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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) - Experimental evaluation of low-cost interrogation techniques for FBG sensors
摘要： In this paper, the experimental investigation of two simple, cost-effective interrogation techniques based on optical power measurement for fiber Bragg gratings (FBG) sensors are presented. The first technique proposed employs each channel of a CWDM demultiplexer as an edge filter to modulate the optical power reflected by each sensing FBG, allowing for an array of FBG sensors to be interrogated simultaneously, sharing the same broadband light source (BLS) and interrogation system. In the second technique, the optical power reflected by a single sensing FBG is modulated directly by the transmission spectrum of the BLS, allowing for a simpler interrogation system. Both techniques rely on a compact, low-cost optoelectronic circuit developed for the acquisition and measurement of the optical signals. With resolutions of up to 1.26 pm for a mechanical strain sensor, or an equivalent 0.09 oC for a temperature sensor, experimental results show that both techniques are accurate, reliable, and suitable for applications where the only requirement is the monitoring of the spectral position of the Bragg wavelength (λB) of the FBG sensors, replacing more expensive, general-purpose FBG interrogators available in the market. Since FBGs are passive, lightweight, and provide dielectric insulation, the proposed techniques are suitable for temperature or mechanical strain measurements in hostile environments in which the use of conventional sensors must be avoided, such as in high voltage power lines and cables, and explosive atmospheres.
关键词： fiber Bragg gratings,temperature measurement,temperature sensors,optical fiber sensors
更新于2025-09-10 09:29:36
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Sensitivity-enhanced strain sensor based on thin-core fiber modal interferometer interacted with tilted fiber Bragg grating
摘要： A sensitivity-enhanced strain sensor constructed by a 7 mm-long thin-core fiber (TCF) splicing with a 10 mm-long tilted fiber Bragg grating (TFBG) was proposed. The modal interferometer formed by the TCF will interact with the spectrum of the TFBG to form an overlapped spectrum, which will extremely increase the axial strain sensitivity of the TFBG. Experimental results showed that the wavelength shifts of the resonant dip in the overlapped spectra for the applied axial strain has a high sensitivity of 0.67 pm/με. Meanwhile, the proposed sensor has the temperature self-compensation function for the variation of the external temperature simply by measuring the relative wavelength shifts of the Bragg mode of the TFBG.
关键词： Strain sensor,Tilted Fiber Bragg gratings
更新于2025-09-10 09:29:36
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Application of Additive Layer Manufacturing Technique on the Development of High Sensitive Fiber Bragg Grating Temperature Sensors
摘要： This paper presents the development of temperature sensors based on fiber Bragg gratings (FBGs) embedded in 3D-printed structures made of different materials, namely polylatic acid (PLA) and thermoplastic polyurethane (TPU). A numerical analysis of the material behavior and its interaction with the FBG sensor was performed through the finite element method. A simple, fast and prone to automation process is presented for the FBG embedment in both PLA and TPU structures. The temperature tests were made using both PLA- and TPU-embedded FBGs as well as an unembedded FBG as reference. Results show an outstanding temperature sensitivity of 139 pm/°C for the FBG-embedded PLA structure, which is one of the highest temperature sensitivities reported for FBG-based temperature sensors in silica fibers. The sensor also shows almost negligible hysteresis (highest hysteresis below 0.5%). In addition, both PLA- and TPU-embedded structures present high linearity and response time below 2 s. The results presented in this work not only demonstrate the feasibility of developing fully embedded temperature sensors with high resolution and in compliance with soft robot application requirements, but also show that the FBG embedment in such structures is capable of enhancing the sensor performance.
关键词： 3D printing,temperature sensor,fiber Bragg gratings,additive layer manufacturing
更新于2025-09-10 09:29:36
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Tunable optoelectronic oscillator working in the Ku band
摘要： An improved tunable optoelectronic oscillator (OEO) based on a dual-parallel Mach–Zehnder (MZ) modulator embedded with a sub-MZ modulator is designed and experimentally demonstrated for Ku band applications. Single-mode oscillator operation is achieved with a single feedback loop and without any electrical filters, which improves the tunability of the proposed OEO. The microwave power expression at the output of photodetector is developed using the well-known Taylor series expansion method to calculate the electrical spectrum and accumulated dispersion (ps nm?1) of the dispersive element (linearly chirped fiber Bragg grating). Phase noise is also examined, which allows us to conclude that our proposed oscillator is suitable for optical wireless communication, radar and phase array antenna applications. Furthermore, its application as a strain and temperature sensor is investigated and it is found to have maximum strain sensitivity (Kε) of 58.75 MHz με?1 and temperature sensitivity (KT) of 1.752 GHz °C?1.
