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Lorentzian demodulation algorithm for multimode polymer optical fiber Bragg gratings
摘要： For strain sensing applications, we develop a simple and accurate Lorentzian demodulation algorithm for fiber Bragg gratings (FBGs) inscribed in multimode optical fibers. As multimode FBG spectra generally exhibit multiple peaks, simply tracking some particular spectral peaks (i.e., maximum detection) results in measurement failure when the strain is large. Here, using an FBG inscribed in a perfluorinated graded-index multimode polymer optical fiber, we experimentally evaluate the new method by comparing its performance with those of other demodulation algorithms, such as the maximum and centroid detection methods. Finally, using this method, we demonstrate the accurate measurement of strain of up to 1.0%.
关键词： fiber Bragg gratings,FBG,Lorentzian demodulation algorithm,strain sensing,multimode polymer optical fiber Bragg gratings
更新于2025-11-28 14:24:03
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Recent Advances in Brillouin Optical Correlation-Domain Reflectometry
摘要： Distributed ?ber-optic sensing based on Brillouin scattering has been extensively studied and many con?gurations have been developed so far. In this paper, we review the recent advances in Brillouin optical correlation-domain re?ectometry (BOCDR), which is known as a unique technique with intrinsic single-end accessibility, high spatial resolution, and cost ef?ciency. We brie?y discuss the advantages and disadvantages of BOCDR over other Brillouin-based distributed sensing techniques, and present the fundamental principle and properties of BOCDR with some special schemes for enhancing the performance. We also describe the recent development of a high-speed con?guration of BOCDR (slope-assisted BOCDR), which offers a beyond-nominal-resolution detectability. The paper is summarized with some future prospects.
关键词： Brillouin scattering,optical fiber sensing,temperature sensing,distributed sensing,structural health monitoring,optical correlation-domain reflectometry,strain sensing,nonlinear optics
更新于2025-09-23 15:21:21
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Development of a non-contact and non-destructive laser speckle imaging system for remote sensing of anisotropic deformation around fastener holes
摘要： Strain sensing around the fastener holes is fundamentally significant in structural health monitoring and failure detections. Conventional non-destructive testing (NDT) techniques typically have limitations in performing reliable and efficient inspections. Here, a laser speckle imaging system (LSIS) has been developed to achieve non-contact, non-destructive and remote strain sensing. Methods for determining optimal laser speckle patterns have been investigated to achieve remote sensing of strain up to a working distance of 5 m. This LSIS was applied to study the anisotropic properties of un-notched and circular notched specimens in cold-rolled aluminium sheet, an important material for the construction of lightweight aircraft structures. The results showed that strain distributions determined by LSIS are consistent with finite element (FE) predictions in which the evolution of strain concentrations not only depends on the notch size but also on material anisotropy. This study demonstrates the potential application of LSIS as an effective NDT technique for full-field, non-contact and remote sensing of anisotropic deformation around fastener holes.
关键词： Non-destructive testing,Digital image correlation,Laser speckle imaging,Remote strain sensing
更新于2025-09-19 17:13:59
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Sensing characteristics of long period grating by writing directly in SMF-28 based on 800?nm femtosecond laser pulses
摘要： A long period grating is fabricated in standard SMF-28 ?bers without hydrogen loading by adopting point-by-point direct writing based on femtosecond laser pulses with 800 nm wavelength and 100 fs pulse width. Its sensing characteristics is investigated and the sensing sensitivities to temperature, external refractive index (RI) and strain are systematically examined as well. The experimental results show that the sensing sensitivity of the long period grating to temperature, RI and strain is about 124 pm/°C with a linearity of 0.989 within temperature ranging from 20 °C to 800 °C, ?582.5 nm/RIU (refractive index unit) with a linearity of 0.998 in the RI ranging from 1.342 to 1.380, and ?9.45 × 10-4 dB/με with a linearity of 0.98 in the strain ranging from 0 to 2925 με, respectively. The high sensitivity of prepared LPG will have potential application values in sensing measurement of multi-parameters and in the ?eld of high temperature and harsh environments detection.
关键词： Refractive index (RI),Long Period Gratings (LPGs),Femtosecond laser,Strain sensing,Temperature sensitivity
更新于2025-09-12 10:27:22
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Characterisation of silicon fibre Bragg grating in near-infrared band for strain and temperature sensing
摘要： Fibre Bragg grating inscription in the crystalline silicon (Si)-core fibre is described using visible light femtosecond laser pulses. The femtosecond pulses at 517 nm propagate through the transparent silica glass cladding and are fully absorbed by the Si core generating locally high temperatures and stress fields in forming the grating periods. The Si FBGs were characterised in reflection, calibrated for a first time as strain and temperature sensors and compared with that of FBGs inscribed in standard silica fibres.
关键词： temperature sensing,femtosecond laser inscription,silicon fibre Bragg grating,near-infrared band,strain sensing
更新于2025-09-11 14:15:04
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[IEEE 2018 IEEE International Instrumentation and Measurement Technology Conference (I2MTC ) - Houston, TX, USA (2018.5.14-2018.5.17)] 2018 IEEE International Instrumentation and Measurement Technology Conference (I2MTC) - Temperature compensation method for FBG-based current sensors for transmission lines
摘要： A method to compensate the temperature influence on electrical current sensors based on fiber Bragg gratings (FBG) is presented in this paper. The operating principle of the method is the employment of a second fiber Bragg grating in the measurement system, called fixed filter, in order to interrogate the output signal from the sensing grating. Once both gratings have been attached to Terfenol-D rods close to each other and subjected to the same temperature variations inside a protective cover, the separation of magnetostrictive strain from the one related to temperature in the output signal can be obtained.
关键词： magnetostrictive strain,sensing grating,fiber Bragg gratings,Current sensors,Terfenol-D,fixed filter
更新于2025-09-11 14:15:04
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Distributed Strain Sensing Using Electrical Time Domain Reflectometry With Nanocomposites
摘要： The objective of this study is to validate distributed strain sensing using electrical time domain reflectometry (ETDR) with multi-walled carbon nanotube (MWCNT)-based thin film sensing elements. The proposed ETDR sensor composed of two types of transmission lines: parallel-wire-type transmission line and parallel-plate-type transmission line with MWCNT-based sensing elements. The hypothesis was that the greater strain-induced impedance changes of the nanocomposite would enhance ETDR sensing performance. In this paper, four different types of ETDR sensing elements were subjected to one-cycle uniaxial tensile strains to validate strain sensing. Three sensing elements were then integrated in an ETDR setup, and strain patterns were applied for validating their distributed strain sensing behavior.
关键词： transmission line,Carbon nanotubes,thin film,strain sensing,electrical time domain reflectometry
更新于2025-09-09 09:28:46