Performance Of Optical Sensor Research Articles

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.

Design of conception on lightning monitoring system for strikes to structures

The object of research is the monitoring system (MS) for lightning, which strikes specific objects or happening nearby. It is based on the use of regular (not high-speed) video cameras. Among drawbacks of some existing MS having video capturing of strike position, one can indicate that in automatic setting modes they are able to record comparatively reliably only discharges including continuous current component. Also, the triggering to start saving of video fragment with lightning into memory and transmission to server is provided usually by optical sensor only. Other sensors are used rarely or their characteristics are not well substantiated. High-speed cameras are also utilized sometime, but this is expensive and usually related to research projects. Two variants of MS conception were worked out during the study – complex and simplified. It is suggested to use additional sensors (electric and magnetic field, acoustic) for reliable triggering of MS and also several video cameras. In both variants of MS, for extraction of only frames containing captured lightning strikes from the whole recorded video row, it is suggested to use software based on computer vision library (Open CV). Characteristics of all sensors are substantiated and recommended, in particular: – video cameras – IP-type, 25…50 fps, 1080р or better; – optical sensor – sensitivity range 0.4…1 μm, time resolution – 1 μs, distance – up to 500 m; – «slow» electric field antenna – electronic type, 0.1…10 Hz; – «fast» electric field antenna – rode or plate type, 1 kHz…5(20) MHz; – magnetic field registration – compact ferrite antenna, 3…30(100) kHz; – thunder recording – capacitor microphones at 0 to 1…2 kHz. Experimental laboratory tests are carried out regarding designed optical sensor performance by using impulse current, which have parameters corresponding to actual lightning.

MEH-PPV film thickness influenced fluorescent quenching of tip-coated plastic optical fiber sensors

Abstract The performance of plastic optical fiber sensors in detecting nitro aromatic explosives 1,4-dinitrobenzene (DNB) have been investigated by fluorescence spectroscopy and analyzed by using fluorescence quenching technique. The plastic optical fiber utilized is 90 degrees cut tip and dip-coated with conjugated polymer MEH-PPV poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] thin films for detection conjugants. The thicknesses of the MEH-PPV coating were varied to improvise the sensitivity whilst slowly reducing the fluorescence intensity. It was shown that fluorescence intensity from thinner film decreased by (82% in 40 s) in the presence of DNB signifying an improvement of 28% reduction with time 13 s less than that of the thicker film.

Optimization of Detection Accuracy of Closed-Loop Optical Voltage Sensors Based on Pockels Effect.

The influence of optical parameters on the performance of closed-loop optical voltage sensors (OVSs) based on Pockels effect is analyzed and a control algorithm is proposed to suppress the nonlinearity caused by the unideal parameters of optical devices for optimizing the detection precision of OVSs. First, a quantified model of the feedback phase demonstrates how the optical parameters of optical devices (including light source, polarizer, 45° fusion point, Faraday rotator and half-wave plate) result in the nonlinearity of closed-loop OVSs. Then, the parameter indexes of different optical devices are put forward to instruct the manufacturing process of the optical system. Furthermore, a closed-loop control algorithm is investigated to improve the measurement accuracy of nonlinear OVSs considering the unideal parameters. The experiment results indicate that additional bias caused by undesirable optical parameters is obviously decreased so that the measurement accuracy of OVSs satisfies the demand of IEC60044-3 for 0.1 level measurement accuracy, which verifies the effectiveness and correctness of the methods for suppressing the impact of unideal optical parameters on OVSs.

