Performance Of Optical Sensor Research Articles

Prediction of Absorption Spectrum Shifts in Dyes Adsorbed on Titania

Dye adsorption on metal-oxide films often results in small to substantial absorption shifts relative to the solution phase, with undesirable consequences for the performance of dye-sensitized solar cells and optical sensors. While density functional theory is frequently used to model such behaviour, it is too time-consuming for rapid assessment. In this paper, we explore the use of supervised machine learning to predict whether dye adsorption on titania is likely to induce a change in its absorption characteristics. The physicochemical features of each dye were encoded as a numeric vector whose elements are the counts of molecular fragments and topological indices. Various classification models were subsequently trained to predict the type of absorption shift i.e. blue, red or unchanged (|Δλ| ≤ 10 nm). The models were able to predict the nature of the shift with a good likelihood (~80%) of success when applied to unseen data.

Effect of PMMA and PVA coating on the performance of optical microbottle resonator humidity sensors

AbstractThis article compares the performances of uncoated and coated optical microbottle resonators (MBR) for humidity sensing. A technique called “soften‐and‐compress” was used to form the MBR with midriff diameter of D b = 190 μm, stem diameter of D s = 125 μm and bottle length of L b = 182 μm. The MBRs were prepared in three different conditions, which are noncoated MBR, PMMA (poly methyl meth acrylate) coated MBR, and PVA (polyvinyl‐alcohol) coated MBR. The MBRs characteristic was investigated by employing a 2 μm tapered microfiber and tested for humidity sensing within a humidity range of 40% to 95%. The Q‐factor obtained were >104 for all MBRs. The performance as humidity sensor was defined by the sensitivity and linearity of MBRs, which were investigated based on wavelength shift and also the transmitted power. The MBRs are undergoing a 180‐seconds stability test at 65% RH humidity level. It is found that the PVA coated MBR performed better than other MBRs as a humidity sensor based on sensitivity, linearity, and stability measurements.

Experimental study of the influence of FBG length on optical shape sensor performance

This paper compares the performance of optical Multicore Fibres (MCFs) with inscribed Fibre Bragg Gratings (FBGs) used as curvature and shape sensors in relation to strain sensor length. Two fibre optic shape sensors, consisting of FBGs written in standard optical multicore fibre (diameter 124.5 μm), were assembled in the Institute for Telecommunications and Multimedia Applications (iTEAM) of the Universitat Politècnica de València. The optical sensors were then positioned on an aluminium mould and quasi-distributed curvature and shape sensing were performed to compare the accuracy of the arrays. It was found that the MCF shape sensor performance strongly depended on FBG length and that sensors based on long FBGs were significantly more accurate, showing that long FBGs can considerably improve shape sensor accuracy at equal grating densities and achieve substantially better performance. This is a great advantage when wavelength division multiplexing is used, when only a limited number of usable FBGs can be applied. These new results, applicable to both multiple single-core optical fibres and multicore optical fibres with embedded quasi-distributed strain sensors, show the connection between strain sensor length and accuracy, hardly taken into account in previous studies, and lay the foundation for the design of new long-FBG-based shape sensors.

Simulation of Moon-based Earth observation optical image processing methods for global change study

Global change affected by multiple factors, the consequences of which continue to be far-reaching, has the characteristics of large spatial scale and long-time scale. The demand for Earth observation technology has been increasing for large-scale simultaneous observations and stable global observation over the long-term. A Moon-based observation platform, which uses sensors on the nearside lunar surface, is considered a reasonable solution. However, owing to a lack of appropriate processing methods for optical sensor data, global change study using this platform is not sufficient. This paper proposes two optical sensor imaging processing methods for the Moon-based platform: area imaging processing method (AIPM) and global imaging processing method (GIPM), primarily considering global change characteristics, optical sensor performance, and motion law of the Moon-based platform. First, the study proposes a simulation theory which includes the construction of a Moon-Sun elevation angle model and a global image mosaicking method. Then, coverage images of both image processing methods are simulated, and their features are quantitatively analyzed. Finally, potential applications are discussed. Results show that AIPM, whose coverage is mainly affected by lunar revolution, is approximately between 0% and 50% with a period of 29.5 days, which can help the study of large-scale instant change phenomena. GIPM, whose coverage is affected by Earth revolution, is conducive to the study of long term global-scale phenomena because of its sustained stable observation from 67°N-67°S on the Earth. AIPM and GIPM have great advantages in Earth observation of tripolar regions. The existence of top of the atmosphere (TOA) albedo balance line is verified from the GIPM perspective. These two imaging methods play a significant role in linking observations acquired from the Moon-based platform to Earth large-scale geoscience phenomena, and thus lay a foundation for using this platform to capture global environmental changes and new discoveries.

