Enlarging Dynamic Strain Range in UWFBG Array-Based Φ-OTDR Assisted With Polarization Signal

Abstract

Phase-sensitive optical time-domain reflectometry ( <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) measures the dynamic strain by extracting the phase of the scattering signal. However, the dynamic strain measurement range in conventional <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 is restricted by the phase unwrapping algorithm. In this letter, a new phase unwrapping algorithm, combining the phase and polarization information, is proposed and demonstrated to enlarge the dynamic strain measurement range 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 based on ultra-weak fiber Bragg grating (UWFBG) array. By correcting the phase signal with the assistance of polarization signal, the large dynamic strain can be recovered. In experiments, the dynamic strain measurement range is demonstrated to increase by about three times, which cannot be achieved by the conventional unwrapping algorithm. Further, the proposed method has the potential to achieve a large amplitude range determined by polarization signal and a good sensitivity determined by phase signal at the same time.