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1
Zhang, Shao Jun, and Yue Ming Liu. "Fabrication of FBG Strain Gauge Used for High Temperature Strain Monitoring." Applied Mechanics and Materials 668-669 (October 2014): 920–23. http://dx.doi.org/10.4028/www.scientific.net/amm.668-669.920.
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Fiber Bragg Grating (FBG) sensing technology is widely used in detection of temperature, strain and etc. Now the application of FBG sensor is limited below 200°C. Application over 200°C is still an engineering challenge since no suitable FBG strain gauge. In this paper, FBG strain gauge structure which consists of three FBGs is designed and fabricated based on the theoretical strain and stress analysis. This strain gauge can be used for the real-time high temperature strain monitoring situation. The elastic high-temperature alloy (10MoWVNb) is chosen as the substrate. The three FBGs with a similar performance are fabricated on the substrate by high-temperature glue. Among the three FBGs, FBG1 is used for the horizontal strain monitoring, FBG2 is used for the longitudinal strain monitoring, and FGB3 is used for high temperature cross-sensitive compensation. The fabricated high temperature FBG gauge is demonstrated suitable for high temperature strain monitoring by experiment.
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Yu, Yang, Bo Liu, and Feng Xia. "Design Optimization of Sensitivity-Enhanced Structure for Fiber Bragg Grating Acoustic Emission Sensor Based on Additive Manufacturing." Sensors 22, no. 2 (January 6, 2022): 416. http://dx.doi.org/10.3390/s22020416.
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A four-loop shaped structure of fiber Bragg grating (FBG) acoustic emission (AE) sensor based on additive manufacturing (AM) technology is proposed in the letter. The finite element analysis (FEA) method was used to model and analyze the sensor structure. We aimed at improving the sensitivity, the static load analysis, and the dynamic response analysis of the normal FBG acoustic emission sensor and the FBG AE sensor with improved structure parameters. We constructed the FBG AE sensor experimental system based on a narrowband laser demodulation method and test on real acoustic emission signals. The results demonstrated that the response sensitivity of the FBG acoustic emission sensor was 1.47 times higher than the sensitivity of the normal FBG sensor. The sensitivity coefficient of PLA-AE-FBG2 sensor was 3.057, and that of PLA-AE-FBG1 was 2.0702. Through structural design and parameter optimization, the sensitivity and stability of the FBG AE sensor are improved. The four-loop shaped sensor is more suitable for the health monitoring in fields such as aero-engine blade, micro-crack of structure, and crack growth in bonded joints. While ensuring the sensing characteristics, sensitivity, and stability of the four-loop shaped sensor have been enhanced. It is possible to apply the FBG AE sensor in some complex engineering environments.
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Morais, Eliton, Maria José Pontes, Carlos Marques, and Arnaldo Leal-Junior. "Liquid Level Sensor with Two FBGs Embedded in a PDMS Diaphragm: Analysis of the Linearity and Sensitivity." Sensors 22, no. 3 (February 7, 2022): 1268. http://dx.doi.org/10.3390/s22031268.
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This paper presents a fiber optic, liquid level sensor system based on a pair of fiber Bragg gratings (FBGs), embedded in a circular silicone (PDMS—polydimethylsiloxane) rubber diaphragm. The measurement principles of this sensor, whose diaphragm structure is about 2.2 mm thick with 45 mm in diameter, are introduced. To analyze the linearity and sensitivity of the sensor, the diaphragm was subjected to compression tests as well as to liquid level loading and unloading. The force and liquid level increase tests showed that inserting two FBGs (0.99453 for force and 0.99163 for liquid level) in the diaphragm resulted in a system with greater linearity than that with individual FBGs. This occurred where FBG1 showed 0.97684 for force and 0.98848 for liquid level and FBG2 presented 0.89461 for force and 0.93408 for liquid level. However, the compression and water level decrease tests showed that the system (R2 = 0.97142) had greater linearity with FBG2 (0.94123) and lower linearity with FBG1 (0.98271). Temperature characterization was also performed, and we found that sensitivity to FBG1 temperature variation was 11.73 pm/°C and for FGB2 it was 10.29 pm/°C. Temperature sensitivity was improved for both FBGs when compared with uncoated FBGs with typical values of 9.75 pm/°C. Therefore, the proposed FBG-based sensor system is capable of simultaneous measurement of force and temperature in a compact diaphragm-embedded system.
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Chen, Xi Yuan, and Lin Fang. "Performance Analysis and Experimental Verification for FBG Sensors Applied for Smart Structure." Key Engineering Materials 336-338 (April 2007): 1357–60. http://dx.doi.org/10.4028/www.scientific.net/kem.336-338.1357.
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Among a variety of fiber sensors, the fiber Bragg grating (FBG) sensor has numerous advantages over other optical fiber sensors. One of the major advantages of this type of sensors is attributed to wavelength-encoded information given by the Bragg grating. Since the wavelength is an absolute parameter, signal from FBG may be processed such that its information remains immune to power fluctuations along the optical path. This inherent characteristic makes the FBG sensors very attractive for application in smart material structure, health monitoring field et al. But FBG sensors are sensitive to temperature and strain simultaneously; it is necessary to analyze the characteristics of temperature and strain of FBG applied for smart structure. Short overview of the FBG sensing principle as well as theoretical analyses is presented at first; then the paper proposes a simple, convenient, and low cost experimental method to verify the performance of FBGs. The improved high-accuracy experimental instrument of thermal deformation, which consists of an accurate temperature controlling and measuring subsystem, supporting and adjusting subsystem, collimating and positioning subsystem and fine motion and measuring sub-system, is simply introduced. The proposed experimental method involves bonding one uniform FBG to the center of the pole, which is about 89.5mm long; another FBG temperature sensor is free in the temperature-control box. The temperature in the box is -20°C-+50°C is adjusted according to experimental schedule. The characteristics of the FBG are analyzed by actual datum, which are simultaneously collected by a PC through a FBG interrogator. Comparing the data of FBG bonded to the pole with another FBG temperature sensor in the free state, the characteristics of the temperature and the thermal strain of the FBG can be obtained. The experimental result shows the FBGs used to the smart material have good agreement characteristics with theoretical calculation of the FBGs.
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Xiong, Pengwen, Xin Huang, Yulong Li, and Peter X. Liu. "A Fiber Bragg Grating Sensing Structure for the Design, Simulation and Stress Strain Monitoring of Human Puncture Surgery." Sensors 19, no. 14 (July 11, 2019): 3066. http://dx.doi.org/10.3390/s19143066.
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In order to improve the precision and stability of puncture surgical operations to assist doctors in completing fine manipulation, a new of type puncturing needle sensor is proposed based on a fiber Bragg grating (FBG). Compared with the traditional puncture needle sensor, the new type of puncturing needle sensor is able to sense not only the axial force, but also the torque force during the puncture process. A spoke-type structure is designed near the needle tip. In order to eliminate the influence of temperature and realize temperature compensation, a reference fiber method using three FBGs is applied. FBG1 and the reference FBG2 are pasted on the upper and lower surfaces of the new-type elastic beam, and FBG3 is pasted into the groove on the surface of the new type of puncturing needle cylinder. The difference of Bragg wavelength between FBG1 and the reference FBG2 is calibrated with the torque force, while the difference between the Bragg wavelength of the FBG3 and the reference FBG2 is calibrated with the axial force. Through simulation and sensing tests, when the torque force calibration range is 10 mN·m, the torque average sensitivity is 22.8 pm/mN·m, and the determination coefficient R2 is 0.99992, with a hysteresis error YH and repetition error YR of 0.03%FS and 0.81%FS, respectively. When the axial force calibration rang is 5 N, the axial force average sensitivity is 0.089 nm/N, and the determination coefficient R2 is 0.9997, with hysteresis error YH and repetition error YR of 0.014%FS and 0.11%FS, respectively. The axial force resolution and torque resolution of the new type of puncturing needle sensor are 0.03 N and 0.8 mN·m, respectively. The experimental data and simulation analysis show that the proposed new type of puncturing needle sensor has good practicability and versatility.
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Fadzlina Naim, Nani, Nur Shahira Anuar, Suzi Seroja Sarnin, and Norsuzila Yaa’cob. "Design of metal plate temperature sensor based on fiber bragg grating (FBG)." Indonesian Journal of Electrical Engineering and Computer Science 15, no. 3 (September 1, 2019): 1282. http://dx.doi.org/10.11591/ijeecs.v15.i3.pp1282-1289.
