Biaxial Optical Accelerometer Based on Ultra-High Numerical Aperture Fiber

In this paper, we describe the implementation and test of a biaxial optical accelerometer based on fiber Bragg gratings using ultra-high numerical aperture (UHNA) optical fiber. The characteristics of the UHNA optical fiber, such as the decrease of the fiber Bragg gratings reflectivity after the sensor mounting, were compared with the GF1 photosensitive one. The proposed sensor enables to measure acceleration in two orthogonal directions, making it suitable for vibration analysis in electrical machines and structural health monitoring. The initial project was based on finite-element analysis, experimental test, and analytical response, where it was possible to predict the resonant frequency of the mechanical system of approximately 650.00 Hz. After mounting with the optical fiber, the system was characterized allowing the determination of the resonant frequencies in both sensitive directions; the values of 1232.50 Hz and 1272.50 Hz were estimated for the x-axis and the y-axis. This paper enabled to validate the application of the UHNA optical fiber in the development of small sensors and high radius of curvatures, thus providing the motivation for future applications.