Simultaneous Measurement of Strain and Acoustic Emission Using a Passive Homodyne Demodulated Fiber-Optic Sensor
Simultaneous measurement of strain and acoustic emission is often required in fiber optic structural sensing. This is of particular importance in aircraft structural integrity monitoring where weight saving, minimum perturbation, and safety are essential.1 Over the past few years a number of different sensor configurations (with their respective advantages and disadvantages) have been proposed.2 Most of the techniques require either a narrow linewidth laser that is continuously tunable over a wavelength range of about 20nm without mode-hops or a relatively high power broad-band lightsource that has low intensity noise. This paper proposes a technique that uses the standard fiber Michelson interferometer with a 3x3 directional coupler to obtain quadrature outputs and to process the strain and acoustic emission signals in parallel.
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