Homodyne interferometric displacement measurement using multimode fiber speckles

Abstract

A homodyne optical fiber interferometer was constructed for measurement of thedisplacement of a moving object at the accuracy of a half wavelength of He-Ne laser. Speckles in the far-field image of the fiber end, representing guided modes of the multimode fiber, were utilized to sense the direction of movement of the target as well as its velocity. The displacement of a vibrating voice coil driven by sinusoidal and triangular wave currents was measured.