Large-range phase-difference sensing technology for low-frequency strain interrogation
Jinhui Shi, Dong Guang, Shili Li, Xuqiang Wu, Cheng Zuo, Lei Gui, Wujun Zhang, Guosheng Zhang, Qiang Ge, Gang Zhang, Rui Wang, Benli Yu
Abstract
Phase-difference sensing technology (PDST) has been applied to strain measurement, but its completeness is destroyed by the phase-difference measurement range. A scheme that can realize the completeness of the PDST for low-frequency strain interrogation is proposed. It is built on dual-interferometers and the elliptic-fitting algorithm. To break the measurement range limitation (0, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mi>π</mml:mi> </mml:math> ), a phase compensation setting is applied. The experimental results demonstrate that the method can obtain low-frequency strain signals, and the low-frequency signal whose phase amplitude is greater than <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mi>π</mml:mi> </mml:math> is recovered. The scheme is an efficient and complete method for measuring the strain of low-frequency optical fiber length, which could be applied to low-frequency seismic wave monitoring and rock deformation detection.