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防災科学技術研究所が保有する4 m 岩石摩擦試験機を用いた岩石摩擦実験において，fiber Bragg grating （FBG）センサによる岩石試料のひずみ計測，およびmicroelectromechanical system （MEMS），圧電式（PZ）加速度センサによる加速度計測を実施し，岩石試料のひずみ変化やすべりイベント時の変位を推定した．FBG センサのノイズレベルは，すべりイベント時のひずみ変化を計測する上で十分小さいことが半導体ひずみゲージとの比較から確認できた．しかし，その計測分解能がすべりイベント時の岩石のひずみ変化と同程度（～ 1 με）であったため，より精度良くひずみ変化を計測するためには分解能の改善が必要であることが明らかになった．PZ センサでは共振によって入力加速度の高周波成分が増幅し，加速度の測定範囲を超えるオーバーロードが発生した一方で，MEMS 式加速度センサによる計測ではPZ センサとは異なる共振特性による高周波帯の減衰のためオーバーロードを避けることができた．MEMS 一軸型加速度センサによる加速度波形を本研究で提案した一連の手順で処理することで，すべりイベント時の変位推定をロバストに行うことができた．本研究で行った解析は，今後FBGセンサや加速度センサを用いてより詳細な断層破壊様式を議論するための基盤となる．We measured local strain change and co-seismic displacement of rock specimen installed in 4 m biaxial rock friction apparatus using fiber Bragg grating (FBG) sensors, microelectromechanical system (MEMS) accelerometers and piezoelectric (PZ) accelerometers. The measurements of strain using the FBG sensors are verified with those of semiconductor strain gauges (SGs), showing the noise level of FBG sensors is low enough to quantify the strain change due to the co-seismic slip. However, the measurement resolution of the strain needs to be improved as its co-seismic change associated with a single slip event is nearly in the same order of its resolution. We then developed a process flow of converting the acceleration during the slip event measured with accelerometers near the fault to the co-seismic displacement. PZ accelerometers were overloaded due to the amplification of its highfrequency response, while we obtained the acceleration without overload for the case with MEMS accelerometers because of the attenuation in high-frequency components. We obtained a reasonable estimation of the co-seismic displacement using MEMS uniaxial accelerometer in comparison to the slip on the fault measured with eddy current displacement (GAP) sensor. This study provides the accuracy and quantitative objectives of FBG sensors and accelerometers for the measurements of strain and co-seismic displacement during stick-slip experiments, which help for further applications on the large-scale biaxial rock friction experiments to discuss the nucleation and rupture process of faults.

The FBG sensors, embedded in triangle region of composite T-stiffened panels, were used to monitor the strain change during curing process and quasi-static compression real-timely. The results show that the compression load of stiffened panels with the FBG sensor embedded along the stiffener is the same as that without the FBG sensor. The FBG sensor embedded in the triangular area of the stiffened panels can effectively monitor during the curing process, and it can also be used to monitor the temperature and strain changes real-timely after curing process. In the quasi-static compression process, the strain curve measured by the FBG sensor is the same as the force-displacement curve. The FBG sensors can monitor accurately the damage such as lamination and cracking in the stiffened panels without affecting the property of the stiffened panels.

This article studies the influence of fiber Bragg grating (FBG) head length on insulated gate bipolar transistor (IGBT) direct on-chip thermal sensing performance of FBG sensors. To this end, the surface of a commercial IGBT chip is thermally simulated and experimentally characterized. Uniform FBG sensors with three head sizes are then tested in two promising thermal sensing locations. The study has found that the large thermal gradients in this application create an additional constraint when using longer head lengths. A distortion in the reflected spectrum of the 5-mm FBG sensor is used to illustrate the underlying physical effect, which causes this limitation for IGBT junction temperature measurement. This additionally affects the length of head sizes providing accurate temperature readings of the IGBT surface hotspots, and significantly, this limit is location-dependent in a given IGBT geometry.

Carbon fiber reinforced plastic (CFRP) structures are vulnerable to low-speed impacts, which will lead to almost invisible impact damage. Therefore, the timely localization of impact is of great si...

形態: 図版あり, Physical characteristics: Original contains illustrations, 資料番号: PA2120068000

An IGBT finite element model aimed at facilitating the assessment of Fibre Bragg Grating sensing based direct on-chip temperature monitoring is first presented in this paper. A commercial off-the-shelf IGBT module geometry is characterised, and a thermo-electrical finite element model is then established using its features. The model is subsequently employed to evaluate the local thermal disturbances that may be introduced by the installation of the optical based temperature sensor directly on the top surface of the IGBT chip. The effects of the sensor thermal interface material characteristics, e.g., thermal conductivity and size, in the local temperature environment are investigated.

