High sensitivity fiber sensor for measurement of Cd²⁺ concentration in aqueous solution based on reflective...

We propose a novel fiber chemical sensing system based on reflective Mach-Zehnder interference with temperature calibration for the measurement of Cd²⁺ in aqueous solution. The sensing system has high measurement sensitivity of Cd²⁺ with an estimated minimum detection limit of 4×10^-7 mol/L at a spectral resolution of 0.02 nm and with long-term stability. The fiber sensing head is prepared by coating a sensing membrane on a fused tapering single-mode fiber. The thiourea group of the sensing membrane has an effective combination effect on Cd²⁺. Disturbance from ambient temperature fluctuation on the measurement of Cd²⁺ concentration can be eliminated with the fiber Bragg grating.