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We present experimental results on the reconstruction of the 2D temperature field on the surface of a 250 × 250 mm sensor panel based on the distributed frequency shift measured by an optical backscatter reflectometer. A linear regression and a feed-forward neural network algorithm, trained by varying the temperature field and capturing thermal images of the panel, are used for the reconstruction. In this approach, we do not use any information about the exact trajectory of the fiber, material properties of the sensor panel, and a temperature sensitivity coefficient of the fiber. Mean absolute errors of 0.118 °C and 0.086 °C are achieved in the case of linear regression and feed-forward neural network, respectively. [ABSTRACT FROM AUTHOR]

A high-efficiency dual-purpose plasmonic perfect absorber sensor based on LiNbO3 and graphene layers was investigated in this paper for the refractive index and thermal sensing. The sensor design was kept simple for easy fabrication, comprising a LiNbO3 substrate with a quartz layer, thin layer of graphene, four gold nanorods, and a nanocavity in each unit cell. The nanocavity is located in the middle of the cell to facilitate the penetration of EM energy to the subsurface layers. The proposed sensor design achieved an output response of 99.9% reflection, which was easy to detect without having any specialized conditions for operability. The performance of the device was numerically investigated for the biomedical refractive index range of 1.33 to 1.40, yielding a sensitivity value of 981 nm/RIU with a figure-of-merit of 61.31 RIU−1. By including an additional polydimethylsiloxane polymer functional layer on the top, the device was also tested as a thermal sensor, which yielded a sensitivity level of −0.23 nm/°C. [ABSTRACT FROM AUTHOR]

Safety is the first priority in production. The situation is complex in the deep underground of coal mines, and safety accidents often occur. Wire rope is a kind of safety device. With the help of wire rope, the safety of miners can be guaranteed to a certain extent. It is a very important tool for mining production. However, the current detection of coal mine wire rope still relies on the data from the factory, and it is impossible to achieve nondestructive testing in use. This article aims to study the degree of wear of mining wire ropes to ensure the safety of miners as much as possible. According to the characteristics of the wire rope, any defect (rust, broken wire, broken wire, etc.) changes in the cross-sectional area of the wire rope will change the magnetic permeability of the wire rope. With the help of equipment, we can collect data on changes in the magnetic field (MF). Based on this experimental design, the steel wire rope is given an MF, and the magnetic sensor is used to monitor the MF signal and convert it into an electrical signal. According to the collected electrical signal analysis and judgment, the sensor model is constructed, the size and position of the wire rope cross-sectional change are deduced, and the defect of the wire rope is judged. The experimental results in this study show that the magnetic sensor is an effective measure to monitor the nondestructive degree of the wire rope, with a sensitivity of more than 80%. [ABSTRACT FROM AUTHOR]

Hydrogen gas (H 2) detection plays an important role in many fields. With the continuous demand and development of clean energy, it is urgent to study new hydrogen gas sensors for stable and accurate H 2 detection. The purpose of this research is to develop a new H 2 sensor based on the resonant photoacoustic (PA) cell as the sensing element. The sensitivity of the resonant PA cell to the resonant frequency is sufficiently utilized. The optimization of its resonance frequency was investigated minutely for the H 2 sensor. Detection utilizes resonance frequency differences between H 2 and air as a sensing mechanism. The resonance frequency tracking is adopted and implemented by the field-programmable gate array (FPGA) device. The minimum detection limit of about 74 ppm for H 2 has been demonstrated by preliminary experiments. The response time of the sensor is about 5 s. This sensor detects concentrations ranging from 74 ppm to 100% in 1 atm. The preliminary test result shows that the H 2 sensor based on this structure has a larger application perspective. [Display omitted] • Hydrogen gas detection by a resonant photoacoustic cell. • The resonant photoacoustic cell is sensitive to the resonance frequency. • A resonance frequency tracking method is used to detect hydrogen gas. • Tracking resonance frequency by the field-programmable gate array device. [ABSTRACT FROM AUTHOR]

Polymer optical fibre Bragg grating (POFBG) sensors are of high interest due to their enhanced fracture toughness, flexibility in bending, and sensitivity in stress and pressure monitoring applications compared to silica-based sensors. The POFBG sensors can also detect humidity due to the hydrophilic nature of some polymers. However, multi-parameter sensing can cause cross-sensitivity issues in certain applications if the temperature and humidity measurements are not adequately compensated. In this work, we demonstrate the possibility of selectively tuning sensors' temperature and humidity sensitivities to the desired level by applying a certain amount of fibre pre-strain. The temperature sensitivity of POFBG sensors fabricated in perfluoropolymers (CYTOP) can be selectively tuned from positive to negative values, having the option for insensitivity in specific temperature ranges depending on the amount of the applied pre-strain. The humidity sensitivity of sensors can also be changed from positive values to insensitivity. The importance of thermal annealing treatment of POFBG sensors for improved repeatability in temperature measurements is also reported. An array of 4 multiplexed POFBGs was fabricated, and each sensor was pre-strained accordingly to demonstrate the possibility of having targeted temperature and humidity sensitivities along the same fibre. [ABSTRACT FROM AUTHOR]