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<p>This paper presents the design and characterization for metal plate temperature sensor based on Fiber Bragg Grating (FBG). Five types of FBGs were used such as Acrylate FBG, Bare FBG, Bimetallic Acrylate FBG, Bimetallic Bare FBG and Ceramic FBG to determine the sensitivity on four different plates at 23℃ to 70℃, experimentally. The four different plates are Aluminium, Aluminium Coating, Zinc and Zinc Coating has been used because of their excellent thermal conductivity. Two metals which are Copper and Zinc have been chosen to design the Bimetallic Strips FBG due to the Coefficient Thermal Expansion (CTE) to improve their sensitivity. The results show that Ceramic FBG has been chosen as the best temperature sensor because it has the highest sensitivity compared to other FBGs with sensitivity value of 50.4 and 59.7 pm <!--?mso-application progid="Word.Document"?--> 16(℃)-1"> when in contact with Aluminium and Zinc plates, respectively. In addition, Aluminium and Zinc plates has been chosen as the most reliable metal plates where it can transfer heat efficiently due to high thermal conductive which is 237 W/mK and 116 W/mK thus it gives the highest sensitivity when measured using Bimetallic Acrylate, Bimetallic Bare and Ceramic FBG.</p>
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Her, Shiuh-Chuan, and Wei-Nan Lin. "Simultaneous Measurement of Temperature and Mechanical Strain Using a Fiber Bragg Grating Sensor." Sensors 20, no. 15 (July 29, 2020): 4223. http://dx.doi.org/10.3390/s20154223.
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Based on the shift of the Bragg wavelength, fiber Bragg grating (FBG) sensors have been employed to measure a variety of physical parameters such as stress, strain, displacement, temperature, vibration and pressure. In this work, a simple and easy way to be implemented FBG sensing methodology was proposed to measure the temperature and strain simultaneously. Half of the FBG was bonded on the host structure, while the other half of the FBG was left free. The host structure was an aluminum test specimen with dimensions of 20 × 3.8 × 0.5 cm3. As the host structure subjected to mechanical and thermal loadings, the Bragg wavelengths reflected from the bonded and unbonded FBGs are different. Theoretical predictions of the Bragg wavelength shifts of the bonded and unbonded FBGs were presented. Utilizing the Bragg wavelength shift of unbonded FBG, the temperature can be determined and is independent of mechanical strain. The Bragg wavelength shift of the bonded FBG allows the determination of the mechanical strain. The temperature measured by FBG sensor was compared with the result from a thermocouple, while the mechanical strain was validated with the theoretical prediction. Good agreement between the experimental measurement and theoretical prediction demonstrates that temperature-strain discrimination can be realized using the proposed method with one single FBG sensor.
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Jin, Xiu Mei, Yu Mei Lv, and Li Feng Du. "Research on a New Detection Technique of FBG Using OTDR." Advanced Materials Research 317-319 (August 2011): 2346–50. http://dx.doi.org/10.4028/www.scientific.net/amr.317-319.2346.
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A new technique of using Optical Time Domain Reflectometry (OTDR) to detect the reflected power of FBG sensing array was researched systematically. The theoretical model between the reflected power detected by OTDR and the reflected wavelength of FBG was established by analyzing, and consequently the selection rule of FBG wavelength in OTDR detection system was proposed. Moreover, experiments about multi-combination of FBGs with high reflectivity were carried out. The cause of dummy peak and resonance peak in OTDR test curves were analyzed, and meanwhile the selection basis of FBG reflectivity was also given. Based on time division multiplexing theory, detecting low-reflectivity FBG by OTDR can increase the FBG multiplexing number greatly, which has wide prospect to be applied in FBG array detection.
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Lawrence, SO, TW Wright, CW Francis, PJ Fay, and PJ Haidaris. "Purification and functional characterization of homodimeric gamma B- gamma B fibrinogen from rat plasma." Blood 82, no. 8 (October 15, 1993): 2406–13. http://dx.doi.org/10.1182/blood.v82.8.2406.2406.
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Abstract Heterogeneity in the human and rat plasma fibrinogen (FBG) gamma chains is due to differential splicing of the primary gamma chain mRNA transcript. The subunit composition of FBG containing the predominant form of the gamma chain is homodimeric (human: A alpha 2, B beta 2, gamma 50-gamma 50; rat: A alpha 2, B beta 2, gamma A-gamma A). The subunit composition of FBG containing the longer, minor form of the gamma chain is heterodimeric (human: A alpha 2, B beta 2, gamma 50- gamma 57.5; rat: A alpha 2, B beta 2, gamma A-gamma B). The variant gamma chain-FBGs comprise about 10% of the total plasma FBG in the human and 30% in the rat. Although the presence of homodimeric gamma B- gamma B FBG has been speculated, proof of its existence has been difficult to obtain experimentally. We now show that 5% to 6% of rat plasma FBG is found as homodimeric FBG with a subunit composition of A alpha 2, B beta 2, gamma B-gamma B. Commercially purified rat FBG was further purified by diethylaminoethyl-Sephacel chromatography with a combined pH and ionic strength gradient. The enriched gamma B-gamma B FBG fraction eluted at the lowest pH (6.3) and highest ionic strength (4.5 mmho) due to its increased net negative charge. To further purify gamma B-gamma B FBG, a Mono Q column with an NaCl gradient was used. The subunit composition of the purified gamma B-gamma B FBG was confirmed by its electrophoretic mobility under reducing and denaturing conditions both as FBG, and clotted and cross-linked fibrin. Homodimeric gamma B-gamma B FBG was unable to support adenosine diphosphate (ADP)-induced platelet aggregation, whereas heterodimeric gamma A-gamma B FBG was able to support ADP-induced platelet aggregation at 40% of that achieved with homodimeric gamma A-gamma A FBG, similar to previous observations with human FBGs. Taken together, these results support the hypothesis that the A alpha-RGD sites alone are not sufficient for dimeric FBG support of platelet aggregation. Furthermore, the data suggest that at least one intact platelet recognition site at the carboxyterminus of the gamma A or gamma 50 chain is required.
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Lawrence, SO, TW Wright, CW Francis, PJ Fay, and PJ Haidaris. "Purification and functional characterization of homodimeric gamma B- gamma B fibrinogen from rat plasma." Blood 82, no. 8 (October 15, 1993): 2406–13. http://dx.doi.org/10.1182/blood.v82.8.2406.bloodjournal8282406.
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Heterogeneity in the human and rat plasma fibrinogen (FBG) gamma chains is due to differential splicing of the primary gamma chain mRNA transcript. The subunit composition of FBG containing the predominant form of the gamma chain is homodimeric (human: A alpha 2, B beta 2, gamma 50-gamma 50; rat: A alpha 2, B beta 2, gamma A-gamma A). The subunit composition of FBG containing the longer, minor form of the gamma chain is heterodimeric (human: A alpha 2, B beta 2, gamma 50- gamma 57.5; rat: A alpha 2, B beta 2, gamma A-gamma B). The variant gamma chain-FBGs comprise about 10% of the total plasma FBG in the human and 30% in the rat. Although the presence of homodimeric gamma B- gamma B FBG has been speculated, proof of its existence has been difficult to obtain experimentally. We now show that 5% to 6% of rat plasma FBG is found as homodimeric FBG with a subunit composition of A alpha 2, B beta 2, gamma B-gamma B. Commercially purified rat FBG was further purified by diethylaminoethyl-Sephacel chromatography with a combined pH and ionic strength gradient. The enriched gamma B-gamma B FBG fraction eluted at the lowest pH (6.3) and highest ionic strength (4.5 mmho) due to its increased net negative charge. To further purify gamma B-gamma B FBG, a Mono Q column with an NaCl gradient was used. The subunit composition of the purified gamma B-gamma B FBG was confirmed by its electrophoretic mobility under reducing and denaturing conditions both as FBG, and clotted and cross-linked fibrin. Homodimeric gamma B-gamma B FBG was unable to support adenosine diphosphate (ADP)-induced platelet aggregation, whereas heterodimeric gamma A-gamma B FBG was able to support ADP-induced platelet aggregation at 40% of that achieved with homodimeric gamma A-gamma A FBG, similar to previous observations with human FBGs. Taken together, these results support the hypothesis that the A alpha-RGD sites alone are not sufficient for dimeric FBG support of platelet aggregation. Furthermore, the data suggest that at least one intact platelet recognition site at the carboxyterminus of the gamma A or gamma 50 chain is required.
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Szécsi, Á., A. Szekeres, T. Bartók, G. Oros, M. Bartók, and Á. Mesterházy. "Fumonisin B1-4-producing capacity of Hungarian Fusarium verticillioides isolates." World Mycotoxin Journal 3, no. 1 (February 1, 2010): 67–76. http://dx.doi.org/10.3920/wmj2009.1152.
