Study On Key Techniques Of Fiber Bragg Grating Displacement Sensoring

Fiber grating is a new optical passive component which can be made novel sensors. It has several distinguished advantages over normal sensors. Fiber grating sensors,which are now widely applied in the fields of the civil and military projects, have been concerned by the researchers worldwide in recent years.The project is from the scientific research fund doctor items (20030056017) of the ministry of education. The main aim of this research was to have a discussion and a basic study on the displacement sensing technique of fiber Bragg grating .The paper aimed at fiber Bragg grating and studied the key technique of the fiber Bragg grating displacement sensoring system. The theory and experiment research on the sensor characteristic, displacement tuning methods, across sensitivity and demodulation technology of fiber grating are processed.The light-wave travel law in the fiber Bragg grating and the sensing model of even cycle fiber Bragg grating was studied in this paper. According to the theory of coupling the cycle transmission characteristic of FBG is deduced. The refective chart of fiber Bragg grating is numeric simulated. The model of strain and temperature sensing and the cross sensitivity of strain and temperature was studied, in addition the phenomenon how to delete across sensitivity is analysed.An isosceles triangle cantilever sensitive construction is designed which can delete the influence of environmental temperature. The cantilever sensitive construction can turn the change of micro-displacement into the strain of the equal intension cantilever. Then the optical measurement of micro-displacement is realized. The novel demodulation method of fiber Bragg grating displacement sensor is proposed which make use of the linearity tune characteristic of the equal intension cantilever. The experiment result shows the sensitivity of the system is1.2 mV /μm.Combining the multiplexing technology, the key technique of the fiber grating displacement sensing system is analysed. The wavelength division multiplexer is adopt to realize the demand of the change of different fiber Bragg grating wavelength. The fiber grating displacement sensing system is built on the demodulation theory of non-balanced Mach-Zehnder interferometer. The controlling and phase measuring system with PIC single-chip is designed. The experimental results of tune characteristic and displacement sensing shows the sensitivity of the system is 4.6 rad /nm and the measuring range exceeds 8mm . The fiber Bragg grating can be used to measure dynamic strain in impact machine system. So a system of dynamic strain measuring system with Fiber Bragg Grating based on the phase generated carrier and unbalanced M-Z interference system was designed, which the cut-off frequency is 10 kHz. The standard sine wave driving measuring experiment and the impact signal measuring experiment were made to validate the system is workable. The prophase research of fiber Bragg grating hydrophone is prepared.