This paper presents a study of the influence of bimetallic layer covers of a tapered optical fiber surrounded by a low refractive index liquid crystal on the properties of light propagation in the taper structure. This research follows previous works on the effect of monometallic thin films (Au and Ag). In this case, the total thicknesses of the bimetallic layers were h = 10 nm, and the participation of gold and silver was equal. The films were deposited on one side of the tapered waist area. The liquid crystal cells were controlled with a voltage U from 0 to 200 V, with and without amplitude modulation at a frequency of fmod = 5 Hz. For the purposes of this research, spectral characteristics were obtained for a wavelength λ ranging from 550 to 1200 nm. Measurements were carried out at room temperature for three types of rubbed layers orientation—orthogonal, parallel, and twist in relation to the fiber axis. Obtained resonant peaks were compared with the previous results regarding the resonant wavelength, peak width, SNR, and maximum absorption. In the presented paper, the novelty is mainly focused on the materials used and their time stability, as well as corresponding changes in the technological parameters used. [ABSTRACT FROM AUTHOR]

In this paper, we investigated the evolution of the dispersion curves of long-period fiber gratings (LPFGs) from room temperature down to 0 K. We considered gratings arc-induced in the SMF28 fiber and in two B/Ge co-doped fibers. Computer simulations were performed based on previously published experimental data. We found that the dispersion curves belonging to the lowest-order cladding modes are the most affected by the temperature changes, but those changes are minute when considering cladding modes with dispersion turning points (DTP) in the telecommunication windows. The temperature sensitivity is higher for gratings inscribed in the B/Ge co-doped fibers near DTP and the optimum grating period can be chosen at room temperature. A temperature sensitivity as high as −850 pm/K can be obtained in the 100–200 K temperature range, while a value of −170 pm/K is reachable at 20 K. [ABSTRACT FROM AUTHOR]

This work presents a novel approach for imaging the visible emissions from plasmas in pulsed power experiments using high-resolution plastic optical fibers. The diagnostic consists of a 2 mm diameter core commercial cable constructed of 13 000 individual acrylic fibers. The fibers are fused together to create a single high-resolution bundle. Different designs were investigated to cover a wide range of resolutions and fields of view (3–700 µm and 0.05–45 mm, respectively). The system was tested on the 1-MA Mykonos accelerator at Sandia National Laboratories and successfully imaged visible emission from a hybrid x-pinch target. Diagnostic development and preliminary results are presented. [ABSTRACT FROM AUTHOR]

The accumulation of tangential small slips at contact interfaces may occur in mechanical assemblies when subjected to cyclic loadings, and cause failure of parts. However, the slip is difficult to measure directly. In this paper, a self-powered displacement sensor based on triboelectric nanogenerator (TENG) is fabricated, which is used to measure the microslip of the specimen in the designed test bench. When the specimen slips under the cyclic tangential load with a frequency of 10 Hz, the resulted average slip displacement of the specimen under a single load cycle is 9.01 μm, which is measured by the Keithley DAQ 6510 multimeter (Tektronix, Shanghai, China). This value is close to that measured by the Keithley 6514 electrometer. In addition, adding a BaTiO 3 thin film with a thickness of 100 nm between the Kapton triboelectric layer and the Cu electrode, the output voltage of the sensor is increased by 51.5%. Thus, the sensitivity of the self-powered sensor is improved effectively. [ABSTRACT FROM AUTHOR]

Optimization of light source wavelength for ammonia detection in surface water is presented in this work. For the ammonia detection, the surface water sample is mixed with sodium chloride and nessler reagent, whereas the sensor head consists of unclad plastic optical fiber. The unclad region has a length of 1 cm and the cladding is removed by immersing it in acetone solution. Experimental results indicate that the output light intensity of the sensor has linear relationship with the ammonia concentration. At the wavelength of 510 nm, the output light increases linearly as the ammonia concentration varies from 0.07 mg/L to 8.97 mg/L. At the same wavelength, the proposed sensor achieves the sensitivity of 0.0139 (mg/L)-1, accuracy of 99.59% and resolution of 0.72 µg/L. The analysis of light source wavelength reveals that a wavelength range from 450 nm to 580 nm produces the optimized performances. Within this wavelength range, the proposed sensor achieves sensitivity of higher than 0.01 (mg/L)-1, accuracy of higher than 99% and resolution of less than 1 µg/L. [ABSTRACT FROM AUTHOR]

In this investigation, we introduce a surface plasmon resonance temperature sensor photonic crystal fiber based (SPR-PCFs). The switching coupling phenomena between single modes within the PCF core that are penetrated with a nematic liquid crystal (NLC) and surface plasmon mode (SPs mode) surrounding nanowires of metals are studied. The metals silver (Ag), gold (Au), and titanium nitride (TiN) are added to the PCF structure separately to generate SPs mode. When the phase matching between the core-guided and SPs modes is fulfilled, they are coupled at a certain resonance wavelength. Based on the simulation, TiN with a PCF structure has a high wavelength sensitivity of 13 nm/°C in the temperature range of 35 to 45 °C with an amplitude sensitivity of 21.90 °C−1, whereas Au has a low value of 2 nm/°C in the temperature range of 25 to 35 °C with an amplitude sensitivity of 32.715 °C−1. [ABSTRACT FROM AUTHOR]