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The fumonisin B1-4 (FB1-4) toxin-producing capacities of 60 strains of Fusarium verticillioides isolated in the main maize-cultivating areas of Hungary were screened on rice grains in vitro. The amounts of FB1, FB2, FB3 and FB4 in the extracts of the culture material were determined by RP-HPLC/ESI-IT MS without any sample clean-up. All F. verticillioides strains produced all analogues (FB1-4) of the fumonisin B series. The strains did not differ significantly in their cultural characteristics, though the analytical results allowed the distinction of three idiosyncratic FB1-4-producing chemotypes with characteristic proportions of the fumonisin B analogues. The dominant chemotype produced them in the sequence FB1 > FB2 > FB3 > FB4, with large amounts of FB1 and FB2. A second chemotype produced a higher amount of FB3 than of FB2, while the third chemotype produced large amounts of FB2 and FB4. The proportion of FB1 in the extracts was inversely correlated with the total FB yield. No differences in FB1-4 producing capacity were observed between strains isolated from various locations or different sources.
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Leal-Junior, Arnaldo, Jonathan Casas, Carlos Marques, Maria Pontes, and Anselmo Frizera. "Application of Additive Layer Manufacturing Technique on the Development of High Sensitive Fiber Bragg Grating Temperature Sensors." Sensors 18, no. 12 (November 24, 2018): 4120. http://dx.doi.org/10.3390/s18124120.
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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.
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Huang, Xiao, Zhenkun Jin, and Qing Shen. "New Method of Temperature and Strain Decoupling Based on Directivity of Fiber Bragg Grating Sensing." Journal of Physics: Conference Series 2101, no. 1 (November 1, 2021): 012023. http://dx.doi.org/10.1088/1742-6596/2101/1/012023.
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Abstract Fiber Bragg Grating (FBG) has been widely used in temperature and strain measurement. Its center wavelength drift is affected by both temperature and strain. The influence of temperature and strain on center wavelength should be decoupled when measuring. In this paper, the sensing characteristics of FBG which pasted at different angles were simulated and analyzed, and it was found that FBG sensing for strain has strong directivity. A dual FBG composite construction based on the directivity of FBG sensing was proposed. Two FBGs were at an Angle of 62°. One FBG was sensitive to both temperature and strain, and the other was only sensitive to temperature. The structure can realize the decoupling of temperature and strain, and it doesn’t depend on feature of cantilever beam. It was verified by experimental analysis that the decoupling result was good by utilizing the combined FBG structure, and decoupling was realized easily.
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Wang, Xiao Xia, Chun Ying Wu, and Win Lin Wang. "The Application Research of the Matrix in Multi-Parameter Measurement FBGs." Advanced Materials Research 461 (February 2012): 702–6. http://dx.doi.org/10.4028/www.scientific.net/amr.461.702.
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The sensitivity of the FBG sensor based on multi-parameter measurement was established and determined by the matrix theory. The condition number of matrix was proposed to deduced the relationship among the measurement multi-parameters of the coated FBGs. The ill-conditioned matrix parameters can be removed, and the relationship between the FBGs sensitivities and many attribute parameters of the coated-FBG was found. As indicated by the experiment, when measure the temperature and the pressure at the same time, the sensitivities of FBG is higher by coated with different thickness of copper,and the second radius is less than 0.4mm,and the FBGs sensitivities can be improved to 5~10 times.
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Kokhanovskiy, Alexey, Nikita Shabalov, Alexandr Dostovalov, and Alexey Wolf. "Highly Dense FBG Temperature Sensor Assisted with Deep Learning Algorithms." Sensors 21, no. 18 (September 15, 2021): 6188. http://dx.doi.org/10.3390/s21186188.
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In this paper, we demonstrate the application of deep neural networks (DNNs) for processing the reflectance spectrum from a fiberoptic temperature sensor composed of densely inscribed fiber Bragg gratings (FBG). Such sensors are commonly avoided in practice since close arrangement of short FBGs results in distortion of the spectrum caused by mutual interference between gratings. In our work the temperature sensor contained 50 FBGs with the length of 0.95 mm, edge-to-edge distance of 0.05 mm and arranged in the 1500–1600 nm spectral range. Instead of solving the direct peak detection problem for distorted signal, we applied DNNs to predict temperature distribution from entire reflectance spectrum registered by the sensor. We propose an experimental calibration setup where the dense FBG sensor is located close to an array of sparse FBG sensors. The goal of DNNs is to predict the positions of the reflectance peaks of the reference sparse FBG sensors from the reflectance spectrum of the dense FBG sensor. We show that a convolution neural network is able to predict the positions of FBG reflectance peaks of sparse sensors with mean absolute error of 7.8 pm that is slightly higher than the hardware reused interrogator equal to 5 pm. We believe that dense FBG sensors assisted with DNNs have a high potential to increase spatial resolution and also extend the length of a fiber optical sensors.
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Navratil, Andrew, Junghyun Wee, and Kara Peters. "Ultrasonic frequency response of fiber Bragg grating under direct and remote adhesive bonding configurations." Measurement Science and Technology 33, no. 1 (November 3, 2021): 015204. http://dx.doi.org/10.1088/1361-6501/ac2fea.
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Abstract Ultrasonic inspection based structural health monitoring is a powerful technique for damage detection in a structure. Ultrasonic waves are often excited at different frequencies to detect damages of different sizes, therefore understanding the frequency response of the sensor can be used to optimize the sensor performance. Fiber Bragg gratings (FBGs) are widely used for this ultrasound collection. The sensitivity of FBGs to a particular ultrasonic frequency is a function of the FBG length and the ultrasonic wavelength. Recently the authors demonstrated that its ultrasound sensitivity is improved for some conditions when the FBG is bonded at a distance away from the adhesive bond, referred to as remote bonding. However, the frequency response of this configuration has not been studied. Therefore, in this paper we measure and compare the ultrasonic frequency responses between a conventional directly bonded FBG and remotely bonded FBG. In theory, the FBG sensitivity varies as a function of ultrasound wavelength-to-grating length (λ/L) ratio. Therefore, for this experimental study, we maintain L constant and vary λ by changing the frequency of the input ultrasonic waves. We demonstrate that there is a region, below a cut-off values of λ/L, for which the remotely bonded FBG output has a higher sensitivity to the Lamb wave amplitude than the directly bonded FBG. The exact value of this λ/L cut-off depends on the mechanical properties of the structure, the windowing of the input Lamb wave, and the FBG properties. We also demonstrate that windowing the Lamb wave excitation signal has a similar affect to apodizing the FBG sensor in modifying the sensitivity response curve.
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Wachtarczyk, Karol, Marcel Bender, Ewald Fauster, Ralf Schledjewski, Paweł Gąsior, and Jerzy Kaleta. "Gel Point Determination in Resin Transfer Molding Process with Fiber Bragg Grating Inscribed in Side-Hole Elliptical Core Optical Fiber." Materials 15, no. 18 (September 19, 2022): 6497. http://dx.doi.org/10.3390/ma15186497.
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Material as well as process variations in the composites industry are reasons to develop methods for in-line monitoring, which would increase reproducibility of the manufacturing process and the final composite products. Fiber Bragg Gratings (FBGs) have shown to be useful for monitoring liquid-composite molding processes, e.g., in terms of online gel point detection. Existing works however, focus on in-plane strain measurements while out-of-plane residual strain prevails. In order to measure out-of-plane strain, FBG inscribed in highly birefringent fiber (HB FBG) can be used. The purpose of this research is the cure stage detection with (a) FBG inscribed in single mode and (b) FBG inscribed in highly-birefringent side-hole fiber in comparison to the reference gel point detected with an in-mold DC sensor. Results reveal that the curing process is better traceable with HB FBG than with regular FBG. Thus, the use of HB FBG can be a good method for the gel point estimation in the RTM process.
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Tavares, Cátia, Daniela Real, Maria de Fátima Domingues, Nélia Alberto, Hugo Silva, and Paulo Antunes. "Sensor Cell Network for Pressure, Temperature and Position Detection on Wheelchair Users." International Journal of Environmental Research and Public Health 19, no. 4 (February 15, 2022): 2195. http://dx.doi.org/10.3390/ijerph19042195.
