Magnetic field strength measurement using tailored dispersion characteristics of phase-shifted fibre Bragg gratings

Orr, Philip and Niewczas, Pawel and Stevenson, Michael and Canning, John (2010) Magnetic field strength measurement using tailored dispersion characteristics of phase-shifted fibre Bragg gratings. In: Fourth European Workshop on Optical Fibre Sensors, 2010-09-08 - 2010-09-10.

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Abstract

Magneto-optical activity giving rise to circular birefringence and Faraday rotation is not usually an appropriate basis for point measurement of magnetic field strength, acting as it must over extended lengths. In this paper we report on investigations into the dispersion characteristics of structured fibre Bragg gratings for the purposes of implementing novel polarimetric point sensors. Phase-shifts inscribed along the grating profile introduce windows in transmission that correspond to highly resonant wavelengths undergoing large group delay. We demonstrate through fabrication of structured gratings that their dispersion characteristics can be tailored, producing regions of spectrally co-located reflection and large group delay. Importantly, it is shown how a number of such regions can contribute to a single enhanced group delay in reflection. Through simulation we discuss the potential for implementing polarimetric magnetic field sensors which operate in reflection.