Sensor technology plays an important role in the field of measurement science and engineering. Fabry-Perot (F-P) sensor has always been the focus of research due to its high precision and sensitivity. Traditional F-P sensor demodulation algorithms have limitations in terms of demodulation time and precision. In order to pursue higher accuracy and achieve faster demodulation, we report a joint demodulation algorithm based on Fibonacci and cross-correlation. The Fibonacci search method is used to quickly search the cavity length corresponding to the maximum cross-correlation number, and the target accuracy is achieved through search iteration. Experimental results show that this algorithm is used for DualCavity Fabry-Perot Interferometer (DFPI) sensor demodulation, with a resolution of 10 pm and a cavity length demodulation time of less than 0.06 s. This study provides new insights for improving the demodulation efficiency and accuracy of F-P sensors.
Thermal runaway of lithium batteries is a matter of great concern to relevant scholars. The gas pressure during the charge and discharge control process of lithium batteries is directly related to the performance of lithium batteries. Relevant scholars have been pursuing a method that can safely monitor the internal gas pressure of lithium batteries. Based on the characteristics of optical fiber sensors such as small size, anti-electromagnetic interference, and intrinsic safety, this paper designs and prepares an optical fiber gas sensor that can be used to measure the internal gas of lithium batteries. The measurement range of the sensor is 0-240kPa, and the resolution of the sensor is 0.5kPa, the sensor's accuracy reaches 5kPa, which can be used as a feasible detection method for gas generated during the working process of lithium batteries.
In view of the technical bottlenecks of eutectic salt electric superheat detector used in aircraft duct leakage monitoring, such as poor electromagnetic compatibility, low measurement accuracy and slow response time, a linear fiber optical sensor for aircraft duct leakage detection is studied in this paper. The research demonstrates that the sensor is capable of adapting to the operational conditions of pipeline bending assembly, with a temperature sensing accuracy of 0.1m, positioning accuracy of 1m, temperature measurement accuracy within ±3℃, and a working temperature range from 0- 180℃. Moreover, it can replace the eutectic salt leak detection sensors to achieve remote distributed measurement.
This paper designs and makes a high precision and miniature fiber Bragg grating (FBG) gas flow sensor for the low measurement accuracy and large volume of traditional electromagnetic flow sensor in complex working environment. The flow sensor is selected, and the high ratio diameter nozzle is used as the throttle element to produce the pressure difference on both sides of the nozzle. By pasting the FBG along the radial direction on the sensitive diaphragm, the deformation caused by the induction diaphragm due to the pressure difference, so as to associate the flow change with the FBG wavelength drift. The mathematical relationship between the measured gas flow and FBG wavelength values is derived from theoretical and simulation, and the dynamic flow characteristics of the flow sensor are obtained through experimental calibration. The experimental results show that the flow change and FBG wavelength drift, consistent with the theoretical analysis, the flow sensor dynamic flow measurement sensitivity is 11.04 NL/min. The FBG gas flow sensor designed in this paper has the advantages of high precision, miniaturization, strong anti-electromagnetic interference ability and easy integration in the complex working environment.
Pipeline plays an important role in petrochemical production, and its health monitoring is related to safety production. At present, the petrochemical production mainly relies on manual inspection to judge the pipeline status, which cannot achieve the full-time domain health monitoring. The purpose of this paper is to propose a method that uses a single weak fiber grating array as a sensor, extracts the vibration signal generated in the pipeline operation by the phase-sensitive optical time-domain reflection system, and improves the LSTM algorithm by using the variational mode decomposition principle and the arrangement entropy theory to predict the pipeline operation signal, so as to realize the abnormal state early warning. The experimental results show that the improved VMD-PE-LSTM model proposed in this paper has a very high accuracy in the prediction of pipeline vibration signals and provides a new direction for the early warning of abnormal pipeline operation.
In recent years, as a clean and efficient energy storage technology, lithium iron phosphate battery is widely used in large energy storage power stations, new energy vehicles and other fields. However, lithium-ion batteries still face obstacles that limit their application space. Once the temperature exceeds the working range of the battery, lithium iron phosphate battery will rapidly degrade, increasing the risk of facing fire and explosion and other safety problems. Multi-physical field full-coupling simulation is one of the important means to study the temperature of lithium iron phosphate battery operation process. Based on the electrochemical-thermal coupling full model of iron phosphate battery, this paper analyzes and studies the temperature change of battery operation process and obtains the temperature change of battery under adiabatic and actual conditions, which provides a basis for solving the thermal management problem of lithium iron phosphate battery operation process.
