Fiber Bragg Grating Dynamic Strain Sensing Technology

Fiber Bragg grating ( FBG) sensor, which uses the property that the Bragg wavelength is sensitive to temperature and strain, is a new kind of fiber optic sensor. In addition to having the same functions as the traditional electric sensors, the FBG sensor also has some special characteristics such as distributed sensing, immune to electromagnetic interference, high precision and long-term stability. So it has widely applicable perspective in many fields such as the structure monitoring of large compound material and concrete, the performance monitoring of the intelligent materials, electrical power industry, medicine industry, chemical engineering et.The main contents are taken as follows:The fundamental theory of the fiber grating is introduced and the spectrum of FBG is analyzed by the coupling-mode theory. The temperature and strain- sensing characteristic of FBG is systematically investigated and the contrast and comparison of current demodulation methods is done.A high dynamic strain resolution FBG sensor system based on temperature controlled filter FBG is designed and established. The reflected light from sensor FBG is modulated by the dynamic strain, and is filtered by temperature controlled FBG. The sensor system measures the transmitted light power and demodulates the dynamic strain. The sensor system is ensured at the best measurement condition with the modulated temperature controlled FBG. And the high dynamic resolution is achieved with the high rate of filter slope of Temperature controlled FBG. The natural vibration of the free beam is researched by the sensor system. The resonant vibration frequency in bandwidth of 1-3200Hz is measured effectively, and the dynamic strainresolution reaches as high as 6.7×10^-10 ε/Hz^1/2. Finally, the experimentresults gained from the FBG sensor system and traditional PZT sensor are companioned.A new project which uses strain FBG sensor as filter FBG is designed to extend the variation range of filter FBG wavelength. The new system is established and the variation range of strain filter FBG and temperature filter FBG are gained. Finally, the results which are analyzed by the FBG sensor theory prove that using strain FBG sensor as filter FBG extend the variation range.