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. (c) 2023 Optica Publishing Group