Two types of fiber optics, namely macro etched silica single mode fiber (SMF) and Fiber Bragg Grating (FBG) (Bragg wavelength of 1550 nm and 1554 nm) had been used to detect various types of honey samples, such as Apis Dorsata Honey, Trigona Honey and Capilano Australian Honey. To study the effect of exposure period in open environment at room temperature, all honey samples were exposed in open environment at room temperature from 2 to 10 days. In comparison with macro etched SMF and FBG (λB=1554 nm), the FBG (λB=1550 nm) portrays an excellent sensing properties with sensitivity and selectivity of 33.56 dB/RIU and 24.07 dB/RIU respectively. The output of this work concludes that the quality of honey based on optical output power reduces up to 0.35% as period of exposure to the open environment increased.

Multi-parameter sensing technology plays an important role in structural health monitoring. In this paper, a novel FBG sensor with a pendulum structure for simultaneous measurement of tilt and acceleration is proposed. The design, principle and performance of the FBG sensor is introduced and tested in detail. The results show that the tilt sensitivity and acceleration sensitivity of the proposed FBG sensor can reach 408.3 pm/° and 2.43 nm/(m/s2), respectively, and that it works below 32 Hz in weak vibration detection. The theory analysis and the test result are in good agreement with each other. A wavelet transform method is utilized to separate the tilt and acceleration from the original signal received by the proposed FBG sensor. Cross sensitization of tilt and acceleration can be avoided effectively using this method. Finally, a field test is conducted in a railway slope. The recorded data is analyzed, which confirms further that the proposed FBG sensor can detect tilt and acceleration simultaneously. This novel FBG sensor provides a new method for multi-parameter monitoring.

The advancement of age and the increased awareness of public health have resulted in increased demand for continuous vital sign monitoring devices. Therefore, we developed a noninvasive vital sign measurement device without physical resistance to the user using a fiber Bragg grating (FBG) sensor. The FBG sensor was fixed on the wrist, and a pulse wave signal was obtained. Additionally, we focused on the similarity between this pulse wave signal and the second derivative of the plethysmogram (SDPTG). Classifying this signal, we found that its shape changed according to the age and blood pressure. We found that the change in the shape of the pulse wave signal and the SDPTG have the same tendency. Therefore, it is feasible to estimate the vascular age and arteriosclerosis with the signal obtained by an FBG sensor. On the basis of these results, the FBG sensor system can measure multiple vital signs and monitor health more comprehensively.

Pipe internal pressure measurement is of utmost importance in the oil & gas industry to monitor the extraction process, and thus to prevent hydrate-plugs formation which may occur in specific temperature and pressure conditions. Traditional solutions usually rely on pressure sensors in direct contact with the fluid to monitor, therefore requiring one hole per sensor, but they also weaken the pipe structure, which may prematurely lead to significant leaks. Attempts to develop non-intrusive pressure sensors relying, for instance, on acoustic waves detection or even strain measurements (the pipe wall acting, in some way, like the membrane of a traditional intrusive sensor), are up to now not fully satisfying, mainly due to poor temperature cross-sensitivity compensation. Thus, 1 °C temperature compensation error typically leads for Fiber Bragg Grating (FBG) transducers to pressure measurement biases greater than 26% at 100 bar (e.g.: Ø 4” NPS Sch. 160 steel pipe). Consequently, if such non-intrusive, but biased, solutions could possibly have been considered to monitor, for instance, a Nuclear Power Plant (NPP) primary coolant circuit, it was with the risk of dramatic consequences since the fluid can reach temperatures up to 320 °C. On the other hand, the solution detailed here truly achieves to cancel the temperature cross-sensitivity, and potentially any additional effect on pressure measurement, provided that each effect has the same influence on all transducers. It first relies on a better understanding of the pipe behavior under hydrostatic pressure, supported by a dedicated model developed on purpose, which demonstrates that the internal pressure and the surface temperature variations of a closed pipe can be recovered with at least two direction-sensitive transducers, the temperature dependence of the pressure measurement being simply removed by a straightforward compensation process. This paper explains the underlying principle, thanks to a formal model established with only few hypotheses, but extended to more complex field conditions. It ends with a lab-test validation involving FBG transducers attached to a pressure circuit submitted to temperature variations greater than several tens of °C, and concludes about the advantages and limitations of this novel approach for non-intrusive sensing, and its potential extensions to other measurement techniques.

