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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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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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Kulchin, Yuriy N., Anatoly M. Shalagin, Oleg B. Vitrik, Sergey A. Babin, Anton V. Dyshlyuk, and Alexander A. Vlasov. "Differential Reflectometry of Fiber Bragg Gratings." Key Engineering Materials 437 (May 2010): 324–28. http://dx.doi.org/10.4028/www.scientific.net/kem.437.324.
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A reflectometric approach is proposed for interrogation of multiple fiber Bragg grating (FBG) sensors recorded in a single fiber optic line, based on the differential registration FBGs’ response to a short probing laser pulse using conventional OTDR. A special optical layout has been developed allowing transformation of FBG’s spectrally modulated signals into intensity modulated signals and at the same time eliminating the susceptibility of the system to light power fluctuations. Threshold sensitivity of the method amounted to ~50 μstrain within the measurement range of ~4000 μstrain. The maximum number of FBGs interrogated by the proposed technique is estimated at several hundred, which by far surpasses the requirements of most practical applications. Due to its simplicity, efficiency and usage of conventional OTDR equipment the proposed FBG interrogation technique can find a wide range of applications, in particular in structural health monitoring.
4
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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Lupi, Carla, Ferdinando Felli, Alessandro Dell’Era, Erwin Ciro, Michele Caponero, Hypolito Kalinowski, and Cristian Vendittozzi. "Critical Issues of Double-Metal Layer Coating on FBG for Applications at High Temperatures." Sensors 19, no. 18 (September 4, 2019): 3824. http://dx.doi.org/10.3390/s19183824.
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Use of fiber Bragg gratings (FBGs) to monitor high temperature (HT) applications is of great interest to the research community. Standard commercial FBGs can operate up to 600 ∘ C. For applications beyond that value, specific processing of the FBGs must be adopted to allow the grating not to deteriorate. The most common technique used to process FBGs for HT applications is the regeneration procedure (RP), which typically extends their use up to 1000 ∘ C. RP involves a long-term annealing of the FBGs, to be done at a temperature ranging from 550 to 950 ∘ C. As at that temperature, the original coating of the FBGs would burn out, they shall stay uncoated, and their brittleness is a serious concern to deal with. Depositing a metal coating on the FBGs prior to process them for RP offers an effective solution to provide them with the necessary mechanical strengthening. In this paper, a procedure to provide the FBG with a bimetallic coating made by copper and nickel electrodeposition (ED) is proposed, discussing issues related to the coating morphology, adherence to the fiber, and effects on the grating spectral response. To define the processing parameters of the proposed procedure, production tests were performed on dummy samples which were used for destructive SEM–EDS analysis. As a critical step, the proposed procedure was shown to necessitate a heat treatment after the nickel ED, to remove the absorbed hydrogen. The spectral response of the FBG samples was monitored along the various steps of the proposed procedure and, as a final proof test for adherence stability of the bimetallic coating, along a heating/cooling cycle from room temperature to 1010 ∘ C. The results suggest that, given the emergence of Kirkendall voids at the copper–nickel interface, occurring at the highest temperatures (700–1010 ∘ C), the bimetallic layer could be employed as FBG coating up to 700 ∘ C.
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He, Jun, Baijie Xu, Xizhen Xu, Changrui Liao, and Yiping Wang. "Review of Femtosecond-Laser-Inscribed Fiber Bragg Gratings: Fabrication Technologies and Sensing Applications." Photonic Sensors 11, no. 2 (April 1, 2021): 203–26. http://dx.doi.org/10.1007/s13320-021-0629-2.
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AbstractFiber Bragg grating (FBG) is the most widely used optical fiber sensor due to its compact size, high sensitivity, and easiness for multiplexing. Conventional FBGs fabricated by using an ultraviolet (UV) laser phase-mask method require the sensitization of the optical fiber and could not be used at high temperatures. Recently, the fabrication of FBGs by using a femtosecond laser has attracted extensive interests due to its excellent flexibility in creating FBGs array or special FBGs with complex spectra. The femtosecond laser could also be used for inscribing various FBGs on almost all fiber types, even fibers without any photosensitivity. Such femtosecond-laser-induced FBGs exhibit excellent thermal stability, which is suitable for sensing in harsh environment. In this review, we present the historical developments and recent advances in the fabrication technologies and sensing applications of femtosecond-laser-inscribed FBGs. Firstly, the mechanism of femtosecond-laser-induced material modification is introduced. And then, three different fabrication technologies, i.e., femtosecond laser phase mask technology, femtosecond laser holographic interferometry, and femtosecond laser direct writing technology, are discussed. Finally, the advances in high-temperature sensing applications and vector bending sensing applications of various femtosecond-laser-inscribed FBGs are summarized. Such femtosecond-laser-inscribed FBGs are promising in many industrial areas, such as aerospace vehicles, nuclear plants, oil and gas explorations, and advanced robotics in harsh environments.
