Defence-area optical fiber perimeter protection pre-warning system

The utility model relates to a defence-area optical fiber perimeter protection pre-warning system, relating to the field of the technology for measuring mechanical vibration and impact and piping system. A system monitoring host (1) connects each defence-area unit (2) in series through two common transmission optical fibers I (3) and a transmission optical fiber II (4); the length of each defence area is set as 500m, 100m or 200m according to the requirement of safety protection; the number of the defence areas are set randomly and the maximum number of the defence areas is 100; each defence area is formed by four optical fibers; a no.5 optical fiber and a no.6 optical fiber form a sensing arm; a no.7 optical fiber and a no.8 optical fiber form a transmission arm; the no.5 optical fiber and the no.6 optical fiber are connected in parallel, and two ends are respectively connected with an optical fiber coupler I (9) and an optical fiber coupler II (10); the other end of the optical fiber coupler I (9) is connected with the no.8 optical fiber; and the other end of the optical fiber coupler II (10) is connected with the no.7 optical fiber. The defence-area optical fiber perimeter protection pre-warning system has the advantages of having high positioning accuracy, accurately determining the position, being able to be used in short-distance perimeter defence, being simple in construction, and being low in cost.