Development of corrosion sensors using a single-pitch Bragg grating fiber with temperature compensations

A simple method to measure metal corrosion using a single-pitch Bragg grating sensor is presented. The prestrained Bragg grating that is only partially coated with a metal can be designed as a corrosion sensor, and the section without coating can be used as a temperature sensor for compensations. After releasing the preloading, the residual stress inside the section with a metal coating can be used to predict the corrosion. Consequently, the two Bragg wavelengths reflecting from the corrosion sensor are separated and have no cross-talk problem in corrosion and temperature signals. The principle of corrosion sensors is that environmental corrosion will result in a thinner thickness on coating, of course, the residual strain will release and cause a Bragg wavelength shifting. Therefore, after the temperature variation is obtained from the free section, the environmental corrosion can be determined according to the released residual strain on the Bragg grating fiber. Two analytical models for corrosion sensors are developed and they are in good agreements. Also, experimental data shows that corrosion Bragg grating sensors are feasible for quantitative analysis.