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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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Dedyulin, Sergey, Elena Timakova, Dan Grobnic, Cyril Hnatovsky, Andrew D. W. Todd, and Stephen J. Mihailov. "Accurate Measurements of a Wavelength Drift in High-Temperature Silica-Fiber Bragg Gratings." Metrology 1, no. 1 (April 14, 2021): 1–16. http://dx.doi.org/10.3390/metrology1010001.
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Fiber Bragg gratings (FBG) are extensively used to perform high-temperature measurements in harsh environments, however the drift of the characteristic Bragg wavelength affects their long-term stability resulting in an erroneous temperature measurement. Herein we report the most precise and accurate measurements of wavelength drifts available up to date on high-temperature FBGs. The measurements were performed with a set of packaged π-phase-shifted FBGs for high wavelength resolution, in caesium and sodium pressure-controlled heat pipes for stable temperature environment and with a tunable laser for stable wavelength measurements with a 0.1 pm resolution. Using this dataset we outline the experimental caveats that can lead to inconsistent results and confusion in measuring wavelength drifts, namely: influence of packaging; interchangeability of FBGs produced under identical conditions; birefringence of π-phase-shifted FBGs; initial transient behaviour of FBGs at constant temperature and dependence on the previous thermal history of FBGs. In addition, we observe that the wavelength stability of π-phase-shifted gratings at lower temperature is significantly improved upon by annealing at higher temperature. The lowest value of the wavelength drift we obtain is +0.014 pm·h−1 at 600 °C (corresponding to +0.001 °C·h−1) after annealing for 400 h at 1000 °C, the longest annealing time we have tried. The annealing time required to achieve the small drift rate is FBG-specific.
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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.
10
Ferdinand, Pierre, Sylvain Magne, Véronique Dewynter-Marty, Stéphane Rougeault, and Laurent Maurin. "Applications of Fiber Bragg Grating Sensors in the Composite Industry." MRS Bulletin 27, no. 5 (May 2002): 400–407. http://dx.doi.org/10.1557/mrs2002.126.
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AbstractOptical-fiber sensors based on fiber Bragg gratings (FBGs) provide accurate, nonintrusive, and reliable remote measurements of temperature, strain, and pressure, and they are immune to electromagnetic interference. FBGs are extensively used in telecommunications, and their manufacture is now cost-effective. As sensors, FBGs find many industrial applications in composite structures used in the civil engineering, aeronautics, train transportation, space, and naval sectors. Tiny FBG sensors embedded in a composite material can provide in situ information about polymer curing (strain, temperature, refractive index) in an elegant and nonintrusive way. Great improvements in composite manufacturing processes such as resin transfer molding (RTM) and resin film infusion (RFI) have been obtained through the use of these sensors. They can also be used in monitoring the “health” of a composite structure and in impact detection to evaluate, for example, the airworthiness of aircraft. Finally, FBGs may be used in instrumentation as composite extensometers or strain rosettes, primarily in civil engineering applications.
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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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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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Rodriguez-Cobo, Luis, Rosa Perez-Herrera, María Quintela, Rubén Ruiz-Lombera, Manuel Lopez-Amo, and José Lopez-Higuera. "Virtual FBGs Using Saturable Absorbers for Sensing with Fiber Lasers." Sensors 18, no. 11 (October 23, 2018): 3593. http://dx.doi.org/10.3390/s18113593.
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The spectral narrowing of Fiber Bragg Gratings (FBGs) introduced by unpumped Er-doped fiber (EDF) was analyzed for fiber lasers (FL). Owing to spatial hole burning (SHB), the spectral response of a virtual FBG can be employed for narrowing the band pass filter employed to determine the lasing wavelength of laser cavities. A common FL was mounted to analyze the spectral stability of the method, and a FL sensor for strain and temperature measurements was experimentally characterized to determine the stability of the narrowing effect achieved by the unpumped EDF, which acts as a virtual FBG. The results exhibited remarkably good narrowing effects of the spectral response of uniform FBGs.
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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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Zhu, Ping Yu, D. Liu, and Y. Lin. "Measurement of Strain Induced by Impact with Fiber Bragg Grating." Key Engineering Materials 381-382 (June 2008): 435–38. http://dx.doi.org/10.4028/www.scientific.net/kem.381-382.435.
