Research On Key Technologies Of High-precision Accelerometer Based On Short-cavity DBR Fiber Laser

With the development of technology and manufacture, sensing technology has made great progress in both theory and application, and various types of sensors based on the optical fiber structures become the research hotspot in the sensing field. As an important class of fiber sensors, optical fiber accelerometer is mainly used for measurement of vibration acceleration, related to many areas of modern industrial production. Owing to the unique excellent performances including high precision, immune to electromagnetic interference, suitable for long distance transmission and easy to multiplexing,it is widely used in some specific areas, such as aerospace, mine monitoring, warning of geological disasters, and building structure monitoring, etc.Aiming at the application requirement of high precision optical fiber accelerometer, two kinds of accelerometers based on short-cavity distributed Bragg reflector(DBR) fiber laser are designed and manufactured in this thesis. By converting the vibration acceleration signal into the beat frequency signal of the output orthogonal polarized light of the laser, sensing demodulation becomes more simple and reliable. Consequently, high sensitive and precision acceleration measurement is achieved in experiment.The main work is as follows:(1) Based on the mode coupling theory of fiber Bragg gratings, the operating characteristics and sensing mechanism of the short cavity DBR fiber laser are analyzed theoretically. Then, the fabrication process of the short cavity DBR fiber laser is studied and implemented, and the performances of several samples are tested.(2) The mechanical model of the accelerometer is analyzed. A short-cavity DBR fiber laser based accelerometer is proposed by using the transducer of the spring-mass structure. The sensing theory is analyzed and the structural parameter of the transducer is designed. Then the sensing performance is tested on the micro-vibration platform. The sensitivity of the sensor for low frequency vibration signal could reach to 35.0MHz/g.(3) In order to make the sensor head miniaturization and lightweight, the structure of the accelerometer is further improved. An short-cavity DBR fiber laser based accelerometer with the cantilever beam structure is proposed. The theoretical analysis shows that the cantilever structure can effectively amplify the mechanical effect caused by micro-vibration. Through structural parameter design and optimization, the accelerometer sample is developed. The field experimental results demonstrate that the acceleration sensitivity of the sensor is significantly increased to 1.4202GHz/g within the 100 Hz to 250 Hz frequency response band.(4) Finally, the work is summarized, and the further optimization of the sensor is discussed.