Fiber-optic interferometric strain gauge producing asymmetric fringes by using nonlinear feedback

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 fringes under fiber strain. The dependence of the theoretically predicted fringe asymmetry on feedback gain is verified experimentally. Elimination of the fringe counting directional ambiguity via differentiation of the asymmetric closed loop interference signal is demonstrated for the first time.<
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