A method and apparatus is disclosed for use in fiber optic signature recognition to analyze buried optical fiber to identify a non-threat area along a fiber route and to discontinue monitoring for disturbances along that area of the cable route. The technique includes determining the location of the zone of non-threatening disturbances from comparing an optical signal to the representation of a prearranged optical signal identified as friendly. Once a zone of non-threatening disturbances is identified, all subsequent disturbances in that zone are considered friendly. Cable monitoring is discontinued in the identified zone of non-threatening disturbances so as to avoid monitoring fiber cable when permitted workers are in the area.