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由于马赫-曾德尔(Mach-Zehnder)光纤干涉传感系统的定位精度在实际应用中受到初始相位偏移的影响,本文针对系统的光路结构,提出了一种基于3×3耦合器的被动数字化解调方法。利用3×3耦合器的2路输出信号构成椭圆曲线,在约束条件下对信号系数进行最小二乘拟合,然后采用微分交叉相乘法解调出相位信号。与传统的解调方法相比,提出的方法降低了对耦合器高对称性的要求,不需限制其它参数;约束条件下椭圆拟合的鲁棒性好,尤其是对于椭圆度较差的数据点具有很强的适应能力,适用于微弱振动信号的解调。仿真结果和现场实验数据证明该方法切实有效,运算量小,利用现场数据解调出的相位信号相关性达到0.992 0;互相关计算显示其在总长43km的管道上的定位误差为81.2m,有效提高了系统性能。
Since Mach-Zehnder fiber-optic interferometric sensing system positioning accuracy is affected by the initial phase shift in practical applications, this paper presents a passive digitalization based on a 3 × 3 coupler for the optical structure of the system. Demodulation method The output signals of 3 × 3 couplers are used to form an elliptic curve, and the signal coefficients are fitted by least squares under constraint conditions. Then the phase signals are demodulated by differential cross multiplication. Compared with the traditional demodulation method, the proposed method reduces the requirement for the high symmetry of the coupler without restricting other parameters. The robustness of the elliptic fitting under the constraint condition is good, especially for the data with poor ovality Point has a strong adaptability for weak vibration signal demodulation. Simulation results and field experimental data show that the proposed method is effective and efficient. The correlation of phase signals demodulated by on-site data reaches 0.992 0. The cross-correlation calculation shows that the positioning error of this method is 81.2 m on a pipeline with a total length of 43 km Improve system performance.