MEMS Chip-Based Miniaturized Fiber-Optic Fabry–Pérot Sensor for Highly-Sensitive and Wide-Band Acceleration Detection

Fiber-optic Fabry-Perot (FP) sensor has the advantages of small structural size, high sensitivity, and immunity to electromagnetic interference, which has been widely used in acceleration detection. However, due to the fact that the acceleration sensing structure is mainly based on the mass inertia model, this leads to a mutual constraint between the natural frequency and sensitivity of the sensor. Therefore, it is difficult for fiber-optic FP accelerometers to achieve both wide operating frequency band and high sensitivity simultaneously. In this work, we propose and demonstrate a wide-band and highly-sensitive optical accelerometer based on dual cascaded spring resonators, which is microfabricated by Micro Electro Mechanical Systems (MEMS) technique. Its unique in-plane vibration mode is used to expand the operating frequency band of the sensor, and two different structures of cascaded spring resonator accelerometers are combined to compensate for frequency loss caused by resonance peaks. The entire MEMS chip exhibits a uniform thickness of 300μm, greatly simplifying silicon microfabrication and improving process yield. The experimental results show that the flat response range of the sensor is 1 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\sim$</tex-math></inline-formula> 1780 Hz, and the detection sensitivity is 11.55 dB re rad/g, which is nearly 16 dB higher than the sensitivity of traditional same frequency band accelerometers. The minimum detectable acceleration of the sensor is 2.23 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mu \rm {g}/$</tex-math></inline-formula>√Hz@10Hz, 409 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\rm {ng}/$</tex-math></inline-formula>√Hz@100Hz and 359 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\rm {ng}/$</tex-math></inline-formula>√Hz@1kHz. The overall crosstalk is less than 1.33 %. These excellent performances demonstrate that it is an ideal solution for detecting wideband and weak vibration signals.