An evaluation of the performance of a lens-based plastic optical fiber strain sensor

One of the key parameters monitored in structural health monitoring applications is strain. In this work an extrinsic plastic optical fiber (POF) sensor developed previously has been optimised to increase its strain sensitivity. The extrinsic POF sensor basic design used here and previously comprises of two fiber units. As the distance of separation between the cleaved surfaces of the two fibers increases, the intensity of light detected by the receiving end of the fiber changes due to the loss of light associated with the increased separation. The two factors affecting the sensitivity of the POF sensor are the diameter of the fiber and the angle at which the light exits the emitting fiber. Here, in the new sensing scheme a ball lens is introduced at the emitting end of the optical fiber. This lens converges the light from the fiber into a spot. The cone of light emitted from this source depends on the numerical aperture and the size of the spot. For this sensor design, approximately six fold increase in strain sensitivity is achieved compared to the previous strain sensor design without the ball lens. Experiments were carried out to test the new sensor design for repeatability and cyclic response. The free vibration response was also evaluated. Based on the results of the experiments it is concluded that the sensor is able to detect strains as small as 30 με for a 15 mm gauge length.

CMOS-compatible plasmonic hydrogen sensors with a detection limit of 40 ppm

Sensing of leakage at an early stage is crucial for the safe utilization of hydrogen. Optical hydrogen sensors eliminate the potential hazard of ignition caused by electrical sparks but achieve a detection limit far higher than their electrical counterparts so far. To essentially improve the performance of optical hydrogen sensors in terms of detection limit, we demonstrate in this work a plasmonic hydrogen sensor based on aluminum-palladium (Al-Pd) hybrid nanorods. Arranged into high-density regular arrays, the hybrid nanorods are capable of sensing hydrogen at a concentration down to 40 ppm, i.e., one thousandth of the lower flammability limit of hydrogen in air. Different sensing behaviors are found for two sensor configurations, where Pd-Al nanorods provide larger spectral shift and Al-Pd ones exhibit shorter response time. In addition, the plasmonic hydrogen sensors here utilize exclusively CMOS-compatible materials, holding the potential for real-world, large-scale applications.

Development of an optical tyrosinase biosensor (TCA) for detection of “Parathion-Methyl”

PurposeThis paper aims to present a novel and cost-effective optical biosensor design by simple preparation method for detection of “parathion-methyl,” which is a model pesticide pose to public health and the environment.Design/methodology/approachThe optical enzyme biosensor (TCA) for detection of pesticide “parathion-methyl” was developed on the basis of immobilization of tyrosinase enzyme on chitosan film by adsorption technique. The analytic performance of TCA was investigated by measuring its activity with Ultraviolet (UV) visible spectrophotometer.FindingsUniform porous network structure and protonated groups of chitosan film provided a microenvironment for tyrosinase immobilization evident from Fourier transform infrared (FTIR) spectroscopy and Atomic Force Microscopy analysis. TCA has a wide linear detection range (0-1.03 µM) with high correlation coefficient and it can detect the parathion-methyl concentration as low as 159 nM by noncompetitive inhibition kinetics. Using the TCA sensor both for ten times and at least 45 days without a significant loss in its activity are the indicators of its good operational and storage stability. Moreover, TCA can be applicable to tap water, providing a promising tool for pesticides detection.Originality/valueThis is the first time to use the in situ analytical technique that can improve the performance of optical enzyme sensor provided to control the pesticide residue better with respect to traditional techniques. The effect of organic solvents on the performance of optical enzyme biosensor was investigated. Inhibition kinetic of the solvents rarely encountered in literature was also studied besides the pH and temperature tolerance of the optical biosensor.

