Phase-sensitive optical time-domain reflectometry (φOTDR) is a simple and effective tool allowing the distributed monitoring of vibrations along single-mode fibers. We show in this Letter that modulation instability (MI) can induce a position-dependent signal fading in long-range φOTDR over conventional optical fibers. This fading leads to a complete masking of the interference signal recorded at certain positions and therefore to a sensitivity loss at these positions. We illustrate this effect both theoretically and experimentally. While this effect is detrimental in the context of distributed vibration analysis using φOTDR, we also believe that the technique provides a clear and insightful way to evidence the Fermi-Pasta-Ulam recurrence associated with the MI process.
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http://dx.doi.org/10.1364/OL.38.000872 | DOI Listing |
Nat Commun
January 2025
State Key Laboratory of Information Photonics and Optical Communications, Beijing University of Posts and Telecommunications, Beijing, China.
Complex-valued neural networks process both amplitude and phase information, in contrast to conventional artificial neural networks, achieving additive capabilities in recognizing phase-sensitive data inherent in wave-related phenomena. The ever-increasing data capacity and network scale place substantial demands on underlying computing hardware. In parallel with the successes and extensive efforts made in electronics, optical neuromorphic hardware is promising to achieve ultra-high computing performances due to its inherent analog architecture and wide bandwidth.
View Article and Find Full Text PDFBiomed Opt Express
December 2024
Department of Medical Physics and Biomedical Engineering, University College London, Malet Place, Gower Street, London WC1E 6BT, UK.
Optical coherence tomography (OCT) is a technique that performs high-resolution, three-dimensional, imaging of semi-transparent scattering biological tissues. Models of OCT image formation are needed for applications such as aiding image interpretation and validating OCT signal processing techniques. Existing image formation models generally trade off between model realism and computation time.
View Article and Find Full Text PDFBiomed Opt Express
December 2024
Department of Cardiology, Cardiovascular Institute, Thorax Center, Erasmus MC, The Netherlands.
Photothermal optical coherence microscopy (PT-OCM) combines the high-resolution, label-free morphological imaging of OCM with the ability to discriminate tissue composition through phase-sensitive photothermal imaging. In this study, we perform 2D imaging of human carotid endarterectomies to spectrally determine lipid distribution, with verification via histologically stained samples. The structural information from OCM is combined with the spectral information gained from measuring the resulting sample surface displacement from thermoelastic expansion, following light irradiation.
View Article and Find Full Text PDFNanophotonics
April 2024
School of Electronic and Information Engineering, and School of Cyber Science and Technology, Beihang University, Beijing, China.
Understanding the ultrafast excitation, detection, transportation, and manipulation of nanoscale spin dynamics in the terahertz (THz) frequency range is critical to developing spintronic THz optoelectronic nanodevices. However, the diffraction limitation of the sub-millimeter waves - THz wavelengths - has impaired experimental investigation of spintronic THz nano-emission. Here, we present an approach to studying laser THz emission nanoscopy from W|CoFeB|Pt metasurfaces with ∼60-nm lateral spatial resolution.
View Article and Find Full Text PDFThis work demonstrates that the phase-based decorrelation compensation method outperforms the amplitude-based approach in low signal-to-noise ratio (SNR) regions of phase-sensitive optical coherence tomography (PhS-OCT). Building on this finding, an adaptive decorrelation compensation approach for digital-image-correlation (DIC)-assisted PhS-OCT is introduced. This method utilizes the maximum correlation coefficient from amplitude maps to adaptively determine the need for secondary tracking of decorrelated displacement using the phase-based approach.
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