Discriminating Interference Fading Locations in Φ-OTDR Using Improved Density Clustering Algorithm

The phase-sensitive optical time-domain reflectometer (Φ-OTDR) system is a distributed optical fiber sensing technology capable of measuring weak vibration signals in real time. However, while the use of a narrow-linewidth laser source enhances the system's sensitivity, the accompanying high coherence introduces an inherent drawback: fading noise. This phenomenon can lead to significant phase demodulation distortion, severely compromising the system's reliability. Consequently, interference fading represents a fundamental challenge in Φ-OTDR systems. We propose an optimized density clustering algorithm, termed adaptive principal component analysis DBSCAN++ (AP-DBSCAN). The procedure begins by identifying fading regions based on the fading principle. Subsequently, AP-DBSCAN integrates the K-distance to adaptively determine parameters, and incorporates PCA technology and the DBSCAN++ algorithm to efficiently and accurately distinguish fading points within these regions. Finally, the compromised data points are reconstructed using a nearest-neighbor interpolation method. Experimental results demonstrate the superior performance of the proposed method over DBSCAN, FDBSCAN, and DBSCAN++. Our approach achieves adaptive determination of the eps and Minpts parameters, maintaining a high fading-point detection accuracy of 99.92% while significantly improving computational efficiency by 67.33% to 76.29%.