Vinyl ester (VE) resin has strong environmental tolerance and is the matrix commonly used in the composite materials of fiber-reinforced plastics (FRP). VE resin is often combined with glass fiber in different maritime structures, such as wind turbine blades, spinner cases, and nacelle cases. However, VE resin exhibits exothermic reactions and shrinkage during curing, which often generates residual strain in large structures and those with a high stacking number. This study explored the exothermic reaction and shrinkage of VE resin and glass fiber during the vacuum-assisted resin transfer molding process, as measured using a fiber Bragg grating sensor. The experiment results verified the relationship between the stacking number and residual strain shrinkage. In addition, the symmetric laminate method was used to prevent the bending–twisting coupling effect and subsequent warping deformation of the FRP laminated plate during curing. The experiment results also verified that the bottom layers of the FRP laminated plates produced using VE resin were closer to the mold, and exhibited more shrinkage as the stacking number increased. In addition, this study discovered that during the experiment, the symmetry layer of the FRP laminated plate had a higher exothermic temperature than the bottom layer as a result of the symmetry layer’s ineffective heat dissipation. Therefore, the curing shrinkage of the symmetry layer resin was measured. The experiment results indicated that if the stacking number was between 10 and 30, the residual strain shrinkage of the symmetry layer was greater than that of the surface layer. However, because of the symmetric laminate, the residual strain of the symmetry layer did not increase when the temperature increased. Therefore, the greatest residual strain occurred at the surface of the bottom layer of the laminated plate with a stacking number of 40.

Model tests are carried out on the jacked single piles of different diameters and pile lengths under the model pile of different diameters and pile lengths in clayey soil, which aims to investigate the penetration mechanical mechanism. How to accurately test the pile end resistance and pile side resistance during jacked pile sinking is particularly important. In this paper, a full-section spoke-type pressure sensor, a double diaphragm temperature self-compensating fiber Bragg grating (FBG) earth pressure sensor and a sensitized miniature FBG strain sensor are jointly applied to a single pile penetration model test to test a single pile driving force, pile end resistance and pile body stress during penetration. The test results show that the load transfer performance of test piles will be affected by different diameters, and the axial force transfer capability of a large diameter in the depth direction is better than that of a small diameter since the compacting effect is more obvious. The unit skin friction of the pile increases gradually as the depth increases, which is larger due to the lateral extrusion force increasing as the diameter increases. At the same depth, the unit skin friction of two different diameter piles demonstrates “friction fatigue”, which also decreases obviously as the depth increases. Under the conditions of this test, the maximum frictional resistance of the pile TP1 pile side is about 27.7% higher than that of the test pile TP2. In the static pile sinking process of three test piles in cohesive soil, 50% is end bearing; therefore, there is 50% friction, and the diameter influences the end bearing and the length influences the friction.

We propose a conductive carbon coated fiber Bragg grating (FBG) temperature sensor for enhancing temperature sensitivity. The temperature sensitivity of the proposed sensor is effectively enhanced by approximately 4 times higher than those of the bare-type FBG sensors due to thermal expansion and physical stress possessed by the conductive carbon coating, with the operating temperature ranging from 40 °C to 260 °C. The proposed sensor is much more convenient to fabricate compared to other similarly coated FBG sensors, giving a leap advantage of easy reformation of the coating to fit various housings. This proposed sensor is significantly ideal for various applications such as optoelectronic circuit and waveguide temperature measurement.

Fiber Bragg Gratings (FBGs) are one of the most preferred high technology sensors in the sensor market. Although, FBG based strain sensors are widely used they are most likely to get affected by climate changes such as temperature. Thereby, most of the time they have to be used along with a reference temperature sensor. Otherwise, one should be ensuring that the FBG sensor is isolated from the climate changes which requires more effort and is a less reliable approach as compared to using an additional temperature sensor. In this study, a novel design of temperature compensated FBG sensor package, manufacturing of polyimide coated FBG sensors, and finally montaging of the manufactured FBG sensors to the corresponding package with an appropriate adhesive is presented. In addition, the designed package has been tested under discrete and continuous loading conditions. Obtained results showed that with the designed package it is possible to measure the strain change in terms of sensing capability of 1.2 microstrains (με) up to 80℃ with an extensive compensation ratio.

