POCKELS AND KERR EFFECT INVESTIGATION IN FIBRE BRAGG GRATINGS

Branislav Korenko - Jozef Jasenek - Jozefa Červeňová

   The paper deals with linear electro–optical Pockels effect and quadrature electro–optical Kerr effect investigation inside the fibre Bragg gratings (FBG) structures. Due to lateral electric fields applied to optical fibre (OF) or FBG structure disturbances o f refractive index in silica fibre occur. In our paper we bring a deep investigation of Pockels and Kerr effects utilization in context of semi distributed optical fibre sensors based on FBG. With advanced optical measuring methods like Optical Frequency Domain Refle ctometry (OFDR) such disturbances could be localized and investigated. Trough spectral analysis of reflectivity or transmission characteristics of FBG one can detect wavelength shifting which corresponds to the measured electric field. If the transform mechanism like electro–optical effect is known, one can simply implement the transformation of measured field into the refractive index change. By combination with reflectivity or transmission a model of simple FBG sensor for electric or magnetic fields c ould be obtained. Designing a structure with semi distributed OF sensors provides the possibility to measure electric fields in more dimensional manner. Also a real time measurement is possible. The advantage of using OF sensors with semi distributed parameters instead of those using conventional methods is that only the access to one end of the fibre is needed and it is also possible to measure more dimensional structures with point space resolution. Also such OF sensors could be applied in environments with radiation, with explosion hazard or labs with electro static sensitive devices. The usage of conventional sensors needs to create a complicated monitoring net structure with multiple sensors. The wiring of each sensor requires multiplexing and data processing. From the point of realization it is economically more demanding and also more complicated.

Keywords: fibre Bragg gratings, Pockels effect, Kerr effect, electro-optical effect

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