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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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FIBRE BRAGG GRATING SENSOR SYSTEM FOR TEMPERATURE APPLICATION
摘要： A practical pass-through type fibre Bragg grating (FBG) temperature sensor system have been designed and experimentally investigated. The performance of FBG was evaluated with the varying of focusing elements in harsh environments, under direct sunlight. The sensor head of FBG was designed to be focused with convex and hand lens. Results shows that the Bragg wavelength shift, ????? increase proportionally with the temperature for both systems. The sensitivities of FBG were recorded to be 0.0107 and 0.0122 nm °C-1 for the system where convex and hand lens applied to the FBG’s sensor head respectively.
关键词： focusing element,temperature sensor,Fibre Bragg grating,Bragg wavelength shift
更新于2025-09-23 15:21:01
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[IEEE 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Huangshan, China (2019.8.5-2019.8.8)] 2019 18th International Conference on Optical Communications and Networks (ICOCN) - A Fiber Bragg Grating-based Wind Erosion Monitoring System
摘要： This paper proposes a wind erosion monitoring system includes a shunt-hedging and cyclone-separation sand sampler built by Fluent and a weighting sensor based on FBG. According to the simulation and experiment, this system had anti strong wind interference performance and time, passively, in real continuously, and in a long distance. it could measure
关键词： wind erosion,weighting sensor,sand sampler,fiber Bragg grating
更新于2025-09-23 15:21:01
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High-peak-power and narrow-linewidth Q-switched Ho:YAG laser in-band pumped at 1931 nm
摘要： We describe a high-peak-power, narrow-linewidth Q-switched Ho:YAG laser at 2097 nm wing-pumped by a high power and high brightness Tm:fiber source at 1931.5 nm. The laser was wavelength locked and spectrum narrowed utilizing a volume Bragg grating as the input coupler, resulting a linewidth (FWHM) of less than 0.1 nm. At 22.7 W of incident pump power, stable pulses of 5.5 mJ pulse energy and 17.5 ns of pulse duration have been generated at repetition frequency of 1 kHz, corresponding to peak power of 314.3 kW.
关键词： narrow-linewidth,Q-switched Ho:YAG laser,volume Bragg grating,1931.5 nm,high-peak-power
更新于2025-09-23 15:21:01
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Slit beam shaping technique for femtosecond laser inscription of enhanced plane-by-plane FBGs
摘要： In this work, the development of plane-by-plane (Pl-b-Pl) fiber Bragg gratings (FBGs) by using a single pulse is reported. A slit oriented along the longitudinal axis of the fiber is employed for this. The purpose is to shape the beam so that the focal volume is spatially wider in the transverse direction of the fiber. In this way, it is possible to make 2-D modifications of the refractive index whose width and height depends on the slit width and the pulse energy, respectively. Through an analytical mathematical modelling, the relationship between the diameter of the Gaussian laser beam (Dx) and the slit width (s = Dy) is determined in order to obtain a circular cross-section. In the experimental results carried out, it can be observed that Dx/Dy=3 ratio cause positive and uniform refractive index changes, compared to the negative and inhomogeneous refractive index changes corresponding to point-by-point (PbP) FBGs. Likewise, Pl-b-Pl FBGs, presenting a broader modification of the core cross-section, show significantly lower losses in transmission (0.3 dB), as well as better reflectivity and FWHM. It is observed that these three parameters (losses, reflectivity and FWHM) have a monotonous tendency according to the slit width. Polarization-dependence is also evaluated.
关键词： Optical Fiber Sensor,Slit beam technique,Femtosecond laser,Plane-by-Plane,Fiber Bragg grating
更新于2025-09-23 15:21:01
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[IEEE 2018 IEEE 7th International Conference on Photonics (ICP) - Langkawi, Malaysia (2018.4.9-2018.4.11)] 2018 IEEE 7th International Conference on Photonics (ICP) - Etched Fiber Bragg Grating Sensor for Nitrate Sensing Application
摘要： We demonstrate a reliable method to detect the concentration of Nitrate in water using an etched Fiber Bragg Grating (FBG) sensor. The sensor was etched using 48% Hydrofluoric (HF) acid solution to function as a chemical sensor and interact with Nitrates. The Bragg wavelength ((cid:2)b) shifted due to the changes of Nitrate concentration. The sensitivity achieved by this sensor is 2.4 x 10-3 nm/ppm. The overall shift of the Bragg wavelength is 0.12 nm from 0 – 50 ppm.
关键词： Nitrate ions,Fiber Bragg Grating sensor
更新于2025-09-23 15:21:01
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Nuclear Power Plant Prestressed Concrete Containment Vessel Structure Monitoring during Integrated Leakage Rate Testing Using Fiber Bragg Grating Sensors
摘要： As the last barrier of nuclear reactor, prestressed concrete containment vessels (PCCVs) play an important role in nuclear power plants (NPPs). To test the mechanical property of PCCV during the integrated leakage rate testing (ILRT), a fiber Bragg grating (FBG) sensor was used to monitor concrete strain. In addition, a finite element method (FEM) model was built to simulate the progress of the ILRT. The results showed that the strain monitored by FBG had the same trend compared to the inner pressure variation. The calculation results showed a similar trend compared with the monitoring results and provided much information about the locations in which the strain sensors should be installed. Therefore, it is confirmed that FBG sensors and FEM simulation are very useful in PCCV structure monitoring.
关键词： structure health monitoring (SHM),finite element method (FEM),integrated leakage rate test (ILRT),fiber Bragg grating (FBG),prestressed concrete containment vessel (PCCV)
更新于2025-09-23 15:21:01
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Efficient polymer waveguide grating coupler with directionality enhancement
摘要： Polymer is viewed as an ideal platform for integrated photonics sensing. We propose a polymer waveguide grating coupler with the enhancement of directionality. A gold film mirror beneath the grating coupler is introduced to prevent the power leakage into the substrate. A Bragg grating reflector in series with the coupler is adopted to reverse the forward diffraction light. The finite-difference time-domain method is used to theoretically investigate the dimensional parameters of grating coupler, gold film mirror, as well as the grating reflector. With both two methods, an enhanced coupling efficiency of 51.31 % can be obtained at the wavelength of 1550 nm. The 62-nm wide 1-dB bandwidth covers the C-band. The proposed design has potentials in integrated optical circuit and monolithic integrated sensors.
关键词： Polymer,Grating coupler,Bragg grating,Waveguide
更新于2025-09-23 15:19:57