Sites prone to vibration waves such as mining, earthquake-prone areas or also border regions under vibration monitoring increasingly require vibration sensors with a wide frequency range and good sensitivity. In this article, we propose a fiber Bragg grating (FBG) vibration sensor based on a boundary (BM) or warning marker. By dimensioning the warning marker by adding a low reflectivity FBG vibration detector with a sensitive mass attached to the central part of the fiber, a vibration detection zone is thus set up. By producing several vibratory excitations of different frequencies in the main-axis of measurement of the sensor and in the cross-axis, the results show that the sensor resonance frequency is about 10 Hz, it has a good sensitivity, a wide working frequency range of 40-500 Hz in the main-axis of measurement and a good crossinterference test result of 2.4%. The sensor dynamic range is at least 39 dB and can achieve up to 67 dB for the precision of 0.4 pm, when the interrogator has readings taken at this wavelength precision.
Aiming at small size, compact structure, strong light-collecting ability, and low loss requirements of optical coherence tomography (OCT) probes used for human body detection, we design an all-fiber OCT probe, which is composed of a single-mode fiber and a multimode fiber (MMF) with spherical lens. By measuring the optical performance of these probes, we found that, when the length of the MMF of the composite probe is 372 μm and the diameter of the ball lens is 300 μm, it has the strongest focusing effect and a large reflected light signal receiving angle. Furthermore, the OCT probe studied was applied to a self-made spectral domain OCT system for validation. The results show that our probe can obtain a clear two-dimensional grayscale image of three layers of glass and fish scales, i.e., the probe manufacturing scheme can be used. Furthermore, it meets the needs of miniature OCT probes, which provides more effective options for measuring human blood vessels or other biological tissues.
A distributed optical fiber grating sensing system with large capacity and high spatial resolution is presented. Since highdensity identical weak grating array was utilized as sensing fiber, the multiplexing number was greatly increased, meanwhile, optical frequency domain reflectometry (OFDR) technology was used to implement high resolution distributed sensing system. In order to eliminate the nonlinear effect of tunable light source, a windowed FFT algorithm based on cubic spline interpolation was applied. The feasibility of the algorithm was experimentally testified, ultimately, the spatial resolution of system can reach mm-level. The influence of the crosstalk signal in the grating array on the OFDR system was analyzed. A method that a long enough delay fiber was added before the first FBG to remove crosstalk signal was proposed. The experiment was verified using an optical fiber with 113 uniform Bragg gratings at an interval of 10cm whose reflectivity are less than 1%. It demonstrates that crosstalk signal and measurement signal can be completely separated in the distance domain after adding a long enough delay fiber. Finally, the temperature experiment of distributed grating sensing system was carried out. The results display that each raster’s center wavelength in the fiber link is independent of each other and the center wavelength drift has a good linear relationship with the temperature. The sensitivity of linear fitting is equal to 11.1pm/°C.
This paper presents a method that uses fiber Bragg grating (FBG) sensors to distinguish the temporal gait patterns in gait cycles. Unlike most conventional methods that focus on electronic sensors to collect those physical quantities (i.e., strains, forces, pressure, displacements, velocity, and accelerations), the proposed method utilizes the backreflected peak wavelength from FBG sensors to describe the motion characteristics in human walking. Specifically, the FBG sensors are sensitive to external strain with the result that their backreflected peak wavelength will be shifted according to the extent of the influence of external strain. Therefore, when subjects walk in different gait patterns, the strains on FBG sensors will be different such that the magnitude of the backreflected peak wavelength varies. To test the reliability of the FBG sensor platform for gait pattern detection, the gold standard method using force-sensitive resistors (FSRs) for defining gait patterns is introduced as a reference platform. The reliability of the FBG sensor platform is determined by comparing the detection results between the FBG sensors and FSRs platforms. The experimental results show that the FBG sensor platform is reliable in gait pattern detection and gains high reliability when compared with the reference platform.
Optical coherence tomography based on ultra technology is used for the assessment of subcutaneous tissue. Using high swept laser technology based on Fourier domain mode locking (FDML), the system operated in the 1300 nm wavelength range with axial scan rate of 150 kHz. Imaging at this wavelength range reduces optical scattering and improves imaging penetration depths in the tissues. The laser consists of a semiconductor amplifier as the gain medium, a tunable Fabry-Perot filter to change the wavelengthcand a long fiber ring cavity. The tuning range of laser is 102 nm. A balanced detector is used for spectra collection instead of the expensive CCD.
KEYWORDS: Visualization, Microsoft Foundation Class Library, Fiber optics sensors, Software development, Process modeling, Carbon, Interference (communication), Data acquisition, Signal processing, Sensors, Computing systems, Signal detection, Sensing systems, Optical fibers
The relationship model of the sound signal and the coke state can be established through multiple test and comparison of the noise signal and the coke operation. By collecting data, we summarize the main frequency power fluctuation range of the sound signal in kinds of state, and extract the nearest 5 decision results for reference. The weighted value of each result according to the update time has gradually increased. On the basis of that, we developed visualization software, real-time reflect out coke coking tower state. Animation refresh rate is second level, and the vertical height can be accurate to 0.1m.
