Optical fiber vibration sensor for bearing fault detection based on Sagnac interferometer

Bearings are crucial components in mechanical equipment, and bearing failure is one of the reasons for mechanical equipment safety accidents. In this work, an optical fiber vibration sensor based on Sagnac interferometer (SI) is proposed and applied to bearing fault detection. The polarization-maintaining fiber (PMF) is spliced between two single-mode fibers (SMFs) to form a SMF-PMF-SMF (SPS) fiber structure, which is connected with a 3 dB coupler to form a SI based on SPS fiber structure. The mass block is fixed in the middle of the PMF. When the monitored surface or structure vibrates, the stress of PMF will change and the Sagnac interference spectrum will be shifted, so that the vibration can be measured. The fabrication technology of sensor based on 3D printing is studied, and the structural parameters of the sensor are optimized through experiments and theoretical analysis. A vibration detection system and a rolling bearing vibration test platform based on SI and fiber ring laser are built. The experimental results show that the relative error between the experimental and theoretical results of healthy and faulty bearings is less than 1.60%, and the fault detection of bearings is realized. Temperature cross-sensitivity and stability of the sensing system are analyzed. The sensor has the advantages of simple structure, easy fabrication, anti-interference, etc, and has wide application prospects in engineering, machinery, security and other fields.