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Nowadays, smart composite materials embed miniaturized sensors for structural health monitoring (SHM) in order to mitigate the risk of failure due to an overload or to unwanted inhomogeneity resulting from the fabrication process. Optical fiber sensors, and more particularly fiber Bragg grating (FBG) sensors, outperform traditional sensor technolog...
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... Use of FBGs photo-inscribed at two different wavelengths in a single optical fiber [14]. Table 1 summarizes temperature and strain sensitivities for a standard optical at different wavelengths, taken from [15]: Exploitation of the first and second diffraction orders of a single FBG [16]. As in the previous solution, using different wavelengths provides different sensitivities. ...
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Fiber optic metrology developed at the CEA LIST laboratories involves fiber Bragg grating sensors, distributed Brillouin optical time domain reflectometry and optically stimulated luminescence dosimetry. Recent activities in optical fiber sensing are reviewed from laboratory experiments to field trials.
Citations
... More importantly, their susceptibility to electromagnetic interference and limited range makes their use in carbon fibre composite tools prohibitive [5]. Photonic structures can bridge that gap, with optical fibre configurations already deployed in sensing applications [6][7][8], for structural health monitoring [9,10] and especially in the composite industry [11][12][13][14]. However, these sensors are either embedded at a certain depth in the tool or the produced part, making monitoring at the tool-resin interface difficult. ...
Composite materials have increased in use across multiple industries due to their low weight, thermal stability and design flexibility. As applications grow, the importance of accurate process-monitoring techniques grows, with various research teams investigating a variety of in situ cure-monitoring sensors. Photonic integrated circuits (PICs) can be a feasible solution in tracking curing cycles due to their resistance to harsh conditions and ease of integration into the production tool. This paper demonstrates the integration and performance evaluation of an embedded phase-shifted Bragg grating solution, instead of commonly used fiber sensors, based on 220 nm height silicon-on-insulator platform for in-situ monitoring of the RTM-6 resin curing process in a composite tool. The embedded optical sensor presents high sensitivity (75 pm/°C) and linearity (R²=0.995) up to 120 °C, enabling precise temperature measurements throughout the curing cycle. The experimental results show consistency with previously reported simulations, throughout the calibration, dry run characterization and the curing process, up to 120 °C, allowing for accurate monitoring of the curing process.
... One of the crucial benefits of fiber optics is that the same sensor can carry dual purposes. It can act in the same way as the sensing element for measuring the critical physical parameters and as a transmission medium for the detected signal [6]. ...
This article discusses the use of distributed acoustic sensing (DAS) for monitoring gas–liquid two-phase slug flow in horizontal pipes, using standard telecommunication fiber optics connected to a DAS integrator for data acquisition. The experiments were performed in a 14 m long, 5 cm diameter transparent PVC pipe with a fiber cable helically wrapped around the pipe. Using mineral oil and compressed air, the system captured various flow rates and gas–oil ratios. New algorithms were developed to characterize slug flow using DAS data, including slug frequency, translational velocity, and the lengths of slug body, slug unit, and the liquid film region that had never been discussed previously. This study employed a high-speed camera next to the fiber cable sensing section for validation purposes and achieved a good correlation among the measurements under all conditions tested. Compared to traditional multiphase flow sensors, this technology is non-intrusive and offers continuous, real-time measurement across long distances and in harsh environments, such as subsurface or downhole conditions. It is cost-effective, particularly where multiple measurement points are required. Characterizing slug flow in real time is crucial to many industries that suffer slug-flow-related issues. This research demonstrated the DAS’s potential to characterize slug flow quantitively. It will offer the industry a more optimal solution for facility design and operation and ensure safer operational practices.
... Khác biệt rõ rệt của FBG so với các công nghệ cảm biến khác là khả năng cung cấp thông tin về bước sóng, một tham số tuyệt đối, từ đó tạo ra một sơ đồ đo lường tuyệt đối, tự tham chiếu. Cảm biến quang đã chứng minh được tính ưu việt của nó so với các cảm biến truyền thống khác trong lĩnh vực SHM [3], [4]. Cảm biến FBG có độ nhạy cao từ đó dễ dàng nắm bắt các dao động dù là rất nhỏ trong kết cấu. ...
