Wide Measurement Range Distributed Strain Sensing With Phase-Accumulation Optical Frequency Domain Reflectometry

Abstract

In this paper, a wide measurement range strain sensing method based on phase-accumulation optical frequency domain reflectometry (OFDR) is proposed. Different from the traditional phase demodulation method that analyzes the relative phase between the measurement signal and the reference signal, we achieve large measurement range strain sensing by accumulating the relative phases of adjacent scanning cycles. The proposal can break through the limitation of phase unwrapping in the traditional phase method, and realize the low measurement error in the accumulation process. In the experiments, when the wavelength scanning range is only 0.138 nm, we achieve quasi-static strain measurement with a spatial resolution of 1.8 cm, a maximum strain value of about 14000 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μϵ</i> , and the noise level of about 0.601 rad representing the strain resolution of 0.48 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μϵ.</i> We also analyze the influence of random noise on the method, and verify the good robustness of the phase accumulation method. The research of this paper provides a useful reference for the development of low-cost OFDR system for distributed strain/temperature measurement.