Demodulation of polarimetric optical fibre sensors by dispersive Fourier transform spectroscopy

Abstract

We describe an interrogation technique for polarimetric optical fibre sensors, based on the measurement of the differential group delay between the eigenmodes of the birefringent sensing element by tandem interferometry using a low-coherence source. Measurement of the group delay has the advantage of avoiding the 2π rad ambiguity inherent in the phase measurement. This differential group delay is strongly dispersive, inhibiting measurement using central fringe identification. We measure the delay by dispersive Fourier transform spectroscopy, thus avoiding the errors introduced by dispersion. We demonstrate the application of this technique to temperature and strain measurement.