Academic literature on the topic 'FBG sensors, fast sensing system, innovative applications'

Abstract The recent adoption of high-T c superconductor (HTS) wires for ultra-high field magnet windings provide great promise for future applications, such as high-power generators and Tokamak fusion reactors. However, an open issue with the use of HTS is the challenge of rapidly detecting a hot spot which could lead to a quench. Optical fiber sensors have been shown to be promising alternatives to the voltage-based quench detection method. In this paper, we report on ultra-long fiber Bragg gratings (ULFBG) for hotspot detection at cryogenic temperatures using a new detection algorithm. This novel sensing system is suitable for applications in which solely the occurrence of a hotspot but not its precise location is of importance. This is the case e.g. for quench detection in HTS. The developed system provides the advantages of cost reduction and faster response time compared to conventional FBGs with wavelength-division multiplexing and continuous FBGs with time-division multiplexing, respectively. We demonstrate the functionality of the system for the ULFBG with a grating length of 100 mm and 500 mm at 77 K and 90 K respectively. The ULFBG is shown to respond as fast as conventional FBG, to a hot spot as small as 1 K temperature rise. Furthermore, using the proposed signal processing algorithm, ULFBG exhibits much higher signal to noise ratio than that from the conventional FBG. It is believed that artificial intelligence based technique can assist the signal processing algorithm in detecting a small hot spot more rapidly from the big spectral data in real-time.

High spatial ground resolution and highly flexible and timely control due to reduced planning time are the strengths of unmanned aerial vehicle (UAV) platforms for remote sensing applications. These characteristics make them ideal especially in the medium–small agricultural systems typical of many Italian viticulture areas of excellence. UAV can be equipped with a wide range of sensors useful for several applications. Numerous assessments have been made using several imaging sensors with different flight times. This paper describes the implementation of a multisensor UAV system capable of flying with three sensors simultaneously to perform different monitoring options. The intra-vineyard variability was assessed in terms of characterization of the state of vines vigor using a multispectral camera, leaf temperature with a thermal camera and an innovative approach of missing plants analysis with a high spatial resolution RGB camera. The normalized difference vegetation index (NDVI) values detected in different vigor blocks were compared with shoot weights, obtaining a good regression (R2 = 0.69). The crop water stress index (CWSI) map, produced after canopy pure pixel filtering, highlighted the homogeneous water stress areas. The performance index developed from RGB images shows that the method identified 80% of total missing plants. The applicability of a UAV platform to use RGB, multispectral and thermal sensors was tested for specific purposes in precision viticulture and was demonstrated to be a valuable tool for fast multipurpose monitoring in a vineyard.

Personalised healthcare has seen significant improvements due to the introduction of health monitoring technologies that allow wearable devices to unintrusively monitor physiological parameters such as heart health, blood pressure, sleep patterns, and blood glucose levels, among others. Additionally, utilising advanced sensing technologies based on flexible and innovative biocompatible materials in wearable devices allows high accuracy and precision measurement of biological signals. Furthermore, applying real-time Machine Learning algorithms to highly accurate physiological parameters allows precise identification of unusual patterns in the data to provide health event predictions and warnings for timely intervention. However, in the predominantly adopted architectures, health event predictions based on Machine Learning are typically obtained by leveraging Cloud infrastructures characterised by shortcomings such as delayed response times and privacy issues. Fortunately, recent works highlight that a new paradigm based on Edge Computing technologies and on-device Artificial Intelligence significantly improve the latency and privacy issues. Applying this new paradigm to personalised healthcare architectures can significantly improve their efficiency and efficacy. Therefore, this paper reviews existing IoT healthcare architectures that utilise wearable devices and subsequently presents a scalable and modular system architecture to leverage emerging technologies to solve identified shortcomings. The defined architecture includes ultrathin, skin-compatible, flexible, high precision piezoelectric sensors, low-cost communication technologies, on-device intelligence, Edge Intelligence, and Edge Computing technologies. To provide development guidelines and define a consistent reference architecture for improved scalable wearable IoT-based critical healthcare architectures, this manuscript outlines the essential functional and non-functional requirements based on deductions from existing architectures and emerging technology trends. The presented system architecture can be applied to many scenarios, including ambient assisted living, where continuous surveillance and issuance of timely warnings can afford independence to the elderly and chronically ill. We conclude that the distribution and modularity of architecture layers, local AI-based elaboration, and data packaging consistency are the more essential functional requirements for critical healthcare application use cases. We also identify fast response time, utility, comfort, and low cost as the essential non-functional requirements for the defined system architecture.

