<title>Fiber optic precision position sensor based on reciprocal interferometry</title>

We report a fiber optical nanometer range position sensor based on reciprocal interferometry, a concept of import in interferometric fiber-optic gyroscopes. The configuration resembles a modified Michelson interferometer with only one of the two arms used. The principle of operation is the interference between the reflected light wave from the fiber end and that from a reflective object. As both the reference and the sensing light waves shares the expected interference behavior, which agrees well with its mathematical simulation. A position sensing resolution of about 20 nm, which is limited by the choice of available components, has been demonstrated. The systems immunity to the influence of temperature change has also been verified.