Scientific Applications of Distributed Acoustic Sensing: State-of-the-Art Review and Perspective

Abstract

This work presents a detailed review of the development of distributed acoustic sensors (DAS) and their newest scientific applications. It covers most areas of human activities, such as the engineering, material, and humanitarian sciences, geophysics, culture, biology, and applied mechanics. It also provides the theoretical basis for most well-known DAS techniques and unveils the features that characterize each particular group of applications. After providing a summary of research achievements, the paper develops an initial perspective of the future work and determines the most promising DAS technologies that should be improved.

Keywords: distributed acoustic sensing (DAS); fiber optic sensors; optical reflectometry.

Figure 1

An illustration of a ϕ-OTDR sensor operation. Here $E_1$ and $E_2$ are the probe pulse and backscattering field amplitudes; $I_1$, $T$, and $W$ are the pulse’s peak power, duration, and period; $x$ is the coordinate along the sensing fiber, $\rho \left(x\right)$ is the relative reflectivity of the Rayleigh backscattering centers distributed along the fiber length.

Figure 2

Typical time behavior of the simulated backscattered signal $$I_D\left(t_D\right)$$. The distribution of the reflection centers $\rho \left(x\right)$ is calculated as a delta-correlated Gaussian stochastic process with zero mean, for simplicity $\alpha \left(x\right)=0$ is taken.

Figure 3

The sensitivity factor $K\left(t_D\right)$ (a) and its probability distribution (b) simulated for the case shown in Figure 1.

Figure 4

Scheme of a generic FBG-assisted DAS setup and theoretical power levels of reflected signals from a single FBG pair (FBG_N and FBG_N+1). L—distance between the FBGs. W—the interrogator pulse width.

Figure 5

Schematic representation of multi-reflection crosstalk for an example case when a single-pulse reflectometer interrogates equally spaced FBGs. Possible 3-reflection and 5-reflection paths are superposed on the target signal from FBG₈.

Figure 6

Schematic diagram of the DAS system for pipeline protection. Adapted from [83].

Figure 7

Optical scheme of the OFDR for absolute measurements. EDFA—Erbium-doped fiber amplifier, PD—photodiode. Adapted from [84].

Figure 8

Sensing cable configuration for the measurement of the distance between the cable and the impact source. Adapted from [85].

Figure 9

Schematic representation of the experimental setup for EOM-facilitated heterodyning measurements. The Allan variance and signal-to-noise ratio of Φ-OTDR signal can be determined for the same laser under test. Adapted from [88].

Figure 10

Rayleigh backscatter of a train ride. The peaks from 30 to 48 s represent wheel pairs passing a sensor point. Original obtained data.

Figure 11

The used DAS-system (a) and the locations of accelerometers and strain gauges on the surface of the wing (b) for the verification of flutter frequencies. Adapted from [106].

Figure 12

Fiber amid the stirrups. Adapted from [108].

Figure 13

Scheme of a ϕ-OTDR sensor installation for window monitoring. Adapted from [110].

Figure 14

Schematic diagram of the distributed liquid level sensor based on the φ-OTDR system. SEP—scattering enhanced points, SEOF—scattering enhanced optical fiber. Adapted from [112].

Figure 15

Schematic configuration of the all-fiber homodyne Mach–Zehnder interferometer and acoustic test bench. AE waves—acoustic emission waves, PC—personal computer. Adapted from [113].

Figure 16

Longitudinal and shear waves in an optical fiber. Adapted from [122].

Figure 17

Schematic of the sensor system. PD stands for photodetector, FBG—fiber Bragg grating, EDFA—Erbium-doped fiber amplifier, SMF—single-mode fiber, AOM—acoustic optical modulator. Adapted from [153].

Figure 18

Typical spectra of sounds produced by 12-day old weevil larvae. Adapted from [153].

Figure 19

Detection of the 190 g weight dropping from the 41.5 cm height in a conditioning chamber at −70 degrees Celsius. Adapted from [157].

Figure 20

(a) Schematic representation of the optical fiber telecom cable used for this study; (b) Thunder quake detected. Adapted from [138]. The more precise colors are available in the reference paper.

Figure 21

(a) Plants from the test group; (b) Plants from the control group. Adapted from [164]. See the photo in the reference paper.

Figure 22

A spectrum of a picked acoustic guitar D3 string: recorded simultaneously with a FBG sensor, piezoelectric pickup, and condenser microphone. Adapted from [167].

Figure 23

The excitation–emission matrix spectrum illustrates the feedback of the guitar’s soundboard to distortion from a speaker at different excitation frequencies. The color scale bar ranges from −220 to −180 dB. Adapted from [168]. The precise colors are available in the reference paper.

Figure 24

Schematic of the experimental setup. LW—linewidth, Mod—modulator, FUT—fiber under test, BPD—balanced photodetector, MIMO—multiple input multiple outputs. Adapted from [176].

Figure 25

Blue line—the original signal of the human voice, saying “Bonjour,” brown color—the detected phase. The waveform is repeated by the review authors, please find the original waveform in [176].

Figure 26

(a) Distortion spectrum before resampling; (b) Undesired sampling period variations; (c) Distortion spectrum after resampling; (d) Spectrum of a sinusoidal 41 kHz localized perturbation; (e) Spectrum of a 12.3 m long 50 kHz sinusoidal distortion. Adapted from [177]. The precise colors are available in the reference paper.