In this study, a tungstenâ€"rhenium thin-film thermocouples (TFTCs) is fabricated via magnetron sputtering on silicon carbide ceramics. Cuboid TFTCs probe is sealed with stainless steel shell to make the TFTCs probe sensor. This sensor has an average Seebeck coefficient of 27.2 µV °Câˆ'1 at 1167 °C (temperature difference). The thermal volatilization characteristics, electromotive force behavior, and response time of this tungstenâ€"rhenium TFTC sensor are investigated. The real engine experimental results show that the TFTCs probe sensor can work normally under the high temperature and high-speed air flow environment of 4 Mach and 900 °C. In addition, the correlation between the response speed, substrate thickness, and film thickness is discussed based on simulations of the response to carbon dioxide laser pulses. As indicated by the dynamic experiment results, the laser response time is from 0.49 to 1.51 ms, which is much shorter than that of traditional armored C-type thermocouples (for tungstenâ€"rhenium thermocouples, the response time is around 1 s). Tungstenâ€"rhenium TFTCs probe sensor is a suitable alternative to conventional thermocouples to meet the requirements of measuring high temperatures with a quick response. [ABSTRACT FROM AUTHOR]

Hydrogen peroxide is a useful molecule in biological and chemical reactions, but in excess harmful. Developing simple, low cost, and quick analytical method capable of detecting H2O2 is still critical. In this proposed work, our main objective was to synthesize nanocomposite of Musa paradisiaca L. peels (MPLP) by fine tuning its structure and properties with magnetite (Fe3O4). The characterization study, such as UV–Vis, FT-IR, SEM, EDX, XRD, VSM, Zeta potential, and BET were carried out effectively. The change in color from the initial grey to blue could be observed with naked eye (approximately 30 s) and the sensor established a colorimetric response in a relatively wide range of 0.01 μM to 0.9 mM with a lower detection limit (LOD) of 0.008 μM and limit of quantitation (LOQ) of 0.02 μM. Interference tests (using cations and organic chemicals) and real samples application (Tap water and milk) were used to evaluate the sensor's selectivity with recovery values ranging from 96 to 99% close to the H2O2 detection endpoint. The MPLP nanocomposite reflected a strong peroxidase-like activity for 3, 3, 5, 5, tetramethylbenzidine (TMB) oxidation in the presence of H2O2, having enzyme mimicking properties. Our study established a sensitive and selective optical sensing platform based on the green plant material for H2O2 detection. [ABSTRACT FROM AUTHOR]

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The piezoelectric ceramic sensor was fixed on Glass Fiber Reinforced Plastic (GFRP) composite civil materials, using the external paste method for damage detection test. The effect of the depth and number of cracks on the surface of the GFRP specimen on the signal received by the piezoelectric ceramic sensor was studied. The time-domain signal graph and energy graph based on wavelet packet were drawn, combining the active induction method and the energy method based on wavelet packet. It is found that the greater the damage degree of GFRP specimens, the smaller the voltage value of the signal, the smaller the energy of the signal, and the greater the damage index based on wavelet packet. The results showed that the active induction method can be used to collect the data of GFRP specimens by piezoelectric ceramic sensor. The collected data are processed by using the damage index principle based on wavelet packet. The maximum voltage value of the specimen, the energy of wavelet packet, and the damage index based on wavelet packet can all accurately judge the damage change of GFRP specimens. The active induction method based on piezoelectric ceramic sensor can detect the damage change of GFRP specimens in real time. It provides an effective method for damage analysis of GFRP composite civil materials. [ABSTRACT FROM AUTHOR]

This paper presents a novel in‐home communication system employing plastic optical fibers (POFs) acting both as transmission medium and access point for wireless links to user devices, hence no separate luminaires or optical–electrical–optical conversions is required. All active devices, such as lasers/detectors, can be remotely placed from the room ceilings, resulting in fully passive optical front‐ends, which is beneficial for maintenance and upgrading. We approach two concepts, the first aims to realize small but high‐capacity hotspots in a room, the second creates larger coverage areas to increase the number of users and allow user's mobility. The wavelength division multiplexing concept is used to maximize the wireless throughput and to serve different wireless access points on the ceilings from a single POF feeder. A transmission link comprising eye‐safe transceivers, 1‐mm core diameter step‐index POF, and free space link, achieving multi‐gigabit throughputs using spectral efficient modulation formats, is demonstrated. [ABSTRACT FROM AUTHOR]

To address the problems of poor measurement accuracy and long service life of SO2 electrochemical gas sensors when used in thermal power plant areas, fly ash emitted from a thermal power plant in China was used as the research object. Based on the analysis of the morphological characteristics of fly ash particles, theoretical calculations were used to obtain the settling speed of fly ash particles and the amount of fly ash deposited at different times, and then the impact of fly ash on the measurement error of a SO2 electrochemical gas sensor was investigated by experimental tests. The research results show that the particle size distribution of fly ash is 2–11 μm, the average settling speed of fly ash particles is 1.34 × 10−3 m/s, and the deposition amount of fly ash on the surface of the sensor inlet film is 0.95 mg per day. The deposition time of fly ash affects the sensor measurement error, and the longer the deposition time, the larger the sensor measurement error, which is due to the reduction of gas diffusion area S and diffusion coefficient K in the sensor caused by fly ash deposition. Fly ash deposition has a greater impact on the sensor when measuring low concentration gases. The higher the gas concentration, the lower the measurement error, because the higher the gas concentration, the faster the gas reaches the working electrode area and the higher the effective SO2 concentration detected in the limited response time. When using SO2 electrochemical sensors in environments with high concentrations of fly ash or dust, it is recommended to install dust-proof devices (such as air-permeable filter membranes with a pore size of less than 4 μm) and regularly clean the deposited fly ash, which can improve the accuracy of the sensor measurement and extend the service life. [ABSTRACT FROM AUTHOR]

