The Research Of Fiber Optic Accelerometer Based On Modal Interference

Fiber optic accelerometers have the advantages of immunity to electromagnetic interference, resistance to harsh environments, small size, and easy reuse networking, so they have good application prospects in these fields, such as seismic monitoring, intruder detection, aerospace and so on. Combined the current status of fiber optic accelerometers, two kinds of fiber optic accelerometers based on modal interferometer are proposed, and the theoretical analysis and experimental research are carried out for fiber optic accelerometer. The main contents are as follows:In the first chapter, based on the analysis and research of modal interference technology and the current of fiber optic accelerometers, significance and innovation of the paper are expounded.In the second chapter, from the viewpoint of modal interference principle and mechanical sensing mechanism, fiber optic accelerometers proposed in the paper are analyzed. The function formula between excitation acceleration and the output voltage of the fiber-optic accelerometer and the resonant frequency formula are derivated in detail, and the influence of the relevant parameters on the performance of fiber optic accelerometer is analyzed by numerical simulation.The third chapter studies a fiber optic accelerometer based on modal interference. By misaligned splicing a short section of thin-core fiber between two sections of single-core fiber, modal interference can be achieved. The experimental results show that the fiber optic accelerometer has a minimum detectable acceleration of 3.3mg and the resonance frequency is 1451 Hz.In forth chapter, a cantilever fiber-optic accelerometer based on the reflection of silver film is designed. By misaligned splicing a short section of single-mode fiber, which a silver diaphragm is coated at the end face of fiber used as reflecting mirror, modal interference can be achieved. Secondly, the performance of fiber optic accelerometer is tested, and the influence of offset distance on the fiber optic accelerometer is analyzed. The results show that the minimum detectable acceleration and the resonance frequency are 1.36mg and 520Hz, respectively. Besides, the angle between the direction of the fiber dislocation and the plane of vibration impacted on the cantilever fiber-optic accelerometer is analyzed. The results show that the accelerometer has a angle dependence. The frequency response curves are similar to cosine function, which shows good directionality, and the difference between the maximum and minimum output intensity can be up to 18dB.In the fifth chapter, we summarize the work of the first two chapters, the experimental results indicate the feasibility of the fiber-optic accelerometer system for acceleration measurement. Besides, we discuss the shortcomings of the paper, and put forward some suggestions on the further works.