Trong Giám sát sức khỏe kết cấu (Structural Health Monitoring - SHM), việc sử dụng dữ liệu dạng chuỗi thời gian thu được từ các cảm biến được sự quan tâm của cộng đồng nghiên cứu trên thế giới. Với sự phát triển của các công nghệ cảm biến, các dữ liệu này ngày càng nhiều và phức tạp. Tuy nhiên, các phương pháp Học máy (Machine learning - ML) truyền thống, chẳng hạn như Mạng thần kinh nhân tạo, không còn đủ hiệu quả để xử lý và chẩn đoán chính xác các hư hỏng cấu trúc dựa trên dữ liệu phụ thuộc vào thời gian. Để giải quyết vấn đề này, nghiên cứu này đề xuất một phương pháp học sâu mới tích hợp mạng thần kinh tích chập 1 chiều (1D Convolutional Neural Network-1DCNN) và mạng bộ nhớ ngắn hạn dài (Long Short-Term Memory - LSTM) để nâng cao hiệu quả phát hiện hư hỏng kết cấu dựa trên dữ liệu dạng chuỗi thời gian được thu thập từ cảm biến quang. Hiệu quả của phương pháp đề xuất được đánh giá thông qua bộ dữ liệu cầu dây văng trong phòng thí nghiệm, được xây dựng tại Trường Đại học Giao thông Vận tải. Theo đó, kết quả đã chứng minh thấy phương pháp đề xuất hoàn toàn vượt trội so với phương pháp học sâu truyền thống với kết quả lần lượt trên tập kiểm thử và kiểm tra là 77.5 và 74.1%.
... However, a challenge arises in practical applications because of the Letter similar sensitivity of both core and cladding modes in standard silica optical fibers to temperature and strain due to their inherent properties. Such similar sensitivities can potentially diminish the accuracy of the sensor probe in real applications [16]. ...
... For the stain measurement, the sensitivity of the core mode and cladding modes is 0.61 pm/µε and up to 0.54 pm/µε, respectively, in the range 0-2400 µε. Due to the determinant of the core and cladding mode 2 × 2 matrix, this proposed sensor probe features a high decoupling efficiency [16], which is an ideal candidate for a simultaneous measurement of temperature and strain. ...
In this Letter, we propose an in-line tilted fiber Bragg grating sensor for temperature and strain measurements. The grating is inscribed in a specialty optical fiber using tightly focused femtosecond laser pulses and the line-by-line direct writing method. Beside the central core in which the grating is produced, a hollow channel filled with glycerol aqueous solution significantly improves the sensitivity of the fiber cladding modes due to its high thermo-optic coefficient. We show that the temperature sensitivity of the core mode is 9.8 pm/°C, while the one of the cladding modes is strongly altered and can reach −24.3 pm/°C, in the investigated range of 20–40°C. For the strain measurement, sensitivities of the core mode and the cladding modes are similar (∼0.60 pm/με) between 0 and 2400 με. The significative difference of temperature sensitivity between the two modes facilitates the discrimination of the dual parameters in simultaneous measurements.
... As a result of these unique properties of TFBGs, it is possible to discriminate between bending and temperature effects simultaneously 74 . TFBGs can be used as sensors in various applications such as structural health monitoring 75 , biomedical sensing 76 , and chemical sensing 77 . Similarly to uniform FBGs, TFBGs can be used as flexible optical fiber sensors encapsulating the TFBG sensors in flexible structures ensuring sensor integrity while the bending resistance is increased [78][79][80] . ...
