3C fiber-optic quasi-distributed acoustic sensing (3C-QDAS)

In the field of acoustic sensing, compared with traditional acoustic sensors, fiber-optic distributed acoustic sensing (DAS) system is a revolutionary technology with many unique capabilities, such as high sensitivity, large sensing scale, real-time dynamic strain detection, excellent compatibility to standard optical fibers. However, DAS is limited by the single-component sensing characteristic of fiber itself, 3-component (3C) DAS technology is still a major challenge to date. 3C-DAS is of great significance to acoustic target tracking aloft and underwater, as well as seismic exploration underground. In this paper, we demonstrate a 3C fiber-optic quasi-distributed acoustic sensing (QDAS) system to detect 3C strains applied to optical fibers, which are mounted on 3C elastomers. 3C strain changes when placing the acoustic source at different positions. We use an ultra-sensitive DAS (uDAS) system with ~5 pε/√Hz strain sensitivity to detect the acoustic field. When the acoustic source is placed 0.5m away from the elastomers, 3C strain detected by uDAS are 5.70 nε, 6.37 nε and 35.88 nε, respectively. The experimental results verify the feasibility of the proposed 3C-QDAS scheme.