Simultaneous interrogation of interferometric and Bragg grating sensors

Abstract

A new method for the simultaneous interrogation of conventional two-beam interferometers and Bragg grating sensors is proposed and demonstrated. An unbalanced Mach-Zehnder interferometer illuminated by a low coherence source is used to act as a wavelength tunable source for the grating and as a path matched filter for a Fizeau cavity. The technique gives high phase resolution. The grating sensor gave a dynamic strain resolution of approximately equals 0.05 µ.epsilon/√Hz at 20Hz and the interferometric resolution was better than 1 mrad/√Hz at 20Hz, corresponding to an rms mirror displacement of 0.08nm.