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.
Proc. SPIE. 9854, Image Sensing Technologies: Materials, Devices, Systems, and Applications III
KEYWORDS: Carbon, Optical fibers, Visualization, Sensors, Computing systems, Interference (communication), Fiber optics sensors, Data acquisition, Signal processing, Software development, Sensing systems, Microsoft Foundation Class Library, Signal detection, Process modeling
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.
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.
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.
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.
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.
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
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.