An Adaptive Reference Scheme to Extend the Functional Range of Optical Backscatter Reflectometry in Extreme Environments

Daniel C. Sweeney; Adrian M. Schrell; Christian M. Petrie

doi:10.1109/JSEN.2020.3013121

An Adaptive Reference Scheme to Extend the Functional Range of Optical Backscatter Reflectometry in Extreme Environments

Daniel C. Sweeney, Adrian M. Schrell, Christian M. Petrie

Research output: Contribution to journal › Article › peer-review

31 Scopus citations

Abstract

Optical frequency domain reflectometry (OFDR) measurements are performed by recording the interference pattern of light backscattered by density fluctuations or Bragg gratings along the length of an optical fiber. Changes in local temperature or strain in the fiber cause shifts in the backscattered light spectrum, which can be calibrated to the applied temperature or strain. Comparing the backscattered optical spectra from each reflection site with a reference (unstrained) spectrum allows for quantification of local spectral shifts. While mature OFDR-based technologies can provide high-precision spatially distributed measurements over kilometer lengths, the post-processing approaches used to recover spectral shifts from raw optical intensity data can limit the use of OFDR in harsh environments. This paper presents a novel approach to post-processing OFDR data which extends the usability of optical fibers exposed to harsh environments. This approach is the first to use the spectral shift quality, calculated for two OFDR measurements, to identify an appropriate reference scan from which the spectral shift can be determined. Three experimental data sets are used to test the algorithm: (1) an optical fiber heated to >950°C, (2) an aluminum-embedded optical fiber under strain from differential thermal expansion, and (3) an optical fiber exposed to a total neutron flux of 2× 1013 n/cm2/s over 40 hours in a nuclear test reactor. Results show that using a metric of quality to select an appropriate reference measurement extends the functional range of OFDR strain and temperature sensors. Furthermore, this algorithm can be applied to existing OFDR data.

Original language	English
Article number	9153138
Pages (from-to)	498-509
Number of pages	12
Journal	IEEE Sensors Journal
Volume	21
Issue number	1
DOIs	https://doi.org/10.1109/JSEN.2020.3013121
State	Published - Jan 1 2021

Funding

Development of the inchworm algorithm was sponsored by the Transformational Challenge Reactor (TCR) Program (https://tcr.ornl.gov/) of the U.S. Department of Energy Office of Nuclear Energy (DOE-NE). Neutron irradiation in the Ohio State University Research Reactor was funded by a Rapid Turnaround Experiment through the DOE-NE Nuclear Science User Facilities Program. The embedding of sensors in aluminum was supported by the Laboratory Directed Research and Development Program at Oak Ridge National Laboratory (ORNL). The authors would like to kindly acknowledge Kelly McCary, Brandon Wilson, and Thomas Blue (Ohio State University, Columbus, OH, USA) for their assistance in acquiring the neutron irradiation data. The embedding of fiber optic sensors was performed by Adam Hehr and Mark Norfolk (Fabrisonic, LLC, Columbus, OH), with input from John Sheridan (Sheridan Solutions, LLC, Saline, MI) and Niyanth Sridharan (ORNL). The U.S. government retains and the publisher, by accepting the article for publication, acknowledges that the U.S. government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for U.S. government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan). Manuscript received June 11, 2020; revised July 27, 2020; accepted July 28, 2020. Date of publication July 30, 2020; date of current version December 4, 2020. This work was supported by the UT-Battelle, LLC with the U.S. Department of Energy (DOE) under Contract DE-AC05-00OR22725. The associate editor coordinating the review of this article and approving it for publication was Dr. Carlos Marques. (Corresponding author: Daniel C. Sweeney.) The authors are with the Oak Ridge National Laboratory, Oak Ridge, TN 37830 USA (e-mail: [email protected]). Digital Object Identifier 10.1109/JSEN.2020.3013121

Keywords

Adaptive methods
Rayleigh backscatter
extreme environments
harsh environments
optical backscatter reflectometry
optical sensors
strain
temperature

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title = "An Adaptive Reference Scheme to Extend the Functional Range of Optical Backscatter Reflectometry in Extreme Environments",

abstract = "Optical frequency domain reflectometry (OFDR) measurements are performed by recording the interference pattern of light backscattered by density fluctuations or Bragg gratings along the length of an optical fiber. Changes in local temperature or strain in the fiber cause shifts in the backscattered light spectrum, which can be calibrated to the applied temperature or strain. Comparing the backscattered optical spectra from each reflection site with a reference (unstrained) spectrum allows for quantification of local spectral shifts. While mature OFDR-based technologies can provide high-precision spatially distributed measurements over kilometer lengths, the post-processing approaches used to recover spectral shifts from raw optical intensity data can limit the use of OFDR in harsh environments. This paper presents a novel approach to post-processing OFDR data which extends the usability of optical fibers exposed to harsh environments. This approach is the first to use the spectral shift quality, calculated for two OFDR measurements, to identify an appropriate reference scan from which the spectral shift can be determined. Three experimental data sets are used to test the algorithm: (1) an optical fiber heated to >950°C, (2) an aluminum-embedded optical fiber under strain from differential thermal expansion, and (3) an optical fiber exposed to a total neutron flux of 2× 1013 n/cm2/s over 40 hours in a nuclear test reactor. Results show that using a metric of quality to select an appropriate reference measurement extends the functional range of OFDR strain and temperature sensors. Furthermore, this algorithm can be applied to existing OFDR data.",

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An Adaptive Reference Scheme to Extend the Functional Range of Optical Backscatter Reflectometry in Extreme Environments

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