Interference Phenomena in Fraunhofer Holograms and in Their Reconstructions of Tapered Glass Fibers

Fraunhofer holograms and their reconstructions show interference fringes when applied to tapered glass fibers, which do not occur with opaque fibers. The fringes are shown to be quantitatively related to fiber profile. The phase lag of fiber transmitted light is recorded as identifiable hologram fringes by interference with fiber-diffracted light. This also results in fringes in the reconstructed image. One fringe of both types, for a fiber refractive index n, represents a diameter change lambda/(n-1). Shape changes along a fiber not directly resolved by the optics are measurable. Profile measurement of attenuating glass fibers in the continuous filament process is described.