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After deriving the propagation formula of stress wave through incident bar, the measured signals both in horizontal impact test and drop impact tests are investigated with novel fiber Bragg grating sensors(FBGs). Especially those strain signals from FBGs which mounted on the surface of an incident bar are studied. The signals in impactor and the FBGs embedded in the composite material under similar test condition are compared. The dropping and impacting models have been setup. The experiment data measured in a lab are analyzed both in time-domain and in frequency domain. Those ultra-high frequency components in the above strain signals can not be obtained by current FBG measurement system due to frequency limit of the demodulation system. Further study to improve the frequency of demodulation system will be done in next step.
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Guo, Yongxing, Dongsheng Zhang, Jianjun Fu, Shaobo Liu, Shengzhuo Zhang, and Fangdong Zhu. "Development and operation of a fiber Bragg grating based online monitoring strategy for slope deformation." Sensor Review 35, no. 4 (September 21, 2015): 348–56. http://dx.doi.org/10.1108/sr-01-2015-0012.
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Purpose – The purpose of this paper is to investigate an online monitoring strategy that incorporates fiber Bragg gratings (FBGs) for deformation displacement detection, with the background that slope deformation monitoring is crucial to engineering safety supervision and disaster prevention. Design/methodology/approach – A “beam element” method has been proposed, introduced and experimentally verified in detail. The deformation displacement along a flexible bar can be obtained based on this method, using the distributed strain detected by the FBGs embedded in the bar. A novel sensor structure containing inclinometer casings and a series of connected flexible pipes with FBGs embedded has been proposed. Based on the features of this structure, two FBG deformation sensors have been manufactured and installed into a slope. A matched monitoring station which permits real-time supervision, warning and remote access across the Internet was established and operated. Findings – Displacement data from September 2013 to August 2014 are obtained, which is basically consistent with the practical situation. Originality/value – The FBG deformation sensors demonstrated a robust and reliable measurement performance, which is promising for real-time disaster warning in slope engineering.
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González del Val, Miguel, Julio Mora Nogués, Paloma García Gallego, and Malte Frövel. "Icing Condition Predictions Using FBGS." Sensors 21, no. 18 (September 9, 2021): 6053. http://dx.doi.org/10.3390/s21186053.
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Icing is a hazard which is important for the aerospace industry and which has grown over the last few years. Developing sensors that can detect the existence not only of standard icing conditions with typically small droplet size, but also of Supercooled Large Droplet (SLD) conditions is one of the most important aims in order to minimize icing hazards in the near future. In the present paper a study of the Fiber Bragg Grating Sensors’ (FBGSs) performance as a flight icing detection system that predicts the conditions of an icing cloud is carried out. The test matrix was performed in the INTA Icing Wind Tunnel (IWT) with several icing conditions including SLD. Two optic fibers with 16 FBGS in total were integrated in the lower and upper surface of an airfoil to measure the temperature all over the chord. The results are compared with a Messinger heat and mass balance model and the measurements of the FBGS are used to predict the Liquid Water Content (LWC) and Ice Accretion Rate (IAR). Finally, the results are evaluated and a sensor assessment is made. A good correlation was observed between theoretical calculations and test results obtained with the FBGS in the IWT tests. FBGS proved to detect the beginning and end of ice accretion, LWC and IAR quickly and with good precision.
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Kocaman, Esat S., Casey J. Keulen, Erdem Akay, Mehmet Yildiz, Halit S. Turkmen, and Afzal Suleman. "An experimental study on the effect of length and orientation of embedded FBG sensors on the signal properties under fatigue loading." Science and Engineering of Composite Materials 23, no. 6 (November 1, 2016): 711–19. http://dx.doi.org/10.1515/secm-2014-0029.
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AbstractFiber Bragg grating (FBG) sensors provide excellent capability for the structural health monitoring (SHM) of load-bearing structures by allowing for local internal strain measurements within structures. However, the integration of these sensors to composite materials is associated with several challenges that have to be addressed to have the correct strain measurement and in turn to perform reliable SHM. One of the most important issues is the presence of uneven strain fields around FBGs, which significantly affect the response of the sensors and hence the reliability of the acquired data. The uniformity of the strain fields around sensors is important for dependable data acquisition; however, to generate such a condition, tow width-to-FBG length relationship, optical fiber configuration with respect to reinforcement fiber orientation, and crack density resulting from fatigue loading are very important factors that have to be considered. In this paper, these issues are addressed by investigating the signal properties of FBG sensors with 1 and 10 mm lengths embedded within the composite specimens during the manufacturing process. After fatigue testing of the specimens, it is shown that 1-mm-long FBGs embedded in-line with adjacent reinforcement fibers with tow widths of ∼2 mm provide much more reliable signals than 10-mm-long FBGs embedded perpendicular to adjacent tows.
