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In this review, we summarize the latest advances in the design of optical frequency-domain reflectometers (OFDRs), digital signal processing, and sensors based on special optical fibers. We discuss state-of-the-art approaches to improving metrological characteristics, such as spatial resolution, SNR, dynamic range, and the accuracy of determining back reflection coefficients. We also analyze the latest achievements in the OFDR-based sensors: the accuracy of spatial localization of the impact, the error in detecting temperatures, deformation, and other quantities, and the features of separate measurement of various physical quantities. We also pay attention to the trend of mutual integration of frequency-domain optical reflectometry methods with time-domain optical reflectometry, which provides completely new sensing possibilities. We believe that this review may be useful to engineers and scientists focused on developing a lab setup, complete measurement instrument, or sensing system with specific requirements.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC11359119 | PMC |
http://dx.doi.org/10.3390/s24165432 | DOI Listing |
Sensors (Basel)
August 2025
Petroleum Engineering Department, Colorado School of Mines, Golden, CO 80401, USA.
This study investigates the performance of Distributed Acoustic Sensing (DAS) for detecting gas pipeline leaks under controlled experimental conditions, using multiple fiber cable types deployed both internally and externally. A 21 m steel pipeline with a 1 m test section was configured to simulate leakage scenarios with varying leak sizes (¼", ½", ¾", and 1"), orientations (top, side, bottom), and flow velocities (2-18 m/s). Experiments were conducted under two installation conditions: a supported pipeline mounted on tripods, and a buried pipeline laid on the ground and covered with sand.
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August 2025
School of Civil and Transportation Engineering, Shenzhen University, Shenzhen 518060, China.
Due to the slender geometry and low-amplitude vibrations of stayed cables, existing vision-based methods often fail to accurately identify their full-field dynamic parameters, especially the higher-order modes. This paper proposes a novel holographic vision-based method to accurately identify the high-order full-field dynamic parameters and estimate the tension of the stayed cables. Particularly, a full-field optical flow tracking algorithm is proposed to obtain the full-field dynamic displacement information of the stayed cable by tracking the changes in the optical flow field of the continuous motion signal spectral components of holographic feature points.
View Article and Find Full Text PDFLarge-scale strain (i.e., large strain in wide-range optical fiber) distorts distance referencing in spectrum-based optical frequency-domain reflectometry (OFDR), resulting in severe position segment mismatches and degraded accuracy.
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August 2025
NanoLund and Solid State Physics, Lund University, S-22100 Lund, Sweden.
We report a Mueller matrix ellipsometer design using dual continuously rotating anisotropic meta wave plates, which determines the full set of Mueller matrix elements in the terahertz spectral range. The instrument operates in the frequency domain and employs a frequency tunable, solid state synthesizer based, continuous wave terahertz source with sub-MHz bandwidth. The implemented source permits operation within 82-125 and 170-250 GHz, without and with an additional frequency doubler, respectively.
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