Miniaturization and evaluation of fiber-optic probes for low-coherence interferometry

Low-coherence interferometry (LCI) is air established metrological technique, that has proven its capability to measure both fast and highly accurate. To provide these advantages for the measurement inside small spaces like bore holes or micro-tubes, the design of a miniaturized probe tip is necessary. The use of fiber optics fulfills the requirements for the realization of flexible and small probes, which are it the same time suitable for low-coherence interferometry. In this work the development of miniaturized probes in all-fiber design for the use in a, 110 system is described, which consists of a, modified Michelson interferometer with non-moving optical elements. Beam shaping is achieved by the use of graded-index fibers. Thus sensor tip diameters can be reduced down to 125 mu m for bare fiber design. Furthermore, validation measurements for the combination of probe head and LCI system are presented, that prove the potential and limitations of all-fiber probes for LCI. Conclusively air outlook for potential fields of application is given.