Study on High Temperature Resistant Packaging of Ultra High Temperature Fabry–Perot Optical Fibre Vibration Sensor

Thermal stress failure is the bottleneck that is restricting the development of ultra-high temperature sensors, and reliable packaging is crucial in their development process. In this paper, a two-step packaging structure was proposed for the high temperature resistant failure packaging challenges of the ultra-high temperature Fabry–Perot optical fibre vibration sensor. First, a high temperature resistant AlN base was selected according to thermal simulation. A reliable bond between the AlN base and the 6H-SiC vibration-sensitive element was designed, which could effectively avoid the failure of thermomechanical stress adaptation during drastic temperature change. In addition, a high temperature resistant ZrO
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support tube with a length of 20 cm, an outer diameter of 16 mm, and an inner diameter of 12 mm was designed as the optical fibre lead-out support structure by using finite element simulation and optimisation. Moreover, the influence of fastening fixtures on the sensor mode was analysed. The simulated first-order resonance frequency of the sensor was 2644.9 Hz, while the actual measurement was 2620 Hz. The difference was only 0.9%. Finally, the validity of the design was verified by experiments, and the sensor achieved reliable operation at 1200 °C.