Study And Design Of General Demodulation System For Fiber F-P Sensor And FBG Sensor

In the health monitoring of structures, Fiber optical sensor has been used widely due to its good performance. Fiber Bragg grating (FBG), one of the fiber optical sensors, is often needed owe to its wavelength-decoded characteristic and multiplexing ability. While fiber Fabry Perot (F-P) sensor is also utilized as the advantages of high measurement accuracy, low cost and insensitivity of temperature fluctuation. However, the demodulation unit can only demodulate FBG or F-P sensor at present. In many practical complicated sensing systems, fiber F-P sensor and FBG sensor are both needed. Therefore, in order to reduce the using cost, enhance system's integrated lever and reliability. A set of general demodulation system for FBG and F-P is demanded.In this paper, the general demodulation principle of fiber F-P sensor and FBG sensor is analyzed, and the emphasis of study is decided according to the shortage of foregone research. The main work of this thesis includes:(l)The parameter of tunable fiber F-P filter (the core component of demodulated system) is analyzed, including the influence of transmission bandwidth and Free Spectrum Range of filter, then its main parameters are decided. The necessity and deficiency of setting wavelength reference to the influence by nonideal performance of tunable fiber F-P filter, the principle of increasing demodulation precision by double wavelength reference is analyzed theoretically.(2)The function of present evaluated system is improved, and human-computer interface, date transmission circuit is designed with DSP and MCS as its controlling core.(3)The software design including date acquisition, date processing, human-computer interface, date transmission and HPI communication module is done with its emphasis on fiber F-P sensor's demodulation software through analysis of functional module of system.(4)Demodulation experiment is done using fiber F-P sensor and FBG sensor respectively, the results are as following: The choosing tunable fiber F-P filter can meet the requirement of system; the demodulation system achieves the predicted purpose with faster demodulated speed and better stability, and its demodulation precision is improved clearly by using double wavelength reference and DGT algorithm.