Fiber Optic Method Research Articles

Study on calibration model of soil water content based on actively heated fiber-optic FBG method in the in-situ test

• The calibration model for water content measurement is studied by AHFO-FBG method. • Two semi-empirical calibration models for calculating water content are deduced. • The modified calibration model considering dry density is proposed. • The feasibility of the modified calibration model is verified and analyzed. • AHFO-FBG method has unique advantages for laboratory tests accurately. In the water content measurement technology based on actively heated fiber-optic (AHFO) method, how to establish the calibration model between the temperature characteristic value and the water content is very important. Given shortcomings of the existing calibration models, the optimal calibration model was established. On this basis, a modified calibration model considering the change of dry density was proposed by using the actively heated fiber-optic fiber Bragg grating (AHFO-FBG) method, and the feasibility of the model was verified and analyzed. The results show that the Côté and Konrad model is the best model for water content calculation; in the in-situ water content measurement, if the dry density of the soil is small (≤1.5 g/cm 3 ), the modified Côté and Konrad calibration model should be used. The research results are of great significance to guide the application of the AHFO-FBG method in the in-situ soil water content monitoring.

Feasibility study of using integrated fiber optical sensors to monitor laser-assisted metal\u2013polymer joining

The possibilities and challenges of using fiber optical sensors to monitor the laser-assisted joining of metal–polymer joints have been described in this article. Fundamental investigation proves the basic suitability of the measuring method for this application and studies the effect of essential influencing variables of the joining process—e.g., the clamping force—on the resulting sensor signals. In addition, the strain state (because of the process temperature and shrinkage of the polymer) of the parts to be joined can be traced as a function of the joining partners, the process parameters, and the material thicknesses. It is shown that the fiber optical method is suitable for process monitoring directly in the joining zone of metal–polymer hybrids and providing a tool for detailed strain measurements in the joint zone during subsequent component testing.

Ultra sensitive molybdenum disulfide (MoS2)/graphene based hybrid sensor for the detection of NO2 and formaldehyde gases by fiber optic clad modified method

Here we design and fabricate the molybdenum disulfide (MoS2)/graphene based hybrid sensor and evaluated the gas sensing performance of numerous kind of gases (Ethanol, methanol, acetone, CO, NO2 and formaldehyde) using clad removed fiber optic method. The hybrid sensors were characterized by XRD, SEM, TEM, EDS, Raman and BET analysis. The interconnect of MoS2 spherical nanoparticles with 2D graphene sheet offer large active surface area, which facilitate the more absorption properties of gas molecules with presence evanescent wave light. The hybrids sensor showed outstanding sensitivity (61%), rapid response (22 s) and recovery time (35%) towards NO2 gas than bare MoS2 sensor. The enhanced gas sensing properties is due to the synergistic effect of MoS2 and 2DG. Thus, the proposed field sensor would be gorgeous due to its low cost production, effortlessness and accuracy. It would be a prospective application on high performance gas sensor device. The gas sensing mechanism of the proposed sensor is discussed in briefly.

Challenges in determining soil moisture and evaporation fluxes using distributed temperature sensing methods

To protect fragile groundwater-dependent environments of arid zones, it is important to monitor soil moisture and groundwater evaporation. Hence, it is important to assess new methods to quantify these environmental variables. In this work, we propose a new method to determine groundwater evaporation rates by combining the actively heated fiber-optic (AHFO) method with vadose zone modeling, assuming that the evaporation front remains at the soil surface. In our study, the AHFO method yielded estimates of the soil moisture (θ) profile with a spatial resolution of ~6.5 mm and with an error of 0.026 m3 m−3. The numerical model resulted in a slightly different θ profile than that measured, where the largest differences occurred at the soil surface. Sensitivity and uncertainty analyses highlighted that a better precision is required when determining the soil hydraulic parameters. To improve the proposed method, the soil heat-vapor-water dynamics should be included and the assumption that the evaporation front remains at the soil surface must be relaxed. Additionally, if the AHFO calibration curve is enhanced, the errors of the estimated θ profile can be reduced and thus, successful estimation of the evaporation rates for a wider range of soil textures can be achieved. The spatial scales measured are an important advantage of the proposed method that should be further explored to improve the analysis presented here.

