Development of FBG probes for dimensional metrology with micro parts of high aspect ratio

The development is described of fiber Bragg grating (FBG) probes with single or four cores using spheres fixed onto optical fibers comprising Bragg gratings in their cores. Simulations and preliminary experiments were conducted to evaluate the performance of these FBG probes for dimensional metrology with micro parts of high aspect ratio. Simulation and experimental results indicate that a one-dimensional FBG probe with single core can be used to achieve an axial resolution of 100 nm at an aspect ratio of 15:1. A three-dimensional FBG probe with four cores can be used to achieve a theoretical axial resolution as high as that of a FBG probe with single core, with a capability of decoupling two-dimensional radial displacements with a resolution of 13 nm.