Multi-axis modulated compact fiber-based Fabry-Perot interferometric probe.

This paper presents design and operation of a multi-axis optical probe for independently measuring the relative displacements of external surfaces. Displacement is measured by mechanically modulating the optical cavity formed by an internal surface and the external surfaces, each of which comprise a Fabry-Perot interferometer. Multiple sensing axes are created using a beam splitter, and these sensing axes are separated by modulating the measurement paths at different frequencies.