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Lindner, Markus, Andrea Stadler, Georg Hamann, Bennet Fischer, Martin Jakobi, Florian Heilmeier, Constantin Bauer, Wolfram Volk, Alexander W. Koch, and Johannes Roths. "Fiber Bragg Sensors Embedded in Cast Aluminum Parts: Axial Strain and Temperature Response." Sensors 21, no. 5 (March 1, 2021): 1680. http://dx.doi.org/10.3390/s21051680.
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In this study, the response of fiber Bragg gratings (FBGs) embedded in cast aluminum parts under thermal and mechanical load were investigated. Several types of FBGs in different types of fibers were used in order to verify general applicability. To monitor a temperature-induced strain, an embedded regenerated FBG (RFBG) in a cast part was placed in a climatic chamber and heated up to 120 ∘C within several cycles. The results show good agreement with a theoretical model, which consists of a shrink-fit model and temperature-dependent material parameters. Several cast parts with different types of FBGs were machined into tensile test specimens and tensile tests were executed. For the tensile tests, a cyclic procedure was chosen, which allowed us to distinguish between the elastic and plastic deformation of the specimen. An analytical model, which described the elastic part of the tensile test, was introduced and showed good agreement with the measurements. Embedded FBGs - integrated during the casting process - showed under all mechanical and thermal load conditions no hysteresis, a reproducible sensor response, and a high reliable operation, which is very important to create metallic smart structures and packaged fiber optic sensors for harsh environments.
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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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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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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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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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Shi, Wei Wei, Ting Ting Hu, and Yue Gang Tan. "Experiments of Ultrasonic Sensing Using FBG Sensors." Advanced Engineering Forum 2-3 (December 2011): 148–52. http://dx.doi.org/10.4028/www.scientific.net/aef.2-3.148.
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This research aims at investigating the response characteristics of fiber Bragg grating sensors (FBGs) to ultrasonic signals. The testing system was set up with a tunable laser source and the FBGs installed on the surface of an aluminum plate. Then the response characteristics of FBGs were compared, in condition of putting the ultrasonic driving source in the different longitudinal, lateral and angular separation. Measurements were taken by changing the distance between the sensor and the transducer from 60 mm to 200 mm with a step of 20 mm. Then keeping the distance at 100 mm and 200 mm respectively, do the angular experiment with the angle from 0° to 90° by the step of 10°. Experiment results show that FBG can get better signals when the transducer is along its axial direction. When the location of the transducer is changed linearly, no obvious linear change of the signal strength has been found.
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Lai, Tianting, Pu Cheng, Congliao Yan, Chi Li, Wenbin Hu, and Minghong Yang. "2D and 3D Shape Sensing Based on 7-Core Fiber Bragg Gratings." Photonic Sensors 10, no. 4 (March 4, 2020): 306–15. http://dx.doi.org/10.1007/s13320-020-0579-0.
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Abstract A fiber-optic shape sensing based on 7-core fiber Bragg gratings (FBGs) is proposed and experimentally demonstrated. The investigations are presented for two-dimensional and three-dimensional shape reconstruction by distinguishing bending and twisting of 7-core optical fiber with FBGs. The curvature and bending orientation can be calculated by acquiring FBG wavelengths from any two side cores among the six outer cores. And the shape sensing in three-dimensional (3D) space is computed by analytic geometry theory. The experiments corresponding of two-dimensional (2D) and 3D shape sensing are demonstrated and conducted to verify the theoretical principles. The resolution of curvature is about 0.1m−1 for 2D measuring. The error of angle in shape reconstruction is about 1.89° for 3D measuring. The proposed sensing technique based on 7-core FBGs is promising of high feasibility, stability, and repeatability, especially for the distinguishing ability on the bending orientation due to the six symmetrical cores on the cross-section.
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Njegovec, Matej, and Denis Donlagic. "Interrogation of FBGs and FBGs Arrays Using Standard Telecom DFB Diode." Journal of Lightwave Technology 34, no. 22 (November 15, 2016): 5340–48. http://dx.doi.org/10.1109/jlt.2016.2616725.
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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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Silveira, Mariana L., Helder R. O. Rocha, Paulo F. C. Antunes, Paulo S. B. André, Marcelo E. V. Segatto, Anselmo Frizera, and Camilo A. R. Díaz. "An Optimized Self-Compensated Solution for Temperature and Strain Cross-Sensitivity in FBG Interrogators Based on Edge Filter." Sensors 21, no. 17 (August 30, 2021): 5828. http://dx.doi.org/10.3390/s21175828.
