Hilbert–Huang Transform Time-Frequency Analysis in φ -OTDR Distributed Sensor

Time-frequency analysis is a practical method to analyze the characteristics of vibration signals. We introduce the Hilbert–Huang transform (HHT) to the phase-sensitive optical time-domain reflectometer sensor system for time-frequency analysis. The Hilbert spectral analysis makes the instantaneous frequency meaningful, and acquires the high frequency resolution. Compared with other time-frequency analysis methods, such as the short-time Fourier transform and the continuous wavelet transform, HHT presents high frequency resolution for both stationary and nonstationary signals, and with much less time consuming.