Perimeter security system and perimeter monitoring method
First Claim
1. A perimeter security system including;
- at least a first waveguide and at least a second waveguide buried below ground level and extending along a perimeter which defines an area to be monitored;
means for launching light into the first and second waveguides;
a detector for detecting light which has propagated through the waveguides so as to detect a change in a parameter of the light propagating through the waveguides due to an intrusion across the ground beneath which the waveguides are buried and for providing an indication of that intrusion;
the first and second waveguides being provided in separate cables and the separate cables being buried beneath ground level in a zig-zag spaced apart relationship with respect to one another to define a perimeter region having a substantial width which will be traversed by a person intruding into the area;
a first of the said cables contains said at least one waveguide and a second said cable contains said second waveguide;
a further waveguide being contained within the first cable;
first coupling means at one end of the said first, second and further waveguides for coupling the waveguides so that light launched into the said further waveguide is able to propagate through the further waveguide and then into the said first and said second waveguides to propagate in a first direction through the said first and second waveguides;
second coupling means at the other end of said first and said second waveguides so that the light propagating in the said first direction through said first and second waveguides is able to coherently recombine and interfere at the second coupling means; and
light also being able to be launched through said second coupling means and into said first and second waveguides to travel in a direction opposite said first direction and coherently recombine at the first coupling means so the light travelling in the opposite direction is able to interfere and then propagate through the said further waveguide.
1 Assignment
0 Petitions
Accused Products
Abstract
A perimeter security system is disclosed which includes a first cable (40) and a second cable (60) buried beneath the ground in a zig-zag pattern. The first cable (40) has a first fibre (44) and a further fibre (42). Second cable (60) has a second fibre (62). The first and second fibres (44) and (62) are connected by a coupler (52) at one end so that light can be launched into the first and second fibres (44) and (62) to propagate in one direction. The further fibre (42) is connected to a coupler (70) which also connects to the other end of the first and second fibres (44) and (62) so light can be launched into the fibres from the other end and travel in the opposite direction. Detectors (80) and (82) are provided for detecting an interference pattern produced by interference of the propagating light signals so that if a person attempts to breach the barrier by walking across the ground beneath which the cables are buried, the cables are moved to change the nature of the propagating light to in turn change the interference pattern to provide an indication of the intrusion. The location of the intrusion can also be determined by the time difference between receipt of the altered interference pattern propagating in the first direction, compared to that propagating in the opposition direction.
10 Citations
11 Claims
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1. A perimeter security system including;
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at least a first waveguide and at least a second waveguide buried below ground level and extending along a perimeter which defines an area to be monitored; means for launching light into the first and second waveguides; a detector for detecting light which has propagated through the waveguides so as to detect a change in a parameter of the light propagating through the waveguides due to an intrusion across the ground beneath which the waveguides are buried and for providing an indication of that intrusion; the first and second waveguides being provided in separate cables and the separate cables being buried beneath ground level in a zig-zag spaced apart relationship with respect to one another to define a perimeter region having a substantial width which will be traversed by a person intruding into the area; a first of the said cables contains said at least one waveguide and a second said cable contains said second waveguide; a further waveguide being contained within the first cable; first coupling means at one end of the said first, second and further waveguides for coupling the waveguides so that light launched into the said further waveguide is able to propagate through the further waveguide and then into the said first and said second waveguides to propagate in a first direction through the said first and second waveguides; second coupling means at the other end of said first and said second waveguides so that the light propagating in the said first direction through said first and second waveguides is able to coherently recombine and interfere at the second coupling means; and light also being able to be launched through said second coupling means and into said first and second waveguides to travel in a direction opposite said first direction and coherently recombine at the first coupling means so the light travelling in the opposite direction is able to interfere and then propagate through the said further waveguide. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A perimeter security system for underground use including:
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at least a first waveguide and at least a second waveguide for extending along a perimeter which defines an area to be monitored; means for launching light into the first and second waveguides; a detector for detecting light which has propagated through the waveguides so as to detect a change in parameter of the light propagating through the waveguides due to an intrusion across the ground when the waveguides are buried, and for providing an indication of that intrusion; the first and second waveguides being provided in separate cables, and the separate cables being for location beneath ground level in a zig-zag spaced apart relationship with respect to one another to define a perimeter region having a substantial width which will be traversed by a person intruding into the area; a first of said cables containing said at least one waveguide and a second said cable containing said second waveguide; a further waveguide being contained within the first cable; first coupling means at one end of said first, second and further waveguides for coupling the waveguides so that light launched into said further waveguide is able to propagate through the further waveguide, and then into the said first and said second waveguides to propagate in a first direction through the first and second waveguides; second coupling means at the other end of said first and said second waveguides so that the light propagating in said first direction through said first and second waveguides is able to coherently recombine and interfere at the second coupling means; and light also being able to be launched through said second coupling means and into said first and second waveguides to travel in a direction opposite said first direction, and coherently recombine at the first coupling means so that the light travelling in the opposite direction is able to interfere and then propagate through said further waveguide.
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Specification