A high-sensitivity relative humidity optical fiber sensor based on an intermodal interference structure is proposed. In order to enhance the sensors' sensitivity a tapered no-core fiber is coated with an RH-sensitive material. The material and geometrical parameters of the interferometric structure, as well as the refractive index of the coating material, have a strong influence on sensors' response. Various coating materials for the pure silica and d-PMMA fibers are investigated, including agarose, porous silica, and SiO 2 nanoparticles. When the tapered section has no extension, the d-PMMA fiber with agarose coating presents the highest average sensitivity of 533.46 pm/%RH in the 0% to 60% RH range. Furthermore, variations in the structure's dimensions are investigated, demonstrating that we can tune the sensitivity based on the taper extension length and radius. An extension of the tapered section up to 4000 μ m gives an improvement in the average sensitivity to 1,214.9 pm/%RH. Moreover, a reduction of the tapered radius from 15 to 1.5 μ m gives a rise in the sensitivity to 1,575.7 pm/%RH. [ABSTRACT FROM AUTHOR]

A novel fiber-optic vector magnetic field sensor and its sensing quality dependent of fabrication method has been proposed and investigated. The proposed sensor has two surfaces on the tip of a multimode fiber, which is used as the sensing probe. By plating different thickness of gold film on the surfaces, surface plasmon resonance (SPR) can be generated and the signal can be reflected by the surfaces as well. Meanwhile, magnetic fluid (MF) as the magnetic field sensitive material is packed around the sensing probe. The experimental results prove that the response of MF to external magnetic field can be used to sense magnetic field intensity and direction via monitoring the dip wavelength of SPR. The obtained refractive index (RI) sensitivities are 2105 nm/RIU (RI range: 1.332–1.365) and 6692 nm/RIU (RI range: 1.372–1.411), magnetic field intensity sensitivities are 11.67 nm/mT (0°), and −0.47 nm/mT (90°). Besides, the proposed sensing probe is ultracompact and the footprint is extremely small (the length of sensing part is only 615 μm), which is very helpful for magnetic field detection in narrow space and gradient field. [ABSTRACT FROM AUTHOR]

Humidity measurement is required in various fields. We previously developed a sensor that leverages the sudden change in the transmitted light intensity when switching from leakage mode to waveguide mode. By adjusting the low-refractive-index polymer of the cladding, we achieved measurements at 60% RH. However, for practical use, measurements at low humidity are essential. Therefore, in this study, we developed a sensor using a leakage mode that enables measurements at low humidity. To measure the leakage mode, it is necessary to increase the absorbance of the cladding and the incident angle at the core–cladding interface. Therefore, we developed a sensor in which the core was stretched, and the cladding was doped with a high concentration of dye. The experimental results confirmed that a sensor with a polymer concentration of 4% and a dye concentration of 3% could measure from 0% RH to 95% RH. The sensitivity was 0.1 dB/% RH from 0% RH to 70% RH and 0.32 dB/% RH from 70% RH to 95% RH. The estimated response time for a change from 10% to 90% light transmission for a sensor with 4% polymer concentration and 0.5% dye concentration was 22 s from 45% RH to 0% RH and 50 s from 0% RH to 45% RH. [ABSTRACT FROM AUTHOR]

This work demonstrated a ZnO-coated optical fiber sensor for the detection of a volatile organic compound (VOC) biomarker for diabetes for detecting isopropanol (IPA) markers. A coreless silica fiber (CSF) was connected to a single-mode fiber (SMF) at both ends to achieve a SMF–CSF–SMF structure. CSF is the sensing region where multimode interference (MMI) generates higher light interaction at the interface between the fiber and sensing medium, leading to enhanced sensitivity. Optimization of the CSF length was conducted numerically to attain the highest possible coupling efficiency at the output. Surface functionalization was achieved via hydrothermal growth of ZnO nanorods directly onto the CSF at low temperatures. The optical fiber-based sensor was successfully fabricated and tested with 20%, 40%, 60%, 80%, and 100% of IPA. The sensor response was recorded using an optical spectrometer and analyzed for sensor sensitivity. The fabricated sensor shows the potential to detect isopropanol with the sensitivity of 0.053 nm/%IPA vapor. Further improvement of the sensor sensitivity and selectivity is also proposed for future work. [ABSTRACT FROM AUTHOR]

