Reducing Recovery Signal Distortion of the $\phi$-OTDR Based on 3×3 Coupler Demodulation Using Ellipse Fitting Algorithm

• DOI: 10.1109/jlt.2023.3331378
• Publication Date: 2023-11-09T13:59:26Z
• Authors: Xiang Zhong; Hanyu Cao; Yu Sun; Huaxia Deng; Xiaoshan Chen; Jie Ren; Mengchao Ma; Liang Huang
• Keywords: Distortion (music); Ellipse

3 × coupler demodulation method is widely used in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\phi$</tex-math></inline-formula> -OTDR because of its large dynamic range, high response bandwidth and simple structure. However, when the undergoes a severe amplitude and/or phase mismatch practical applications, results would produce distortions may lead to nuisance alarms static conditions. For this deficiency, Ellipse Fitting Algorithm (EFA) two-path Differential Cross Multiply (DCM) algorithm are proposed paper. EFA calculates characteristic parameters outputs based on least square method, then generates two corrected orthogonal waveforms that provided DCM for demodulation. The experimental show EFA-DCM can improve signal-to-noise ratio by up 31.74 dB compared three-path 14.19 improved we before. Furthermore, under measurement conditions, reduce induced 87%. These significantly recovery signal distortion alarms, further promote wide application method.