Determination of cancer progression in breast cells by fiber optic bioimpedance spectroscopy system

Aim: It is well established that cancer can be most effectively treated when diagnosed at an early stage. Therefore, development, evaluation, and validation of new biomedical approaches for early detection of cancer and precancerous lesions are important priorities. Our aim was to distinguish low metastatic human breast cells from normal human breast cells using the Fiber Optic Bioimpedance Spectroscopy (FOBIS) system.Methods: In the FOBIS system we developed, the diameters of the fibers and platinum wires are 50 and 25µm, respectively. The sensitivity of the system to differentiate different cell types was assessed with high metastatic (MDA-MB-231), low metastatic (MCF-7) and normal breast epithelial cells (MCF-10A). Statistical evaluation of data was performed by using Principle Component Analysis (PCA) and Linear Discriminant Analysis (LDA). Spectroscopic data obtained from FOBIS system on suspended human breast cells were evaluated by multivariate statistical analysis to obtain information about the cell type. Fiber optic and bioimpedance methods allow discrimination of different cell types based on their signature. By combining these two techniques, the sensitivity of the system to the differentiation of human breast cells was evaluated.Results: The discrimination provided the sensitivity of 100% and specificity of 60% in distinguishing MCF-7 from MCF-10A cells.Conclusion: A highly accurate distinction of breast cancer cells was achieved in cell culture by FOBIS system.

Towards high power longwave mid-IR frequency combs: power scalability of high repetition-rate difference-frequency generation

Frequency combs in the mid-IR wavelength are usually implemented by difference-frequency generation (DFG) that mixes pump pulses and signal pulses. Different from most optical parametric amplifiers that operate at a typical low repetition rate of <0.1 MHz, mid-IR frequency combs require that pump/signal pulse repetition rate must be at least as high as tens of MHz (normally >30 MHz). The DFG mixing high repetition rate (HRR) pulses limits the allowed pulse energy to prevent crystal damage. In this paper, we numerically investigate HRR DFG with a focus on the energy scalability of idler pulses. We show that HRR DFG-unlike optical parametric amplifiers-may operate in the linear regime, in which the idler pulse energy scales linearly with respect to the pump/signal pulse energy. Our simulation results suggest an efficient approach to energy scaling the idler mid-IR pulses in a HRR DFG: increase the signal pulse energy to the same level as the pump pulse energy. We also show that DFG seeded by pump/signal pulses at ∼2-µm range benefits from reduced group-velocity mismatch and exhibits better idler energy scalability. For example, 44.2-nJ pulses at 9.87 µm can be achieved by mixing 500-nJ, 2.0-µm pump pulses and 100-nJ, 2.508-µm signal pulses in a 2-mm-thick GaSe crystal. At the end of this paper, we show that such high-energy signal pulses can be derived from the pump pulses using a recently invented fiber-optic method. Therefore, implementation of high-power (>2 W) longwave mid-IR frequency combs is practically feasible.

Fiber optic method of tip clearance measurement in compressor

Fiber optic method of tip clearance measurement in compressor

Study of Potential Distribution of UHV AC Arrester in Different Conditions

As is known to all, uhv ac lightning arrester will be attenuated to varying degrees due to long-term operation on site, including environmental temperature and humidity, breakdown of valve plate and short circuit, leading to uneven capacitor voltage divider, and causing explosion and other dangerous safety accidents in extreme cases. Therefore, it is very important to analyze the electric field potential distribution characteristics of arrester under different operating environment and conditions. In this paper, the equipotential distribution of uhv ac arrester in local damping and local short circuit test is verified theoretically and practically by using fiber optic current method. Based on the field structure and theoretical analysis, the ANSYS 3d theoretical model is constructed to analyze the actual test conditions. The oneness of field test and theoretical calculation shows the accuracy of theoretical calculation.

