber-optical line of transfer, to average quadratic value of noise, thus, if /Φ_i/≥Φ_n the ALARM signal is formed, otherwise after the termination of each j cycles the received size Φ_j is remembered and subtracted from the value received in previous j-1 the cycle, the received difference is compared to in advance set threshold of detection Φ_o and in case /Φ_j-Φ_j-1/≤Φ_o, (4) that for size of average selective value in j+1 a cycle is accepted the size calculated in j cycle, the size used in j-1 a cycle otherwise is accepted.

EFFECT: increase of probability of detection of reserved attempt of unloading an optical signal from a lateral surface of an optical fibre and decrease in probability of false operations at operation.

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