In this paper, we proposed and experimentally demonstrated a small integrator to replace optical spectrum analyzer (OSA) applications for robust remote sensing systems. Moreover, we demonstrated bidirectional Erbium-Doped Fiber Amplifiers (BiDi-EDFA) to improve sensing FBG sensor performance and provide gain for signals by increasing the optical signal-to-noise ratio (OSNR). The result of the experiment indicates that the BiDi-EDFA has a high power, which increases the gain of the transmitted signals. Furthermore, even the FBG sensors are placed after 50 km SMF, the sensing signal of FBGs achieves high OSNR using the proposed FBG integrator method.

We investigate the performance of a cantilever-type force sensor based on PDMS-coated fiber Bragg gratings for robot-assisted surgical applications. The cross section area of PDMS matrix and the location of the FBG sensor inside it are optimized through simulations. The sensitivity of the proposed sensor is obtained to be around 0.5 mN.

The deformation of Carbon Fibre Reinforced Polymer (hereafter referred to as CFRP) will affect the reliability and safety of products when it is applied in the fields of aeronautics & astronautics ...

Optical receiver modules play an important role in receiving signals from the Fiber Bragg Grating (FBG) sensors used for monitoring in civil structures, power facilities, and other sensing applications. When multiple sensors are used, more photo diodes receive optical signals; thin-film beam splitters with polarization characteristics are therefore used to reduce the size of the optical receiver module. Using a reflective semiconductor optical amplifier (R-SOA) with polarization characteristics in a sensing system with an FBG sensor, a structure that is less sensitive to polarization was developed by packaging a quad optical receiver module. A stabilization of ±4.67% was achieved using the dual optical receiver module in polarization and of ±1.20% with the quad optical receiver module in polarization.

We are working on the development of a sensor that can calculate various vital signs from the signals measured by installing a Fiber Bragg Grating (FBG) sensor at the pulsation point of a living body. In this paper, the influence of blood flow parameters and sensor installation conditions on the FBG sensor signal was verified using two blood flow simulation models. From the results of our study, the following observations were made. The fluid pressure increases, the wavelength shift of the FBG sensor beca me larger. By contrast, an increase in the viscosity of the fluid was seen to cause a decrease in the displacement length of the Bragg wavelength. Fluid pressure and viscosity were observed to opposite effects on the FBG sensor signal. The Bragg wavelength shift of the FBG sensor was observed to be larger when the installation direction of the FBG sensor was perpendicular to the blood flow direction than in the parallel direction. However, FBG sensor signals with higher signal-to-noise (S/N) ratio were measured at an angle of 75 degrees than at an angle of 90 degrees, which is perpendicular to the blood flow direction. From the above results, the installation condition of the FBG sensor on the measurement signal and the influence of each parameter of blood flow were established.

In this paper, a simple uniform fiber Bragg grating (FBG) sensor is designed, and maximum reflection of 7.1 dB at 1.55 μm is obtained. As this FBG shows a better reflection, it deserves well for the purpose of sensing and communication predominantly as they are resistant to electromagnetic radiations, light weight, low cost, firm size, and ease of handling. The proposed FBG is used for explosive sensing applications to detect explosives like trinitrotoluene (TNT), nitroglycerin, and royal demolition explosive (RDX). The different strain and temperature wavelength shifts of the explosives also analyzed and plotted.

Compared with the traditional electrical resistance strain gauge, the fibre Bragg grating (FBG) is a new material that can be used to produce the strain sensor, which has many advantages such as convenient installation, low temperature drifting, less signal interference and higher transmitted quality. In this study, FBG sensor system configuration, design principle, numerical simulation and loading tests for the FBG strain gauge are expatiated extensively. At the last, one-axial and three-axial strain gauges are produced and some conclusions have been put forward. So the FBG strain gauge can meet the precision of the structure monitoring and replace the traditional sensors.

Structural health monitoring (SHM) of engineering structures plays a crucial role in ensuring their safety and integrity. Acoustic emissions (AE) can be one of the several ways to monitor the structural health. Fiber Bragg grating (FBG)-based AE measurement technique is emerging as a solution to assess cracks in structures remotely and has advantages of being less bulky and having low noise, high bandwidth and ease of implementation. This paper presents a study on the impact of AE signals on FBGs attached to a substrate, focusing on the directional sensitivity using different configurations. For ease of installation, the FBG sensors are metallically packaged similar to lead zirconium titanate (PZT) sensors in which they can withstand temperatures of up to 250 °C. The directional AE sensitivity of the packaged FBG sensor device is studied and compared with that of a surface attached FBG. Experimentally, the AE signals are generated by a metal ball drop impact on aluminum plate and are measured using an FBG AE interrogation system. A numerical simulation of the design was carried out using ANSYS explicit dynamics and the AE wave propagation in structure was analyzed and experimentally verified.

