Ultrasensitivity Steel Surface Corrosion Noncontacted Monitoring Based on a Mismatching Fused Mach–Zehnder Interferometric Fiber Sensor

This paper presents a novel mismatching fused Mach-Zehnder interferometer (MFMZI) for noncontacted steel corrosion monitoring in real time. Without sputtering or contacting any steel film on the surface of the MFMZI, the corrosion rate of the steel bars can be evaluated with ultrasensitivity even when the concentration of the NaCl solution is only 0.05 wt%. Moreover, simulations have been carried out with variations in the water-based solution to understand the sensitivity response as a function of the effective refractive index (RI). The simulation and experimental results reveal that the sensitivity is up to 10372 nm/RIU, and the speeds of the wavelength shift in 0.05 wt%, 0.1 wt% and 0.2 wt% NaCl solutions are 0.08, 0.12 and 0.17 nm/min under the dynamic corrosion process, respectively.