Self-correlation fiber specklegram sensor using volume characteristics of speckle patterns

Tuning of the dynamic range of a micro-displacement fiber specklegram sensor based on two-wave mixing on a photorefractive material Bi ₁₂SiO ₂₀ (BSO) and self-correlation operations of speckle patterns is experimentally demonstrated. The high modal interference present in a standard plastic optical fiber (POF) allows generating a Gaussian pattern of subjective speckle, which is recorded in the volume crystal. The volume characteristics of the fiber speckle are changed using a pupil aperture adjacent to the imaging lens of the speckle. A notorious effect of the three dimensional structure of the speckle on the dynamic range of the metrological system is observed, such that, the performance of the sensor can be improved by a simple mechanical action on the pupil aperture. The behavior of the self-correlation loss of the sensor can be adequately described by a squared normalized Bessel function.