Method of precise sensing channel positioning forϕ-OTDR-based DAS

Abstract

For the applications of distributed acoustic sensing technology (DAS), such as leakage detection in a pipeline, it is important to precisely identify the sensing channels along a optic fiber to correctly locate the vibrations and improve the accuracy of DAS. A method of precise sensing channel positioning for DAS is proposed. An experimental validation is conducted in consideration of optic fiber types and soil types. A bending element was inserted into the sand and clay to excite the constant-frequency signals point by point along the optic fiber. A DAS interrogator was used to collect the vibrations of the fiber. The average of the normalized time-domain signals and the amplitude of the specific constant frequency in the frequency domain are analyzed. The parameters of the skewness of the amplitude-channel curve (SACC) and the relative shift of the amplitude peak (RSAP) are proposed to identify the boundary of the adjacent sensing channels. The accuracy of the sensing channel positioning is better than the spacing of the excitation points.