Abstract

The principle of using a bifurcated fiber bundle to measure mechanical distances and displacements has been known since the 1960s. In this configuration, the two legs of the fiber bundle are connected to a light emitter and a photodetector. A reflecting surface at a distance d from the common end of the bundle couples light from fibers leading from the emitter to fibers leading to the photodetector. The coupling between the fibers is determined by the overlap of the acceptance cones at the reflecting surface. Theoretical calculations show that for small d, compared with the single-fiber diameter a, the coupling varies with d^3/2 and increases with the numerical aperture.

© 1981 Optical Society of America