A novel point-to-point length measurement concept based on range-resolved interferometry

In many fields of research and high-value industry, the estimation of distances and
displacements is crucial. Due to their extremely high spatial resolution and flexible application possibilities interferometers are cross-sectorally used in measurement practice. However, classical length measuring interferometers are subject to two residual restrictions. On the one hand, only displacements that are exactly aligned to the interferometer optical axis can be measured. On the other hand, deviating refractive indices in the measuring and reference arm due to different atmospheric conditions represent an accuracy-limiting disturbance. In this paper, a new interferometric concept for length measurement is presented. The concept is based on the range-resolved interferometry technology which enables the simultaneous readout and evaluation of two symmetrical interferometric signals which result from the superposition of two non-collimated spherical wavefronts. This allows a point-to-point measurement between two optical fiber ends and the separation of undesired changes of the optical path length outside the measurement cavity and within the measurement cavity.