High-spatial-resolution distributed acoustic sensor based on the time-frequency-multiplexing OFDR

We proposed and experimentally demonstrated a high-spatial-resolution distributed acoustic sensor based on time-frequency-multiplexing (TFM) optical frequency domain reflectometry (OFDR). The TFM technique enhances the frequency response of OFDR by multiplexing the time-frequency channels and suppresses the crosstalk in the meantime. Phase demodulation is employed to achieve high sensitivity, and the impact of end effect in OFDR is studied and suppressed by a dedicated linear interpolation. In the results, a 10.5 kHz vibration is measured with 22 cm spatial resolution and 20 dB signal-to-noise ratio on a 1 km fiber. By adjusting the parameters, the system also shows a good DAS performance on a 33 kHz vibration with up to 200 kHz sampling rate.