Optical Fiber Chemical Sensor Based on the Analysis of Fiber Specklegrams Characteristics

An optical fiber chemical sensor based on the analysis of the projected specklegram characteristics is presented. The multimode no-core fiber is surrounded by the assessed liquid, causing the modulation of the number of modes and the average speckles size. The sensitivity is improved for external refractive indices close to the fiber index as well as for smaller core diameters, so the sensor response can be tuned by properly choosing the fiber dimensions and material.