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Optical fiber sensors based on fiber Bragg gratings (FBGs) are prone to measurement errors if the cross-sensitivity between temperature and strain is not properly considered. This paper describes a self-compensated technique for canceling the undesired influence of temperature in strain measurement. An edge-filter-based interrogator is proposed and the central peaks of two FBGs (sensor and reference) are matched with the positive and negative slopes of a Fabry–Perot interferometer that acts as an optical filter. A tuning process performed by the grey wolf optimizer (GWO) algorithm is required to determine the optimal spectral characteristics of each FBG. The interrogation range is not compromised by the proposed technique, being determined by the spectral characteristics of the optical filter in accordance with the traditional edge-filtering interrogation. Simulations show that, by employing FBGs with optimal characteristics, temperature variations of 30 °C led to an average relative error of 3.4% for strain measurements up to 700μϵ. The proposed technique was experimentally tested under non-ideal conditions: two FBGs with spectral characteristics different from the optimized results were used. The temperature sensibility decreased by 50.8% as compared to a temperature uncompensated interrogation system based on an edge filter. The non-ideal experimental conditions were simulated and the maximum error between theoretical and experimental data was 5.79%, proving that the results from simulation and experimentation are compatible.
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Liaw, Shien-Kuei, Chi-Wen Liao, Meng-Hsuan Tsai, Dong-Chang Li, Shu-Ming Yang, Zhu-Yong Xia, Chien-Hung Yeh, and Wen-Fung Liu. "Hybrid Fiber-Optic Sensing Integrating Brillouin Optical Time-Domain Analysis and Fiber Bragg Grating for Long-Range Two-Parameter Measurement." Sensors 21, no. 12 (June 20, 2021): 4224. http://dx.doi.org/10.3390/s21124224.
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Distributed fiber sensing (DFS) can provide real-time signals and warnings. The entire length of fiber optic cable can act as a sensing element, but the accuracy is sometimes limited. On the other hand, point-to-point fiber sensing (PPFS) is usually implemented using one or more fiber Bragg gratings (FBGs) at specific positions along with the fiber for the monitoring of specific parameters (temperature, strain, pressure, and so on). However, the cost becomes expensive when the number of FBGs increases. A hybrid fiber sensing scheme is thus proposed, combining the advantages of DFS and PPFS. It is based on a Brillouin optical time-domain analysis (BOTDA) fiber system with additional FBGs embedded at certain positions where it is necessary to detect specific parameters. The hybrid fiber sensing system has the advantages of full sensing coverage at essential locations that need to be carefully monitored. In our work, the test results showed that the proposed system could achieve a sensing distance of 16 km with the single-mode fiber with a 2 m spatial resolution. For FBG parameter measurements, the temperature variation was 52 °C, from 25 °C to 77 °C, with a temperature sensitivity of 23 pm/°C, and the strain was from 0 to 400 µε, with a strain sensitivity of 0.975 pm/µε, respectively, using two FBGs.
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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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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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Borotto, Marco, Enrico De Cais, Marco Belloli, Andrea Bernasconi, and Stefano Manzoni. "Metrological Performances of Fiber Bragg Grating Sensors and Comparison with Electrical Strain Gauges." Key Engineering Materials 495 (November 2011): 53–57. http://dx.doi.org/10.4028/www.scientific.net/kem.495.53.
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The fiber Bragg grating sensors (FBGs) have been recently introduced: they present a photorecord grating on the fiber itself, which allows the reflection of a certain wavelength of the input light spectrum. The applied strain is estimated relying on changes of the reflected wavelength. One of the possible applications that has prompted us to study this type of sensors is the possibility to create smart dynamometric structures based on carbon fiber by embedding FBGs. Many papers are available in literature about some applications with smart structures but there is not yet an appropriate metrological characterization about these FBG sensors, their strengths and weaknesses: for these reasons it was deemed useful making several tests on FBG sensors in terms of measurement accuracy, signal to noise ratio, ability to compensate for thermal effects and their behavior for dynamic applications. All these results have been compared to electrical strain gauge ones, which represent the actual reference strain measurement systems. The various solutions to compensate for thermal effects have offered several information for further analyses and the basis for a future use of these sensors for static or semi-static tests. Being fully aware of FBGs characteristics allows to draw down guidelines about their integration in composite materials for the most different applications, understanding in a better way the sensor response.
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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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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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Brotzu, Andrea, F. Felli, A. Paolozzi, L. Caputo, F. Passeggio, and S. Gaeta. "Use of Fiber Optic Sensors for Monitoring Crack Growth in Fatigue and Corrosion-Fatigue Tests." Advanced Materials Research 38 (March 2008): 155–60. http://dx.doi.org/10.4028/www.scientific.net/amr.38.155.