Ventricular assist devices are used to support patients with end-stage heart failure. Many patients on long-term VAD support are treated out-of-hospital where monitoring technology for patients is severely limited; leading to sub-optimal patient management. This paper describes a novel fibre Bragg grating (FBG) pressure sensor which was developed for improved monitoring of patients with ventricular assist devices. The FBG sensor was fabricated in-house and characterised in a circulating heat bath. The FBG pressure sensor demonstrated a sensitivity of −0.0046 nm/mmHg with an accuracy of ± 0.35 mmHg, a resolution of 0.0019 mmHg and a response time of 89.7 mmHg/s. The high sensitivity and resolution combined with the adequate accuracy exhibited by the FBG sensor demonstrated its potential value of the FBG pressure sensor for monitoring patients with ventricular assist devices. Further investigation into device drift, improved manufacturing, and gas-impermeable biocompatible materials are required to prepare the sensor for pre-clinical trials.

In this paper, the effects of three types of commonly used adhesives were studied via experiment and simulation. The results show that the strain sensitivity of fiber Bragg grating (FBG) sensor is about 1.201 pm/μe and the effects of three adhesives of epoxy resin, AB glue and 502 glue with the same thickness and length on sensitivity coefficients of FBG sensors are 99.20%, 93.80% and 96.50%, respectively. Finally, the sensitivity coefficient of the simulated FBG sensor is the same as the test result by ANSYS modeling.

Glass has been widely used as an important component in structures such as reflection glass curtainwalls, high speed trains, and landscape glass bridges with advantages of transparent and easy to clean, which are exposed to extreme weather conditions and external loads. Over time, these factors can lead to a damage of glass. So the health status of glass structure is critical, which should be routinely monitored to improve safety and provide reliable maintenance strategy. In this paper, fiber Bragg grating (FBG) sensors are used to monitor glass damage based on the fact that the main components of both the optical fiber and the glass are silica, which hints that both optical fiber and glass have the similar mechanical properties. Furthermore, the diameter of FBG installed on the glass structure is small, which has little effect on the beauty of glass. In order to validate the feasibility of the damage monitoring method, one common glass panel model with two-side fixations is loaded impact and static loads respectively, on the upper and lower surfaces of which four FBG sensors and two resistance strain gages are installed. A comparison study among the measured strains from the FBG sensors, those from the resistance strain gages, and those calculated from finite element model (FEM) analysis is conducted and the result obtained with experiments agrees with the element result. Test results show that the FBG sensors can effectively measure the glass deformation or damage under the impact and static load.

Carbon Fiber Reinforced Plastic (CFRP) shaft tube structure is widely applied in different fields, including aerospace, automotive, and wind power. Since CFRP shaft tube is often subjected to bending fatigue loads, it is of great significance to research its bending fatigue characteristics. Because of its unique advantages, such as a smaller size, lighter weight, and the outstanding ability to form a sensor network, the Fiber Bragg Grating (FBG) sensor is very applicable for health monitoring research of composite material structures. Taking the CFRP shaft tube under bending load as the research object, based on the theory of composite material mechanics and applying the research idea of combining simulation analysis and experiment, the fatigue life, residual stiffness, and fatigue damage evolution of CFRP tubes under three-point bending fatigue loading were studied. Moreover, the fatigue characteristics of CFRP tubes under different fatigue loading were analyzed. At the same time, the ultrasonic phased array was used to obtain the fatigue damage evolution rule by scanning and analyzing the damage to the CFRP shaft tube after different fatigue loading times. Through the application of the FBG sensors, the whole process of fatigue evolution of the CFRP shaft tube was fully monitored.

In practical engineering applications, the Carbon Fiber Reinforced Polymer(CFRP)encapsulated Fiber Bragg Grating (FBG) sensor was pasted on the substrate surface by the adhesive layer to monitor the strain of the substrate. The strain of the substrate was transferred to the packaging layer through the adhesive layer, and the packaging layer transferred the strain to the FBG sensor. Performance parameters of the FBG sensor in the sensor system stability depends on the measure precision of the sensor system, different kinds of thickness of adhesive, paste, paste the length affects the performance parameters of the FBG sensor, based on the long-term cyclic loading fatigue test to study the adhesive layer to the influence of the performance parameters of the FBG sensor. By comparing the effect of 0.14mm and 0.28mm paste thickness on the performance parameters of the FBG sensor, the performance parameters of the sensor with 0.14mm paste thickness have less change. In engineering application, the small paste thickness should be selected as far as possible to ensure no degumming.

