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Search Results (3)

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Keywords = weak fiber Bragg gratings (WFBG)

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8 pages, 3258 KiB  
Article
High-Spatial-Resolution High-Accuracy OFDR Distributed Sensors Based on Seamless fs-WFBG Array
by Zhengze Jin, Wenzhu Huang, Yuanjing Zhao and Wentao Zhang
Photonics 2025, 12(4), 352; https://doi.org/10.3390/photonics12040352 - 8 Apr 2025
Viewed by 399
Abstract
In optical frequency domain reflectometry (OFDR), the random optical noise in Rayleigh backscattering and the sliding window length in the algorithm cause a trade-off between sensing spatial resolution and accuracy. This paper proposes a novel high-spatial-resolution high-accuracy OFDR distributed sensor based on a [...] Read more.
In optical frequency domain reflectometry (OFDR), the random optical noise in Rayleigh backscattering and the sliding window length in the algorithm cause a trade-off between sensing spatial resolution and accuracy. This paper proposes a novel high-spatial-resolution high-accuracy OFDR distributed sensor based on a seamless femtosecond weak fiber Bragg grating (WFBG) array. Using femtosecond laser point-by-point (PbP) inscription technology, a 5 cm long seamless weak grating array was successfully fabricated on a polyimide fiber, consisting of ten 5 mm long WFBGs. The experimental results demonstrate that a sensing spatial resolution of 533 μm and a wavelength demodulation accuracy of ±2.05 pm were achieved for the first time. Full article
(This article belongs to the Special Issue Recent Advances and Applications in Optical Fiber Sensing)
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18 pages, 7020 KiB  
Article
Instability Compensation of Recording Interferometer in Phase-Sensitive OTDR
by Konstantin V. Stepanov, Andrey A. Zhirnov, Tatyana V. Gritsenko, Roman I. Khan, Kirill I. Koshelev, Cesare Svelto and Alexey B. Pnev
Sensors 2024, 24(11), 3338; https://doi.org/10.3390/s24113338 - 23 May 2024
Cited by 1 | Viewed by 1818
Abstract
In the paper, a new method of phase measurement error suppression in a phase-sensitive optical time domain reflectometer is proposed and experimentally proved. The main causes of phase measurement errors are identified and considered, such as the influence of the recording interferometer instabilities [...] Read more.
In the paper, a new method of phase measurement error suppression in a phase-sensitive optical time domain reflectometer is proposed and experimentally proved. The main causes of phase measurement errors are identified and considered, such as the influence of the recording interferometer instabilities and laser wavelength instability, which can cause inaccuracies in phase unwrapping. The use of a Mach–Zender interferometer made by 3 × 3 fiber couplers is proposed and tested to provide insensitivity to the recording interferometer and laser source instabilities. It is shown that using all three available photodetectors of the interferometer, instead of just one pair, achieves significantly better accuracy in the phase unwrapping. A novel compensation scheme for accurate phase measurements in a phase-sensitive optical time domain reflectometer is proposed, and a comparison of the measurement signals with or without such compensation is shown and discussed. The proposed method, using three photodetectors, allows for very good compensation of the phase measurement errors arising from common-mode noise from the interferometer and laser source, providing a significant improvement in signal detection. In addition, the method allows the tracking of slow temperature changes in the monitored fiber/object, which is not obtainable when using a simple low-pass filter for phase unwrapping error reduction, as is customary in several systems of this kind. Full article
(This article belongs to the Special Issue Feature Papers in Optical Sensors 2024)
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18 pages, 7508 KiB  
Article
The Sensitivity Improvement Characterization of Distributed Strain Sensors Due to Weak Fiber Bragg Gratings
by Konstantin V. Stepanov, Andrey A. Zhirnov, Anton O. Chernutsky, Kirill I. Koshelev, Alexey B. Pnev, Alexey I. Lopunov and Oleg V. Butov
Sensors 2020, 20(22), 6431; https://doi.org/10.3390/s20226431 - 11 Nov 2020
Cited by 25 | Viewed by 3204
Abstract
Weak fiber Bragg gratings (WFBGs) in a phase-sensitive optical time-domain reflectometer (phi-OTDR) sensor offer opportunities to significantly improve the signal-to-noise ratio (SNR) and sensitivity of the device. Here, we demonstrate the process of the signal and noise components’ formation in the device reflectograms [...] Read more.
Weak fiber Bragg gratings (WFBGs) in a phase-sensitive optical time-domain reflectometer (phi-OTDR) sensor offer opportunities to significantly improve the signal-to-noise ratio (SNR) and sensitivity of the device. Here, we demonstrate the process of the signal and noise components’ formation in the device reflectograms for a Rayleigh scattering phi-OTDR and a WFBG-based OTDR. We theoretically calculated the increase in SNR when using the same optical and electrical components under the same external impacts for both setups. The obtained values are confirmed on experimental installations, demonstrating an improvement in the SNR by about 19 dB at frequencies of 20, 100, and 400 Hz. In this way, the minimum recorded impact (at the threshold SNR = 10) can be reduced from 100 nm per 20 m of fiber to less than 5 nm per 20 m of fiber sensor. Full article
(This article belongs to the Special Issue Fiber Optic Sensors and Fiber Lasers)
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