A field experiment of walkaway distributed acoustic sensing vertical seismic profile in a deep and deviated onshore well in Japan using a fibre optic cable deployed inside coiled tubing

ABSTRACTA two‐dimensional walkaway vertical seismic profiling survey using distributed acoustic sensing was conducted at an onshore site in Japan. The maximum depth and the deviation of the observation well were more than 4,000 m and 81 degrees, respectively. Among the several methods for installing fibre optic cables, we adopted the inside coiled tubing method, in which coiled tubing containing a fibre optic cable is deployed. The signal‐to‐noise ratio of the raw shot gather was low, possibly due to poor coupling between the fibre optic cable and the subsurface formation resulting from the fibre optic cable deployment method and the existence of considerable tubewave noise. Nevertheless, direct P‐wave arrivals, P–P reflections and P–S converted waves exhibited acceptable signal‐to‐noise ratios after careful optimization of gauge length for distributed acoustic sensing optical processing and the application of carefully parameterized tubewave noise suppression. One of the challenges in current distributed acoustic sensing vertical seismic profile data processing is the separation of P‐ and S‐waves using only one‐component measurements. Hence, we applied moveout correction using two‐dimensional ray tracing. This process effectively highlights only reflected P‐waves, which are used in subsequent subsurface imaging. Comparison with synthetic well seismograms and two‐dimensional surface seismic data confirms that the final imaging result has a sufficiently high quality for subsurface monitoring. We acquired distributed acoustic sensing vertical seismic profile data under both flowing conditions and closed conditions, in which the well was shut off and no fluid flow was allowed. The two imaging results are comparable and suggest the possibility of subsurface imaging and time‐lapse monitoring using data acquired under flowing conditions. The results of this study suggest that, by adopting the inside coiled tubing method without drilling a new observation well, more affordable distributed acoustic sensing vertical seismic profile monitoring can be achieved in fields such as CO2 capture and storage and unconventional shale projects, where monitoring costs have to be minimized.

Event Detection and Classification for Fiber Optic Perimeter Intrusion Detection System

A perimeter intrusion detection system (PIDS) is critical for the security of a shale gas field. Among many technologies, the fiber optic sensor-based method is the most widely used, due to its passive, low-cost, long-life, and strong anti-interference ability and strong environmental adaptability. This article proposes an event detection and classification method for a fiber optic PIDS. In general, three types of features are extracted for an improved double-threshold method to improve the probability of detection. Also, the detected intrusion events are distinguished by a support vector machine with wavelet features to reduce the nuisance alarm rate. Experiments on the PIDS in Chongqing Fuling's shale gas field show that detection algorithms based on the feature of short-time energy and short-time wavelet coefficient energy are much better, and the performance of event classification is satisfactory.

Noise Characteristics of the Optical Response of Ferrofluids to a Magnetic Field

The noise generated by different ferrofluid samples when probed by the fiber-optic method has been investigated. It is shown that switching on a magnetic field significantly increases the noise, which is presumably related to fluctuations accompanying the process of aggregate formation. The dependences of the rms noise on the field strength and probe-light intensity have been experimentally determined. A slow decrease in the rms noise after switching off the magnetic field has been found, which indicates relaxation of the aggregates formed by the field.

Solubility analysis of venlafaxine hydrochloride polymorphs by shake-flask method and real time monitoring

Aims: The aqueous solubility of two polymorphic forms of venlafaxine hydrochloride was investigated.&#x0D; Methods: The pH-dependent solubility (SpH) over a wide pH range was measured by saturation shake-flask (SSF) method at 25 °C. The solubility of the free base form was depicted by the intrinsic solubility (So). To identify the solid form present at the solubility equilibrium, X-ray powder diffraction (XRPD) and Raman spectroscopy was carried out. The dissolution was studied using real time concentration monitoring applying fiber optic UV probes.&#x0D; Results: No difference was found in the SpH values of Form I and Form II, in the pH range 7.5-12. Solid phase isolated from pH 10-12 suspensions was identified as free base by XRPD and Raman spectroscopy. Precipitates separated from pH 7-8 samples were also identical product. The transition of polymorphs to the free base was supported by the real time dissolution analysis.&#x0D; Conclusion: In this study we demonstrated a good agreement of equilibrium solubility measured by SSF method and in-situ UV fiber optic method. µDISS ProfilerTM has the advantage to provide much more information about dissolution process; with this approach the dissolution kinetic, the supersaturation and the time needed to reach the equilibrium can be easily monitored.&#x0D;

Multivariate approaches for the development of quality control in-situ fiber optics dissolution methods for fixed-dose combination tablets