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This work proposes an optical sensing network to monitor pressure and temperature in specific areas of a wheelchair to prevent pressure ulcers and to monitor the position of the wheelchair user by analyzing its pressure distribution. The sensing network is composed of six optical fiber Bragg grating (FBG)-based sensor cells. Each sensor cell is built from a polylactic acid (PLA) base and has two FBGs, one embedded in epoxy resin to monitor pressure variations (FBGP) and another without resin to monitor temperature (FBGT). Once produced, all sensor cells were experimentally characterized for pressure and temperature variations, resulting in an average pressure sensitivity of 81 ± 5 pm/kPa (FBGP) and −5.0 ± 0.4 pm/kPa (FBGT), and an average temperature sensitivity of 25 ± 1 pm/°C (FBGP) and 47.7 ± 0.7 pm/°C (FBGT). The sensor cells were then placed in six specific areas of a wheelchair (four in the seat area and two in the shoulder blade area) to carry out experimental tests, wherein the response of the sensors to a specific sequence of relief positions was tested. During the execution of the test, the optical signal of all sensors was monitored, in real time, with the pressure and temperature values detected in each zone of the wheelchair. In addition, random position changes were performed in order to evaluate the precision of the proposed sensing network in the identification of such positions.
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Manie, Yibeltal Chanie, Run-Kai Shiu, Peng-Chun Peng, Bao-Yi Guo, Mekuanint Agegnehu Bitew, Wei-Chieh Tang, and Hung-Kai Lu. "Intensity and Wavelength Division Multiplexing FBG Sensor System Using a Raman Amplifier and Extreme Learning Machine." Journal of Sensors 2018 (September 13, 2018): 1–11. http://dx.doi.org/10.1155/2018/7323149.
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A fiber Bragg grating (FBG) sensor is a favorable sensor in measuring strain, pressure, vibration, and temperature in different applications, such as in smart structures, wind turbines, aerospace, industry, military, medical centers, and civil engineering. FBG sensors have the following advantages: immune to electromagnetic interference, light weight, small size, flexible, stretchable, highly accurate, longer stability, and capable in measuring ultra-high-speed events. In this paper, we propose and demonstrate an intensity and wavelength division multiplexing (IWDM) FBG sensor system using a Raman amplifier and extreme learning machine (ELM). We use an IWDM technique to increase the number of FBG sensors. As the number of FBG sensors increases and the spectra of two or more FBGs are overlapped, a conventional peak detection (CPD) method is unappropriate to detect the central Bragg wavelength of each FBG sensor. To solve this problem, we use ELM techniques. An ELM is used to accurately detect the central Bragg wavelength of each FBG sensor even when the spectra of FBGs are partially or fully overlapped. Moreover, a Raman amplifier is added to a fiber span to generate a gain medium within the transmission fiber, which amplifies the signal and compensates for the signal losses. The transmission distance and the sensing signal quality increase when the Raman pump power increases. The experimental results revealed that a Raman amplifier compensates for the signal losses and provides a stable sensing output even beyond a 45 km transmission distance. We achieve a remote sensing of strain measurement using a 45 km single-mode fiber (SMF). Furthermore, the well-trained ELM wavelength detection methods accurately detect the central Bragg wavelengths of FBG sensors when the two FBG spectra are fully overlapped.
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Pereira, Katiuski, Renan Costa Lazaro, Wagner Coimbra de Moraes Coimbra de Moraes Junior, Anselmo Frizera Frizera Neto, and Arnaldo Gomes Leal-Junior. "Simulation of FBG Temperature Sensor Array for Oil Identification via Random Forest Classification." Engineering Proceedings 2, no. 1 (November 14, 2020): 20. http://dx.doi.org/10.3390/ecsa-7-08177.
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Water–oil separation is important in the oil industry, as the incorrect classification of oil can lead to losses in the production and have an environmental impact. This paper proposes the use of fiber Bragg grating (FBG) temperature sensor array to identify the oil in water–emulsion–oil systems, using only the temperature responses for oil classification results in operational and economic benefits. To demonstrate the possibility of using the FBG temperature sensor to classify oil level, the temperature distribution of an oil storage tank, with 2 m height and 0.8 m in diameter, is simulated using thermal distribution models. Then, the temperature effect in a 2 m long FBG array with a different number and distribution of FBGs is simulated using the transfer matrix method. In each case, we extract the wavelength shift (Δλ), total width at half the maximum (FWHM) and the location of the FBG in the fiber. For the oil classification, we dichotomized the fluids into oil and non-oil (water and emulsion). Due to the low separability of the classes, the random forest algorithm was chosen for classification, starting with 200 FBG equidistant sensors and decreasing to 6, with different distributions along the fiber. As expected, the highest accuracy occurs with the 200 FBGs array (96%). However, it was possible to classify the oil with an accuracy of 94.89% with only 8 FBGs, using tests for two proportions (with a significance of 5%); the accuracy of 8 FBGs is the same as of 50 FBGs.
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Zhang, Zhe, Baijie Xu, Jun He, Maoxiang Hou, Weijia Bao, and Yiping Wang. "High-Efficiency Inscription of Fiber Bragg Grating Array with High-Energy Nanosecond-Pulsed Laser Talbot Interferometer." Sensors 20, no. 15 (August 1, 2020): 4307. http://dx.doi.org/10.3390/s20154307.
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A high-energy nanosecond-pulsed ultraviolet (UV) laser Talbot interferometer for high-efficiency, mass production of fiber Bragg grating (FBG) array was experimentally demonstrated. High-quality FBG arrays were successfully inscribed in both H2-free and H2-loaded standard single-mode fibers (SMFs) with high inscription efficiency and excellent reproducibility. Compared with the femtosecond pulse that had a coherent length of several tens of micrometers, a longer coherent length (~10 mm) of the employed laser rendered a wider FBG wavelength versatility over 700 nm band (1200–1900 nm) without the need for optical path difference (OPD) compensation. Dense FBG array with center wavelength separation of ~0.4 nm was achieved and more than 1750 FBGs with separated center wavelength could be inscribed in a single H2-free or H2-loaded SMF in theory, which is promising for mass production of FBG arrays in industry. Moreover, precise focusing of laser beam was superfluous for the proposed system due to the high energy density of pulse. The proposed FBG inscription system was promising for industrialization production of dense FBG arrays.
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Jung, Dal Woo, Il Bum Kwon, and Nak Sam Choi. "Application of a Temperature-Compensating FBG Sensor to Strain Measurement." Advanced Materials Research 26-28 (October 2007): 1089–92. http://dx.doi.org/10.4028/www.scientific.net/amr.26-28.1089.
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A temperature-compensating fiber Bragg grating(FBG) sensor having two different FBGs in one fiber line was applied to the real time measurement of mechanical normal strain in structures. Measurement of mechanical strains of the aluminum beam surface by the double FBG sensor was performed under various thermal conditions, which was compared with results of electrical resistance strain gage. The FBG sensor fabricated in this study could detect accurately values of mechanical strains without containing any thermal strain component.
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CHOI, NAK-SAM, and DAL-WOO JUNG. "A CALIBRATION METHOD OF MECHANICAL STRAINS FROM A TEMPERATURE-COMPENSATING FBG SENSOR." Modern Physics Letters B 22, no. 11 (May 10, 2008): 1111–15. http://dx.doi.org/10.1142/s0217984908015929.
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The sensitivity of a temperature-compensating fiber Bragg grating (FBG) sensor which has different FBGs in one fiber line was analyzed for the real time measurement of mechanical normal strain in structures. Measurement of mechanical strains of the aluminum beam surface by the double FBG sensor was performed under various heating rates and temperature range. The results were compared with those of an electrical resistance strain gage. A considerable delay in the strain measurement by the double FBG sensor during the heating process was shown, which could be quantified for the strain compensation by the introduction of a strain retardation factor to the FBG sensor.
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Wu, Huifeng, Lei Liang, Hui Wang, Shu Dai, Qiwei Xu, and Rui Dong. "Design and Measurement of a Dual FBG High-Precision Shape Sensor for Wing Shape Reconstruction." Sensors 22, no. 1 (December 28, 2021): 168. http://dx.doi.org/10.3390/s22010168.
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FBG shape sensors based on soft substrates are currently one of the research focuses of wing shape reconstruction, where soft substrates and torque are two important factors affecting the performance of shape sensors, but the related analysis is not common. A high-precision soft substrates shape sensor based on dual FBGs is designed. First, the FBG soft substrate shape sensor model is established to optimize the sensor size parameters and get the optimal solution. The two FBG cross-laying method is adopted to effectively reduce the influence of torque, the crossover angle between the FBGs is 2α, and α = 30° is selected as the most sensitive angle to the torquer response. Second, the calibration test platform of this shape sensor is built to obtain the linear relationship among the FBG wavelength drift and curvature, rotation radian loaded vertical force and torque. Finally, by using the test specimen shape reconstruction test, it is verified that this shape sensor can improve the shape reconstruction accuracy, and that its reconstruction error is 6.13%, which greatly improves the fit of shape reconstruction. The research results show that the dual FBG high-precision shape sensor successfully achieves high accuracy and reliability in shape reconstruction.
