Study on the identification of dynamic behavior of beam structure by random access strain histories of Brillouin-based optical fiber sensor

As an accelerometer senses, temporal continuous measurement contains significant structural information to comprehend dynamic behavior. Recent development of optical fiber sensors can allow us to know distributed strain histories. Among the sensors, Brillouin optical correlation domain analysis (BOCDA) shows high signal-to-noise ratio, and thus it has a possibility to make its precision, spatial resolution, and sampling rate higher. These advantages straightforwardly contribute to the estimation of natural frequency and damping ratio of structures by dynamic strain history measurement. In BOCDA, on the other hand, the measured strain distribution profiles are not time-synchronized; therefore, its pitfalls interrupt to calculate a kind of its mode shape. To overcome this obstacle, time-position interpolation is executed to measure on a free oscillation plate test, and compared with synchronized strain gauge results. The results show that the interpolation method enables one to know strain distribution, which stands for vibrating mode, though the frequency of vibrating structure is limited.