The use of novel optode sensor technologies for monitoring dissolved carbon dioxide and ammonia concentrations under live haul conditions

Fish health under live haul transportation on wellboats and in other recirculating aquaculture systems depends on frequent and reliable measurements of water quality, that may change in response to changes in the environmental conditions and treatment processes. While reliable technologies exist for sensors measuring some water quality parameters such as Oxygen concentration and salinity, there is a lack of sensor technologies for the measurement of other critical water quality parameters such as water pCO2 and NH3 concentrations. Presented is the theory of operation and performance of prototype optical sensors for the measurement of pCO2 and NH3, as well as the methods used for their calibration and characterization. In order to evaluate the sensor’s suitability for aquaculture applications we temporarily installed the sensors on a wellboat and monitored the water quality during the transportation of live mature Atlantic salmon between fish farms and slaughter facilities on the Norwegian coast. Under transportation with different stocking weights and recirculation conditions, the CO2 optode prototypes recorded measurements that coincided with measurements from standard laboratory analysis of spot samples. The pCO2 concentration in the well throughout the testing was shown to vary between approximately 300μatm and 20 000μatm. Compared to the pH derived pCO2 estimation method widely applied in aquaculture, the CO2 optode was more sensitive to small fluctuations in CO2 concentration, and gave measurements closer to the CO2 values recorded by laboratory analysis of spot samples. The NH3 optode reported measurements that were consistent with spot samples analyzed using the salicylate–hypochlorite reaction. In contrast to pCO2, the concentration of NH3 during the observed wellboat missions was found to be very low and stable at 0.8±0.3μgL−1. Once fully developed, the CO2 and NH3 optodes could contribute to better water quality control and efficiency during well boat transportations and other recirculating aquaculture systems.

Towards enhanced optical sensor performance: SEIRA and SERS with plasmonic nanostars.

We report the preparation and characterization of plasmonic chip-based systems comprising self-assembled gold nanostars at silicon substrates that enable concomitantly enhanced Raman (surface enhanced Raman spectroscopy; SERS) and mid-infrared (surface enhanced infrared reflection or absorption spectroscopy; SEIRA) spectral signatures. The high-aspect-ratio structure of gold nanostars provides an increased number of hot spots at their surface, which results in an electric field enhancement around the nanomaterial. Gold nanostars were immobilized at a silicon substrate via a thin gold layer, and α-ω-dimercapto polyethylene glycol (SH-PEG-SH) linkers. The Raman and IR spectra of crystal violet (CV) revealed a noticeable enhancement of the analyte vibrational signal intensity in SERS and SEIRA studies resulting from the presence of the nanostars. Enhancement factors of 2.5 × 103 and 2.3 × 103 were calculated in SERS considering the CV bands at 1374.9 cm-1 and 1181 cm-1, respectively; for SEIRA, an enhancement factor of 5.36 was achieved considering the CV band at 1585 cm-1.

Effect of Surface Roughness on the Performance of Optical SPR Sensor for Sucrose Detection: Fabrication, Characterization, and Simulation Study

We propose a surface plasmon resonance (SPR) sensor that makes use of titanium/silver thin film on indium tin oxide (ITO) coated glass. The use of silver enhances the detection accuracy of the sensor, whereas ITO coated glass results in good sensitivity. Fabrication and characterization of the sensor chip, i.e., ITO/Ti/Ag have been carried out. The effect of surface roughness on the performance of the sensor has been systematically studied. This paper reveals that for rough surface, the sensor performance degrades significantly and there is a need for optimization of the thickness of the top layer for the best performance of the sensor. Both experimental and simulation study have been carried out to substantiate the results.

Performance and noise analysis of optical microresonator-based biochemical sensors using intensity detection.

Optical microcavity sensors using intensity detection open up the possibility to realize fully integrated high-performance sensing devices, which are significant for both fundamental study of molecular interaction and rapid disease diagnosis. Although the performance of microresonator-based sensors has been studied focusing on the resonance-tracking method, the situation can be much different for intensity-detection sensors. Here we conducted a systematically investigation on the noises sources in intensity detection scheme and their influences on key performance parameters, e.g., signal-to-noise ratio (SNR), limit-of-detection (LOD), and detection range, for various sensors configurations. Especially, the trade-off between SNR and LOD is identified and theoretically analyzed. With experiment noises taken into consideration, our work aims to provide design guidelines for integrated microresonator sensors with optimized performance.