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Xu, Hongbin, Xinyu Zheng, Weigang Zhao, Xu Sun, Feng Li, Yanliang Du, Bo Liu, and Yang Gao. "High Precision, Small Size and Flexible FBG Strain Sensor for Slope Model Monitoring." Sensors 19, no. 12 (June 17, 2019): 2716. http://dx.doi.org/10.3390/s19122716.
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In this paper, a soft fiber Bragg grating (FBG) strain sensor was constructed of a rubber strip, FBGs and steel plates, which exhibits the advantages of high precision and a small size. A series of FBGs was uniformly pasted on a flexible rubber strip which can monitor the slope deformation by measuring the bending deformation of the rubber strip. Most notably, this sensor can be used to monitor horizontal displacement in the subsurface of the slope model. The relationships among the bending angle of the rubber strip, the strain of the rubber strip, and the subsurface deformation of the slope model were established. In addition, the subsurface deformation of the slope model can be obtained by the FBG strain sensor monitoring. Since a rigid-flexible structure was formed by uniformly pasting a series of steel plates on the other side of the rubber strip, the sensitivity of the FBG strain sensor was improved to be 1.5425 nm/°. The measurement results verify that the FBG strain sensor shows good performance, and the model test results demonstrate that the FBG strain sensor can be used for monitoring the subsurface deformation of the slope model.
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Naim, Nani Fadzlina, Siti Noor Maslizan Sudin, Suzi Seroja Sarnin, Norsuzila Ya'acob, and Latifah Sarah Supian. "Design of fiber bragg grating (FBG) temperature sensor based on optical frequency domain reflectometer (OFDR)." International Journal of Electrical and Computer Engineering (IJECE) 10, no. 3 (June 1, 2020): 3158. http://dx.doi.org/10.11591/ijece.v10i3.pp3158-3165.
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In this paper, the simulation of Fiber Bragg Grating (FBG) as a temperature sensor is conducted. The FBG temperature sensor is designed based on Optical Frequency Domain Reflectometer (OFDR) concept. A continuous wave (CW) laser is used as the optical source and it is transmitted to two FBGs. The two FBGs reflection spectra will produce a beat frequency that can be detected using a Radio Frequency (RF) Spectrum Analyzer. Any temperature change will shift Bragg wavelength, thus produce a shift for the beat frequency. In this work, an FBG with temperature sensitivity 10 pm/˚C is employed. It is found that by using this technique, a high-resolution temperature sensor can be designed with temperature resolution of 0.1˚C.
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Aniskovich, V. A., O. N. Budadin, S. O. Kozelskaya, Yu G. Kutyurin, and A. N. Rykov. "IDENTIFICATION OF TEMPERATURE SENSITIVITY DETECTOR ON FIBER BRAGG GRATING (FBG) SENSOR." Kontrol'. Diagnostika, no. 287 (May 2022): 26–33. http://dx.doi.org/10.14489/td.2022.05.pp.026-033.
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The article presents the results of work on the study of the dependence of the results of temperature measurements using fiber Bragg gratings (FBGs). It was found that FBGs not only have different initial sensitivity, but also exhibit nonlinearity even in a narrow temperature range (from –30 to +70 °C). It is shown that to use the FBG as temperature sensors, it is necessary to precalibrate the FBG by temperature.
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Wei, Jie, Yanpeng Hao, Yuan Fu, Lin Yang, Jiulin Gan, and Han Li. "Experimental Study on Glaze Icing Detection of 110 kV Composite Insulators Using Fiber Bragg Gratings." Sensors 20, no. 7 (March 26, 2020): 1834. http://dx.doi.org/10.3390/s20071834.
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Icing detection of composite insulators is essential for the security and stability of power grids. As conventional methods have met difficulties in harsh weather, a 110 kV composite insulator with embedded Fiber Bragg Gratings (FBGs) was proposed for detecting glaze icing in this paper. FBG temperature compensation sensors in ceramic tubes were adopted for simultaneous measurement of icicle loads and temperature. Then, temperature calibration experiments and simulated icicle load experiments were carried out to obtain temperature and icicle load characteristics of FBGs. The results showed that temperature sensitivities of FBG strain sensors and FBG temperature compensation sensors were 18.16 pm/°C, and 13.18 pm/°C, respectively. Besides, wavelength shifts were linearly related to icicle loads within the polar angle range of −60° to 60°, and the load coefficient of FBG facing the icicle was -34.6 pm/N. In addition, the wavelength shift generated by several icicles was equal to the sum of wavelength shifts generated by each icicle within the polar angle range of −15° to 15°. Finally, icicles can cause wavelength shifts of FBGs within a big shed spacing. The paper provides a novel icing detection technology for composite insulators in transmission lines.
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Wang, Zi, Xiang Zhang, Yue Gang Tan, and Tian Liang Li. "A Research on High-Precision Strain Measurement Based on FBG with Temperature Compensation." Advanced Materials Research 1083 (January 2015): 121–26. http://dx.doi.org/10.4028/www.scientific.net/amr.1083.121.
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FBG (Fiber Bragg Grating) is a new type of optical passive device which can be used in sensing field. This paper demonstrates the feasibility and effectiveness of FBG as the new method of strain measurement, and improves the measuring precision. Based on the strain sensing property of FBG, the study adopts the differential method of double FBGs to make temperature compensation, and conduct the contrast experiment with resistance strain chip. The experimental results show that strain measurement based on FBG agrees well with theoretical calculation. The measurement error: no more than 1%, linear fitting correlation coefficient: almost 1, linearity: 0.17%, sensitivity: 7.92, hysteresis error: 0.347%, repeatability error: 0.333%. The results show FBG’s performance are superior to resistance strain chip, especially in aspect of measuring precision. Therefore, we can conclude that FBG is a feasible and effective method of strain measurement.
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Cardoso, Victor, Paulo Caldas, M. Giraldi R. Thereza, Orlando Frazão, Claudio Carvalho, João Costa, and José L. Santos. "Sensor Based on Multiple Fiber Bragg Gratings for Diameter Measurement." EPJ Web of Conferences 238 (2020): 12013. http://dx.doi.org/10.1051/epjconf/202023812013.
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A method based on multiple Fiber Bragg Gratings (FBG) and a structure fabricated using a 3D printer for diameter measurement is proposed and experimentally demonstrated. The sensor is easily developed inserting the FBG on the structure and fixing the FBG in two points. Due to this arrangement, when the diameter is reduced a force is applied on the sensor and this causes a wavelength shift. The study is divided in two steps using one experimental setup. At first, each FBG response is independently evaluated concerning the diameter variation and after that, the FBGs are evaluated together. The results demonstrated that the structure can be used as a way to monitor the diameter variation in some applications.
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Lu, Huanlang, Shuai Zhang, Yunshuai Yao, Yukun Yan, Zecong Lin, and Pingyu Zhu. "Low temperature characteristics of FBG with free arc shape for low temperature monitoring." Journal of Physics: Conference Series 2366, no. 1 (November 1, 2022): 012015. http://dx.doi.org/10.1088/1742-6596/2366/1/012015.
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Abstract It is important to monitor the iced condition for operating wind turbine blades. However, most sensors are difficult to be used in this quite cold and lightweight environment. Although the fiber bragg grating (FBG) is a good candidate for the case. With the change of the temperature, the thermal expansion coefficient and thermo-optical coeffecient of FBG material will affect the accuracy of characteristics of FBG sensor. Aiming at the application of fiber optic sensor in low temperature environment and ultrathin requirement, the low temperature characteristics of FBG sensor with free arc shape package has been studied. The low temperature calibration experiments of two packaged FBG samples are tested from -35°C ~20°C in a constant temperature freezer with alcohol tank. The effects of low temperature characteristics of two FBGs packaged with free straight and arc shape tubes are compared. The results show that arc shape can effectively reduce the repeatability error and improve its accuracy due to providing possible low temperature contracting of the optical fibers. Flat arc shape makes it possible to package ultrathin FBG temperature sensor.
