METHOD OF DETECTING UNAUTHORISED SIGNAL TAPPING FROM SINGLE-MODE OPTICAL FIBRES Russian patent published in 2014 - IPC H04B10/71 

FIELD: radio engineering, communication.

SUBSTANCE: invention relates to methods of monitoring fibre-optic lines based on single-mode optical fibres and can be used as a method of separating local defects formed through unauthorised tapping from local defects caused by permanent optical connections. The method involves measuring loss reflectograms depending on the length of the optical fibre from each of its terminals using a backscattering method at the operating wavelength and at a wavelength larger than the operating wavelength. Areas with local defects are determined on each reflectogram and areas with local defects on all reflectograms are compared. Unauthorised tapping is indicated by presence of a reflected signal and by the value of direct losses at the longer wavelength being higher than that at the operating wavelength. When measuring reflectograms at different terminals, direct losses at each wavelength must be equal.

EFFECT: high efficiency of detecting unauthorised tapping in single-mode optical fibres.

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