Sensitivity enhanced D-type large-core fiber SPR sensor based on Gold nanoparticle/Au film co-modification

A D-type large core optical fiber sensor with high sensitivity and good stability based on the coupling of gold nanoparticles and Au film was proposed and demonstrated by simulation and experiments. The proposed sensor is numerically simulated based on the finite element method. The simulation shows that the electric field intensity of the gap coupling between gold nanoparticles and Au film is 4–5 times higher than that of Au film, and the electric field intensity on the surface of gold nanoparticles is twice as strong as that on the surface of Au films. The electric field coupling effect between the Au film surface plasmon resonance (SPR) and the gold nanoparticle localized surface plasmon resonance (LSPR) can improve the refractive index sensitivity of the sensor. Experimental results show that the refractive index sensitivity of D-type optical fiber/Au film/gold nanoparticles sensor reaches 3074 nm/refraction index unit (RIU), which is 1.4 times that of D-type optical fiber/Au film sensor. SPR–LSPR coupling effect is a good method to improve the sensing performance of optical fiber sensors, especially for detecting the refractive index changes of surrounding media. Compared with existing similar biosensors, the designed biosensor has higher sensitivity and the sensor proposed in this paper has great application prospects in the field of biological detection.

Performance of Fiber Optical Sensors in the Structure of Concrete Dams to Deal with the Impact Actions (Case Study: Seimare Dam)

Abstract Due to the fact that dams are considered one of the strategic infrastructures of a country, it is very important to protect it against destructive acts. Accordingly, sensors were used at various points to record structural responses to the dam. Based on the questionnaires completed by experts, accuracy had the score of 3.8 so it was considered as the most important feature of the sensors and the optical fiber sensor with a mean score of 3.93 was selected as the best sensor type among the available ones. For this project, a questionnaire was prepared based on Likert scale and SPSS method was used in TOPSIS software. Then, Seimare concrete double curvature arch dam was simulated in ABAQUS 2017 software and the proper positioning of the sensors for optimum performance was determined based on Finite Element Method analysis and according to structural control criteria such as tension, displacement, strain, velocity and so one.

D-Shaped POF Sensors for Refractive Index Sensing-The Importance of Surface Roughness.

In this study the influence of the surface roughness on the transmission capacities of D-shaped plastic optical fibers (POFs) and sensors performance was investigated. Five D-shaped POF sensors were produced and characterized for refractive index sensing between 1.33 and 1.41. The sensors were characterized using a low-cost optical sensing system based on the variation of the transmitted light though the POF with refractive index changes (RI). Higher surface roughness increases the scattering losses through the POF and influences the sensors’ performance; therefore, a balance must be attained. Generally, the best performance was achieved when the sensing region was polished with P600 sandpaper as a final polishing step. Polishing with sandpapers of lower grit size resulted in lower scattering, higher linearity of the sensor response and generally lower performance for RI sensing. A sensor resolution of 10−3–10−4 RIU, dependent on the value of the external refractive index, was obtained through simple and low-cost manufacturing procedures. The obtained results show the importance of surface roughness in the development of POF sensors which can be used in several applications, such as for water quality assessment.

