Research On Key Technologies Of Dual Mach-Zehnder Distributed Vibration Sensing System

On the basis of the speed requirements of distributed vibration sensing for security monitoring field, we researched some key factors in-depth for affecting the positioning accuracy of dual Mach-Zehnder interferometry (DMZI) vibration sensing system, including birefringence of signal-mode fiber, light source frequency fluctuations and linewidth broadening and environment noise, et al. And on the basis of the practical requirements of fence perimeter security, we intensive study the intrusion event discrimination technology. Based on the above studies, we proposed an efficiently polarization control method, a positioning algorithm with high precision and a feasible intrusion event discrimination method, so as to pave the way for the instrumentation and engineering implementation of DMZI.The innovative work of the paper includes:1. Theoretically analysize the error of the correlation time delay estimation, when considering the light source noise, polarization noise and environment noise, and made a conclusion that error of correlation time delay estimation inversely proportional to the signal bandwidth and signal-to-noise ratio. And point out that due to the influence of the environment noise, the output noise of DMZI strongly correlated, then affects the performance of the correlation time delay estimation.2. We proposed an improved polarization control method to reduce Polarization-Induced Phase Shift (PIPS) and Polarization-Induced fading (PIF) in DMZI vibration sensing system. Compared with the traditional polarization control method based on visibility, both the visibility and the synchronization of the signals are taken into account in this method, which can minimize the influence of positioning error induced by polarization effect. The optimizing search of the method is based on an improved chaotic particle swarm optimization algorithm (CPSO), which can greatly enhance the effectiveness and performance of the optimizing search.3. On the basis of issue that the positioning error is affected by the correlated noise in the noise environment, we proposed an improved positioning algorithm for DMZI vibration sensing system. We employ zero-crossing method which can be computed easily to extract the disturbance signal segment with maximum zero-crossing rate. Meanwhile, we use general cross correlation based on Wiener filtering and Gnn subtraction weighting function (WG-GCC) to estimate the time delay of the extracted signal, which is robust to the correlated noise. Finally we experimentally demonstrate that the proposed positioning algorithm can greatly improve the positioning accuracy with positioning error of ±20m. Compared with the traditional positioning algorithm, the positioning error has been reduced by an order of magnitude. This algorithm has a promising potential in real-time fence perimeter applications.4. On the basis of the requirements of safety protection, we developed a DMZI vibration system and realize the design and program of the system software. The DMZI vibration system, video surveillance system and access control system are fused, a hybrid intelligent perimeter security monitoring network is formd.