Open AccessHeated Fiber Optic Distributed Temperature Sensing: A Dual‐Probe Heat‐Pulse Approach
Author(s) -
Benítez-Buelga Javier,
Sayde Chadi,
Rodríguez-Sinobas Leonor,
Selker John S.
Publication year - 2014
Publication title -
vadose zone journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.036
H-Index - 81
ISSN - 1539-1663
DOI - 10.2136/vzj2014.02.0014
Subject(s) - water content , radius , soil thermal properties , range (aeronautics) , thermal , materials science , amplitude , signal (programming language) , environmental science , volumetric heat capacity , heat capacity , optical fiber , fiber , moisture , phase (matter) , temperature measurement , pulse (music) , soil science , mechanics , optics , meteorology , composite material , soil water , computer science , heat transfer , heat flux , thermodynamics , geotechnical engineering , physics , geology , computer security , detector , quantum mechanics , programming language , field capacity
Implementation of the dual‐probe heat‐pulse (DPHP) approach for measurement of volumetric heat capacity ( C ) and water content (θ) with distributed temperature sensing heated fiber optic (FO) systems presents an unprecedented opportunity for environmental monitoring (e.g., simultaneous measurement at thousands of points). We applied uniform heat pulses along a FO cable and monitored the thermal response at adjacent cables. We tested the DPHP method in the laboratory using multiple FO cables at a range of spacings. The amplitude and phase shift in the heat signal with distance was found to be a function of the soil volumetric heat capacity. Estimations of C at a range of moisture contents (θ = 0.09– 0.34 m 3 m −3 ) suggest the feasibility of measurement via responsiveness to the changes in θ, although we observed error with decreasing soil water contents (up to 26% at θ = 0.09 m 3 m −3 ). Optimization will require further models to account for the finite radius and thermal influence of the FO cables. Although the results indicate that the method shows great promise, further study is needed to quantify the effects of soil type, cable spacing, and jacket configurations on accuracy.