Dosimetric Characterization of an Inorganic Optical Fiber Sensor for External Beam Radiation Therapy

The aim of this study was to investigate the dosimetric performance of a novel optical fiber sensor for use in external beam radiation therapy. Repeatability and reproducibility of the output signal, linearity, dose rate, and dose per pulse dependence were evaluated. Angular dependence was investigated in the axial and azimuthal planes. The percentage depth dose and lateral dose profiles were measured using the optical fiber sensor system and compared to commercially available detectors such as Exradin W1 plastic scintillator and a PTW-microdiamond detector. The result of this study shows that the optical fiber sensor system has good repeatability and reproducibility of the output signal with a maximum deviation of 0.17% and 1.00%, respectively. The system also showed an excellent linearity with dose, and its signal was independent of dose rate. However, the system showed a strong dependence on dose per pulse with 27% deviation from the W1 result at the highest dose per pulse value, that was achieved at 75 cm source to surface distance. The system also showed an angular dependence when the incident beam was in the azimuthal plane due to the geometry of the scintillator at the tip of the fiber. The optical fiber sensor over-responded when measuring the percentage depth dose curves and lateral dose profiles due in part to the sensitivity of the scintillating material (Gd2O2S:Tb) to low energy scattered radiation. However, further investigation is needed to quantify the overall contribution of Cerenkov radiation to the over-response of the optical fiber sensor.

Optical Fiber Sensor Performance Evaluation in Soft Polyimide Film with Different Thickness Ratios.

To meet the application requirements of curvature measurement for soft biomedical robotics and flexible morphing wings of aircraft, the optical fiber Bragg grating (FBG) shape sensor for soft robots and flexible morphing wing was implemented. This optical FBG is embedded in polyimide film and then fixed in the body of a soft robot and morphing wing. However, a lack of analysis on the embedded depth of FBG sensors in polyimide film and its sensitivity greatly limits their application potential. Herein, the relationship between the embedded depth of the FBG sensor in polyimide film and its sensitivity and stability are investigated. The sensing principle and structural design of the FBG sensor embedded in polyimide film are introduced; the bending curvatures of the FBG sensor and its wavelength shift in polyimide film are studied; and the relationship between the sensitivity, stability, and embedded depth of these sensors are verified experimentally. The results showed that wavelength shift and curvature have a linear relationship. With the sensor’s curvature ranging from 0 m−1 to 30 m−1, their maximum sensitivity is 50.65 pm/m−1, and their minimum sensitivity is 1.96 pm/m−1. The designed FBG sensor embedded in polyimide films shows good consistency in repeated experiments for soft actuator and morphing wing measurement; the FBG sensing method therefore has potential for real applications in shape monitoring in the fields of soft robotics and the flexible morphing wings of aircraft.

Speech detection enhancement in optical fiber acoustic sensor via adaptive threshold function

Abstract In this paper, we demonstrate a novel speech enhancement method for improving detection performance of optical fiber acoustic sensor. The proposed method is based on a novel threshold function with adaptive threshold for wavelet analysis. For a certain speech signal, the adaptive threshold in the function is set lower in speech presence region and higher in speech absence region, which ensures more speech details preserved as well as noise reduced. At the same time, the new threshold function guarantees the continuity and no deviation of speech signal. Experimental results show that the proposed method is more suitable for optical fiber acoustic sensor to extract speech signal compared with universal wavelet packet method, and it improves speech quality significantly. The clear speech can be obtained via the optical fiber acoustic sensor even if work surroundings of sensing unit is noisy.

High-sensitivity fiber optic hydrogen sensor in air by optimizing a self-referenced demodulating method.

Self-referenced demodulating methods of fiber optic hydrogen sensors based on WO3-Pd2Pt-Pt composite film are studied in this paper. By employing the proper baseline intensity as sensing parameters, fluctuations of the sensing signal of the hydrogen sensor can be obviously depressed, and sensitivity can be greatly improved. Experimental results show that the resolution of the hydrogen sensor can reach 3 parts per million (ppm) when the hydrogen concentration is lower than 1000ppm. Additionally, the hydrogen sensor shows better sensitivity toward lower concentrations of hydrogen, enabling a hydrogen threshold down to 10ppm in air at room temperature. To the best of our knowledge, this is the lowest threshold reported for an optical hydrogen sensor operated at room temperature in air. Moreover, the sensor has good repeatability during hydrogen response. This work proposes a simple and novel method to improve the performance of fiber optic hydrogen sensors, which can greatly promote their potential application in various fields.

