Patent ID: 8013987

Claim:
A perimeter security device comprising: a buried optical fiber cable having a predetermined length wherein a path of the buried optical fiber cable defines a secured perimeter; a fiber threat analysis system comprising: a light source and detector configured to couple to the buried optical fiber cable and send a series of optical pulses into the buried optical fiber cable and receive returned optical signals from points within the length of the buried optical fiber cable; a memory configured to store prearranged optical signals; and a processor coupled to the light source and detector and to the memory configured to use an approximation algorithm to take into account soil packing conditions around the length of the buried optical fiber cable and to identify sections of the buried optical fiber cable as threatened or non threatened, wherein ground disturbances along the path of the buried optical fiber cable manifest low frequency ground vibrations which are impressed at sections of the buried optical fiber cable and affect the returned optical signals; the low frequency vibrations manifested by the ground disturbances being analyzed using the approximation algorithm.