Study On Distributed Perimeter Intrusion Monitoring System Based On ?-OTDR

With increase of the great economic losses caused by human intrusion of the key areas,importance of perimeter intrusion monitoring for key areas can't be ignored.Traditional perimeter intrusion monitoring methods can't meet the needs of the perimeter intrusion monitoring methods in the complex environment because of its high maintenance cost,low monitoring performance and the disadvantage of not being able to achieve a wide range monitoring.Due to the advantage of high sensitivity and high positioning accuracy,distributed sensing technology based on ?-OTDR has been widely used in the field of perimeter intrusion monitoring.On the basis of building a distributed perimeter intrusion monitoring system,this thesis makes a research on distributed perimeter intrusion monitoring system based on ?-OTDR.The main research work is as follows:(1)It describes the principle of Rayleigh Scattering and the distributed sensing technology based on OTDR.On this basis,the structure and principle of the distributed sensing system based on ?-OTDR is described by constructing the discrete model.Also,the spatial resolution,the frequency response range and the dynamic range of the distributed sensing system are also analyzed.(2)A distributed intrusion monitoring system based on ?-OTDR is built in the laboratory,the principle and the performance of the important instruments and materials used in the system are analyzed.The 9740 meter long Corning fiber is used as the sensing fiber,and a cylindrical PZT which is used as simulated vibration point is wounded by this fiber at the position of about 9610 meter.A sine wave whose frequency is 200 Hz,amplitude is 5V is added to the PZT by the arbitrary function generator in order to simulate vibration.Finally fiber wiring in the laboratory is completed.The pulse width of the SOA is set to be 50 ns,the repetition frequency is set to be 10 kHz,the theoretical spatial resolution of the whole system is 5m,and the maximum frequency response is 5kHz.(3)This thesis firstly uses integrated interface software to realize the control of the three active optical instruments used in the sensing system: NKT laser,SOA and EDFA.Through analysis of the serial communication protocol of the three instruments,the corresponding control code is written and all the codes are made into DLL.The control interface programming based on the MFC by calling the DLL made before and using modular programming method is completed.(4)The noise reduction algorithm based on stack average,moving average and moving difference are analyzed.Besides the signal demodulation algorithm and adaptive mean value threshold algorithm are described.We design a complete vibration point positioning scheme,realize the integration of signal acquisition function and vibration point positioning function.The vibration point positioning in the laboratory is realized.In addition,we also design the scheme of the optical cable's wire,the optical cable line map simulation and the vibration point positioning.Finally,the map module of the vibration point map display and the optical cable's wire are obtained.The results can effectively promote the instrumentation research of the distributed perimeter intrusion monitoring system based on ?-OTDR,It can also provide theoretical and technical support to make the practical,reliable distributed perimeter intrusion monitoring instruments with integrated function.