Sensitivity optimization of fiber sensor based on two FBGs using microwave photonic interrogation technology

Sensitivity optimization of fiber sensor based on two FBGs using microwave photonic interrogation technology is proposed and experimentally demonstrated. Two FBGs are attached on the upper and lower surfaces of a rectangular cantilever beam, which results in wavelength drift in opposite direction with external strain and same direction with temperature. As a result, the crosstalk caused by temperature is efficiently eliminated. The wavelength drift is converted into power variation of electrical signal by adopting the two taps microwave photonic filter response formed by two FBGs system. The effects of the modulation frequency and wavelength of the two FBGs on the system sensitivity are analyzed. In the experiment, the strain on two FBGs is demodulated by measuring the power of the recovered RF signal.