Electric field and voltage sensing using thermally poled silica fibre with a simple low coherence interferometer

The polarization dependence of the linear electro-optic effect in poled silica is used to measure electric fields applied transversely across the fibre core using a simple low coherence interferometer. The path imbalance arising through the inherent birefringence of the poled fibre is modulated by the applied electric field. The interferometer produces a spectral modulation, or interferogram, imposed on the background spectrum of the broadband light source used to illuminate the sensor. The interferograms are then recorded using a spectrometer and the small optical path imbalance is calculated by processing the interferogram in a computer using Fourier transforms. Experimental results for linearity, and an analysis of the methods used are presented.