Defensive perimeter detection by polarization change of the fibre optic signal
2019
The accurate measurement of temperature changes is the key skill not only for predictions of various natural phenomena or to detect intrusion of the object. The temperature changes we nowadays measure in local climate zones or Urban Heat Islands. The environmental quality is an essential feature of life quality and to improve it serve many remote sensing-based urban planning indicators, which are the common part of present smart cities. Continuously developing fibre optic sensors allow their benefits to be exploited in more and more applications. Defensive Perimeter Detection by Polarization Change of the Fiber Optic Signal offers an effective possibility to detect quickly and in time disturbing a predefined space. This detection system uses the polarizing properties of light and, in particular, the birefringence of optical fibres. The disclosed detection system focuses on temperature changes that may be caused by external or internal disruption of the site. The main detection equipment is the polarization maintaining optical fibre with the same excitation in both polarization axes. The transmission rate in both axes is in the ideal case the same, but due to birefringence, inhomogeneity, and imperfection of production and next causes the mutual delay of both signals causes the signal polarization state change or even the series of polarization states changes, which can be observed in laboratory conditions and described by known mathematical methods. However, these changes can be transformed by linear polarizer to the intensity changes. This conversion allows the changes significantly easier to evaluate.
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