This paper presents a multi-class support vector machine (MCSVM) based high-efficiency events discrimination method for asymmetric dual Mach-Zehnder interferometers (ADMZI) distributed infrared fiber vibration sensor. This method combined empirical mode decomposition (EMD), kurtosis characteristics with MCSVM, which can improve the recognition rate effectively. Filed experimental results demonstrate that the proposed method can discriminate four common invasive events (climbing the fence, knocking the cable, cutting the fence, and waggling the fence) with an average recognition rate above 90.9%, which can satisfy actual application requirements.
We proposed a gain compensation method to overcome the amplitude fading induced by the gain-bandwidth product (GBP) of the detector, which will seriously deteriorate the positioning accuracy of the distributed disturbance sensor at a long sensing range. To guarantee the performance of this method, we used the time-frequency distribution of the interference signal to distinguish the normal signal and the one need to compensate. A positioning measurement experiment using an asymmetric dual Mach-Zehnder interferometer (ADMZI) was carried out to verify the effectiveness of the proposed method. The experiment result showed that the sensing range can reach 121km, which was improved by over 40% compared to the traditional positioning method without gain compensation.
A novel method to enhance the positioning resolution of distributed disturbance fiber sensor is proposed in this paper. The proposed scheme combines a high speed data acquisition system and a modified time delay estimate algorithm. The sensor performance is significantly improved by eliminating the impact of fluctuation of the interference signal generated by the environment disturbance. Theoretical analysis shows that with the proposed spatial resolution enhanced method, the disturbance sensing system is more suitable for various environments and provides low uncertainty in long term operation with meter-scale spatial resolution. Compared with the traditional time delay estimate method in distributed disturbance sensing system based on the criterion of spatial resolution, the positioning error of the sensor using our proposed method has been reduced at least an order of magnitude.
A novel method to auto-correct the fluctuation of calibration in Raman distributed temperature sensor is proposed in this paper. The proposed scheme combines a fiber coil configuration with a Pt-resistance in the front section to cancel out the impact of fluctuation generated by perturbations of the laser and APD, instability of power supply and environment temperature changes. The sensor performance is significantly improved by exploiting the fiber coil and Pt-resistance to correct the temperature calibration. Our theoretical analysis shows that with the calibration of temperature autocorrection method the sensing system is more suitable for various environments and provides low uncertainty in long term operation, and it has the potential to accurate temperature calibration with simple equipment and to reduce costs of the system.
KEYWORDS: Sensing systems, Error analysis, Signal detection, Signal to noise ratio, Backscatter, Data acquisition, Interferometry, Interference (communication), Interferometers, Polarization
A positioning algorithm for two-wavelength dual Mach-Zehnder interferometry (TDMZI) vibration sensing system is proposed. We employ the reciprocal of the interval between neighboring zero-crossing (NZC) points to represent the frequency distribution of the interference signal in time domain. Meanwhile, these reciprocal points are used to fit a curve and we use cross correlation to estimate the time delay of the two fitted curves. Finally we analysis the positioning error caused by the proposed positioning algorithm and experimentally demonstrate that the algorithm can be used to locating with positioning error of ±50m. This algorithm has a promising potential in long distance two-wavelength vibration sensing system.
KEYWORDS: Correlation function, Super resolution, Sensors, Interferometry, Signal to noise ratio, Fourier transforms, Data acquisition, Zoom lenses, Signal detection, Optoelectronics
A novel positioning algorithm based on super-resolution time delay estimation in dual Mach-Zehnder interferometry disturbance sensor is employed. We first compute the twice correlation function of the two output signal of DMZI by using modified chirp z-transform. Then fine interpolation of correlation peak is adopted to compute waveform of the main correlation peak only using the main segment of the cross power spectrum to improve the resolution of the twice correlation function. At last, in order to enhance the capacity of peak detection, we calculate the difference between the correlation function and its Hilbert transform to sharpen the peak of the correlation function. We have experimentally demonstrated that the proposed positioning algorithm can improve the positioning resolution and accuracy, and it has the potential to accurate positioning in low sampling rate and reduce costs of the system.
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