This paper presents a review of optical sensor systems for wearable applications aiming at the new demands on healthcare motivated not only by the new paradigms in internet of things, but also in photonics development and artificial intelligence algorithms. In this context, the overview of musculoskeletal disorders and the role of wearable sensor systems in such applications are discussed. In addition, there is a comprehensive discussion of the components of wearable sensor systems with the novel developments and approaches in different wearable applications. Thus, the optical fiber sensor developments, approaches and applications are discussed for their use in smart textiles, biosensors and intrusive applications. Moreover, new developments on power supplies are discussed aiming at self-powered sensor systems. Therefore, this review paper can aid in the development of the new generation of wearable sensor systems in healthcare applications using optical fiber sensors and general optical based sensors, which can overcome or mitigate the shortcomings of conventional sensor technologies.
... High-precision pressure monitoring is vital in industries such as resource extraction [1,2], aerospace [3], health monitoring [4,5], and industrial automation [6,7]. Recently, fiber-optic pressure sensing technology has garnered significant attention for its accuracy and stability detection of small pressure changes [8]. ...
In this paper, a highly sensitive pressure sensor based on fiber-optic Fabry–Perot interferometers (FPIs) and the Vernier effect (VE) is proposed and experimentally demonstrated. We employ a closed capillary-based FPI s for the sensing cavity, and an FPI r created through femtosecond laser refractive index modulation for the reference cavity, which remains impervious to pressure changes. Connecting these two FPIs in series produces a VE-based cascaded sensor with a clear spectral envelope. The femtosecond laser micromachining technique provides precise control over the length of FPI r and facilitates adjustments to the VE’s amplification degree. Experimental results reveal significant pressure sensitivities of −795.96pm/MPa and −3219.91pm/MPa, respectively, representing a 20-fold and 80-fold improvement compared to FPI s (−39.80pm/MPa). This type of sensor has good sensitivity amplification and, due to its all-fiber structure, can be a promising candidate for high-temperature and high-pressure sensing, especially in harsh environments.
... For monitoring parts made of fiber-reinforced plastic (FRP), a multitude of principles for strain measurement have been investigated [1,2]. Material-integrated systems are gaining relevance due to frequent outside invisibility of internal defects in FRP (e.g., delamination, broken fibers [3,4]) and the higher sensitivity of in situ measurements compared to surface-based measurements [1]. Most established systems (e.g., using Fiber Bragg Gratings [4]), though precise, are usually complex, costly, and mechanically sensitive, thereby complicating integration and automated industrial application [2,4,5]. ...
... Material-integrated systems are gaining relevance due to frequent outside invisibility of internal defects in FRP (e.g., delamination, broken fibers [3,4]) and the higher sensitivity of in situ measurements compared to surface-based measurements [1]. Most established systems (e.g., using Fiber Bragg Gratings [4]), though precise, are usually complex, costly, and mechanically sensitive, thereby complicating integration and automated industrial application [2,4,5]. Most importantly, nearly all established techniques employ wired sensors, fundamentally complicating vacuum setup and part handling. ...
... Material-integrated systems are gaining relevance due to frequent outside invisibility of internal defects in FRP (e.g., delamination, broken fibers [3,4]) and the higher sensitivity of in situ measurements compared to surface-based measurements [1]. Most established systems (e.g., using Fiber Bragg Gratings [4]), though precise, are usually complex, costly, and mechanically sensitive, thereby complicating integration and automated industrial application [2,4,5]. Most importantly, nearly all established techniques employ wired sensors, fundamentally complicating vacuum setup and part handling. ...
... Each small segment has monitoring points, as shown in Figures 3 and 4. The data for the entire process are collected using fiber-optic grating sensors, which offer advantages such as high precision, strong anti-interference capability, compact size, and fast response compared to other monitoring methods. They are more suitable for long-term monitoring of tunnel structures [31,32]. The equation for calculating soil pressure is as follows: ...