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Nan, Ying-Gang, Nazila Safari Yazd, Ivan Chapalo, Karima Chah, Xuehao Hu, and Patrice Mégret. "Properties of Fiber Bragg Grating in CYTOP Fiber Response to Temperature, Humidity, and Strain Using Factorial Design." Sensors 22, no. 5 (March 1, 2022): 1934. http://dx.doi.org/10.3390/s22051934.
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The characteristics of fiber Bragg grating (FBG) in cyclic transparent fluoropolymer (CYTOP) optical fiber have attracted more and more attention in recent years. However, different results of the FBG response to environmental parameters are reported. This work presents a three-variable two-level factorial experimental method to investigate the FBG response to temperature, humidity, and strain in CYTOP fiber. Two uniform FBGs are inscribed separately in CYTOP fiber with and without over-clad. With only eight measuring points, the interactions among three variable parameters are computed and the parameter sensitivities and cross-sensitivities are estimated. Similar temperature and strain sensitivities were found for both gratings, whereas significant cross-sensitivity between humidity and temperature was present only in FBG inscribed in CYTOP fiber with over-clad.
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Chen, Lawrence R., Maria-Iulia Comanici, Parisa Moslemi, Jingjing Hu, and Peter Kung. "A Review of Recent Results on Simultaneous Interrogation of Multiple Fiber Bragg Grating-Based Sensors Using Microwave Photonics." Applied Sciences 9, no. 2 (January 15, 2019): 298. http://dx.doi.org/10.3390/app9020298.
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We review recent results on exploiting microwave photonics to enable simultaneous interrogation of multiple fiber Bragg grating (FBG)-based sensors. In particular, we describe the use of (1) microwave photonic filtering and (2) chirped microwave pulse generation and compression as a means to map the wavelength (spectral) changes in the response of FBG-based sensors (specifically, an in-fiber Fabry-Pérot cavity sensor based on FBGs, FBG sensors directly, and a linearly chirped FBG sensor) to applied temperature (or strain) to the power of a radio-frequency signal (i.e., a wavelength-to-power mapping) or to the correlation peak of the compressed microwave signal. The approaches support high-resolution and high-speed interrogation and can be suitable for large scale sensing networks.
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Che, Zonglun, Pan Xu, Chunyan Cao, XiJia Gu, Lina Ma, Jing Zhu, and Jun Wang. "Single-core multi-channel moiré fiber grating and multi-wavelength LMA fiber grating fabricated based on two-dimensional spatially encoded phase mask." AIP Advances 12, no. 12 (December 1, 2022): 125120. http://dx.doi.org/10.1063/5.0124468.
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A two-dimensional optical fiber grating with multi sub-gratings based on a 2D spatially encoded phase mask is designed in this study. The 2D fiber Bragg grating (FBG) is composed of two non-overlapping sub-FBGs, which are laterally separated along the radial direction of the fiber core. Unlike traditional FBGs, the refractive index of the 2D FBG is modulated both on the axial and radial directions of the fiber core, which are realized by spatially encoded diffraction based on a 2D spatially encoded phase mask. Compared with the overlapping grating, the 2D FBG can be fabricated at one time to achieve multi-wavelength output, and its compact structure provides a new idea for multi-wavelength multiplexing. As examples, a single-core multi-channel moiré fiber grating and 2D FBG with three subgratings are designed and fabricated on a single-mode fiber and LMA fiber, respectively. Using a 2D spatially encoded mask can improve the optical fiber refractive index modulation from one- to two- or even three-dimensions, which is helpful for precise manipulation of the complex optical field of optical fiber.
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Dehnaw, Amare Mulatie, Yibeltal Chanie Manie, Ya Yu Chen, Po Han Chiu, Hung Wei Huang, Guan Wei Chen, and Peng Chun Peng. "Design Reliable Bus Structure Distributed Fiber Bragg Grating Sensor Network Using Gated Recurrent Unit Network." Sensors 20, no. 24 (December 21, 2020): 7355. http://dx.doi.org/10.3390/s20247355.
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The focus of this paper was designing and demonstrating bus structure FBG sensor networks using intensity wavelength division multiplexing (IWDM) techniques and a gated recurrent unit (GRU) algorithm to increase the capability of multiplexing and the ability to detect Bragg wavelengths with greater accuracy. Several Fiber Bragg grating (FBG) sensors are coupled with power ratios of 90:10 and 80:10, respectively in the suggested experimental setup. We used the latest IWDM multiplexing technique for the proposed scheme, as the IWDM system increases the number of sensors and allows us to alleviate the limited operational region drawback of conventional wavelength division multiplexing (WDM). However, IWDM has a crosstalk problem that causes high-sensor signal measurement errors. Thus, we proposed the GRU model to overcome this crosstalk or overlapping problem by converting the spectral detection problem into a regression problem and considered the sequence of spectral features as input. By feeding this sequential spectrum dataset into the GRU model, we trained the GRU system until we achieved optimal efficiency. Consequently, the well-trained GRU model quickly and accurately identifies the Bragg wavelength of each FBG from the overlapping spectra. The Bragg wavelength detection performance of our proposed GRU model is tested or validated using different numbers of FBG sensors, such as 3-FBG, 5-FBG, 7-FBG, and 10-FBG, separately. As a result, the experiment result proves that the well-trained GRU model accurately identifies each FBG Bragg wavelength, and even the number of FBG sensors increase, as well as the spectra of FBGs, which are partially or fully overlapped. Therefore, to boost the detection efficiency, reliability, and to increase the multiplexing capabilities of FBG sensor networks, the proposed sensor system is better than the other previously proposed methods.
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Heilmeier, Florian, Robert Koos, Michael Singer, Constantin Bauer, Peter Hornberger, Jochen Hiller, and Wolfram Volk. "Evaluation of Strain Transition Properties between Cast-In Fibre Bragg Gratings and Cast Aluminium during Uniaxial Straining." Sensors 20, no. 21 (November 4, 2020): 6276. http://dx.doi.org/10.3390/s20216276.
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Current testing methods are capable of measuring strain near the surface on structural parts, for example by using strain gauges. However, stress peaks often occur within the material and can only be approximated. An alternative strain measurement incorporates fibre-optical strain sensors (Fiber Bragg Gratings, FBG) which are able to determine strains within the material. The principle has already been verified by using embedded FBGs in tensile specimens. The transition area between fibre and aluminium, however, is not yet properly investigated. Therefore, strains in tensile specimens containing FBGs were measured by neutron diffraction in gauge volumes of two different sizes around the Bragg grating. As a result, it is possible to identify and decouple elastic and plastic strains affecting the FBGs and to transfer the findings into a fully descriptive FE-model of the strain transition area.We thus accomplished closing the gap between the external load and internal straining obtained from cast-in FBG and generating valuable information about the mechanisms within the strain transition area.It was found that the porosity within the casting has a significant impact on the stiffness of the tensile specimen, the generation of excess microscopic tensions and thus the formation of permanent plastic strains, which are well recognized by the FBG. The knowledge that FBG as internal strain sensors function just as well as common external strain sensors will now allow for the application of FBG in actual structural parts and measurements under real load conditions. In the future, applications for long-term monitoring of cast parts will also be enabled and are currently under development.
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Chen, Runxiao, Jun He, Xizhen Xu, Jiafeng Wu, Ying Wang, and Yiping Wang. "High-Quality Fiber Bragg Gratings Inscribed by Femtosecond Laser Point-by-Point Technology." Micromachines 13, no. 11 (October 23, 2022): 1808. http://dx.doi.org/10.3390/mi13111808.
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We experimentally studied the inscription of fiber Bragg gratings by using femtosecond (fs) laser point-by-point (PbP) technology. The effects of the focusing geometry, grating order, laser energy and grating length on the spectral characteristics of the PbP FBG were investigated. After optimizing these parameters, a high-quality first-order PbP FBG with a reflectivity > 99.9% (i.e., Bragg resonance attenuation of 37.7 dB) and insertion loss (IL) of 0.03 dB was successfully created. Moreover, taking advantage of the excellent flexibility of the fs laser PbP technology, high-quality FBGs with various Bragg wavelengths ranging from 856 to 1902.6 nm were inscribed. Furthermore, wavelength-division-multiplexed (WDM) FBG arrays consisting of 10 FBGs were rapidly constructed. Additionally, a Fabry-Perot cavity was realized by using two high-quality FBGs, and its birefringence could be reduced from 3.04 × 10−5 to 1.77 × 10−6 by using a slit beam shaping-assisted femtosecond laser PbP technology. Therefore, such high-quality FBGs are promising to improve the performance of optical fiber sensors, lasers and communication devices.