Failure Mechanisms of Fiber Optic Temperature Sensors in High Temperature and Vibration Environments

ABSTRACTFiber optic temperature sensors are used in a variety of harsh environment applications. We have explored use of such temperature sensors in commercial gas turbines to measure the temperature at various regions of interest within the turbine system. More specifically, fiber optic temperature rakes were designed and installed on a commercial gas turbine under full load conditions. This work will focus on failure mechanisms observed at multiple length scales that impact the performance of high temperature optical fiber sensors. It was found that Au-coated silica fibers, which are a standard in the industry, undergo various failure modes when subjected to combinations of high temperature and high vibration. More specifically, the Au coating became soft/ductile as the temperature is increased. We also observed that the Au coating was not well bonded to the silica fiber, as expected since there were no adhesion layers present. These effects led to significant damage of the fiber optic under high vibrations. We also found that vibrations from the gas turbine coupled into fundamental modes of the fiber optic probe assembly, which were analyzed by detailed dynamic mechanical analysis. This led to the fiber impacting the internal wall of the probe assembly, which caused further damage and failure of the fiber and the Au coating. The silica fibers returned from the field also exhibited significant twisting throughout most of their length. This suggests the fibers reached temperatures above their strain point (about 1000 C for pure silica glass), which is explained by either a) the strain point had been significantly reduced by the presence of the Ge dopant, or b) the temperature was higher than expected in the gas turbine exhaust region. It was also hypothesized that complex anelastic effects may play a role under the high temperature, high vibration environment experienced by the probes. Detailed structural analysis of the fiber optic temperature sensors by scanning electron microscopy, ToF-SIMS, and X-ray microscopy will be presented to corroborate the above simulations and proposed damage mechanisms. Finally, we note that the fiber Bragg gratings (FBG) present within the temperature probes provided promising temperature data, and were in fact not damaged/erased by the high temperature environment.

Methodology for the design, production, and test of plastic optical displacement sensors

Abstract Optical displacement sensors made entirely from plastic materials offer various advantages such as biocompatibility and high flexibility compared to their commonly used electrical and glass-based counterparts. In addition, various low-cost and large-scale fabrication techniques can potentially be utilized for their fabrication. In this work we present a toolkit for the design, production, and test of such sensors. Using the introduced methods, we demonstrate the development of a simple all-optical displacement sensor based on multimode plastic waveguides. The system consists of polymethylmethacrylate and cyclic olefin polymer which serve as cladding and core materials, respectively. We discuss several numerical models which are useful for the design and simulation of the displacement sensors as well as two manufacturing methods capable of mass-producing such devices. Prior to fabrication, the sensor layout and performance are evaluated by means of a self-implemented ray-optical simulation which can be extended to various other types of sensor concepts. Furthermore, we discuss optical and mechanical test procedures as well as a high-precision tensile testing machine especially suited for the characterization of the opto-mechanical performance of such plastic optical displacement sensors.

Effect of heat treatments on the performance of polymer optical fiber sensor.

Although the numerous advantages of polymer optical fiber (POF) sensors have been applied in different fields, the measurement consistency and sensitivity of POF evanescent wave (EW) sensors are still affected by its thermal stability and water absorption. Therefore, we perform a study to demonstrate the mechanism of the effect of heat treatments on physical and optical properties of POF EW sensors. We investigate the surface morphology, composition, refractive index, geometry, and weight of the fiber-sensing region subjected to water and vacuum heat treatments. We examine the spectral transmission and transmitted light intensity of POF sensors. We present a theoretical investigation of the effect of heat treatments on the sensitivity of POF EW sensors. The performance of the prepared sensor is evaluated using glucose and Chlorella pyrenoidosa analytes. We discovered that the spectral transmission and transmitted light intensity of the fibers shows little effect of vacuum heat treatments. In particular, the sensors, which subject to vacuum heat treatment at 110 °C for 3 h, exhibit temperature-independent measuring consistency and high sensitivity in glucose solutions in the temperature range 15-60 °C and also show high sensitivity in Chlorella pyrenoidosa solutions.

