Patent ID: 7292743

Claim:
A portable optical intrusion detection apparatus for detecting perimeter intrusion, said apparatus comprising: a light source for transmitting a light signal; at least one fiber optic cable optically connected at a first end to said light source; at least one portably mounted cable attenuator, said attenuator including a first cable looping means which defines a first cable loop in said at least one fiber optic cable; an upper cable loop setting means which defines an upper cable loop in said fiber optic cable adjacent to said first cable loop, wherein said upper cable loop has a first maximum effective diameter; a cable loop stopping means which defines a predetermined minimum sized upper cable loop when said at least one fiber optic cable is subject to an external force, wherein said predetermined minimum sized upper cable loop includes a second maximum effective diameter that is smaller dimensioned than said first maximum effective diameter of said upper cable loop, wherein said upper cable loop remains fixed at said second effective diameter when said external force dissipates; attenuator securing means for securing said at least one cable attenuator to a fixed structure; light detecting means which receives and measures the intensity of said light signal at a second end of said at least one fiber optic cable; and alarm means responsive to said light detecting means, wherein said alarm means provides a detectable signal when the intensity of said light signal falls below a predetermined threshold.