SIMULTANEOUS INTERROGATION OF INTERFEROMETRIC AND BRAGG GRATING SENSORS

We propose a new method for the simultaneous interrogation of conventi onal two-beam interferometers and Bragg grating sensors. The technique employs an unbalanced Mach-Zehnder interferometer illuminated by a si ngle low-coherence source, which acts as a wavelength-tunable source f or the grating and as a path-matched filter for the Fizeau interferome ter, thus providing a high phase resolution output for each sensor. Th e grating sensor demonstrates a dynamic strain resolution of similar t o 0.05 mu epsilon/root Hz at 20 Hz, while the interferometric phase re solution is better than 1 mrad/root Hz at 20 Hz, corresponding to an r ms mirror displacement of 0.08 nm.