KEYWORDS: Sensors, Acoustics, Fiber optics sensors, Metals, Signal detection, Signal processing, Temperature metrology, Optical engineering, Signal generators, Fiber optics
A Fabry–Perot (F-P) fiber acoustic sensor, which can work under high-temperature harsh environment with temperature self-compensation, is designed and prepared. A condenser was used to maintain the sensor to work in a stable temperature environment. Because of the special structure of the sensor and the function of the condenser, the cavity variation of the sensor caused by changes of external temperature from −10°C to 500°C would not exceed 8 nm. The experimental results show that the sensor has a good frequency response in a range of 1 to 5 kHz and the field experiment results show that it could be used for hydraulic decoking online monitoring by judging the acoustic frequency spectrum.
The vibration sensors with high sensitivity and wide frequency range have a large application demand for in the engineering project. Combining with the advantages of optical fiber sensor monitoring technique, in the paper, a kind of optical fiber Fabry-Perot (F-P) vibration sensor has been designed based on the differential-type structure of the double V-shaped cantilever a optical fiber F-P cavity. Through two different differential vibration of the cantilever beam, change the F-P cavity length, the realization of the vibration signal of large frequency range measurement the differential-type optical fiber F-P vibration sensor with large frequency range.
One of the most important equipment in high voltage power grid system is power transformer, however there are still some limitations on traditional methods of online partial discharge monitoring. Considering the advantages of optical fiber sensing technology, in this paper we do some research on fiber optics F-P sensing which can be used in transformer on online partial discharge monitoring. It also contributes to the improvement of the reliability of power system safety monitoring. This paper designs an equipment scheme for fiber optics F-P sensor, strictly fabricates the sensor according to the fabrication procedure. Moreover, we build a reasonable signal demodulation system for fiber optics F-P sensing, doing a preliminary analysis of online partial discharge signal monitoring,Partial discharge online monitoring system including different intensity discharge with a same sensing distance and a same intensity discharge with different sensing distances. Finally we make a detailed analysis of experimental result.
An optical fiber Fabry-Perot (F-P) sensor with quartz diaphragm for gas pressure testing was designed and fabricated. It consisted of single-mode fiber, hollow glass tube and quartz diaphragm. It uses the double peak demodulation to obtain the initialized cavity length. The variety of cavity length can be calcultated by the single peak demodulation after changing the gas pressure. The results show that the sensor is small in size, whose sensitivity is 19 pm/kPa in the range of the 10 ~ 260 kPa gas pressure. And it has good linearity and repeatability.
We present that an improved optical fiber acoustic emission sensor has been applied to the hydraulic decoking on-line monitoring system for the first time, meanwhile the characteristics of the improved acoustic emission sensor are analyzed. The actual research results of China Petrochemical Wuhan Petrochemical Corporation Group show that hydraulic decoking on-line monitoring system can monitor the real-time and accurate states of hydraulic decoking based on the optical fiber acoustic emission sensor technology, the system can realize the automation of hydraulic decoking monitoring effectively.
On the basis of the analysis of the current hydraulic decoking monitoring system, it is proposed that use optical fiber Bragg grating (FBG) vibration sensor and fiber Fabry-Perot (FP) acoustic sensors to online monitor vibration signal and audio signal hydraulic of the coke drum in the running state progress, analysis the vibration sensor and acoustic sensor used in the system. Based on the actual monitoring results in Sinopec Wuhan Branch , the fiber optic acoustic emission sensors is more suitable for the hydraulic decoking online monitoring system than the FBG vibration sensor ,which can more accurate monitor of hydraulic decoking.
Intracranial pressure is an important monitoring indicator of neurosurgery. In this paper we adopt all-fiber FP fiber optic sensor, using a minimally invasive operation to realize real-time dynamic monitoring intracranial pressure of the hemorrhage rats, and observe their intracranial pressure regularity of dynamic changes. Preliminary results verify the effectiveness of applications and feasibility, providing some basis for human brain minimally invasive intracranial pressure measurement.
In this paper, an optical fiber Fabry-Perot(F-P) acoustic emission(AE) sensor system for the detection of steel crack
initiation has been investigated. The F-P sensors were fabricated by using quartz diaphragm, glass tube and fiber optic.
And the signal processing circuit was designed by using an intensity demodulation method. The test of steel crack
initiation was simulated by using a pencil lead break experiment. The results indicate that the F-P sensing system can
detect weak AE signals at the frequency between 20 kHz and 1MHz, which could be used to on-line monitor of the steel
structure health.
In this paper, a novel Fiber Bragg gratings (FBGs) high alternating current sensor is proposed to measure alternating
current. The principle and sensing structure are introduced. The sensitivity of the high alternating current sensor is
13.8pm/A when the current is 1000A. The trend shows a good linearity between the wavelength shift and the square of
the current value which is consistent well with the principle and indicates that the proposed sensor is capable of
measuring high alternating current.
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