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High sensitivity fiber optic sensor for hydrogen detection in gas and transformer oil
摘要： This paper reports on the characterisation of a palladium (Pd) based fiber optic hydrogen (H2) sensor for health monitoring of distribution and power transformers in the electrical grid. The sensor consists of a Pd foil, which expands due to H2 absorption, and a fiber Bragg grating (FBG) that measures this expansion. Fifteen sensors were manufactured and characterised in gas and oil environments at various H2 concentrations and temperatures. In gas, the sensors were evaluated at 60°C, 75°C, 90°C, 105°C and 120°C and H2 concentrations from 0.01 to 5%. In oil, the same sensors were evaluated at 90°C and dissolved H2 concentrations from 5 to 2700 ppm. Furthermore, the influence of carbon monoxide (CO), which is often present in transformers and can impact H2 response of the sensor, was investigated. At 90°C in gas, the response to 0.01%, and 5% H2 was on average 28 pm, and 719 pm respectively. At 90°C in oil, the response to 5 ppm, and 2700 ppm dissolved H2 was on average 11 pm, and 763 pm respectively. The average, relative accuracy is better than 20% over the whole measurement range in gas and for measurements above 100 ppm in oil. These specifications make the sensor a promising candidate for online monitoring of H2 in transformers.
关键词： transformer monitoring,Hydrogen,fiber Bragg grating,palladium,gas detection
更新于2025-09-23 15:22:29
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[IEEE 2018 IEEE Photonics Conference (IPC) - Reston, VA (2018.9.30-2018.10.4)] 2018 IEEE Photonics Conference (IPC) - 3-Gbps Free Space Optical Link Based on Integrated Indium Phosphide Transmitter
摘要： A free space optical link was demonstrated with an integrated indium phosphide transmitter, tunable from 1521 nm to 1565 nm. Error-free operation was achieved at 3 Gbps for an equivalent link length of 180 m (up to 300 m with forward error correction).
关键词： sampled grating DBR laser,photonic integrated circuits,optical interconnect,Free space communication
更新于2025-09-23 15:22:29
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Agar-coated fiber Bragg grating sensor for relative humidity measurements: influence of coating thickness and polymer concentration nm
摘要： The importance of humidity control is spreading through a broad spectrum of applications, from food and pharmaceutical industries to biomedical and chemical fields. During the last decades, the growing interest in fiber Bragg gratings (FBG) led to new approaches and applications for the humidity measurement by means of the deposition of hygroscopic materials on gratings. The influence of the coating material and its features such us coating thickness (tk) and concentration (wt%) on static and dynamic metrological properties have been investigated in the literature. In this study, four agar-coated FBG sensors for humidity measurements have been fabricated, and the influence of tk and wt% on the sensors’ sensitivity and response time has been experimentally assessed. Sensitivity increases with tk and wt%: for instance, at 1 wt% it was 0.0024 nm·%-1 and 0.0052 nm·%-1 for tk=87 μm and tk=212 μm, respectively. Results showed that also the response time increased with tk and wt%: for instance, at 1 wt% it was 56.7 s and 107.6 s for tk=87 μm and tk=212 μm, respectively.
关键词： Moisture sensitive polymers,Hygroscopic materials,Relative humidity sensing,Fiber Bragg grating sensors,Fiber optic sensors
更新于2025-09-23 15:22:29
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Optical Interferometry || Applications of Fiber-Optic Interferometry Technology in Sensor Fields
摘要： Optical interferometry as a precision metrology has been widely employed in many aspects for accurate measurements of various physical quantities. As an important branch of measurement technology, now the fiber-optic interferometry technology, based on fiber-optic and laser technologies, has been developed and widely applied in sensor fields for detections of various unknown or uncontrolled physical parameters. In this chapter, basic concepts of fiber-optic interferometry are presented and clarified. Also, three novel fiber-optic sensors, based on the optical interferometry technology and mainly used in the power industry for equipment failure monitoring, are demonstrated.
关键词： optical interferometry,fiber-optic sensor,fiber Bragg grating-based interferometer,interference fringe,laser
更新于2025-09-23 15:21:21
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Point-by-Point Femtosecond-Laser Inscription of 2-μm-Wavelength-Band FBG through Fiber Coating
摘要： We propose a point-by-point inscription method for fiber Bragg grating (FBG) fabrication using a femtosecond pulsed laser focused through a fiber polyimide coating, realizing a 2-μm-wavelength-band FBG. A femtosecond laser acts as the inscription laser, focused by a 63× oil lens. A first-order FBG was fabricated with a grating interval of 700 nm. The 15- μW pulsed laser was focused directly on the fiber core through the polyimide coating and cladding. A first-order FBG for 2004.8-nm light with more than 56% reflectances was fabricated. High wavelength sensitivity and linearity of the FBG were demonstrated by temperature and strain-sensing testing. The first-order FBG of 2004.8 and 2000.2 nm resonant wavelengths could be realized simultaneously through parallel inscription method in 3000μm long grating area.
关键词： 2-μm-wavelength-band,Fiber Bragg grating,Erbium-doped fiber laser,Femtosecond pulsed laser
更新于2025-09-23 15:21:21
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[IEEE 2018 9th International Conference on Ultrawideband and Ultrashort Impulse Signals (UWBUSIS) - Odessa, Ukraine (2018.9.4-2018.9.7)] 2018 9th International Conference on Ultrawideband and Ultrashort Impulse Signals (UWBUSIS) - Effective Microwave Electromagnetic Response of the Infinite Chain of Dielectric Coated Circular Metal Cylinders
摘要： Microwave approximations for effective electric and magnetic responses of the infinite chain have been obtained in this study. This infinite chain is comprised of long dielectric coated circular metal cylinders infinitely periodically space. The obtained approximations have been derived on the basis of the long wave approximation for the diffraction problem of a plane electromagnetic wave on the cylindrical chain using the Effective Medium Theory. Comparisons of the analytically obtained results with the numerically calculated ones have made in the study.