Human eyes are masterpiece of nature, which can realize powerful image sensing with a very concise structure. Biomimetic eyes with characters comparable to human eyes are highly desirable in many technological applications, particularly in the fields of visual prosthesis and machine vision. The World Health Organization reported that globally there are over 252 million people suffering from visual impairment in the year of 2020. This number is exploding due to the prevalence of various mobile devices with small displays. Bionic eyes implantation is one the most effective strategy for vison restoration. However, today, even the most mature bionic eyes have only 300 clinical trials, which is merely 1 ppm of all the visual impaired patients, mainly due to their poor performance and high cost. In addition, industrial applications such as autonomous driving and humanoids also desire cameras with high performance. To achieve biomimetic eyes with imaging performance on a par with human eyes, innovative device structure design and material selection have to be carried out simultaneously. Among all the photosensing material candidates, the ordered one-dimensional (1D) semiconductor nanowire (NW) arrays exhibit unique advantages such as fast carrier transportation and strong light-material interaction due to their anisotropic structure in axial and radial direction, thereby leading to fast response and high responsivity. This presentation focuses on our work on the NW arrays image sensing and can be highlighted as: 1) Controlled growth of well aligned, high-density NW arrays Despite the advantages abovementioned, the integration of NWs has always been a bottleneck challenge hurdling their practical applications. Direct growth of NW arrays can be an effective way to tackle this challenge. We reported for the first time a unique fabrication process to form large-scale, 3D, high-density arrays of lead halide perovskite NWs with well-engineered geometry through a template-assisted growth approach. The array demonstrated amazingly geometry dependent optoelectronic properties and thereby can be used to improve performance of various devices. Particularly, its high regularity leads to the possibility to electrically addressable individual NWs which makes it an ideal candidate for very-large-scale integrated (VLSI) electronics and optoelectronics. The interaction between nanotemplate and sensing materials can introduce unique device performance such as tunable photoresponse and improved stability of perovskites. 2) Assembly of integrated, NW arrays based planar image sensors To demonstrate the technological potency of the NW arrays, we have developed new process to fabricate them into proof-of-concept image sensors. Each image sensor consists of 1,024 photodiode pixels made of vertical perovskite NWs, and the imaging functionality has been verified by recognizing various optical patterns projected onto it. The high density of this NW array and the addressability of individual NW enable this unique image sensor design a potential, extremely high resolution approaching optical diffraction limit. To realize the device assembly, we have developed a PDMS-assisted dry transfer process which can transfer the thin (µm scale) and large-area (cm scale) film onto any substrate without any bubbles and wrinkles. This unique NW manipulation strategy, together with NW geometrical and compositional tunability, may lead to new functionality and inspire novel device design in the future. 3) Invention of a 3D, biomimetic eye with a hemispherical NW array retina The high performance of human eyes originates from the dome shape of retina and the high-density photoreceptors in it. However, the commercial image sensors are dominantly using planar device structures shaped by the mainstream planar microfabrication processes, making it hardly possible for hemispherical device fabrication. In our work, we have developed a novel artificial visual system using a spherical biomimetic electrochemical eye with hemispherical retina made of a high-density perovskite NW array. The device has high similarity to human eyes with part of its photodetection performance superior to human eyes. The hemispherical artificial retina has NW density much higher than that of photoreceptors in a human retina thus can potentially achieve a higher image resolution which is bolstered by implementation of a single-NW ultra-small photodetector. The work may lead to a new generation of photosensing devices based on a bioinspired design that can benefit a wide spectrum of technological applications. In all, with the unique structural properties of NW arrays as the starting point, we realized their controlled growth, developed strategies to manipulate them and designed proper device structures to fully fulfill their advantages. In the future, we will combine them with brains, either biological or digital brains, to explore their applications in fields such as visual prothesis and artificial intelligence. Figure 1

Ocean observation becomes increasingly important as the ocean climate changes diversely and the marine disasters (such as tsunamis, typhoon, and earthquakes) occur frequently, which typically requires widespread and reliable monitoring techniques. In such a scenario, this paper presents a submarine optical fiber sensing system to realize real-time monitoring of the environmental parameters. The system consists of an undersea optical interrogation module together with multiple fiber Bragg grating (FBG)-based sensors, particularly for the measurement of depth, vibration, and temperature. The experimentally demonstrated sensitivities of the pressure, temperature, and vibration sensors are -1.993 nm/MPa, 0.08 nm/°C, and 0.139 nm/g (g = 9.8 m/s2), corresponding to the resolutions of 0.25 kPa, 0.006°C, and 0.004 g, respectively, based on the interrogation resolution of ~0.5 pm. To verify the feasibility and reliability of the proposed submarine sensing system, a prototype was developed and a proof test under the sea was conducted in an area close to Pearl River Estuary in China. The achieved results from the sea test show promising accuracy that is comparable to the commercially available electric-based sensors. Good characteristics of the surface water wave were observed by conducting the fast Fourier transform of the measured depth change, which shows a dominant frequency of ~0.25 Hz. The system provides the flexibility of replacing various optical fiber sensors easily and the capability of real-time monitoring in a remote way. The demonstrated submarine sensing system could find potential applications in real-time monitoring of the undersea ecosystem and the environmental evolution where multiparameter sensing is in demand.

The increasing number, size, and complexity of nuclear facilities deployed worldwide are increasing the need to maintain readiness and develop innovative sensing materials to monitor important to safety structures (ITS). Assessing and supporting next generation nuclear materials management and safeguards for future U.S. fuel cycles with minimum human intervention is of paramount importance. Technologies for the diagnosis and prognosis of a nuclear system, such as dry cast storage system (DCSS), can improve verification of the health of the structure that can eventually reduce the likelihood of inadvertently failure of a component. In the past decades, an extensive sensor technology development has been used for structural health monitoring (SHM). Fiber optical sensors have emerged as one of the major SHM technologies developed particularly for temperature and strain measurements. However, the fiber optical sensors and sensing system has not been developed with adequate solutions and guideline for DCSS applications. This paper presents an experimental study of temperature effect on fiber Bragg grating (FBG) sensors. The reflective spectrum of FBG sensors on the structure was measured with a tunable laser source. The shift of FBG reflective spectrum reflected the thermal expansion on the structure. The shift of the spectrum due to the temperature effect was correlated to the temperature changes. In addition, the FBG sensing methodology including high frequency guided ultrasonic waves (GUW) under different temperatures were also performed to check the performance of high frequency, small strain sensing. The potential of FBG sensors for DCSS applications was explored. The paper ends with conclusions and suggestions for further work.