Research on Signal Processing in φ-OTDR System Based on Single Frequency IIR Trap

In the traditional phase sensitive optical time domain reflectometer (φ-OTDR) system, after locating of the vibration source, the spectrum diagram of the vibration signal can be obtained through the non-uniform Discrete Fourier Transform (NDFT) by extracting the data at this position. However, spectral aliasing noise included in the spectrum of the obtained vibration signal at this time. Because spectrum aliasing noise is generated in the process of NDFT transformation, traditional noise reduction methods have little effect on it. Therefore, this paper proposes a kind of IIR notch device based on single frequency for use in φ-OTDR. The change of standard deviation in discrete frequency domain is used to locate the vibration source, the large frequency components are filtered out from the time domain to solve the small signal components. The performance of IIR notch filter is verified by simulation. The results show that the notch filter can be used to calculate the small signal components of non-uniformly sampled signals successfully. It is convenient for φ-OTDR to use time-frequency images of different vibration types to identify vibration signals, so as to improve the recognition efficiency and monitoring ability of the system. (paper)