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As a new type of sensing element, fiber Bragg grating (FBG) has advantages of wavelength modulation, hightemperature resistance, and anti-electromagnetic interference. In this paper, a medium-frequency FBG accelerometer based on a symmetrical double-semicircle cantilever is designed and fabricated. In the sensor, the double-semicircle cantilever acts as the elastic element. FBG is suspended and pasted on the double-semicircle cantilever by its two ends. When the sensor is subjected to the external vibration, the free end of the double-semicircle cantilever will vibrate under the action of inertial force. Correspondingly, the FBG is driven to produce axial strain. The structure and working principle of the sensor are well illustrated, the natural frequency and sensitivity of the sensor are analyzed as well. In order to verify the dynamic sensing characteristic of the sensor, some experiments are performed. Experimental results show that the natural frequency of the sensor is 410 Hz, the working frequency range is 50~300Hz, and the average acceleration sensitivity is almost 133pm/g. In the range of working frequency, FBG wavelength has a good response to the vibration acceleration, and the linearity is better than 99%. Research indicates that the proposed FBG accelerometer can be used to measure the vibration acceleration of 50 ~ 300Hz with higher sensitivity, and the sensor has the merits of small size, light mass, high sensitivity, wide working band and easy fabrication, which makes it a good candidate for acceleration measurement.
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