In this work, a simple side-polish plastic optical fiber (POF)-based surface plasmon resonance (SPR) sensor is proposed and demonstrated for simultaneous measurement of refractive index (RI) and liquid level. The effects of side-polish depths on the sensing performance were studied. The experimental results show that the SPR peak wavelength will be changed as the RI changes, and the SPR peak intensity will be changed with the liquid level variation. By monitoring the changes in peak wavelength and intensity, the RI and liquid level can be detected simultaneously. Experimental results show that an RI sensitivity of 2008.58 nm/RIU can be reached at an RI of 1.39. This sensor has the advantages of simple structure and low cost, which has a good prospect in the field of biochemical sensing. [ABSTRACT FROM AUTHOR]

Bicomponent photoluminescent polymer optical fibers (PL-POFs) have been melt-spun and in-situ drawn to different extents. The results suggest that scattering in the sheath can effectively increase the photoluminescent dye excitation probability in the fiber core. The core/sheath PL-POFs are made of a semi-crystalline fluoropolymer sheath of low refractive index (RI) and an amorphous cycloolefin polymeric core of high RI, which is doped with a luminescent dye. The axial light emission, as well as the guiding attenuation coefficients of the core/sheath PL-POFs, have been measured using a side-illumination set-up. The incident blue laser is down-converted to red light, which is re-emitted and partially guided by the core. The axial light emission is measured at the fiber tip as a function of the distance from the illumination position to the integrating sphere. It is demonstrated that the presence of a semi-crystalline sheath significantly enhances the axial light emission and that it also lowers the attenuation coefficient, compared to the emission and guiding properties of PL core-only fibers. Additionally, the attenuation coefficient has been found to be lower in more strongly drawn PL-POFs. Wide-angle X-ray diffraction and small-angle X-ray scattering experiments reveal structural differences in differently drawn PL-POFs that can be linked to the observed differences in the optical properties. [ABSTRACT FROM AUTHOR]

The formation quality of a frozen wall is one of the prerequisites for tunnel excavation using artificial ground freezing techniques. However, the non-uniformity of temperature distribution along the length direction of the freezing pipe is often ignored in the actual freezing engineering, which leads to a thin frozen wall at a local position that does not meet the design requirements. Therefore, exploring the evolution law of three-dimensional non-uniform freezing temperature fields is necessary. In this paper, a tunnel horizontal freezing model test system was established based on the similarity criterion of hydro–heat coupling, and the temperatures at three sections were tested using thermocouple temperature sensors. The results show that the temperature drop curves of measurement points suffer from three periods: steep drop, slow drop and tending to be stable. The temperature curves on the main and vice planes of the frozen wall all present a "V" type; specifically, the temperature on the axis plane is the lowest, while the temperature away from the axis plane is higher, and the temperature gradient outside the axis plane is greater than that inside. The frozen wall develops from frozen soil columns to a sector ring, and the average thickness of the frozen wall at three sections is 50.6, 40.7 and 75.1 mm after freezing for 60 min, respectively, which shows an obvious non-uniformity. The temperature distribution along the length of the freezing pipe is T = −0.000045z2 + 0.0205z − 13.5125. The freezing temperature contours calculated by ABAQUS are basically consistent with those calculated by the model test after calling the temperature function of the freezing pipe wall. [ABSTRACT FROM AUTHOR]

[Display omitted] • Dual-spectroscopy to classify plastics based on elemental and molecular properties. • LIBS-Raman techniques in single platform for reliable and cost-effective sorting. • Classification of real-world plastics in industry-like environment. • Classification capability evaluated using multivariate analysis. Ever-accumulating amounts of plastic waste raises alarming concern over environmental and public health. A practical solution for addressing this threat is recycling, and the success of an industry-oriented plastic recycling system relies greatly on the accuracy of the waste sorting technique adapted. We propose a multi-modal spectroscopic sensor which combines laser-induced breakdown spectroscopy (LIBS) and Raman spectroscopy in a single optical platform for characterizing plastics based on elemental and molecular information to assist the plastic identification-sorting process in recycling industries. The unique geometry of the system makes it compact and cost-effective for dual spectroscopy. The performance of the system in classifying industrially important plastic classes counting PP, PC, PLA, Nylon-1 1, and PMMA is evaluated, followed by the application of the same in real-world plastics comprising PET, HDPE, and PP in different chemical-physical conditions where the system consumes less than 30 ms for acquiring LIBS-Raman signals. The evaluation of the system in characterizing commuting samples shows promising results to be applied in industrial conditions in future. The study on effect of physical–chemical conditions of plastic wastes in characterizing them using the system shows the necessity for combining multiple techniques together. The proposal is not to determine the paramount methodology to characterize and sort plastics, but to demonstrate the advantages of dual-spectroscopy sensors in such applications. The outcomes of the study suggest that the system developed herein has the potential of emerging as an industrial-level plastic waste sorting sensor. [ABSTRACT FROM AUTHOR]

In this paper, a high sensitivity fiber temperature sensor based on surface plasmon resonance is designed and studied. In the simulation, the single mode fiber is polished to remove most of the cladding, and then gold and silver films are added. Finally, it is embedded in the heat shrinkable tube filled with a thermo-optic coefficient liquid for curing. The numerical simulation results show that the sensing characteristics are sensitive to the remaining cladding thickness of the fiber, the thickness of the gold film and the thickness of the silver film. When the thermo-optic coefficient of the filling liquid is −2.8 × 10−4/°C, the thickness of the gold film, the thickness of the silver film and the thickness of the remaining cladding of the fiber are 30 nm, 20 nm and 1 μm, respectively. The sensitivity of the sensor designed in this paper can reach −6 nm/°C; this result is slightly higher than that of similar research in recent years. It will have a promising application prospect in flexible wearable temperature sensors, smart cities and other fields. [ABSTRACT FROM AUTHOR]

