Ultra-Compact Optical Fiber Strain Sensor Based On Mach-Zehnder Interference

With the rapid development of society and economy,the normal work of large-scale engineering structure has become an important factor restricting the stable development of society.Strain is an important parameter in the safety assessment of engineering structures.It is very important to detect and evaluate the strain in real-time for a long time.Compared with traditional electronic sensors,optical fiber sensors stand out because of their strong anti-electromagnetic interference capability,small structure,strong reusability and large transmission capacity.In this type of structure,the Mach-Zehnder interferometer has become people's research focus because of its compact structure,cost-effective and other advantages.This thesis designed an ultra-compact optical fiber strain sensor based on Mach-Zehnder interference,introduced the manufacturing process and test system of the sensor.The specific research contents are as follows:An ultra-compact fiber optic strain sensor based on Mach-Zehnder interference is designed in this paper.It is a sandwich fiber sensor composed of an air cavity formed by two steps:(1)splicing together a single mode fiber and a photonic crystal fiber to form a spherical air-cavity;(2)tapering the air-cavity.The mathematical model of all-fiber Mach-Zehnder interferometer is established.Based on the basic model,the interference fringes and the electric field distribution of each part of the interferometer are simulated by FDTD Solutions.In this thesis,the transmission process of optical signal in air cavity is analyzed,and the cavity configuration and other factors on the performance of interferometer are studied.The relationship between the interference fringe wavelength and the strain of strain sensor is simulated and investigated,and the strain sensitivity at different wavelength is also discussed.The simulation results show that the strain sensitivity at different wavelengths is different,and the strain sensitivities at wavelengths of 1530 nm and 1550 nm are 0.76 pm/??and 1.01 pm/??,respectively.The processing technology of Mach-Zehnder strain sensor is studied.According to the actual process preparation level,the process flow is formulated.The sensor is made,and an experimental testing platform is built to test the performance of Mach-Zehnder strain sensor.This system is used to measure the strain of the sensor.Its strain sensing characteristics is discussed..The experimental results show that a strain sensor with an air cavity length of274.5 ?m is fabricated with a sensitivity of 0.39 pm/??.