High-fidelity distributed fiber-optic acoustic sensor with fading noise suppressed and sub-meter spatial resolution

In order to solve fading problem and realize sub-meter spatial resolution in DAS, this paper proposes a novel configuration of time-gated digital optical frequency domain reflectometry (TGD-OFDR) based on optical intensity modulator (IM). IM has a large modulation bandwidth and the positive and negative harmonics can be fully used to suppress fading while the spatial resolution remains unchanged. In experiments, with fading suppressed, the spatial resolution of DAS is 0.8 m and the strain resolution is about 245.6 pε√Hz along the total 9.8-km sensing fiber. The response bandwidth of vibration is 5 kHz, only/limited by the fiber length.