Closed Micro-fiber Fabry-perot Sensor Strain Characteristics

Ever since the appreance of fiber sensor, it has become a rapid development of fiber passive device industry and attracted lots of attention due to its high realibility, immunity to electromagnetic interference, capacity of multiplexing, low attenuation and long distance transmission. Among various fiber sensors, fiber Fabry-Perot (F-P) interferometer is one of the most mature fiber sensors, widely used in a large number of applications, shows great potential in sensing field. As significant efforts been exerted to fabricate small, light, and high-temperature-resistant sensors and sensors which could work in flammable environment, the microstructure sensor has become one of the hot research spots.A novel self-closed micro-fiber F-P sensor was proposed by our project team under the guidance of Pro. Yunjiang Rao in 2006, and was successfully fabricated by a 157nm excimer laser on the end face of fiber. This dissertation is based on the self-closed fiber F-P sensor, its basic strain property was studied and its applications were explored. The main work and accomplishments are as follow1. The 157nm excimer laser micro-machining technique and the process of fabricating self-closed micro-fiber F-P sensor were described. And the basic strain property of this sensor in the range of 0με-2000μεunder room temperature, and temperature property in the range of -50℃-50℃were studied. The experiment result showed the novel structure fiber F-P sensor employed good strain linear response (linearity of 0.9985) and insensitivity to temperature (sensitivity of 0.001nm/℃). It could be used as a regular strain sensor, applied in healthy monitoring of large buildings such as high way, bridge and dam.2. Based on the strain property obtained from room temperature experiment, high-temperature-strain property of elf-closed micro-fiber F-P sensor was further studied and a combined sensor cascaded by Long Period Fiber Grating (LPFG) and it was proposed. The experiment demonstrated that the combined sensor could not only conduct precise strain measurement under high temperature (eg.650℃) and also could solve the long lasting problem of single fiber sensor as the thermal strain induced by temperature change for the strain sensor can be derectly compensated via the LPFG nearby. It could be used as a sensor for simultaneous high-temperature and strain measurement, applied in health monitoring of engines, aeronautics test of aircrafts and airplanes, and production process monitoring of composite materials.3. The quasi-static strain property of the self-closed micro-fiber F-P sensor was studied and was in comparison with strain gauge. The experiment indicated the self-closed micro-fiber F-P sensor outperformed traditional strain gauge in aspects such as immunity to electromagnetic interference and micro strain measurement. Meanwhile, demodulation system for dynamic strain signal was studied. The experiment results showed self-calibration dual channel intensity demodulation system could be used to develop simple, low cost, miniature, reliable and sensitive detecting systems.