Simultaneous interrogation of interferometric and Bragg grating sensors.

We propose a new method for the simultaneous interrogation of conventional two-beam interferometers and Bragg grating sensors. The technique employs an unbalanced Mach-Zehnder interferometer illuminated by a single low-coherence source, which acts as a wavelength-tunable source for the grating and as a path-matched f ilter for the Fizeau interferometer, thus providing a high phase resolution output for each sensor. The grating sensor demonstrates a dynamic strain resolution of ~0.05 microepsilon/ radicalHz at 20 Hz, while the interferometric phase resolution is better than 1 mrad/ radicalHz at 20 Hz, corresponding to an rms mirror displacement of 0.08 nm.