Simultaneous AC and DC measurement based on an FBG-magnetostrictivefiber sensor

Simultaneous alternating current (AC) and direct current (DC) measurement is demonstrated with a new fiber sensor that combines fiber Bragg gratings (FBGs) with giant magnetostrictive materials (GMMs). Deformation of GMMs, proportional to the central wavelength shift of FBGs, is different when applying DC and AC to a solenoid where the whole sensing structure is located. DC introduces a constant deformation while AC causes a periodic variation. Therefore, the central wavelength of FBG has a periodic harmonic variation, which makes it possible to demodulate the values of DC and AC at the same time. In addition, the proposed method has potential significance for reducing temperature cross talk caused by the thermal sensitivity of FBGs. The experimental results show that the sensitivity of the AC current can reach up to 0.090576 nm/A in the range of 0 to 1 A, and in different AC environments, the sensitivity of the DC current can reach up to 0.2378 nm/A.