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Geometric characterization of offshore sacrificial anodes by ultrasonic FBG sensing using FMCW interferometry.

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Title: Geometric characterization of offshore sacrificial anodes by ultrasonic FBG sensing using FMCW interferometry.
Authors: Fu, Guangwei1,2 (AUTHOR) earl@cust.edu.cn, Zhang, Jiatong2,3 (AUTHOR), Zhang, Tiexin3 (AUTHOR), Xia, Xuetao1,2 (AUTHOR), Jia, Jing1,2 (AUTHOR), Wang, Mengye2 (AUTHOR), Bi, Weihong2 (AUTHOR), Fu, Xinghu3 (AUTHOR)
Source: Optics Communications. Nov2026, Vol. 617, pN.PAG-N.PAG. 1p.
Subjects: Fiber Bragg gratings, Cathodic protection, Interferometry, Ultrasonic imaging, Ultrasonic measurement, Signal processing, Offshore wind power plants
Abstract: Sacrificial Anode Cathodic Protection (SACP) is critical for offshore wind foundations, yet ensuring the real-time integrity of anode materials remains a challenge as traditional monitoring methods are susceptible to electromagnetic interference (EMI) and lack quantitative spatial capabilities. This paper proposes a quasi-distributed monitoring system based on Fiber Bragg Grating (FBG) pulse-echo ultrasound detection, utilizing optical Frequency Modulated Continuous Wave (FMCW) technology to precisely address multiple sensing units via beat frequency mapping. The optimized FBG sensor had a center wavelength of 1549.2 nm, a grating length of 1.2 cm, and a 3 dB bandwidth of 0.1 nm, and was interrogated by a linearly swept Distributed Feedback (DFB) laser operating around 1549.2 nm with a sweep frequency of 50 Hz. Ultrasonic excitation frequencies of 22 kHz and 400 kHz were used for modulation mechanism verification and pulse-echo thickness detection, respectively. A high-overlap sliding Short-Time Fourier Transform (STFT) algorithm was developed to extract 400 kHz ultrasonic echoes with sub-microsecond resolution. Continuous 50-frame stability tests demonstrated a standard deviation of 0.297 mm and a mean relative error of 1.03%. Furthermore, quasi-distributed array reconstruction successfully characterized irregular geometries with a surface area fitting error within 2.7%. Eliminating the need for reference electrodes, this EMI-immune scheme offers a novel quantitative tool for the intelligent O&M of offshore wind structures. • A quasi distributed ultrasonic FBG and optical FMCW system resolves multiunit sacrificial anode addressing. • Optimized 1.2 cm grating length, 0.1 nm bandwidth, and sliding STFT enable 1.03% mean relative error and 0.297 mm SD. • 3D irregular anode morphology is quantified within 2.7% surface area fitting error for EMI immune offshore wind O&M. [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
Description
Abstract:Sacrificial Anode Cathodic Protection (SACP) is critical for offshore wind foundations, yet ensuring the real-time integrity of anode materials remains a challenge as traditional monitoring methods are susceptible to electromagnetic interference (EMI) and lack quantitative spatial capabilities. This paper proposes a quasi-distributed monitoring system based on Fiber Bragg Grating (FBG) pulse-echo ultrasound detection, utilizing optical Frequency Modulated Continuous Wave (FMCW) technology to precisely address multiple sensing units via beat frequency mapping. The optimized FBG sensor had a center wavelength of 1549.2 nm, a grating length of 1.2 cm, and a 3 dB bandwidth of 0.1 nm, and was interrogated by a linearly swept Distributed Feedback (DFB) laser operating around 1549.2 nm with a sweep frequency of 50 Hz. Ultrasonic excitation frequencies of 22 kHz and 400 kHz were used for modulation mechanism verification and pulse-echo thickness detection, respectively. A high-overlap sliding Short-Time Fourier Transform (STFT) algorithm was developed to extract 400 kHz ultrasonic echoes with sub-microsecond resolution. Continuous 50-frame stability tests demonstrated a standard deviation of 0.297 mm and a mean relative error of 1.03%. Furthermore, quasi-distributed array reconstruction successfully characterized irregular geometries with a surface area fitting error within 2.7%. Eliminating the need for reference electrodes, this EMI-immune scheme offers a novel quantitative tool for the intelligent O&M of offshore wind structures. • A quasi distributed ultrasonic FBG and optical FMCW system resolves multiunit sacrificial anode addressing. • Optimized 1.2 cm grating length, 0.1 nm bandwidth, and sliding STFT enable 1.03% mean relative error and 0.297 mm SD. • 3D irregular anode morphology is quantified within 2.7% surface area fitting error for EMI immune offshore wind O&M. [ABSTRACT FROM AUTHOR]
ISSN:00304018
DOI:10.1016/j.optcom.2026.133429