| 摘要 |
<p>A fiber optic interferometric perimeter security apparatus is provided for detection and location of a disturbance on a sensor cable caused by an intruder attempt to climb over, or cut through, a perimeter fence-mounted sensor cable or walk over a hidden perimeter defined by a buried sensor cable. A single modulated laser source and optical time delay elements which have been strategically located in the optical paths of optical sensors comprising two back-to-back Michelson interferometer and a sensor cable are used to generate pseudo-IF responses from each Michelson interferometer. The interferometer responses are used to isolate desired in-phase and quadrature-phase responses while suppressing undesired inherent interferometer responses. The in-phase and quadrature-phase responses each comprise a distortion signal wherein the distortion may be represented by an inherent range cosine filter (RCF) which is a function of the range (i.e. distance) along the cable of the disturbance. Digital signal processing is applied to the isolated in-phase and quadrature-phase response signals and to corresponding inferential RCFs to form a bridge, and iterative bridge measurements are performed using different range bins (i.e. distances to partitions dividing the length of the cable) for the inferential bridges. The location of the disturbance over a brief window in time is determined to be in the range bin which balances the bridge measurement. If desired, the location of the disturbance within that range bin may be determined by further processing using a tangent function and interpolation.</p> |
