Measurement of Corrosion and Temperature Using a Single-Pitch Bragg Grating Fiber Sensor

Abstract

A new 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 transducer, and the section without a metal coating can be used as a temperature sensor. After releasing the preloading, the two Bragg wavelengths reflecting from the Bragg grating are sufficiently separated and have no cross-talk problems between the corrosion and temperature signals. The principle of corrosion sensors is that environmental corrosion changes the coating thickness; consequently, the residual strain inside the section with a metal coating is released and then causes a Bragg wavelength shift. Since the temperature variation is obtained from the free section, the temperature effect in the Bragg grating corrosion sensor can be measured and compensated. Two analytical methods for the Bragg grating corrosion sensor are developed and they are in good agreement. Also, experimental data shows that Bragg grating corrosion sensors are feasible for a quantitative analysis.