Vibration Sensor Based on Fiber Optic Sagnac Structure

In this work, we build a vibration sensing system based on the Sagnac structure. The sensor is based on the Sagnac interference structure and by changing the cavity length of the Fabry-Perot (F-P) sensor point, so the interference spectrum is blueshifted, which causes the change of light intensity at the wavelength of 1550 nm. The sensing system detects vibration frequency by converting changes in light intensity into voltage variations through a photoelectric converter, and then processes the vibration signal using frequency domain analysis. The accuracy of this frequency detection is verified using a frequency-tunable vibration source. The ability of the sensing system to detect changes in the amplitude of the vibration signals was verified through impact experiments on the same metallic iron at different energies. The vibration frequency of different metals under the same impacts is proved by the experiments that the vibration frequency of the same metal is proved to be able to overcome the influence of a certain amount of noise in the practical application. Based on the above experimental results, it is proved that the vibration sensor based on the Sagnac structure has good performance in the detection of vibration frequency and vibration amplitude.