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Fibre Bragg Gratings (FBGs) are optical strain gages manufactured directly inside the fiber core. They provide several advantages with respect to conventional strain gages. In particular it is possible to put several FBGs along the same fibre (multiplexing), they are immune to corrosive environments and to electromagnetic interferences. They can be embedded in almost all types of materials and are very useful in Structural Health Monitoring. An innovative approach for testing specimens in this area is reported in this work. An aluminium alloy 2024-T3 CT specimen has been manufactured with one small feed-through hole and a superficial groove. Two FBG sensors, multiplexed on the same fibre, have been glued one inside the hole and one inside the groove. Fatigue test has been carried out monitoring the crack length both with standard measure system and with the FBG strain sensors placed in front of the crack tip.
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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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Fernández-Ruiz, María R., and Alejandro Carballar. "Fiber Bragg Grating-Based Optical Signal Processing: Review and Survey." Applied Sciences 11, no. 17 (September 3, 2021): 8189. http://dx.doi.org/10.3390/app11178189.
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This paper reviews the state of the art of fiber Bragg gratings (FBGs) as analog all-optical signal processing units. Besides the intrinsic advantages of FBGs, such as relatively low cost, low losses, polarization insensitivity and full compatibility with fiber-optic systems, they have proven to deliver an exceptional flexibility to perform any complex band-limited spectral response by means of the variation of their physical parameters. These features have made FBGs an ideal platform for the development of all-optical broadband filters and pulse processors. In this review, we resume the main design algorithms of signal processors based on FBGs, and we revisit the most common processing units based on FBGs and the applications that have been presented in the literature.
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Li, Yanxin, Xin Liu, Xuewen Shu, and Lin Zhang. "Arbitrary-Order Photonic Hilbert Transformers Based on Phase-Modulated Fiber Bragg Gratings in Transmission." Photonics 8, no. 2 (January 21, 2021): 27. http://dx.doi.org/10.3390/photonics8020027.
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Photonic Hilbert transformers are fundamental components for optical computing and signal processing. Here, for the first time we propose all-optical arbitrary-order Hilbert transformers using phase-modulated fiber Bragg gratings (PM-FBGs) in transmission to our best knowledge. The PM-FBG is a kind of fiber grating, whose coupling strength remains almost uniform and period varies along the fiber length. For demonstration, we have designed and numerically simulated 0.5th-order, first-order, and 1.5th-order photonic Hilbert transformers, respectively. The profiles of those PM-FBGs are obtained employing quasi-Newton optimization algorithm. Simulation results show that the designed three Hilbert transformers are all in good agreement with the ideal results in bandwidths up to 500 GHz and can tolerate a large range of input pulse width.
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Iadicicco, Agostino, Antonello Cutolo, and Andrea Cusano. "Fiber Bragg Grating Sensors - Advancements and Industrial Applications." Advances in Science and Technology 55 (September 2008): 213–22. http://dx.doi.org/10.4028/www.scientific.net/ast.55.213.
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Over the last few years, optical fiber sensors have seen increased acceptance and widespread use for a variety of applications ranging from structural sensing and health monitoring of composites and structures in civil and aeronautic areas; to pressure and temperature sensors for oil and gas reservoir monitoring to name just a few. Among them Fiber Bragg Grating (FBG) based sensors have become widely known and popular within and out the photonics community and seen a rise in their utilization and commercial growth. Given the capability of FBGs to measure a multitude of parameters such as strain, temperature, pressure, chemical and bio-logical agents and many others coupled with their flexibility of design to be used as single point or multi-point sensing arrays and their relative low cost, make them ideal devices to be adopted for a multitude of different sensing applications and implemented in different fields and industries. This work first focuses on some recent experiences in the use of FBGs for opto-acoustic sensors and railway monitoring and then reviews the advances in the area of FBGs evanescent wave sensors as valuable technological platforms for chemical and biological applications.
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Chen and Shin. "An Improved Impact Source Locating System Using FBG Rosette Array." Sensors 19, no. 16 (August 7, 2019): 3453. http://dx.doi.org/10.3390/s19163453.
