Frequency-modulated dual-pulse phase-sensitive optical time-domain reflectometry with direct detection

Abstract

In this paper, frequency-modulated dual-pulse probe is utilized to achieve quantitative demodulation of external vibrations in phase-sensitive optical time-domain reflectometry (Φ-OTDR) with direct detection. In the proposed scheme, only a single acousto-optic modulator (AOM) is required to simultaneously generate the dual-pulse with four different frequencies spacing at 2.5 MHz. In the experiment, the vibrations from 0.1 Hz to 2000 Hz can be successfully recovered with 12.2 m spatial resolution at sampling rate of only 10 MHz. The proposed method is capable of quantitative demodulation of vibrations in wide frequency range, showing potential applications in the area of cost-effective distributed acoustic sensing.