Research On High-speed Data Acquisition And Real-time Processing Of Fiber Optic Hydrophone System

Since the fiber optic hydrophone has been invited, it changed from the laboratory state to the engineer application state for the huge value of military application and civil application. Large scale fiber optic hydrophones array brings the high requirement of signal processing. At present, it has been proven that web-based modular architecture could meet the various requests of large-scale fiber hydrophone array.In the various methods of fiber optic hydrophone signal detection, PGC (Phase Generated Carrier) modulation and demodulation technique has been the principal method because of its advantages such as large dynamic range, broad band, the capability of detecting microradian signal, etc. In most fiber optic hydrophone array systems which are based on all kinds of multiplexing, PGC demodulation technique is also the principal signal detect method.In the context of specific projects, this paper proposed parameter request for the high-speed data acquisition and real-time processing based on the work and demodulation principles of interferometric hydrophone. For the characteristics of narrow optical pulse signal, large of array data and high real time, a method is introduced with high speed ADC +FPGA+DSP+MPC8347 for data acquisition and real-time processing based on the basic hydrophone system scheme, In the design program, ADC converts analog signal to digital signal quickly and the DSP takes charge of processing signals aquired in time. The FPGA concentrates the timing control circuit and dispersive component into an independent circuit block. Because it can not only reduce print area, but also advance reliability of the system. It is suitable for mini-type high-speed data acquisition system. After complex calculation of the PGC demodulation, DSP gains the phase information of each hydrophone element. Then it is brought into a Gigabit Ethernet interface of the MPC8347 through FPGA. The MPC8347 finish the phase information and send it through Ethernet data into a computer store and follow-up of the acoustic signal processing. This system relates complex signal processing, data synchronization and so on.With regard to hardware design, this paper discusses the circuit of the analog-to-digital converting, the control circuit based on FPGA(field programmable gate arrays), the FIFO(first in first out) buffer circuit, SDRAM (synchronous dynamic random access memory) and FLASH memory circuit, DSP circuit module, Gigabit Ethernet output modules and so on. Furthermore, the key parts in each circuit module were introduced in detail.In signal processing, the development of DSP software based on CCS, the flow chart of the main program and bootstrap guide of the system are given. The demultiplexing of signals was analyzed. It was simulated for signal filtering and extraction and carrier phase delay with MATLAB.