Study Of Demodulation Project For Optic Fibre Hydrophone Based On FPGA

Since the fibre optic hydrophone came into being, it had turned from the laboratory state to the engineering application state for the reason of the huge value for the military affairs application and civil application. At the same time, the incessant development of the fiber optic hydrophone demands for high ability of underwater acoustic signal check technology and digital signal processing. Based on this background, a lot of researches have been made and a new scheme, 3×3 coupler demodulation project which is based on FPGA(Field Programmable Gate Array) ,has been brought forward.Nowadays, among the signal demodulation projects for the fibre optic hydrophone, the commonly used are PGC demodulation project based on DSP and 3×3 coupler demodulation project based on FPGA. Considering the demodulation project, the PGC demodulation imported carrier wave signal during its demodulation process, so it needs for high level sampling rate and laser instrument. So we turned our eyes to the latter. In this thesis, the demodulation theory is expressed, how to confirm the sampling rate is discussed, and that the three outputs of the interferometer are unsymmetry completely is analyzed. At the end of the thesis's conclusion, the mending method is put forward.The hardware for the fibre signal digital demodulation usually is DSP(Digital Signal Processing)signal processor. Compared with DSP, FPGA has some advantages such as high speed, engrossing less resource and easy to expand etc. In this thesis, the DSP, FPGA and ASIC projects are compared, the characteristic which the arithmetic implementation fit for using FPGA should have is analyzed, how to design each module of the 3×3 coupler demodulation project is introduced, the system's working state ,the construction of the hardware and the choice of the chips are analyzed. At last the feasibility of using FPGA to implement the 3×3 coupler demodulation arithmetic is validated.