With the advancement of engineering techniques, underground shield tunneling projects have also started incorporating emerging technologies to monitor the forces and displacements during the construction and operation phases of shield tunnels. Monitoring devices installed on the tunnel segment components generate a large amount of data. However, due to various factors, data may be missing. Hence, the completion of the incomplete data is imperative to ensure the utmost safety of the engineering project. In this research, a missing data imputation technique utilizing Random Forest (RF) is introduced. The optimal combination of the number of decision trees, maximum depth, and number of features in the RF is determined by minimizing the Mean Squared Error (MSE). Subsequently, complete soil pressure data are artificially manipulated to create incomplete datasets with missing rates of 20%, 40%, and 60%. A comparative analysis of the imputation results using three methods-median, mean, and RF-reveals that this proposed method has the smallest imputation error. As the missing rate increases, the mean squared error of the Random Forest method and the other two methods also increases, with a maximum difference of about 70%. This indicates that the random forest method is suitable for imputing monitoring data.
... One of the commercially available and commonly used fiberoptic sensors was the FBGs [3], [4]. Various applications of FBGs for measuring strain and temperature in industries were widely discussed [5], [6]. In recent years, the application of FBGs for temperature measurements in the steel industry has been extensively reported [7]- [10]. ...
... These distributions are normalized to unit power, indicating the relative strength of the electric fields in each mode. The order of an FBG is given by [37], [45] Bragg = 2 (6) where, m = 5 corresponds to the order of FBG, and neff represents the effective refractive index of the fiber. Multimode fiber-based FBGs offer numerous benefits compared to their single-mode counterparts. ...
... The microfabrication system was controlled by a computer through a custom-built graphical user interface (GUI). In this study, the effective refractive index (neff) for each Bragg wavelength is evaluated both experimentally and analytically using eq (6). In order to make strong FBG reflectors, a high pulse repetition rate and high laser intensity were employed, which led to a larger spot size, resulting in selecting a larger grating period. ...
This research reports a distributed fiber optic high-temperature sensing system tailored for applications in the steel industry and various other sectors. Recent advancements in optical sensor technology have led to the exploration of sapphire crystal fibers as a solution for sensing in harsh environments. Utilizing a femtosecond (fs) laser, cascaded fiber Bragg gratings (FBGs) were meticulously fabricated within a multimode sapphire optical fiber. These FBGs endowed the system with distributed sensing capabilities and underwent rigorous testing under extreme temperatures, reaching up to 1,800 °C. The study delves into the investigation of the FBG reflection spectrum, facilitated by the development of a sophisticated multimode demodulation system, which contributed to the attainment of precise temperature measurements with a performance accuracy of 99.9%. Demonstrating exceptional thermal stability, the sapphire FBGs endured temperatures of 1,600 °C for a sustained duration of 22 hours. Furthermore, the paper explores the application of distributed temperature sensing employing multiple sapphire FBGs, showcasing their utility in temperature measurements related to molten steel studies. Index Terms-Fiber Bragg gratings (FBGs), fiber sensors, sapphire optical fiber, femtosecond (fs) laser, molten steel, submerged entry nozzle (SEN).
... A fiber Bragg grating (FBG)-based optical sensors had a substantial market value because of a number of benefits including; their compact size, light, weight, lack of electrical connections, and compatibility with nonintrusive remote sensing [33]. A variety of wavelength of light was primarily flowed through the FBG, but one particular wavelength was reflected back [34]. ...
Viruses are dangerous pathogenic biological agents as they are highly infectious, very small in size, and have no real cure. Thus, early detection is the crucial step in defense against such threats. The optical biosensor is one of the appropriate approaches to the detection of viruses. An optical biosensor is a compact analytical device that contains a biorecognition sensing element integrated with an optical transducer system. This review is aimed at reporting the basic concept of optical biosensors with the recent biomedical applications of its varied forms briefly. Also, this paper focuses on the gold nanoparticles (AuNPs) based on optical biosensors and their few forms. Further, we discuss the varied forms of AuNPs-based biosensors in detecting various viruses in recent decades. This study has presented some recent achievements of AuNPs-based optical biosensors in virus detection in the last decade. Also, we have discussed some challenges being faced by the optical sensors and also their future prospects.
