We offer a complete range of fiber optic based intrusion detection systems for protection and pipeline security that offer Long range – up to 80km of sensor optical path length for some systems.
OPTICAL fiber intrusion detection systems have been extensively studied over the last 20 years , especially for their widely usage in security monitoring of railway assets, oil / gas pipelines, homeland, etc. Up to now, the distributed intrusion event could be detected and located mainly by two kinds of structures: the interferometric systems and backscattering systems.
The interferometric systems
The most common tool in interferometry, the Michelson Interferometer was invented by Albert Abraham Michelson in 1887, the first American to win a Nobel Prize for science. He came up with a system of mirrors and semi-transparent mirrors (beamsplitters) for merging separated beams of light, which are coming from the same source. Laser interferometry is a well-established method for measuring distances with great accuracy.
Typically a single incoming beam of coherent light source will be split into two identical beams by a Michelson interferometer. Each of these beams travels a different route, called a path, and they are recombined before arriving at a detector. The difference in the distance travelled by each beam creates a phase difference between them.
Backscattering systems
The backscattering method is also employed in fiber optics applications to detect optical faults. Light propagating through a fiber optic cable gradually attenuates due to Rayleigh scattering. Faults are thus detected by monitoring the variation of part of the Rayleigh backscattered light. Since the backscattered light attenuates exponentially as it travels along the optical fiber cable, the attenuation characteristic is represented in a logarithmic scale graph. If the slope of the graph is steep, then power loss is high. If the slope is gentle, then optical fiber has a satisfactory loss characteristic.
The loss measurement by the backscattering method allows measurement of a fiber optic cable at one end without cutting the optical fiber hence it can be conveniently used for the construction and maintenance of optical fibers.
