Enhancement of Signal Identification and Extraction in a Φ-OTDR Vibration Sensor

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 has been widely used in vibration sensing applications due to its high sensitivity and distributed sensing capability. However, the real vibration behavior is hard to be distinguished from ambient interferences by conventional Φ-OTDR, since the responses to simultaneous behaviors are nonlinearly added together. Fortunately, if we focus on the phase information of backscattered light, it would be much easier to obtain the accurate vibration signal and separate different intrusions, due to the linear strain–phase response. Based on this technique, we present a vibration separation method by analyzing the time difference between two fiber positions in this paper. A proof of principle experiment is designed and implemented, and double vibrations influencing the same fiber zone are identified and extracted, which demonstrates the improvement of signal identification in the Φ-OTDR system.