A monitoring system evaluates the integrity of a fiber optic cable, having a weave pattern and being attached to a security fence. To establish and calibrate the monitoring system, the present invention provides a system and method for establishing a look-up table to be stored in a memory. Any breakage in, bending of, or stress on the fiber optic cable is noted by the monitoring system by an alarm, and a length of cable between the monitoring system and the affected portion of the fiber optic cable is determined. The look-up table is indexed to determine a zone of potential breach. Further, an average weave density of the affected zone is computed, so that an approximate location of the potential breach within the affected zone, in terms of ground distance, can be accurately determined and displayed.