Fiber‐Optic Sensing for Environmental Applications: Where We Have Come From and What Is Possible

Abstract

The use of fiber‐optic sensors has flourished in many fields over the past 30 years. One particular branch of fiber‐optic sensing, distributed temperature sensing, has become a well‐explored and widely‐accepted tool for a diverse range of environmental applications over the past decade. Peer‐reviewed work on fiber‐optic distributed temperature sensing advanced significantly, moving from innovations in instrumentation, deployment techniques, calibration, and analysis methods to applications. However, exciting advancements in other branches of fiber optics, such as fiber Bragg gratings, optical frequency domain reflectometry, and distributed acoustic sensing, have thus far been underutilized in environmental studies and await exploitation by environmental scientists. These additional techniques offer immense possibilities for novel applications in hydrology, hydrogeology, geophysics, and other environment fields where high‐accuracy, high‐frequency, and/or high spatial resolution measurements are needed.

Deformation‐Based Monitoring of Water Migration in Rocks Using Distributed Fiber Optic Strain Sensing: A Laboratory Study

“…This study suggested that distributed strain sensing, as an emerging application of fiber optic sensing (Shanafield et al, 2018), has the potential to provide not only geomechanical information, which gives critical constraints in geomechanical risk assessments of subsurface fluid injection and extraction operations (Burghardt, 2018) and landslides (Kogure & Okuda, 2018), but also unique insights into the hydromechanical link between fluid flow and rock deformation. The information derived from such monitoring may 10.1029/2019WR024795…”

Beyond Classical Observations in Hydrogeology: The Advantages of Including Exchange Flux, Temperature, Tracer Concentration, Residence Time, and Soil Moisture Observations in Groundwater Model Calibration

“…Recent advances in airborne and fiber optic (FO) techniques have enabled distributed temperature sensing (DTS). In the case of FO‐based DTS, for example, temperature changes can be recorded continuously in space and in time (Shanafield et al, ; Vogt et al, ). Temperature measured with airborne hyperspectral and near‐infrared cameras, on the other hand, allows for the generation of detailed maps of surface temperature, albeit at lower temporal resolution than with FO‐DTS (Cardenas et al, ).…”

A Comparison of Different Methods to Estimate the Effective Spatial Resolution of FO-DTS Measurements Achieved during Sandbox Experiments

“…Over the last decade, the ability of this tool in hydrology has been widely demonstrated [3], especially for soil moisture determination [4,5], surface waters monitoring [6,7], hydrogeological applications [8], and at the groundwater-surface water interface [9][10][11]. In a commentary, Shanafield et al highlighted the increase of environmental application of DTS and identified around 500 peer-reviewed articles published in hydrologic applications in seven years [12].…”

“…Thus, DTS instrument manufacturers define the specifications of each DTS device, including the minimum sampling interval and the spatial resolution. For Raman spectra DTS, the highest performing devices can provide a 0.125 m sampling interval with a 0.29 m spatial resolution, whereas some devices provide a 2 m sampling interval with a 4 m spatial resolution [12,15].…”

“…In environmental sciences, and especially in geosciences, FO-DTS technology has been widely applied considering its ability to monitor spatial and temporal temperature changes with a high-accuracy [12,18]. The value of the spatial resolution controls partly the ability of the user to detect local temperature variations, and the choice of the DTS device depends on the application and on the scale of temperature contrast [17].…”