Bending sensing was realized by constructing a tapered four-core optical fiber (TFCF) sensor. The four-core fiber (FCF) between the fan-in and fan-out couplers was tapered and the diameter became smaller, so that the distance between the four cores arranged in a square became gradually smaller to produce supermodes. The two ends of the TFCF were respectively connected to the fan-in and fan-out couplers so that the individual cores in the FCF could link to the separate single-mode fibers. A broadband light source (superluminescent diodes (SLD)) spanning 1250–1650 nm was injected into any one of the four cores, and the orientation was thus determined. In the tapering process, the remaining three cores gradually approached the excitation core in space to excite several supermodes based on the tri-core structure first, and then transited to the quadruple-core structure. The field distributions of the excited supermodes were asymmetric due to the corner-core excitation scheme, and the interference thus resulted in a higher measurement sensitivity. When the diameter of the TFCF was 7.5 μm and the tapered length was 2.21 mm, the sensitivity of the bending sensor could reach 16.12 nm/m−1. [ABSTRACT FROM AUTHOR]

This paper proposes a simple, high-efficiency refractive index (RI) sensor, with a structure based on the planar lightwave circuit (PLC) probe type. The optical sensor has a 1 × 2 splitter structure with reference and sensing channels, each consisting of a U-shaped waveguide structure that is configured by connecting C bends. This design allows for the sensor device to have a probe structure wherein the surface interconnected with activity devices (i.e., an optical source and optical detector) is placed on one side. The reference channel is bent with a minimum optical loss, and the sensing channel has a bent structure, involving a C-bend waveguide with a maximum loss. The C-bend waveguide with a maximum loss is conformally aligned to have a trench structure with the same bending radius, designed to selectively expose the sidewall of the core layer. The local index contrast varies depending on the material in contact with the trench, resulting in a change in the optical output power of the waveguide. The sensitivity of the proposed sensor was 0 and 2070 μW/refractive index unit (RIU) for the reference and sensing channels, respectively, as the RI changed from 1.385 to 1.445 at a 1550 nm wavelength. These results suggest that the proposed structure enables efficient RI measurement through the use of a simple dip-type method. [ABSTRACT FROM AUTHOR]

The traditional optical fiber-based twist sensing has the disadvantage of low sensitivity and difficulty of distinguishing the twist direction. Moreover, chiral isomerism may lead to sensing errors. In this paper, a six-hole helical microstructured optical fiber (HMSF) with a thin-gold-film-coat based on the surface plasmon resonance (SPR) effect was designed. The twist sensing characteristics of this fiber were further analyzed. Numerical calculation and analysis show that the combination of helical effect and SPR effect can design an HMSF-based sensor that is very sensitive to distortion. In the torsion range of ±300°, the distortion sensitivity can reach 2470.7 pm/(rad/m), and the linear correlation coefficient is 0.99996. Based on the special sensing mechanism, it has a good linear coefficient over a large range. Additionally, the direction of the twist can be easily discerned. The HMSF in this work not only has high sensitivity, high linearity, high fault tolerance rate, and a wide range of measurement, but is also easy to manufacture. Therefore, it is promising in the field of twist sensing and has a good application prospect. [ABSTRACT FROM AUTHOR]

To realize continuous real-time monitoring of the large-scale internal strain field of coal and rock mass, a bidirectional strain sensor based on FBGs encapsulated using a hollow cylindrical steel tube was designed. The sensor's structural parameters were optimized through unidirectional loading, and the strain change laws of the sensor were analyzed under unidirectional and bidirectional loading conditions, in which the stress-strain fitting curves of the sensor and the relationships of the strain in the vertical and horizontal directions were obtained under different lateral pressure loading conditions. A similar theoretical model was established to verify the accuracy of the linear relationship between the surrounding rock stress and the strain measured by the sensor system. [ABSTRACT FROM AUTHOR]

A micro-groove photonic crystal fiber sensor based on surface plasmon resonance (SPR) is proposed to simultaneously detect the refractive index and temperature of liquid. The sensor structure has three air holes and a micro-groove. The gold film was deposited on the micro-groove for refractive index measurement. The gold film was deposited in the air hole on the right side and filled with polydimethylsiloxane (PDMS) for temperature measurement. The finite element method is used to analyze the sensor characteristics. The numerical results show that the two channels of measuring refractive index and temperature do not interfere, reducing the complexity of two-parameter sensor measurement. When the refractive index of the liquid is in the range of 1.34–1.42 and the temperature is in the range of 0–100 ℃, the maximum spectral sensitivity of the sensor is 14300 nm/RIU and 6.4 nm/℃, respectively. The results also show that the sensor's performance is not sensitive to the change of structural parameters. Therefore, the sensor is easy to manufacture. This high-sensitivity sensor based on micro-groove photonic crystal fiber and surface plasmon resonance has excellent potential in biochemical detection, environmental monitoring, and medical sensing. [ABSTRACT FROM AUTHOR]