关键词： optoelectronic oscillator,fiber Bragg gratings,microwave generation,phase noise,photonic sensor
更新于2025-09-10 09:29:36
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Fabrication and Characterization of a Magnetized Metal-Encapsulated FBG Sensor for Structural Health Monitoring
摘要： A novel means of metal packaging of a fiber Bragg grating (FBG) sensor using stainless steel and tin, together with high temperature resistant samarium cobalt (SmCo) magnet is proposed in this paper. The inclusion of high temperature-capable SmCo magnets enable the metal packaging of the FBG sensor with magnetic capabilities. This packaged sensor can be placed in direct contact with the substrate structures such as iron pipelines and other ferromagnetic components without any adhesives, making them easily detachable and reusable. This is a significant improvement compared with other commercial fiber optic sensors which are, surface attached using epoxies or welded to the substrate. The design parameters and characteristic properties such as load, temperature, and vibration sensitivity of the magnetic metal-packaged FBG sensor are studied numerically and validated experimentally to demonstrate the feasibility of using the encapsulated reusable FBGs for structural health monitoring of compatible structures.
关键词： fiber Bragg gratings,welding,Acoustic emission sensors,temperature,strain
更新于2025-09-10 09:29:36
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Simultaneous Measurement of Axial Strain, Bending and Torsion with a Single Fiber Bragg Grating in CYTOP Fiber
摘要： This paper presents the development of a 3-D displacement sensor based on one fiber Bragg grating (FBG). In order to obtain higher sensitivity and dynamic range, the FBG is inscribed in low-loss, multimode, cyclic transparent amorphous fluoropolymers (CYTOP) using the direct-write, plane-by-plane femtosecond laser inscription method. The proposed sensor is based on the influence of each displacement condition, namely axial strain, torsion and bending on the FBG reflection spectrum. Such influence is analyzed with respect to the FBG wavelength shift, reflectivity and full width half maximum (FWHM). The operation principle and theoretical background of the proposed approach is numerically analyzed by means of finite element analysis for the strain along the grating length and coupled-mode theory with a modified transfer matrix formulation for the FBG spectrum. The sensor is experimentally characterized and validated in which the results show good agreement between the applied axial strain, bending and torsion with relative errors below 5.5%. Thus, the proposed sensor is an interesting alternative for measuring displacements in 3-D applications such as movement analysis and the instrumentation of novel soft robots.
关键词： Polymer optical fiber,3-D displacement,fiber Bragg gratings,CYTOP
更新于2025-09-09 09:28:46
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Magnetic Optical FBG Sensors Using Optical Frequency-Domain Reflectometry
摘要： The optical frequency-domain reflectometry (OFDR) sensing system and signal processing method, which is based on the short-time Fourier transform, enable us to interrogate reflected wavelengths of fiber Bragg gratings (FBGs) and their relative position along the optical fiber with high spatial resolution. An FBG is an optical fiber with an appropriately inscribed periodic refractive index modulation. When a broadband optical signal is launched into the FBG, narrow wavelength bandwidth is reflected. Due to an attached transducer, such as Terfenol-D, the reflected wavelength changes with the applied magnetic field. The proposed magnetic FBG sensor consists of a small rod of magnetostrictive alloy TbDyFe, also known as Terfenol-D, which has large magnetostriction. The FBG is attached to the Terfenol-D rod with UV glue. Consequently, the external magnetic field is applied to the sensor and as a result, the Terfenol-D rod length increases. The reflected wavelength shift is observed and measured by the OFDR sensing system. Therefore, we determine the external magnetic field along the optical fiber from the reflected Bragg wavelength shift. The measurement results show that the proposed magnetic field sensors based on Terfenol-D using OFDR can be successfully used for measurement of the external magnetic field along an optical fiber.
关键词： Terfenol-D,optical frequency-domain reflectometry (OFDR),magnetic field sensor,Fiber Bragg gratings (FBGs)
更新于2025-09-09 09:28:46
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Enhanced stability of higher UV-densified Fiber Bragg Gratings after thermal regeneration
摘要： The stability of the Bragg peak strength during isothermal regeneration of Fiber Bragg Gratings (FBGs) depends on their UV photosensitivity. In low Ge-doped fused silica fibers, lower photosensitivity results in improved thermal stability over time, due to enhanced densification effects occurring during UV-exposure. The contributions of UV-inscription parameters and fiber composition to the power, the spectral width and the wavelength shifts of the transmitted signal through FBGs are examined in detail, indicating how the photosensitivity affects the refractive index, the grating period and the optical coupling inside the fiber core. The changes reported for low- and high-Ge doped fibers are mainly attributed to densification effects induced by UV-imprinting, where stronger compaction is found to significantly improve the long-term stability of FBG sensors after thermal regeneration.
关键词： Photosensitivity,Thermal regeneration process,Fiber Bragg Gratings,Densification
更新于2025-09-09 09:28:46