Force measurement by visibility modulated fiber optic sensor

The birefringence of optic fiber is sensitive to external physical changes. This produces an undesirable effect of reducing fringe visibility for an i nterferometer made up of ordinary single-mode fibers. In this work, we acti vely 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 componen ts are necessary. In addition, the visibility measurement is not sensitive to the ambient temperature fluctuation and no additional control measures a re necessary to eliminate the effect of thermal drift.