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For structures vulnerable to foreign object impact damages, it would be desirable to detect and locate any occurrence of such impacts. This can be achieved by monitoring the stress waves generated by an impact together with certain source localization algorithms. Being small, electromagnetic influence immune and durable, Fiber Bragg grating (FBG) sensors are advantageous for this task. One drawback of FBGs for this purpose is their uneven directional sensitivity, which limits its localization ability to within 50° on either side of the fiber axis. Beyond this range, the signal is too weak and masked by noises and the location errors increase abruptly. Two approaches have been tested on a 0.8 m × 0.8 m × 6 mm plate for possible improvement on the system accuracy: firstly, an interrogation scheme with stronger light source intensity and steeper edge filter is employed to enhance the signal-to-noise ratio and system sensitivity; secondly, rosettes with two orthogonal FBGs are cascaded together to replace single FBGs to alleviate the directional sensitivity problem. It was found that a four-fold increase in signal to noise ratio contributed by stronger light source does improve the location accuracy, but only marginally. For the rosette approach, the relative positions of the Bragg wavelength of the FBGs and the light source spectrum are crucial to accuracy. Three different wavelength configurations have been tested and the reasons for their success or failure are discussed. It was shown that with an optimal wavelength configuration, the rosette array can virtually extend the good location accuracy to all over the plate.
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Zhang, Naizhong, Claire Davis, Wing K. Chiu, Tommy Boilard, and Martin Bernier. "Fatigue Performance of Type I Fibre Bragg Grating Strain Sensors." Sensors 19, no. 16 (August 12, 2019): 3524. http://dx.doi.org/10.3390/s19163524.
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Although fibre Bragg gratings (FBGs) offer obvious potential for use in high-density, high-strain sensing applications, the adoption of this technology in the historically conservative aerospace industry has been slow. There are several contributing factors, one of which is variability in the reported performance of these sensors in harsh and fatigue prone environments. This paper reports on a comparative evaluation of the fatigue performance of FBG sensors written according to the same specifications using three different grating manufacturing processes: sensors written in stripped and re-coated fibres, sensors written during the fibre draw process and sensors written through fibre coating. Fatigue cycling of the fibres is provided by a customized electro-dynamically actuated loading assembly designed to provide high frequency and amplitude loading. Pre- and post-fatigue microscopic analysis and high-resolution transmission and reflection spectra scanning are conducted to investigate the fatigue performance of FBGs, the failure regions of fibres as well as any fatigue-related effects on the spectral profiles. It was found that because of the unique fabrication method, the sensors written through the fibre coating, also known as trans-jacket FBGs, show better fatigue performance than stripped and re-coated FBGs with greater control possible to tailor the optical reflection properties compared to gratings written in the draw tower. This emerging method for inscription of Type I gratings opens up the potential for mass production of higher reflectivity, apodised sensors with dense or complex array architectures which can be adopted as sensors for harsh environments such as in defence and aerospace industries.
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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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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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Wei, Jie, Yanpeng Hao, Yuan Fu, Lin Yang, Jiulin Gan, and Zhongmin Yang. "Detection of Glaze Icing Load and Temperature of Composite Insulators Using Fiber Bragg Grating." Sensors 19, no. 6 (March 16, 2019): 1321. http://dx.doi.org/10.3390/s19061321.
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Conventional methods for the online monitoring of icing conditions of composite insulators suffer from difficulties. To solve this issue, a novel method is first proposed to detect glaze icing load via embedding three optical fibers with fiber Bragg gratings (FBGs) into a 10 kV composite insulator. Specifically, FBG temperature compensation sensors were packaged in ceramic tubes to solve strain and temperature cross-sensitivity. Temperature effect experiments and simulated glaze icing load experiments were performed to verify the feasibility of the proposed method. The results show that temperature sensitivities of all FBGs are identical (i.e., 10.68 pm/°C), which achieves a simultaneous measurement of temperature and strain. In addition, the proposed method can detect glaze icing load of the composite insulator above 0.5 N (i.e., 15% of icicle bridged degree) in the laboratory.
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Yang, Shu Lian, Tian Ze Li, Zhen Mei Li, Bo Xue Tan, and Kai Zhao. "Novel Flowrate Sensor Based on a Couple of Fiber Bragg Gratings." Advanced Materials Research 383-390 (November 2011): 6908–13. http://dx.doi.org/10.4028/www.scientific.net/amr.383-390.6908.
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A novel flowrate sensor based on a couple of fiber Bragg gratings( FBGs) has been proposed, consisting of fiber grating pressure sensing setup and Venturi tube. The expression of relationship between the flowrate and the wavelength shift difference of the FBGs is derived. The pressure that two sides of the cross section of the aluminum foil tube in the pressure sensing setup results in the distortion of an isosceles triangle cantilever structure. The distortion results in the wavelength shift of a couple of FBGs that are mounted at either side of the cantilever. By monitoring the wavelength shift difference of the two FBGs, the flowrate can be obtained. The cross-sensitive problem of the FBGs sensor can be solved by compensating the temperature effect. The preliminary experiments have been carried out, and the results verify the feasibility of the proposed sensor with a measurement range from 8 to 200 mm/s.
