The birefringence of optic fiber is sensitive to external physical changes. This produces an undesirable effect of reducing fringe visibility for an interferometer made up of ordinary single-mode fibers. In this work, we actively modulate the reference arm of a Mach-Zehnder interferometer with a PZT drum. Force sensing is achieved by measuring the visibility of the fringes produced with respect to the force applied to a portion of the sensing arm. Ordinary single-mode fiber is used and no expensive polarization components are necessary. In addition, the visibility measurement is not sensitive to the ambient temperature fluctuation and no additional control measures are necessary to eliminate the effect of thermal drift.
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