The paper made an experimental investigation on reliability of fiber Bragg grating (FBG) sensors packaged with carbon fiber reinforced polymer (CFRP) which would be used in fatigue test of wind turbine blades (WTBs). More and more FBG sensors are applied to the full-scale fatigue test of WTBs. For the size of FBG sensor is very small and easy to break, it must be packaged before used. Compared with other packaging materials, fiber reinforced polymer (FRP) is more suitable for packaging FBG sensors used in WTBs because of its good compatibility with the surface material of the blade. The performance of FRP packaged FBG sensor has been studied in the available literatures, while influences of different FRP layers and sizes on the reliability of FRP packaged FBG sensors are unknown. Thus, in this paper, CFRP is chosen as the packaging material of FBG sensors, and the influences of packaging layers and sizes on the reliability of CFRP packaged FBG sensors are studied by a series of experimental tests. The results show that the orientation angles and lengths have negligible influences on the reliability of CFRP packaged FBG sensors, the layers and sizes of CFRP must be considered when packaging FBG sensors.

Pantograph-catenary system provides electric energy for the subway lines; its health status is essential to the serviceability of the vehicle. In this study, a real-time structural health monitoring method based on strain response inversion is proposed to calculate the magnitude and position of the dynamic contact force between the catenary and pantograph. The measurement principle, calibration, and installation detail of the fiber Bragg grating (FBG) sensors are also presented in this article. Putting this monitoring system in use, an application example of a subway with a rigid overhead catenary is given to demonstrate its performance. The pantograph was monitored and analyzed, running underground at a maximum speed of 80 km/h. The results show that the strain response inversion method has high measurement accuracy, good data consistency, and flexibility on sensor installation. It can accurately calculate the magnitude and location of the contact force exerted on the pantograph.

In this work, we propose a vibration monitoring architecture which is based on the interrogation of a set of FBG sensor arrays and the system state prediction based on the collected data. This architecture can be deployed and parameterized according to the application and the type of the monitored structure (building, bridge, railways, etc). The deployed FBG sensor network allows to compute the fiber elongation under strain, the displacement and the vibration of each FBG node in the network. A decision to reduce the vibration values can be made based on the measurements performed and whether the vibration exceeds a predefined threshold. The efficiency of the proposed architecture is assessed based on a real case study (The San Diego story office Building) and real displacements signals collected by sensor nodes in the presence of an earthquake.

A fiber Bragg grating (FBG) sensor integrated with an epoxy diaphragm was developed for the measurement of pressure and water level. The bending strain of a circular diaphragm induced by uniform pressure was transferred to the FBG sensor. The response of the FBG sensor to the pressure was observed in terms of the Bragg wavelength shift which is linearly proportional to the strain. The effect of epoxy diaphragm thickness on the sensitivity and accuracy was investigated. The experimental results show that the sensitivity of FBG/epoxy diaphragm pressure sensor is decreasing with the increase of the diaphragm thickness. The sensitivities of the FBG pressure sensors with diaphragm thicknesses of 0.5 mm, 0.7 mm, and 1.0 mm were 175.5 pm/kPa, 89.5 pm/kPa, and 43.7 pm/kPa, respectively. The pressure measured by the proposed FBG sensor was compared with theoretical prediction and a close agreement was observed.

This article focuses on the development of a carbon composite bicycle frame using various experimental methods of structural analysis. Two types of frame specimen were used. The complete frame specimen was tested in accordance with ISO test load cases with the addition of an ergometer test in order to refine the operational strain envelope of such a frame. Resistive strain gauges and optical Fiber Bragg Grating (FBG) sensors were used for this analysis. The FBG sensors were embedded inside the head tube joints during the manufacturing process. The head connection was designed as a geometrically precise form–connection of wound composite tubes, reinforced with a wrap of high-strength unidirectional carbon tapes and carbon fabrics. Additional structural strength laboratory tests were conducted using simplified frame specimens, in order to evaluate the range of the limit case strain ranges. The digital image correlation method was used for the evaluation of the strain distribution in the head tube area. Resistive strain gauges were used for local strain analysis in critical areas. The acoustic emission method was used to detect structural defects before they could influence the stiffness response of the frame. It was found that the joints of the frame tubes are crucial for the strength and safety of the frame. Therefore, attention was also focused on the strengthening of the head tube joint, and on its experimental verification. A positive effect on the strength of the reinforced frame was found by doubling the thickness of the carbon fabric in the head tube joint area.