An optical sensor for uranyl has been prepared based on a gold-plated D-shaped plastic optical fiber (POF) combined with a receptor consisting of a bifunctional synthetic molecule, 11-mercaptoundecylphosphonic acid (MUPA), with a phosphonic group for complexing the considered ion, and a sulfide moiety through which the molecule is fixed at the gold resonant surface as a molecular layer in an easy and reproducible way. The sensor is characterized by evaluating the response in function of the uranyl concentration in aqueous solutions of different compositions and real-life samples, such as tap water and seawater. The mechanism of the uranyl/MUPA interaction was investigated. Two different kinds of interactions of uranyl with the MUPA layer on gold from water are observed: a strong one and a weak one. In the presence of competing metal ions as Ca2+ and Mg2+, only the strong interaction takes place, with a high affinity constant (around 107 M−1), while a somewhat lower constant (i.e., around 106 M−1) is obtained in the presence of Mg2+ which forms stronger complexes with MUPA than Ca2+. Due to the high affinity and the good selectivity of the recognition element MUPA, a detection limit of a few μg L−1 is reached directly in natural water samples without any time-consuming sample pretreatment, making it possible for rapid, in situ controls of uranyl by the proposed sensor. [ABSTRACT FROM AUTHOR]

Considering the poor response performance of fiber bragg grating (FBG) sensor based on WO 3 , in this paper, a polymer intercalated method is proposed to accomplish high-performance optical fiber hydrogen sensor. Tetrabutylammonium hydroxide (TBAOH) molecule intercalated WO 3 are synthesized successfully and the effect of the intercalation amount to sensing performance has been investigated. The experiment results show that, at the concentration of 10,000 ppm, the t 90 response time of the sensor based on TBAOH-Pt/WO 3 is improved by 308% compared with that of WO 3 FBG sensor. In addition, the FBG hydrogen sensor based on the novel materials can detect hydrogen concentration ranging from 300 ppm to 12,000 ppm in air, demonstrating excellent stability and repeatability, which show wide application prospect in the future. • A polymer intercalated method can expand the layer spacing of WO 3 effectively. • Larger layer spacing means more exposed active sites. • Larger layer spacing means lower diffusion activation energy for H atom. • The novel sensor shows the fastest response of 34 s to 1% H 2 concentration. [ABSTRACT FROM AUTHOR]

The major motivation behind transistor scaling is the requirement for high-speed transistors with lower fabrication costs. When the fin thickness or breadth is smaller than 10 nm in a trigate FET, charges travel in a nonconfined fashion, resulting in the creation of energy subbands and causing volume inversion. In comparison to the carrier near a surface inversion layer, volume inversion experiences less interface scattering. In large-scale integrations, we have focused on developing a 3D model for surface potential by establishing the three-dimensional Poison's equation and building a unique fin field-effect transistor (FinFET) structure. In this context, there is a growing interest in developing a low-cost, simple solution that combines plastic (polymer) as a substrate and organic materials to create electronics such as monitors and sensors. The research examines characteristics such as silicon width, oxide thickness, doping concentration, metal work-function about gate, and various surface potentials. For different circuit configurations, it also examines the DC and AC characteristics of the FinFET structure. A differential amplifier is built for RF application based on the device specifications. This work is aimed at improving the semiconductor design structure by adjusting device parameters, analyzing the results, establishing the best FinFET device preferences, and selecting an application for the optimized device. The 3D Poisson's equation may be used to create an analytical model of a trigate nanosize FinFET, which can then be tested using a TCAD simulator. By constructing such a FinFET, we can structure and analyze various electrostatic parameters. To facilitate the creation of FinFET-based circuits, including product development, a novel transistor needs a creative device basis. The infrastructure's support denotes a computationally advantageous numerical model that accurately depicts a FinFET. The work presents a compact model for semiconductor manufacturing that permits separate IC productions while achieving higher levels of excellence and using less power. The design outperforms the CMOS by 22.7% in gain, 31.48% in power consumption, and 12.72% in CMRR, while operating at a 5 GHz unity gain frequency. [ABSTRACT FROM AUTHOR]

Temperature measurement and control has an extremely important role in both scientific research and manufacturing. Capacitive liquid crystal (LC) temperature sensors can monitor the temperature using the linear variation of the capacitance of LC cell with temperature, but the sensitivity and other properties need to be improved. In order to improve the performance of capacitive LC temperature sensor, we propose to mix twisted nematic LC (1M10600-100) with ferromagnetic nanoparticles γ-Fe2O3 to prepare LC temperature sensor in this paper. The relationship between the capacitance change rate of different concentrations of nano-doped LC materials at 0.1–20 V and different temperatures was tested, the sensitivity of the sensor was calculated, and the mechanism of the effect of doped nanoparticles on the performance of the device was analyzed. The experimental results show that the sensitivity of the capacitive temperature sensor made of nano-doped LC with the concentration of 0.03 wt% is as high as 9.5 pF/°C at 12 V, which is about 14.87% higher than the undoped device, and its recovery and stability remain almost unchanged. The Pearson correlation coefficient only changes by 0.02%. The results of this paper provide some guidance for the improvement of the performance of capacitive LC temperature sensors, and the development of high-sensitivity temperature sensors based on LC materials. [ABSTRACT FROM AUTHOR]