Double Clad Fiber Improves the Performance of a Single-Ended Optical Fiber Sensor

Single-ended, amplitude- or wavelength-modulated optical fiber sensors provide an attractive platform for minimally invasive chemical and biological sensing applications. However, in many cases, the sensor performance is limited by the collection efficiency of diffuse scattered and/or reflected light at the distal end of the waveguide, relative to background light generated within the waveguide. Using surface-enhanced Raman scattering (SERS) as an exemplary weak source of diffuse back-scattered light, we have evaluated the performance of single-ended sensing schemes based on hollow-core photonic crystal fiber (PCF) and double-clad fiber (DCF) compared with more conventional single-mode fibers (SMF-28 and S405). The SERS substrates were fabricated by oblique-angle deposition on the optical fiber end faces. In order to generate a comparable SERS substrate at the end face of the hollow-core PCF, a graded-index (GRIN) coupler was spliced onto the cleaved end face. Similar GRIN lens couplers were spliced onto the solid-core fibers for comparison with the PCF, as they are not expected to provide any advantage for coupling diffuse scattered light. The PCF offered no reduction in fiber background signal compared with either the single-mode fiber or the DCF with excitation through the inner core. In contrast, the DCF was found to provide up to 12-fold improvement in the signal-to-background ratio. These results indicate that DCF holds great promise as a single-ended optical fiber sensor platform.

Utilisation of Ground and Airborne Optical Sensors for Nitrogen Level Identification and Yield Prediction in Wheat

A healthy crop growth ensures a good biomass development for optimal yield amounts and qualities. This can only be achieved with sufficient knowledge about field conditions. In this study we investigated the performance of optical sensors in large field trails, to predict yield and biomass characteristics. This publication investigated how information fusion can support farming decisions. We present the results of four site-year studies with one fluorescence sensor and two spectrometers mounted on a ground sensor platform, and one spectrometer built into a fixed-wing unmanned aerial vehicle (UAV). The measurements have been carried out in three winter wheat fields (Triticum aestivum L.) with different Nitrogen (N) levels. The sensor raw data have been processed and converted to features (indices and ratios) that correlate with field information and biological parameters. The aerial spectrometer indices showed correlations with the ground truth data only for site-year 2. FERARI (Fluorescence Excitation Ratio Anthocyanin Relative Index) and SFR (Simple Fluorescence Ratio) from the Multiplex® Research fluorometer (MP) in 2012 showed significant correlations with yield (Adj. r 2 ≤ 0.63), and the NDVI (Normalised Difference Vegetation Index) and OSAVI (Optimized Soil-Adjusted Vegetation Index) of the FieldSpec HandHeld sensor (FS) even higher correlations with an Adj. r 2 ≤ 0.67. Concerning the available N (N avail ), the REIP (Red-Edge Inflection Point) and CropSpec indices from the FS sensor had a high correlation (Adj. r 2 ≤ 0.86), while the MP ratio SFR was slightly lower (Adj. r 2 ≤ 0.67). Concerning the biomass weight, the REIP and SAVI indices had an Adj. r 2 ≤ 0.78, and the FERARI and SFR ratios an Adj. r 2 ≤ 0.85. The indices of the HandySpec Field ® spectrometer gave a lower significance level than the FS sensor, and lower correlations (Adj. r 2 ≤ 0.64) over all field measurements. The features of MP and FS sensor have been used to create a feature fusion model. A developed linear model for site-year 4 has been used for evaluating the rest of the data sets. The used model did not correlate on a significant de novo level but by changing only one parameter, it resulted in a significant correlation. The data analysis reveals that by increasing mixed features from different sensors in a model, the higher and more robust the r 2 values became. New advanced algorithms, in combination with existent map overlay approaches, have the potential of complete and weighted decision fusion, to ensure the maximum yield for each specific field condition.

Ultrabright Polymer-Dot Transducer Enabled Wireless Glucose Monitoring via a Smartphone.

