All-fiber vibration sensor based on a Fabry–Perot interferometer and a microstructure beam

We demonstrate an all-fiber sensor for low-frequency vibration measurements. The sensor is based on the configuration of a Fabry–Perot interferometer (FPI), where the first mirror of the FPI is a splice joint between a single-mode fiber and a hollow-core fiber (HCF) and the second mirror is the end face of an etched microstructure support beam inserted into the HCF. The support beam consists of a mass block in the middle and can oscillate freely in the HCF when the sensor is subject to vibration. Our experimental sensor using a 60 mm long support beam with a diameter of 35 μm and a mass block of 2.95×10−8 kg can detect vibrations at frequencies lower than 1 Hz with an acceleration resolution of 8.35×10−7g and a measurement range of ±2.24 g. The sensor output varies by only 2.5% when the temperature changes from 20°C to 120°C. The sensor could be embedded in composite material and find applications in harsh environments.