Interrogator for Vibration and Shape Mode Sensing Using an Address Fiber Bragg Grating Array

The work presents a concept of interrogator design for microwave-photonic sensor system (MWPSS) for real-time distributed acoustic sensing measurement of vibrations (dynamic mode) and shape (quazi-static mode) in intellectual transport means, for example, wings of aircrafts or truck tires. The proposed MWPSS is based on the addressed fiber Bragg structures (AFBSs), consisting from two symmetrical ultra-narrow fiber Bragg gratings (2λ-FBG) each. Ultra-narrow FBGs have common middle wavelength, equal bandwidths and unique address frequency spacing between them, thus realizing the microwave-photonic interrogation method by means of beating signal detection on address frequencies. This multiplicative optical response analysis allows to define the middle Bragg wavelengths shift of each AFBS in array and to correlate it with the value of the influencing physical fields (vibration and shape deformation). These values of interrogator are input parameters for MWPSS.