Optical fiber specklegram sensor analysis by speckle pattern division

An optical fiber specklegram sensor interrogation method based on speckle pattern fragmentation is presented. The acquired specklegram images are divided in a square grid, creating sub-images that are further processed by a correlation technique, allowing the quantification of localized changes in the specklegrams. The methodology was tested on the assessment of linear displacements using a microbending transducer, by evaluating different grid sizes. For a 5 x 5 grid, a 2.53 mm(-1) sensitivity over a 0.27 mm range was obtained, representing an extension of 237.5% in comparison to the standard interrogation technique. Therefore, the presented technique allows enhancing the sensor dynamic range without modifying the experimental setup. (C) 2017 Optical Society of America