关键词： Artificial Dielectrics,Effective Medium Theory,Plane Wave Diffraction,Infinite Grating
更新于2025-09-23 15:21:21
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Direct quantitative material decomposition employing grating-based X-ray phase-contrast CT
摘要： Dual-energy CT has opened up a new level of quantitative X-ray imaging for many diagnostic applications. The energy dependence of the X-ray attenuation is the key to quantitative material decomposition of the volume under investigation. This material decomposition allows the calculation of virtual native images in contrast enhanced angiography, virtual monoenergetic images for beam-hardening artifact reduction and quantitative material maps, among others. These visualizations have been proven beneficial for various diagnostic questions. Here, we demonstrate a new method of ‘virtual dual-energy CT’ employing grating-based phase-contrast for quantitative material decomposition. Analogue to the measurement at two different energies, the applied phase-contrast measurement approach yields dual information in form of a phase-shift and an attenuation image. Based on these two image channels, all known dual-energy applications can be demonstrated with our technique. While still in a preclinical state, the method features the important advantages of direct access to the electron density via the phase image, simultaneous availability of the conventional attenuation image at the full energy spectrum and therefore inherently registered image channels. The transfer of this signal extraction approach to phase-contrast data multiplies the diagnostic information gained within a single CT acquisition. The method is demonstrated with a phantom consisting of exemplary solid and fluid materials as well as a chicken heart with an iodine filled tube simulating a vessel. For this first demonstration all measurements have been conducted at a compact laser-undulator synchrotron X-ray source with a tunable X-ray energy and a narrow spectral bandwidth, to validate the quantitativeness of the processing approach.
关键词： Dual-energy CT,virtual non-contrast images,grating-based phase-contrast,electron density,effective atomic number,material decomposition,quantitative X-ray imaging,virtual monoenergetic images
更新于2025-09-23 15:21:21
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Measuring singularities of cylindrically structured light beams using a radial grating
摘要： Optical singularities, including phase and polarization singularities that are prevalent in vortex beams, cylindrical vector beams, and cylindrical vector vortex beams, were widely investigated in the past few decades because of their physical and application interest. Here, we propose a method for measuring the singularities within these cylindrically structured light beams by using a radial grating (RG), which is fabricated by etching patterns on the chrome plated soda-lime glass and exhibits a broadband performance. We demonstrate the versatility and compatibility of the measuring method by obtaining the topological charge and polarization order that characterize the phase and polarization singularity, respectively. The reliability of the RG was also inspected by analyzing the grating period and the illumination location of the input field on it.
关键词： topological charge,optical singularities,cylindrically structured light beams,radial grating,polarization order
更新于2025-09-23 15:21:21
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Spin-wave generation using MZI embedded plasmonic antennas for quantum communications
摘要： Spin wave generation formed by a soliton pulse within MZI embedded plasmonic antennas has been proposed. A soliton is the orthogonal (entangled) source that can be configured as the vertical and horizontal components in the same way as the polarization components. A dark soliton of wavelength 1.55? μm is selected and fed into the MZI input. The dark-bright soliton pulse entered into the upper and lower branches to form uplink and downlink antennas. The whispering gallery mode (WGM) can be generated by controlling the two side ring phase modulators. The gold grating surface is excited by the WGM input form the circuit, from which the electric dipoles oscillated. The trapped electrons by soliton pulses transmitted. The dipole oscillation of the antennas identified by plasma frequencies (Bragg wavelengths), which can form the spin-waves. The simulation programs are Opti-wave and Matlab programs, from which the used parameters are selected from the realistic device parameters. The simulation results obtained show that the transmission bandwidth of 600? GHz with the antenna directivity of 7.78, and 4.63 for the uplink and downlink respectively and antenna gain (power) of 1.13?dB, and 1.07?dB for the uplink and downlink respectively. The transmission signals and power stability are confirmed by the transmis-sion entanglement. The quantum sensor networks can also be applied, where the trend of the sensor sensitivity linearity is achieved.
关键词： Gold grating,Soliton communication,Microring resonator,Plasmonic antenna,Spin-waves,MZI
更新于2025-09-23 15:21:01
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Handheld pocket-size Fourier transform profilometry using projector-enabled smartphone
摘要： Surface Fourier transform profilometry (FTP) is a technique used for reconstructing three-dimensional (3-D) surface topography using light. It has been widely used in machine vision for biomedical and biometric automations, providing solutions beyond conventional 2-D imaging. This paper proposes an implementation of the handheld pocket-size FTP for 3-D surface profile imaging using a projector-enabled Samsung Galaxy Beam smartphone. In the implementation, a crossed-optical-axes geometry of the FTP is formed by using a mirror positioned over the phone’s projector via an adjustable tilt mounting bracket. Experimental proof-of-concept of the proposed profilometry is done by implementing conventional and non-phase shifting FTPs with different diffuse test objects. The experimental results obtained by using the non-phase shifting technique are in good agreement with those of the direct contact measurement. Besides having superiority of compactness, the proposed profilometry paves the way for the development of real-time 3-D profiling and printing through internet or Bluetooth interconnection.
关键词： 3-D profilometry,non-phase shifting technique,contrast function,sinusoidal grating,projector-enabled smartphone,3-D surface topography,Samsung galaxy beam,Fourier transform,shape measurement
更新于2025-09-23 15:21:01