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Buck, T. C., M. S. Müller, and A. W. Koch. "Theoretical Assessment of an All-Optical Temporal Low-Pass Filter for Dynamic Fiber Bragg Grating Signals." Journal of Sensors 2011 (2011): 1–5. http://dx.doi.org/10.1155/2011/302380.
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Fiber Bragg grating (FBG) sensors are used in numerous applications. Currently, the assessment of dynamic loads with FBGs is of increasing interest. Those applications include vibration analysis, acceleration, or dynamic strain estimation. The acquisition of dynamic signals usually incorporates the application of signal low-pass filtering before signal quantization. FBG interrogators based on spectrometers or scanning lasers inherently have a limited antialiasing capability for dynamic FBG signals. We present a theoretical analysis of an all optical low-pass filter for spectrometer-based interrogators. The low-pass filter is based on the application of a luminescent material onto the detector. Light absorption and continuous light reemission lead to an advanced attenuation of high FBG signal frequencies. An analytic derivation of the system transfer function and numerical signal simulations are presented.
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Usman, Auwalu, Nadiatulhuda Zulkifli, Mohd Rashidi Salim, and Kharina Khairi. "AN ENHANCED G-PON FAULT MONITORING TECHNIQUE USING OPTICAL SENSOR." Science Proceedings Series 1, no. 2 (April 24, 2019): 39–42. http://dx.doi.org/10.31580/sps.v1i2.621.
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In this study a technique for a centralized fault monitoring and detection in Gigabit-capable Passive Optical Network (G-PON) using fiber Bragg grating (FBG) sensor is proposed. The technique detects fault once it occurs at the vulnerable locations in the fiber optic distribution link by the proposed FBG devices. Monitoring signal in the C-band is reflected by a uniform FBG with different Bragg wavelengths and reflectivities. The FBGs serve as branch identifiers in the network. The reflected signal from the FBGs is analyzed at the Optical Line Terminal (OLT) in the Central Office (CO) by an Optical Spectrum Analyzer (OSA), to identify the branch with rupture in the network. The simulated result obtained shows that the system can monitor, and detect a fault in the physical layer of the optical distribution network with negligible effects on data signal transmission.
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Zhang, Wen, Lianqing Zhu, Mingli Dong, Xiaoping Lou, and Feng Liu. "A Temperature Fiber Sensor Based on Tapered Fiber Bragg Grating Fabricated by Femtosecond Laser." Applied Sciences 8, no. 12 (December 14, 2018): 2616. http://dx.doi.org/10.3390/app8122616.
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A temperature fiber sensor based on tapered fiber Bragg grating (tapered FBG) fabricated by femtosecond laser has been proposed and realized with good reproducibility. Firstly, the fiber taper with 25 μm diameter and 1000 μm length is fabricated by arc-discharge elongation using two standard single-mode fibers. Secondly, two first-order FBGs are fabricated in tapered and non-tapered fiber regions for comparison. Both FBGs are point-by-point direct-written by femtosecond laser, and the grating lengths are 1000 μm. Thirdly, a temperature experiment is performed using a heating chamber, and experimental results show that in the range of 30~350 °C, the temperature sensitivity of the tapered FBG has increased from 11.0 pm/°C to 12.3 pm/°C. The tapered FBG proposed here can be further configured for sensing other parameters in physical, chemical, and biomedical applications.
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Manie, Yibeltal Chanie, Jyun-Wei Li, Peng-Chun Peng, Run-Kai Shiu, Ya-Yu Chen, and Yuan-Ta Hsu. "Using a Machine Learning Algorithm Integrated with Data De-Noising Techniques to Optimize the Multipoint Sensor Network." Sensors 20, no. 4 (February 16, 2020): 1070. http://dx.doi.org/10.3390/s20041070.
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In this paper, for an intensity wavelength division multiplexing (IWDM)-based multipoint fiber Bragg grating (FBG) sensor network, an effective strain sensing signal measurement method, called a long short-term memory (LSTM) machine learning algorithm, integrated with data de-noising techniques is proposed. These are considered extremely accurate for the prediction of very complex problems. Four ports of an optical coupler with distinct output power ratios of 70%, 60%, 40%, and 30% have been used in the proposed distributed IWDM-based FBG sensor network to connect a number of FBG sensors for strain sensing. In an IWDM-based FBG sensor network, distinct power ratios of coupler ports can contain distinct powers or intensities. However, unstable output power in the sensor system due to random noise, harsh environments, aging of the equipment, or other environmental factors can introduce fluctuations and noise to the spectra of the FBGs, which makes it hard to distinguish the sensing signals of FBGs from the noise signals. As a result, noise reduction and signal processing methods play a significant role in enhancing the capability of strain sensing. Thus, to reduce the noise, to improve the signal-to-noise ratio, and to accurately measure the sensing signal of FBGs, we proposed a long short-term memory (LSTM) deep learning algorithm integrated with discrete waveform transform (DWT) data smoother (de-noising) techniques. The DWT data de-noising methods are important techniques for analyzing and de-noising the sensor signals, and it further improves the strain sensing signal measurement accuracy of the LSTM model. Thus, after de-noising the sensor data, these data are fed into the LSTM model to measure the sensing signal of each FBG. The experimental results prove that the integration of LSTM with the DWT data de-noising technique achieved better sensing signal measurement accuracy, even in noisy data or environments. Therefore, the proposed IWDM-based FBG sensor network can accurately sense the signal of strain, even in bad or noisy environments; can increase the number of FBG sensors multiplexed in the sensor system; and can enhance the capacity of the sensor system.
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Goossens, Sidney, Francis Berghmans, and Thomas Geernaert. "Spectral Verification of the Mechanisms behind FBG-Based Ultrasonic Guided Wave Detection." Sensors 20, no. 22 (November 17, 2020): 6571. http://dx.doi.org/10.3390/s20226571.
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Ultrasonic guided wave (UGW) detection with fiber Bragg grating (FBG)-based sensors has received increasing attention in the last decades due to the ability to perform non-destructive inspection (NDI) of large plate-like surfaces with a network of lightweight and multiplexed sensors. For accurate UGW measurements, several studies concluded that the ratio between the wavelength of the UGW and the length of the FBG should be above 7. However, shorter FBGs suffer from a lower FBG reflectivity and less steep slopes in the reflection spectrum. In this work we experimentally verified the effect of a passing UGW on the Bragg peak of FBG sensors of different lengths. By performing edge-filtering interrogation throughout the FBG’s reflection spectrum, we were able to reconstruct the FBG’s spectral response to a UGW in function of time. Our experimental findings are partially in line with those in the literature considering the UGW wavelength to FBG length ratio and the corresponding Bragg peak changes. We experimentally show for the first time that for shorter FBG sensors, the strain modulation is translated mostly into Bragg peak shifting, while for longer FBG sensors, Bragg peak deformation takes over as main mechanism. Despite the different mechanism for the latter, the UGW can still be detected by edge-filtering on the steepest slope, and with a much higher sensitivity.
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Chilelli, Sean K., John J. Schomer, and Marcelo J. Dapino. "Detection of Crack Initiation and Growth Using Fiber Bragg Grating Sensors Embedded into Metal Structures through Ultrasonic Additive Manufacturing." Sensors 19, no. 22 (November 12, 2019): 4917. http://dx.doi.org/10.3390/s19224917.
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Structural health monitoring (SHM) is a rapidly growing field focused on detecting damage in complex systems before catastrophic failure occurs. Advanced sensor technologies are necessary to fully harness SHM in applications involving harsh or remote environments, life-critical systems, mass-production vehicles, robotic systems, and others. Fiber Bragg Grating (FBG) sensors are attractive for in-situ health monitoring due to their resistance to electromagnetic noise, ability to be multiplexed, and accurate real-time operation. Ultrasonic additive manufacturing (UAM) has been demonstrated for solid-state fabrication of 3D structures with embedded FBG sensors. In this paper, UAM-embedded FBG sensors are investigated with a focus on SHM applications. FBG sensors embedded in an aluminum matrix 3 mm from the initiation site are shown to resolve a minimum crack length of 0.286 ± 0.033 mm and track crack growth until near failure. Accurate crack detection is also demonstrated from FBGs placed 6 mm and 9 mm from the crack initiation site. Regular acrylate-coated FBG sensors are shown to repeatably work at temperatures up to 300 ∘ C once embedded with the UAM process.
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Agliullin, Timur, Vladimir Anfinogentov, Oleg Morozov, Airat Sakhabutdinov, Bulat Valeev, Ayna Niyazgulyeva, and Yagmyrguly Garovov. "Comparative Analysis of the Methods for Fiber Bragg Structures Spectrum Modeling." Algorithms 16, no. 2 (February 10, 2023): 101. http://dx.doi.org/10.3390/a16020101.
