Unambiguous sawtooth fringe counting for an active homodyne demodulated interferometric strain gauge

Source wavelength modulation by feedback of the interference signal of an unbalanced fiber-optic Michelson interferometer to the driver of the semiconductor laser source gives rise to sawtooth-shaped fringe's under fiber strain. The fringe asymmetry is utilized for elimination of the fringe counting directional ambiguity via differentiation of the closed-loop interference signal. Initial results of quantitative strain measurements agree reasonably well with the readout of a resistive strain gauge as well as with the theoretically predicted sensitivity.<
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