A hydrogen and humidity simultaneous measurement system based on an integrated FBG sensor is proposed. Experimentally results indicate the sensor shows a high degree of hydrogen discrimination ranging from 100ppm-8000ppm and a high degree of humidity discrimination ranging from 20% - 80%, along with the high performance of anti-mutual interference of hydrogen and humidity.

Structural health monitoring techniques have captured much interest and attention of researchers owing to their potential in providing spatial and quantitative information regarding structural damage and the performance of a structure. Integrated health monitoring of structures with advances in sensor technology can improve structural reliability, system performance, and safety. Pipelines exist for the transport of crude/refined petroleum, oil, natural gas, and biofuels. These pipelines are made from steel which are usually buried. These pipelines are prone to natural and man-made damages. Hence, monitoring of these buried pipelines becomes essential. Leakages of oil and gas from pipeline are dangerous for people and environment. Detection of leakage along the pipeline network is an essential part of the maintenance activity which is always a difficult task. The experimental studies carried out on using FBG sensors for monitoring corrosion in buried pipelines has been described in this paper. In this study, the FBG sensor is used for measuring the hoop strain variation in the pipeline and from the variation of hoop strain corrosion is identified. Hence, the FBG sensor technology can be adopted for monitoring corrosion in the buried oil and gas pipelines.

An interrogation technique for fiber Bragg grating (FBG) sensor is devised with customized in-line edge filtering single-multi-single mode fiber (SMS) component and optical time-domain reflectometer (OTDR). The performance of the proposed SMS-OTDR interrogation is established by temperature and strain sensing analysis of a standard FBG. The temperature and strain sensitivity values which are verified by theoretical analysis are estimated as 1.01 × 10−2 dB/℃ and 3.9 × 10−4 dB/µɛ respectively. Furthermore, we have optimized and achieved controlled etching on FBG and tested it for hiking the sensitivity. Using the etched FBG, an enhanced temperature and strain sensitivity of 6.7 × 10−2 dB/℃ and 3.2 × 10−3 dB/µɛ covering the range of 20–200 °C and 100–2015 µɛ respectively are also recorded and analysed by this integration method. Eventually, the efficiency and cost-effectiveness of the proposed method are compared with various reported techniques and presented here.

We evaluate the capabilities of optical fiber sensors to measure traffic flow, speed, weight estimation and pavement degradation. The proper operation of the system has been proved 3.5 years after the installation in a metropolitan road. This work was supported by the Spanish AEI project TEC2016-76021-C2, FEDER Funds, and the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 838143 and the institute of Smart Cities (UPNA) talent grant.

Smartphone-based interrogation of FBG sensor is reported for the first time. Setup consists of a smartphone and low cost off-the shelf available components: a section of DVD disk, razor blade slit and a 3D-printed holder. Smartphone flashlight LED was used as a light source, and FBG spectra were projected on the smartphone camera by a DVD disk.

We present the design of an FBG sensor-based contact microphone and compare its speech quality to that of a calibrated measurement microphone using perceptual evaluation of speech quality score and spectrogram analysis in noisy environment.

The existing fiber Bragg grating (FBG) wavelength demodulation system based on Mach-Zehnder interferometer and phase sensitive optical time domain reflectometer(φ-OTDR) is limited by the system structure and working principle. It can obtain large demodulation capacity through time division multiplexing (TWD), but it can only measure the relative change of wavelength. In this paper, we design and experimentally verify a scheme for measuring the absolute wavelength of FBGs. This scheme can obtain the absolute wavelength of a large-capacity FBG sensor array without affecting the performance of the original technical indexes, and also theoretically improve the accuracy of the system. Its dynamic real-time absolute wavelength demodulation error less than 0.1pm.

Fiber Bragg grating (FBG) sensors are widely used because of their advantages of light weight, corrosion resistance, electromagnetic interference resistance and long life, especially in the field of aerospace. In order to meet the requirements of deformation measurement and structural evaluation of the new generation aircraft, and improve the performance and safety of aircraft, it is of great significance to carry out the research on condition monitoring technology based on FBG sensor in dynamic flight state. In the paper, FBG sensors are applied to the measurement of aircraft wing and the results show that the measurement accuracy of FBG sensor can reach at 1 mm, which has good performance.