Noise induced in optical fibers by double Rayleigh scattering of a laser with a 1/f^ν frequency noise

We study, theoretically and experimentally, intensity noise induced by double Rayleigh scattering in long optical fibers. The results of the theoretical model are compared to experimental results performed with a high-coherence-length laser with a frequency noise spectrum that is dominated by 1/fν noise. Excellent quantitative agreement between theoretical and experimental RF spectra were obtained for frequencies as low as 10 Hz and for fiber lengths between 4 and 45 km. Strong low-frequency intensity noise that is induced by 1/fν frequency noise of the laser may limit the performance of interferometric fiber optic sensors that require high-coherence-length lasers. The intensity noise due to double Rayleigh backscattering can be suppressed by reducing the coherence length of the laser. Therefore, the intensity noise has a complex and non-monotonic dependence on the 1/fν frequency noise amplitude of the laser. Stimulated Brillouin scattering will add a significant noise for input powers greater than about 7 mW for a 30 km length fiber.

On-farm evaluation of an active optical sensor performance for variable nitrogen application in winter wheat

Abstract Winter wheat (Triticum aestivum L.) represents almost 50% of total cereal production in the European Union, accounting for approximately 25% of total mineral nitrogen (N) fertilizer applied to all crops. Currently, several active optical sensor (AOS) based systems for optimizing variable N fertilization are commercially available for a variety of crops, including wheat. To ensure successful adoption of these systems, definitive measurable benefits must be demonstrated. Nitrogen management strategies developed based on small-scale plot research are not always meaningful for large-scale farm conditions. In 2010–2012 (5 site-years) on-farm study was implemented in northern Poland utilizing a strip-trial design. The objective was to evaluate the performance of AOS in combination with a built-in algorithm for variable N rate fertilization. In this study, the reference uniform N rates (farmer’s practice) were comparable to optimum variable N rate recommendations. Side-by-side comparisons of uniform and variable N application revealed inconsistent benefits in terms of grain yield, grain protein content (GPC), N use and N use efficiency (NUE). Anticipated yield increases and/or reduced N rates are typical drivers for AOS adoption. Significant yield increases are not easily attained on farms with winter wheat yields already close to maximum yield potential. Thus, sensor-based variable N rate recommendations for fields previously fertilized with relatively low uniform N rates would often entail more appropriate allocation (redistribution) of the same amount of total N. This would minimize N surplus in areas of lower productivity and to improve the sustainability of N management overall.

Modal reduction in single crystal sapphire optical fiber

A new type of single crystal sapphire optical fiber (SCSF) design is proposed to reduce the number of guided modes via a highly dispersive cladding with a periodic array of high and low index regions in the azimuthal direction. The structure retains a “core” region of pure single crystal (SC) sapphire in the center of the fiber and a “cladding” region of alternating layers of air and SC sapphire in the azimuthal direction that is uniform in the radial direction. The modal characteristics and confinement losses of the fundamental mode were analyzed via the finite element method by varying the effective core diameter and the dimensions of the “windmill” shaped cladding. The simulation results showed that the number of guided modes were significantly reduced in the “windmill” fiber design, as the radial dimension of the air and SC sapphire cladding regions increase with corresponding decrease in the azimuthal dimension. It is anticipated that the “windmill” SCSF will readily improve the performance of current fiber optic sensors in the harsh environment and potentially enable those that were limited by the extremely large modal volume of unclad SCSF.

Comprehensive model for studying noise induced by self-homodyne detection of backward Rayleigh scattering in optical fibers.

Backward Rayleigh scattering in optical fibers due to the fluctuations that are "frozen-in" to the fiber during the manufacturing process may limit the performance of optical sensors and bidirectional coherent optical communication systems. In this manuscript we describe a comprehensive model for studying intensity noise induced by spontaneous Rayleigh backscattering in optical systems that are based on self-homodyne detection. Our model includes amplitude and frequency noise of the laser source, random distribution of the scatterers along the fiber, and phase noise induced in fibers due to thermal and mechanical fluctuations. The model shows that at frequencies above about 10 kHz the noise spectrum is determined by the laser white frequency noise. The laser flicker frequency noise becomes the dominant effect at lower frequencies. The noise amplitude depends on the laser polarization. A very good agreement between theory and experiment is obtained for fibers with a length between 500 m to 100 km and for a laser with a linewidth below 5 kHz.

