Weight responsive intrusion detector using dual optical fibers
First Claim
1. An intruder detection system includinga pulsed light source,at least two optical fibres each having a core and a cladding of lower refractive index than the core, one being arranged as a light transmitting fibre for conducting light pulses away from the source, and the other being arranged as a light receiving fibre disposed adjacent the transmitting fibre with the respective claddings in intimate contact substantially throughout their length,and a light pulse detector arranged for receiving light pulses conducted along the receiving fibre.
2 Assignments
0 Petitions
Accused Products
Abstract
An intruder detection system wherein light pulses are fed from a light source to a detector via a transmitting optical fibre, an optical terminator and a receiving optical fibre, both fibres being either stepped index fibres or poor quality graded index fibres. The fibres are disposed in intimate contact throughout their length within a cable, and compression of the cable at any region of its length sufficient to cause microbending permits light pulses to breakthrough from one fibre to the other. The time interval between arrival at the detector of a light pulse received from the source after passage through the total length of the transmitting fibre and the receiving fibre, and arrival of a breakthrough pulse received after passage through the fibres only so far as the region of microbending and back again, is indicative of the location of the compresion. The cable may be laid around the perimeter of a site to be guarded so that compression will occur when an intruder crosses the cable. The system is not susceptible to interference and infra-red light pulses may be used to make the system totally covert.
24 Citations
12 Claims
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1. An intruder detection system including
a pulsed light source, at least two optical fibres each having a core and a cladding of lower refractive index than the core, one being arranged as a light transmitting fibre for conducting light pulses away from the source, and the other being arranged as a light receiving fibre disposed adjacent the transmitting fibre with the respective claddings in intimate contact substantially throughout their length, and a light pulse detector arranged for receiving light pulses conducted along the receiving fibre.
Specification