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Montoya Alba, David Esteban, Jhonatan Mcniven Cagua Herrera, and Gustavo Adolfo Puerto Leguizam´ón. "Design of a flattening filter using Fiber Bragg Gratings for EDFA gain equalization: an artificial neural network application." Ciencia e Ingeniería Neogranadina 29, no. 2 (June 20, 2019): 25–36. http://dx.doi.org/10.18359/rcin.3818.
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This paper presents a proposal for the non-uniform gain compensation of an Erbium-doped fiber optic amplifier (EDFA) in a Wavelength Division Multiplexed (WDM) system using Fiber Bragg Gratings (FBG). In this proposal, the multilayer perceptron feed-forward artificial neural network with backpropagation was trained under the secant method (one-step secant) and was selected according to mean square error measurement. The proposal optimizes FBG parameters such as center frequency, rejection level and length in order to determine a filtering response based on a reduced number of FBGS that will be used to flatten the non-linear response of the amplifier gain and avoid the per-carrier treatment of a standard flattening filter. While an artificial neural network with a 7-10-6 structure demonstrated the feasibility of equalizing the gain of an EDFA using as few as three FBGS, a 25-18-12 structure improved the results when the configuration consisted of an FBG array of six resonances that provided similar results to that featured by the standard gain-flattening filter. The proposal was evaluated in an amplified WDM system of eight optical carriers located between 195-196.4 THz.
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Ma, Zhen, and Xiyuan Chen. "Verification of Strain Transfer Characteristics of Distributed Surface-attached FBGs on Aircraft Wings." MATEC Web of Conferences 306 (2020): 05001. http://dx.doi.org/10.1051/matecconf/202030605001.
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In order to provide higher accuracy for transfer alignment on aircraft, a surface-attached FBGs is designed for distributed deformation measurement of aircraft wing. To verify the measurement accuracy of the surface-attached FBGs, a strain calibration method of the surface-attached FBGs applied with the wing strain measurement is proposed. Two Aluminium Alloy Test Plates(AATP) with different sizes were designed as the matrix material for tensile test. The test results show that AATP-A has better test effect. Through the two sets of tensile tests, the change of wavelength measured on the surface-attached FBGs is in good agreement with the change of strain value of strain gauge.The experimental results prove that the method based on surface-attached FBGs is feasible for the strain measurement of aircraft wing. The method is simple and reliable, which lays a foundation for the follow-up study of the full-field deformation measurement of aircraft wing.
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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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Dostovalov, Alexander V., Alexey A. Wolf, Kirill A. Bronnikov, Mikhail I. Skvortsov, Alexey E. Churin, and Sergey A. Babin. "Femtosecond Pulse Structuring of Multicore Fibers for Development of Advanced Fiber Lasers and Sensors." Solid State Phenomena 312 (November 2020): 221–26. http://dx.doi.org/10.4028/www.scientific.net/ssp.312.221.
Full textAbstract:
In this paper we investigate the fiber Bragg grating (FBG) arrays selectively inscribed in a multicore fiber for a different sensor and laser applications. Particularly, wavelength-switchable and tunable fiber laser was realized based on uniform and non-uniform FBGs precisely positioned in the selected cores. A quasi-distributed 3D shape sensor based on FBG array inscribed in a multicore fiber with helically twisted side cores was fabricated and applied for shape reconstruction of papillotome.
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Molardi, Carlo, Tiago Paixão, Aidana Beisenova, Rui Min, Paulo Antunes, Carlos Marques, Wilfried Blanc, and Daniele Tosi. "Fiber Bragg Grating (FBG) Sensors in a High-Scattering Optical Fiber Doped with MgO Nanoparticles for Polarization-Dependent Temperature Sensing." Applied Sciences 9, no. 15 (August 1, 2019): 3107. http://dx.doi.org/10.3390/app9153107.
Full textAbstract:
The characterization of Fiber Bragg Grating (FBG) sensors on a high-scattering fiber, having the core doped with MgO nanoparticles for polarization-dependent temperature sensing is reported. The fiber has a scattering level 37.2 dB higher than a single-mode fiber. FBGs have been inscribed by mean of a near-infrared femtosecond laser and a phase mask, with Bragg wavelength around 1552 nm. The characterization shows a thermal sensitivity of 11.45 pm/°C. A polarization-selective thermal behavior has been obtained, with sensitivity of 11.53 pm/°C for the perpendicular polarization (S) and 11.08 pm/°C for the parallel polarization (P), thus having 4.0% different sensitivity between the two polarizations. The results show the inscription of high-reflectivity FBGs onto a fiber core doped with nanoparticles, with the possibility of having reflectors into a fiber with tailored Rayleigh scattering properties.