Image Quality Assessment of a CMOS/Gd2O2S:Pr,Ce,F X-ray Sensor

The aim of the present study was to examine the image quality performance of a CMOS digital imaging optical sensor coupled to custom made gadolinium oxysulfide powder scintillators, doped with praseodymium, cerium and fluorine (Gd2O2S:Pr,Ce,F) screens. The screens, with coating thicknesses 35.7 and 71.2 mg/cm2, were prepared in our laboratory from Gd2O2S:Pr,Ce,F powder (Phosphor Technology, Ltd) by sedimentation on silica substrates and were placed in direct contact with the optical sensor. Image quality was determined through a single index image quality parameter (information capacity). The CMOS sensor/Gd2O2S:Pr,Ce,F screens combinations were irradiated under the RQA-5 (IEC 62220-1) beam quality. The detector response function was linear for the exposure range under investigation. Under the general radiography conditions, both Gd2O2S:Pr,Ce,F screen/CMOS combinations exhibited comparable overall imaging properties, in terms of the information capacity, to previously published scintillators, such as Gd2O2S:Eu.

Analysis and Design of Loop Gains to Optimize the Dynamic Performance of Optical Voltage Sensor Based on Pockels Effect

A design method of loop gains is proposed for improving the fast dynamic tracking performance of optical voltage sensor (OVS) based on Pockels effect. The distribution principle of loop gains is investigated in theory according to the characteristics of closed-loop error of OVS. Based on the obtained distribution principle of loop gains, the hardware circuit and the control parameters of the controller are designed to improve the signal to noise ratio (SNR) of closed-loop error and the dynamic performance of OVS, respectively. The experimental results demonstrate that the system can achieve the high dynamic performance under the high detection precision: OVS can accurately track 13th harmonic with 1.57% measurement error and 4.24° phase error, and the long term steady accuracy of power frequency voltage is within ±0.1%. The experimental results validate the effectiveness of our new design method of loop gains.

Tuning of ZnO 1D nanostructures by atomic layer deposition and electrospinning for optical gas sensor applications

We explored for the first time the ability of a three-dimensional polyacrylonitrile/ZnO material—prepared by a combination of electrospinning and atomic layer deposition (ALD) as a new material with a large surface area—to enhance the performance of optical sensors for volatile organic compound (VOC) detection. The photoluminescence (PL) peak intensity of these one-dimensional nanostructures has been enhanced by a factor of 2000 compared to a flat Si substrate. In addition, a phase transition of the ZnO ALD coating from amorphous to crystalline has been observed due to the properties of a polyacrylonitrile nanofiber template: surface strain, roughness, and an increased number of nucleation sites in comparison with a flat Si substrate. The greatly improved PL performance of these nanostructured surfaces could produce exciting materials for implantation in VOC optical sensor applications.

Determination of the sample number for optical reflectance measurement of vegetable leaf

Visible and near-infrared spectroscopy provides a variety of information regarding leafy vegetables. However, various factors including optical propagation, environmental issues, and experimental issues affect the quality of spectral measurements. Therefore, stability and performance of optical reflectance sensors are affected significantly by sampling scheme. This study investigated the effects of the number of sampling on optical reflectance measurement of Chinese cabbage and kale plant leaves. For that purpose, variability and similarity of multiple measurements for different number of sampling of the leaves were evaluated. A combination of a median filter and the 2nd Savitzky-Golay (S. Golay) method was used to reduce the noise on the reflectance spectra introduced by background effects and other uncertainties. Reflectance difference and cross correlation were used as criteria to evaluate stability (or similarity) of the measurements. Results indicated that the standard deviation of reflectance difference was not considerably different for cabbage and kale leaves with 12 and 9 sampling points, respectively. For similarity of multiple measurements, results of cross correlation showed that the standard deviation of cross correlation was not greater than 5% with 12 and 9 sampling points for cabbage and kale leaves, respectively. Thus, this study concluded that 12 sampling points (cabbage) and 9 sampling points (kale) on a single leaf were the optimal number for spectral reflectance measurement. This study may provide guidelines on the number of sampling for optimum reflectance measurement of leafy vegetables.