Study On The Diaphragm-based Optical Fiber EFPI Sensor

Diaphragm-based optical fiber EFPI sensor, with advantages of high sensitivity, corrosion resistant, immunity to electromagnetic interference and long distance access, has been widely used in industrial applications such as the liquid level monitoring for large oil tanks. In this dissertation, systematic and intensively study on the theory, manufacturing methods and applications in liquid level monitoring of the diaphragm-based optical fiber EFPI sensor are presented. The main research works are summarized as followings:Several common materials and varieties of manufacturing methods for the diaphragm-based optical fiber EFPI sensor are discussed. In addition, the sensor's performance with different materials and manufacturing methods is studied and analyzed. Based on above analysis, an all fused silica structure and the laser-induced fusion bonding method is proposed for manufacturing the diaphragm-based optical fiber EFPI sensor.A carbon dioxide laser-based sensor manufacturing system is deigned and implemented. An all fused silica diaphragm-based optical fiber EFPI pressure sensor is fabricated with this manufacturing system. A pressure test system is set up and the sensors'static pressure sensing performance is tested. Experimental results show that, in the measurement range of 0-50KPa, the pressure sensitivity of the diaphragm-based optical fiber EFPI sensor is 5.3nm/KPa. The resolution of the sensor is 36.58pm, corresponding to a pressure resolution of 6.9Pa.The temperature dependence of the diaphragm-based optical fiber EFPI pressure sensor is studied. A temperature dependence test system is set up and the sensors'temperature dependence is evaluated. Experimental results show that, the temperature dependence of the epoxy based pressure sensor is 3.3nm/℃, while the temperature dependence of the laser bonding based pressure sensor is 0.37nm/℃. For the laser bonding based sensor, the pressure measurement error caused by the temperature is 69.8Pa/℃, which is one ninth of the epoxy based one.The result shows that this kind of diaphragm-based optical fiber EFPI pressure sensor has great potential in liquid level monitoring.