We demonstrate a self-referencing FBG sensor for damage detection. The sensor compensates for changing environmental conditions by measuring the reference and distorted signal simultaneously and uses traveling acoustic waves in optical fibers.

A small-diameter FBG sensor was embedded in 0° ply of a CFRP cross-ply laminate, and reflection spectra from the FBG sensor were measured at various tensile stresses. As a result, it was found that the small-diameter FBG sensors have a potential to detect the occurrence of transverse cracks in 90° ply through the change in the form of the spectrum, and to evaluate the crack density quantitatively by the spectrum width. On the other hand, pre-strained SMA films were embedded between laminas in CFRP laminates and heated. The effects of recovery stresses were demonstrated in the experiments and well predicted using the shear-lag analysis and the nonlinear constitutive equation of SMA films.

Off-shore oil and gas platforms present a harsh environment for their installed infrastructure, with pipelines that are both subjected to a corrosive atmosphere and transport aggressive chemicals being the most critical. These conditions have prompted the industry to substitute metallic pipelines for composite counterparts, often made of fiber reinforced plastics assembled with bonded joints. Various technologies have emerged in the recent years to assess the health of these composite pipelines. In particular, robust speckle metrology techniques such as shearography have produced very satisfactory results. However, these inspection techniques require specialized equipment and trained personnel to be flown to off-shore platforms, which can incur in non-trivial inspection costs. In this paper we propose and demonstrate a robust and cost-effective approach to monitor pipeline bonded joints during assembly and operation using fiber Bragg grating (FBG) sensors embedded into the joints’ adhesive layer. This has been achieved by instrumenting bonded joints between 4” nominal diameter industrial grade Chlorinated Polyvinyl Chloride (CPVC) pipes with 12 sensing fibers, each fiber contains 3 FBGs for a total of 36 strain measurement points. To validate this approach, we present and compare data collected from both structurally sound joints and joints with controlled defects for various situations, including joint and pipeline assemble and operation. Computed tomography has been used as the control technique to evaluate structural soundness of tested joints. This approach allows for informed decisions on when to perform targeted in-depth inspections based on both real-time and long-term feedback of the FBG sensor data, resulting on lower monitoring costs, a severe increase on monitoring uptime (up to full uptime), and increased operational security.

A fast FBG sensor interrogation method based on silicon on insulator (SOI) microring resonators is reported. The simple and effective FBG sensor interrogation scheme is based on the detection of the signal intensity at the drop port of a microring resonator, and its interrogation speed depends only on the photodetector and the front end electronics. The performance of the FBG interrogation method is evaluated in terms of minimum detectable wavelength shift and dynamic strain resolution and compared with a commercial FBG interrogator.

Recently, it has become necessary to develop a monitoring technology that combines an FBG (fiber Bragg grating) sensor as a means for continuously monitoring whether the reinforcing effect of an FRP (fiber-reinforced polymer) is maintained on FRP-reinforced structural members. However, most existing research focuses on the insertion of FBG sensors into bar-shaped FRPs, and there is a lack of studies that analyze the details for an FRP strip combined with FBG sensors. In this regard, this paper seeks to develop a reinforcement for an NSM (near-surface-mounted) retrofit in which an optical fiber with an FBG sensor is combined with FRP strips. For this, a series of experiments were performed to find the adhesive strength of optical fiber-epoxy-FRP interfaces, the tensile strength of the FBG sensor part of optical fiber with a reflection lattice, and the sensing performance depending on the adhesion length between the optical fiber and the FRP strips. As a result of the study, the adhesion length not less than 20 mm in one direction from the center, with a total adhesion length of 40 mm, needs to be secured when the optical fiber with an FBG is attached and fixed between the two FRP strips with epoxy. In addition, it is expected that the proposed model can be used to properly predict the strain transfer of an FRP strip with a fiber optic sensor and can also be utilized when determining optimum dimensions.

We demonstrated in this work a filterless, multi-point and temperature-independent FBG (fiber Bragg grating) dynamical demodulator using pulse-width-modulation (PWM). In this approach, the FBG interrogation system is composed of a tunable laser and a demodulator that is designed to detect the wavelength shift of the FBG sensor without any optical filter making it very suitable to be used in harsh environments. In this work, we applied the proposed method that uses the PWM technique for FBG sensors placed in high pressure and high-temperature environments. The proposed method was characterized in the laboratory using an FBG sensor modulated in a frequency of 6 Hz, with a 1 kHz sweeping frequency in the wavelength range from 1527 to 1534 nm. Also, the method was evaluated in a field test in an engine of a thermoelectric power plant.