The article deals with the exact measurement of wavelength intensities in the vicinity of the frequency of the light source at the output of the polarizing optic fiber sensor. A functional polarizing fiber optic temperature sensor is used as the measuring element, and the frequency variations are induced by a birefringence change in the fiber retaining polarization due to temperature changes. Different speed of light propagation in the two polarization planes of the polarization maintaining optical fiber was used to excite the birefringence. Highly detailed measurements show that the intensity peaks vary depending on the changing temperature of the optical fiber due to the changing birefringence. Thanks to accurate measuring instruments, the dependence between the instantaneous change in the polarization state and the change in the maximum intensity at given wavelengths were observed. The described measurement determines whether wavelength variations may be a suitable alternative to evaluating polarization changes, which in some situations is difficult and costly.
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.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.