Cascade long-period grating structure for Cr (III) and Cr (VI) detection in water environment

This works shows a fiber grating optical sensor that can be used to detect the presence of Cr (III) and Cr (VI) oxidation states in water solutions. The sensing device is a set of two in-series long period gratings produced in a standard telecommunication optical fiber by applying a suitable number of point-to-point electrical arc discharge from a fusion splicer. In order to analyze the Cr (III) and Cr (VI) solutions, the sensing device is kept into a recipient under constant longitudinal stress and temperature, and the chromium solution samples are added to it. In the range of concentrations analyzed (from 0.32 to 2.6 mg/I), the results show that is possible to distinguish between the two-oxidation states.