Optical methods such as absorptiometry, fluorescence, and surface plasmon resonance have long been explored for sensing glucose. However, these schemes have not had the clinical success of electrochemical methods for point-of-care testing because of the limited performance of optical sensors and the bulky instruments they require. Here, we show that an ultrasensitive optical transducer can be used for wireless glucose monitoring via a smartphone. The optical transducer combines oxygen-sensitive polymer dots (Pdots) with glucose oxidase that sensitively detect glucose when oxygen is consumed in the glucose oxidation reaction. By judicious design of the Pdots with ultralong phosphorescence lifetime, the transducer exhibited a significantly enhanced sensitivity by 1 order of magnitude as compared to the one in a previous study. As a result, the optical images of subcutaneous glucose level obtained with the smartphone camera could be utilized to clearly distinguish between euglycemia and hyperglycemia. We further developed an image processing algorithm and a software application that was installed on a smartphone. Real-time dynamic glucose monitoring in live mice was demonstrated with the smartphone and the implanted Pdot transducer.

LeTrungThanh Optical Biosensors Based on Multimode Interference and Microring Resonator Structures

LeTrungThanh Optical Biosensors Based on Multimode Interference and Microring Resonator Structures

Optical Sensor based Chemical Modification as a Porous Cellulose Acetate Film and Its Application for Ethanol Sensor

A new approach to design and construction of an optical ethanol sensor has been developed by immobilizing a direct dye at a porous cellulosic polymer fllm. This sensor was fabricated by binding Nile Red to a cellulose acetate membrane that had previously been subjected to an exhaustive base hydrolysis. The prepared optical ethanol sensor was enhanced by adding pluronic as a porogen in the membrane. The addition of pluronic surfactant into cellulose acetate membrane increased the hydrophilic and porous properties of membrane. Advantageous features of the design include simple and easy of fabrication. Variable affecting sensor performance of dye concentration have been fully evaluated and optimized. The rapid response results from the porous structure of the polymeric support, which minimizes barriers to mass transport. Signal of optical sensor based on reaction of dye nile red over the membrane with ethanol and will produce the purple colored product. Result was obtained that maximum intensity of dye nile red reacted with alcohol is at 630-640 nm. Linear regression equation (r2), limit of detection, and limit of quantitation of membrane with 2% dye was 0.9625, 0.29%, and 0.97%. Performance of optical sensor was also evaluated through methanol, ethanol and propanol. This study was purposed to measure the polarity and selectivity of optic sensor toward the alcohol derivatives. Fluorescence intensity of optic sensor membrane for methanol 5%, ethanol 5% and propanol 5% was 15113.56, 16573.75 and 18495.97 respectively.

Reduced graphene oxide (rGO) based wideband optical sensor and the role of Temperature, Defect States and Quantum Efficiency

We report a facile and cost-effective approach to develop self-standing reduced Graphene Oxide (rGO) film based optical sensor and its low-temperature performance analysis where midgap defect states play a key role in tuning the crucial sensor parameters. Graphite oxide (GO) is produced by modified Hummers’ method and reduced thermally at 250 °C for 1 h in Argon atmosphere to obtain rGO. Self-standing rGO film is prepared via vacuum filtration. The developed film is characterized by HRTEM, FESEM, Raman, and XRD techniques. The developed sensor exhibits highest sensitivity towards 635 nm illumination wavelength, irrespective of the operating temperature. For a given excitation wavelength, photoresponse study at low temperature (123K–303K) reveals inverse relationship between sensitivity and operating temperature. Highest sensitivity of 49.2% is obtained at 123 K for 635 nm laser at power density of 1.4 mW/mm2. Unlike sensitivity, response- and recovery-time demonstrate directly proportional dependence with operating temperature. Power dependent studies establish linear relation between power-density and sensitivity, and a safe limit beyond which sample heating prolongs the recovery time. Wavelength-dependent studies shows that proposed sensor can efficiently operate from visible to near NIR region. To the best of our knowledge such rGO based optical sensor performance at low temperature had not been reported earlier.