In this study, an ultra-high-sensitivity fiber humidity sensor with a chitosan film cascaded Fabry–Perot interferometer (FPI) based on the harmonic Vernier effect (HVE) is proposed and demonstrated. The proposed sensor can break the limitation of the strict optical path length matching condition in a traditional Vernier effect (TVE) FPI to achieve ultra-high sensitivity through the adjustment of the harmonic order of the HVE FPI. The intersection of the internal envelope tracking method allows spectra demodulation to no longer be limited by the size of the FSR of the FPI. The sensitivity of the proposed sensor is −83.77 nm/%RH, with a magnification of −53.98 times. This work acts as an excellent guide in the fiber sensing field for the further achievement of ultra-high sensitivity. [ABSTRACT FROM AUTHOR]

In this study, a ratiometric optical fiber dissolved oxygen sensor based on dynamic quenching of fluorescence from a ruthenium complex is reported. Tris(4,7-diphenyl-1,10-phenanthrolin) ruthenium(II) dichloride complex (Ru(dpp)32+) is used as an oxygen-sensitive dye, and semiconductor nanomaterial CdSe/ZnS quantum dots (QDs) are used as a reference dye by mixing the two substances and coating it on the plastic optical fiber end to form a composite sensitive film. The linear relationship between the relative fluorescence intensity of the ruthenium complex and the oxygen concentration is described using the Stern–Volmer equation, and the ruthenium complex doping concentration in the sol-gel film is tuned. The sensor is tested in gaseous oxygen and aqueous solution. The experimental results indicate that the measurement of dissolved oxygen has a lower sensitivity in an aqueous environment than in a gaseous environment. This is due to the uneven distribution of oxygen in aqueous solution and the low solubility of oxygen in water, which results in a small contact area between the ruthenium complex and oxygen in solution, leading to a less-severe fluorescence quenching effect than that in gaseous oxygen. In detecting dissolved oxygen, the sensor has a good linear Stern–Volmer calibration plot from 0 to 18.25 mg/L, the linearity can reach 99.62%, and the sensitivity can reach 0.0310/[O2] unit. The salinity stability, repeatability, and temperature characteristics of the sensor are characterized. The dissolved oxygen sensor investigated in this research could be used in various marine monitoring and environmental protection applications. [ABSTRACT FROM AUTHOR]

A Fabry-Perot air chamber was prepared at the splicing point of two single-mode fibers by the heating-expansion of liquid glycerin. The morphology of the Fabry-Perot air chamber was optimized by the splicing parameters (drawing process, discharging location, time and intensity) and the fibers' end-face (plane or arc). The in-line Fabry-Perot interferometer was employed to determine the tensile strain from 0 to 1.2 N. A sensitivity of 3.628 nm/N and the resolution of ∼0.005 N were experimentally demonstrated. The reported Fabry-Perot strain sensor is easy to fabricate, low cost, and flexible to connect with other fibers. [ABSTRACT FROM AUTHOR]

When the coolant level and refractive index change simultaneously, the variation of coolant level ( I C i ) and refractive index ( I R i ) can be described as [[22]] HT ht Graph (7)where I i SB 1 sb and I i SB 2 sb represent the wavelength shift of trough 1 (1568 nm) and trough 2 (1550 nm) respectively. Keywords: liquid-level and refractive-index detection; Michelson interference; multi-mode fiber; optic-fiber sensing; thin-core fiber EN liquid-level and refractive-index detection Michelson interference multi-mode fiber optic-fiber sensing thin-core fiber 621 627 7 07/05/22 20220701 NES 220701 1 Introduction The engine is the heart of the car and the source of its power. [Extracted from the article]

Optical fibre sensors have attracted a lot of interest in the field of sensors. However, the limitation of conventional optical fibre sensors such as high fragility and low sensitivity need to be considered. This work demonstrated a simulation of a new optical sensor design, a C–shaped optical fibre sensor to overcome these limitations. The design optimization of the sensor was conducted by changing the remaining cladding thickness ranging from 5 to 0 µm and opening angle ranging from 70 to 110°. The change in refractive index ranging from 1.30 to 1.40 has been performed to evaluate the simulated sensing performance. The simulation results showed that reducing the cladding thickness and wider opening angle can improve the sensor's sensitivity. In cladding thickness optimization, the sensor showed the highest sensitivity with no remaining cladding thickness. In the opening angle optimization, the highest sensitivity can be achieved at the maximum opening angle of 110°, but the sensitivity changes due to the the opening angle range were minimal compared to cladding thickness optimization. The best C–shaped sensing performance with 0 µm remaining cladding thickness and 110° opening angle was selected to be compared to the closest in term of design which is the D—shaped optical fibre sensor. Overall, the C–shaped design has more cladding sector region left providing better physical robustness and has high potential to act as a new refractive index sensor with an estimated sensitivity of up to 2.77893, higher than the simulated D–shaped optical fibre sensor with an estimated sensitivity of 2.77468. [ABSTRACT FROM AUTHOR]