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The work is dedicated to a comparative analysis of the following methods for fiber Bragg grating (FBG) spectral response modeling. The Layer Sweep (LS) method, which is similar to the common layer peeling algorithm, is based on the reflectance and transmittance determination for the plane waves propagating through layered structures, which results in the solution of a system of linear equations for the transmittance and reflectance of each layer using the sweep method. Another considered method is based on the determination of transfer matrices (TM) for the FBG as a whole. Firstly, a homogeneous FBG was modeled using both methods, and the resulting reflectance spectra were compared to the one obtained via a specialized commercial software package. Secondly, modeling results of a π-phase-shifted FBG were presented and discussed. For both FBG models, the influence of the partition interval of the LS method on the simulated spectrum was studied. Based on the analysis of the simulation data, additional required modeling conditions for phase-shifted FBGs were established, which enhanced the modeling performance of the LS method.
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Rybaltovsky, Andrey, Sergei Popov, Dmitry Ryakhovskiy, Alexey Abramov, Andrey Umnikov, Oleg Medvedkov, Viktor Voloshin, et al. "Random Laser Based on Ytterbium-Doped Fiber with a Bragg Grating Array as the Source of Continuous-Wave 976 nm Wavelength Radiation." Photonics 9, no. 11 (November 8, 2022): 840. http://dx.doi.org/10.3390/photonics9110840.
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A random narrow-linewidth lasing at a wavelength of 976 nm was obtained in an ytterbium-doped germanophosphosilicate fiber with an array of weakly reflecting fiber Bragg gratings (FBGs). A random laser cavity was formed by implementing the standard phase mask method of FBG inscription directly during the fiber drawing process. The UV radiation pulses of a KrF excimer laser (248 nm wavelength) synchronized with the fiber drawing speed were used to fabricate the in-fiber array of hundreds of similar FBGs. The developed laser’s slope efficiency in the backward-pumping scheme was measured as high as 33%. The stable continuous-wave operation mode of the laser was detected. The magnitude of the laser power fluctuations depends linearly on the cavity length. The random laser cavity modified with a single highlyreflected (90%) FBG demonstrates significantly better power stability and higher slope efficiency than the same one without an FBG.
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Shin, Dongjoo, Hyeong-U. Kim, Atul Kulkarni, Young-Hak Kim, and Taesung Kim. "Development of Force Sensor System Based on Tri-Axial Fiber Bragg Grating with Flexure Structure." Sensors 22, no. 1 (December 21, 2021): 16. http://dx.doi.org/10.3390/s22010016.
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Fiber Bragg grating (FBG) sensors have an advantage over optical sensors in that they are lightweight, easy to terminate, and have a high flexibility and a low cost. Additionally, FBG is highly sensitive to strain and temperature, which is why it has been used in FBG force sensor systems for cardiac catheterization. When manually inserting the catheter, the physician should sense the force at the catheter tip under the limitation of power (<0.5 N). The FBG force sensor can be optimal for a catheter as it can be small, low-cost, easy to manufacture, free of electromagnetic interference, and is materially biocompatible with humans. In this study, FBG fibers mounted on two different flexure structures were designed and simulated using ANSYS simulation software to verify their sensitivity and durability for use in a catheter tip. The selected flexure was combined with three FBGs and an interrogator to obtain the wavelength signals. To obtain a calibration curve, the FBG sensor obtained data on the change in wavelength with force at a high resolution of 0.01 N within the 0.1–0.5 N range. The calibration curve was used in the force sensor system by the LabVIEW program to measure the unknown force values in real time.
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d’Emden, Michael, Donald McLeod, Jacobus Ungerer, Charles Appleton, and David Kanowski. "Development of a fasting blood glucose-based strategy to diagnose women with gestational diabetes mellitus at increased risk of adverse outcomes in a COVID-19 environment." PLOS ONE 15, no. 12 (December 3, 2020): e0243192. http://dx.doi.org/10.1371/journal.pone.0243192.
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Objective To evaluate the role of fasting blood glucose (FBG) to minimise the use of the oral glucose tolerance test in pregnancy (POGTT) for the diagnosis of gestational diabetes mellitus (GDM). Research design and methods We analysed the POGTTs of 26,242 pregnant women in Queensland, Australia, performed between 1 January 2015 and 30 June 2015. A receiver operator characteristics (ROC) assessment was undertaken to indicate the FBG level that most effectively identified women at low risk of an abnormal result. Results There were 3,946 (15.0%) patients having GDM with 2,262 (8.6%) having FBG ≥ 5.1mmol/l. The ROC identified FBG levels >4.6mmol/l having the best specificity (77%) and sensitivity (54%) for elevated 1 and/or 2hr BGLs. There were 19,321 (73.7%) women having FBG < 4.7mmol/l with a prevalence of GDM of 4.0%, less than 1/3rd the overall rate. Only 4,638 (17.7%) women having FBGs from 4.7–5.0mmol/l would require further evaluation to confirm or exclude the diagnosis. Conclusion This contemporary study of women across the state of Queensland, Australia suggests the FBG can be used effectively to define glucose tolerance in pregnancy, minimising their contact with pathology laboratories and potential exposure to the corona virus. This analysis, used in conjunction with outcome data from the HAPO study, provides reassurance to women and their health professionals that FBG < 4.7mmol/l has both a low rate of abnormal glucose tolerance and minimal adverse pregnancy-associated complications.
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Li, Qi, Kaiqiang Huang, and Haiyan Chen. "Mode competition in Er-doped fiber Bragg grating fiber laser." International Journal of Modern Physics B 29, no. 22 (September 7, 2015): 1550162. http://dx.doi.org/10.1142/s0217979215501623.
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The mode competition in Er-doped fiber (EDF) Bragg grating (FBG) fiber laser is researched experimentally, the effect of the operating temperature of FBG on the oscillation mode is discussed. Experiment results demonstrate that the lasing oscillation mode is limited by the bandwidth of FBGs, which is a function of operation temperature, the temperature sensitivity is [Formula: see text]. When the operating temperature of the two FBGs is 25[Formula: see text]C, the output power of [Formula: see text] dBm and the lasing wavelength of 1549.96 nm with slope efficiency of 0.006% and threshold power of 154 mW are obtained.
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Ross, Michael, R. Jenkins, Charles Nelson, and Peter Joyce. "High Temperature Effects during High Energy Laser Strikes on Embedded Fiber Bragg Grating Sensors." Sensors 19, no. 6 (March 23, 2019): 1432. http://dx.doi.org/10.3390/s19061432.
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As the applications of fiber Bragg gratings (FBGs) continue to grow and become more advanced, it becomes necessary to understand their behavior when exposed to high temperatures in unique situations. In these experiments, uniform 1530-nm fiber Bragg gratings and Type K Cr-Al thermocouples were embedded in three-ply carbon fiber composites. A 100 W high energy laser (HEL) heated the composites to high temperatures over timespans less than one second, and FBG spectral data and thermocouple temperature data were collected during each HEL heating test. The data from three high energy laser tests that represent different levels of damage to the FBG are analyzed to explore the spectral response and thermal decay of embedded FBG sensors when exposed to high temperatures over short timespans. Results are compared to a previously proposed power-law model describing the decay of FBGs in bare fiber when held at constant temperatures over much longer timespans.
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Zhu, Hong Hu, Jian Hua Yin, Hua Fu Pei, Lin Zhang, and Wei Shen Zhu. "Fiber Optic Displacement Monitoring in Laboratory Physical Model Testing." Advanced Materials Research 143-144 (October 2010): 1081–85. http://dx.doi.org/10.4028/www.scientific.net/amr.143-144.1081.
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For physical models, conventional techniques have difficulties in monitoring internal displacements during laboratory testing. In this paper, based on fiber Bragg grating (FBG) sensing technology, a bar-type fiber optic displacement sensor is developed for small-scale models. When the model deforms due to loading or unloading, the embedded displacement sensor can capture the displacement profile along the bar length using the strain data from quasi-distributed FBGs. Laboratory calibration tests have showed that the displacements measured by the FBG sensing bar are in good agreement with those from conventional displacement transducers. For the physical models of a gravity dam and a cavern group, the FBG sensing bars were successfully installed in predefined holes, together with conventional gauges. During testing, the FBG sensing bars measured the displacement distributions within the models. The fiber optic monitoring results demonstrate the deformation characteristics of surrounding rock masses induced by overloading and underground excavation and indicate the overall stability conditions of these two geo-structures.