The purpose of this research was to develop a fiber optic (FO) dissolution method for quantification of multiple actives in combination pharmaceutical tablets. FO dissolution allows direct API quantification in the vessel, obviating the need for error-prone facets of traditional dissolution methods. However, FO dissolution is potentially challenged by overlapping UV spectra, matrix effects, UV-active excipients, API interactions with excipients and media, and undissolved components attenuating the UV signal. These obstacles might render FO dissolution method development more complex than LC-end dissolution. The case study in this manuscript has the added complexity of a triple combination product (Midol), where acetaminophen, caffeine, and pyrilamine maleate exhibit similar release kinetics, share largely overlapping UV spectra and span an order of magnitude difference in concentration. Single-wavelength quantification required unique features for the actives of interest, which were not available for the formulation of interest without preprocessing. The methods employed for the quantification of actives were a partial least squares multivariate calibration and a peak area calibration, both using prepared mixtures as reference data. The selected combination tablet demonstrated collinear API release; therefore, individual quantification required a design of experiments for mixture design. The advantages of FO dissolution will be discussed in the context of the formulation under investigation. Additionally, some general guidelines will be suggested for the development of other FO methods.

Development of ethanol and acetone gas sensing performance of MgCo2O4 nanosensors by clad modified fiber optical method

We have successfully synthesized large scale magnesium cobalt oxide (MgCo2O4) nanosheets (NSs) was synthesized by a facile hydrothermal route. These MgCo2O4 NSs were characterized by X-ray diffractometry, N2 adsorption Brunauer-Emmett-Teller method, scanning electron microscopy and transmission electron microscopy analysis. XRD and TEM results suggest that MgCo2O4 was cubic structure with nanosheets and sizes in the range of 200–250 nm diameter and 10–15 nm thickness. The N2 adsorption–desorption analysis indicates that the BET surface area of MgCo2O4 nanoparticles is calculated to be 98.5 m2/g and the pore size distribution is mostly centered at 30 nm. The MgCo2O4 sensor was exposed two type of reducing gases like ethanol and acetone and the results demonstrates that the sensor showed superior gas sensing performance such as high sensitivity (81 × 10−3 k/Pa), rapid response (15 s) and recovery time (19 s) towards ethanol gas. This could be due to large specific surface area with sufficient sensing active sites, more gas adsorption, and achieving the enhanced gas-sensing performance. The improved gas sensing mechanism of the proposed sensor is also discussed in detail.

Optical enzymatic biosensor membrane for rapid in situ detection of organohalide in water samples

An optical biosensor employing immobilized haloalkane dehalogenase (HLD), the halide degrading enzyme for the detection of halogenated organic in environmental water and drinking water samples was developed. The enzymatic biosensor was fabricated by incorporating H+ ion selective chromoionophore ETH5294 and HLD enzyme in a stacked chitosan films system on a glass slide. Hydrolytic dehalogenation of dichloroethane (DCA) by the carbon-halide degrading HLD enzyme resulting in the release of a halogen, a proton and a primary alcohol. The halocarbon concentration was optically transduced by the pH transducer layer as a result of protonation reaction of the chromoionophore pH indicator dye embedded in the underneath layer. The resulting colour change of the protonated chromoionophore was measured by fiber optic reflectance spectrophotometry method. Under optimized conditions the detection limit of the proposed reflectance-based enzymatic biosensor membrane was estimated to be 1 mg L−1 with a wide dynamic linear concentration range of 5–60 mg L−1 DCA (R2 = 0.9792) and satisfactory reproducibility within the relative standard deviation (RSD) range of 3.4–4.3%. Validation test demonstrated that the optical halocarbon biosensor could be a promising tool for rapid (6 min) in situ and direct evaluation of organohalide in river water, tap water and bottled water samples without any sample pre-treatment or extraction steps.

Assessing soil water content variability through active heat distributed fiber optic temperature sensing

