Highly Sensitive Strain and Vibration Sensors Based on the Microfiber Sagnac Interferometer

In the field of structural health monitoring, it has been pursued to achieve large-range and high-sensitivity strain and vibration measurements. This article proposes a sensor based on an optical microfiber coupler (OMC) and a Sagnac ring to achieve large-range and high-sensitivity strain and vibration measurements. The sensor takes advantage of the high sensitivity of the evanescent field around the OMC and the high tensile resistance of the Sagnac ring. This article analyzes the strain and vibration sensing mechanism, simulates the mode distribution in the OMC, and presents an experimental setup. The experimental results demonstrate that the sensor can achieve strain measurement with a sensitivity of $- 9.11\,\,\text {pm}/\mu \varepsilon $ in the range of 0– $4500 \mu \varepsilon $ and vibration measurement at 0.5 Hz–5 kHz. The proposed sensor provides potential technical support for the fields of structural health monitoring and fault diagnosis.