Harmonic analysis of phase-sensitive optical time-domain reflectometer

Abstract

This study innovatively proposes a method of using harmonics to mitigate the influence of fading noise in Phase-Sensitive Optical Time-Domain Reflectometer (Φ-OTDR). Numerical modeling was conducted to investigate the behavior of the Φ-OTDR. A section optical fiber is coiled around a PZT (piezoelectric transducer). By applying a signal to the PZT, it emulates an external vibration. The response of the simulated vibration was extracted using phase demodulation algorithm. In the response spectrum of the vibration, the fundamental frequency may be submerged because of the fading noise, causing the useful information to be obscured. However, the region impacted by fading noise in the fundamental frequency is unaffected in certain harmonic components. Thus, information from the harmonics can be used to compensate for the missing information in the fundamental frequency. By analyzing multiple harmonic components, the accuracy of vibration detection and localization can be improved. Experiment was performed to corroborate the findings, and the results demonstrated good consistency with the simulated data. Both the simulation and the experiment proved that considering harmonics can enhance the measurement accuracy of Φ-OTDR. This discovery provides new insights and methods for the application of Φ-OTDR.