Soil spatial variability is a key point for the sustainable water management in agriculture. Fractal techniques provide proper tools to analyze soil spatial variability searching for statistical self-similarity patterns among different scales. Although they have been extensively applied to study the soil properties variability, its applicability for the soil water content (SWC) distribution is complicated because requires many data difficult to obtain with the typical point soil water sensors. Recently, a fiber optic distributed temperature sensor has been used to measure soil thermal properties which relate to SWC. These sensors provide large amount of data with high spatial and temporal resolution, thus filling the gap of point soil water sensors. In the present work, soil temperature was measured with a Distributed Temperature Sensing (DTS) and SWC was estimated by different fitting functions which have been studied with focus on spatial variability.Temperature was measured in a 133 m fiber optic cable laid in a sandy soil field plot. A The Active Heat Fiber Optic (AHFO) method was used, with 12 cm sampling resolution, and heat pulses (19,4 W/m during 2 min) were applied. The temperature data were correlated to SWC, considering the integration of temperature during the heat pulse Tcum, and then the datasets Tcum-SWC were fitted to the best fit statistical function (exponential, potential and polynomial). The results showed that the Tcum distribution presented a non-Gaussian pattern. Additionally, highly anti-persistent patterns have been detected for the larger spatial scaling lags. The function`s performance was different thus, the exponential function reproduced better the absolute moments of the temperature profile but it failed reproducing the non-Gaussian behavior.

Actively heated fiber optics method to monitor three-dimensional wetting patterns under drip irrigation

Monitoring dynamics in wetting patterns under drip irrigation is important to optimize the frequency and duration of irrigation, the emitter discharge rate and the spacing. However, difficulties in measurement of soil water content (SWC) at high spatial and temporal resolution and in three-dimensions (3D) restricts direct monitoring around drip emitters. Indirect methods such as actively heated fiber optics (AHFO) has shown the potential to measure SWC at sub-meter intervals. Therefore, the objective of this study was to examine the feasibility of the AHFO method to monitor 3D spatial and temporal variations in wetting patterns under a single drip emitter. Heat pulses of three minutes duration were applied at a rate of 20 Wm−1 through a helically wrapped fiber optic cable in a soil column before, during, and after irrigation. A distributed temperature sensing (DTS) instrument was used to estimate the cumulative temperature increase (Tcum) at locations along the cable. An indirect relationship between Tcum and SWC was developed and validated using the SWC measurements determined by the gravimetric method. Data from the network of 3D points (from fiber optic cable) were used to generate 3D surfaces of SWC. In comparison with the gravimetric method, AHFO showed predictive accuracies; root mean squared error (RMSE) of 0.03 m3 m−3 for SWC <0.05 m3 m−3 (N = 17), 0.03 m3 m−3 for SWC 0.05–0.3 m3 m−3 (N = 19) and, 0.05 m3 m−3 for SWC >0.3 m3 m−3 (N = 6). The time evolution of the 3D SWC helped to identify wetting bulb formation, movement of the wetting front and changes in the dimensions (wetted radius and depth) of wetting bulbs. This study showed not only the potential of AHFO to help design drip emitters but also the ability to provide high resolution SWC information to improve water movement models in the future.

Fiber optic method for obtaining the peak reflected pressure of shock waves.

Most of fiber-optic pressure sensors used in shock wave measurements are based on deformations of sensing elements. These approaches result in low dynamic pressure ranges for these sensors used in the air. A novel fiber-optic method based on the relationship between pressure and the acceleration of a diaphragm is proposed to obtain peak reflected pressure of shock waves in the air. The optical sensor is designed with a thin circular diaphragm as the sensing element, and the Fabry-Perot optical interferometry is used to detect the acceleration of the diaphragm. Shock tube and explosive-blast experiments prove that the proposed fiber optic method is feasible and has the advantages of no calibration, high precision and fast response time. The proposed fiber-optic pressure method has potential in practical applications for shock wave measurements.

基于小波神经网络的光纤陀螺误差补偿方法

基于小波神经网络的光纤陀螺误差补偿方法

Influence of Acousto-Optic Resonances in Electro-Optical Modulator on Fiber Optic Gyro Performance and Method for Its Compensation

The electro-optical modulator is one of the most important parts of the fiber optic gyroscope. Unfortunately, the integral implementation of the modulator has a number of undesirable effects such as parasitic amplitude modulation, phase drift, and acousto-optical resonance effects. Influence of the first two effects on the gyroscope operation has been described in a number of works, but at the moment, there are no published papers aimed at investigating the relationship between the presence of acousto-optic resonances in modulators and changes in the performance of a fiber optic gyroscope. There are several design solutions that provide damping of undesired acoustic waves in electro-optical modulators. However, the use of these solutions requires a method to estimate their effectiveness. The main purpose of the article is to describe such a method and to evaluate the correctness of its application. We also offer an additional way to reverse the effect of the mentioned resonant effects on the characteristics of the fiber gyroscope.