A fiber laser sensor for liquid level and temperature based on two taper structures and fiber Bragg grating
基于双锥形结构和光纤布拉格光栅的液位与温度光纤激光传感器
Optics Communications, Volume 342, 1 May 2015, Pages 243-246
Abstract: A fiber laser sensor for simultaneous measurement of liquid level and temperature is proposed and demonstrated experimentally. The sensor is based on two taper structures and a fiber Bragg grating (FBG). The two taper structures form a novel fiber interferometer, which is fabricated by cascading two tapers in a section of single-mode fiber (SMF). The FBG and the interferometer serve as the filters of the laser cavity. Corresponding to the two filters, the laser outputs are stable dual-wavelength outputs, which have different characteristics to the liquid level and the temperature. The wavelength produced by the FBG is not sensitive to the liquid level. The temperature sensitivity of the wavelength produced by the FBG is 0.0123 nm/°C. The wavelength produced by the interferometer is sensitive to the liquid level and the sensitivity is up to 0.2294 nm/mm. The temperature sensitivity of the wavelength produced by the interferometer is 0.0648 nm/°C. According to the different spectral responses of the liquid level and the temperature, simultaneous measurement can be realized. Furthermore, the proposed sensor has the advantages of less detection limit (DL), higher resolution and higher sensitivity compared to other optical fiber sensors.
A fiber laser intracavity absorption spectroscopy (FLICAS) sensor for simultaneous measurement of CO and CO2 concentrations and temperature
同时测量CO 和 CO2浓度与温度的光纤激光腔内吸收光谱传感器
Sensors and Actuators B: Chemical, Volume 210, April 2015, Pages 431-438
Abstract: We report a method for the simultaneous measurement of carbon dioxide (CO2) and carbon monoxide (CO) absolute concentrations and temperature using fiber laser intracavity absorption spectroscopy (FLICAS). FLICAS uses an erbium-doped broadband laser capable of being tuned in the range 6350–6450 cm−1. The range 6390–6410 cm−1, which is emitted by the laser without tuning, allows for simultaneous observation of the CO, CO2, and methane (CH4) spectra. Truly simultaneous observation of these spectra is possible during one laser pulse with duration as short as 3.7 μs. The sensitivity of the CO measurement is about 20 times higher than that of CO2, a feature which is advantageous for several applications. The concentration of CO can be measured with a sensitivity of 400 ppm at room temperature, and this sensitivity can be improved by increasing the generation time. The experiments were performed in a temperature and flow-controlled cell in order to evaluate the accuracy of the concentration and temperature measurements from 296 to 1200 K. The measured spectra of CO and CO2 are well described by the HITRAN database, allowing for accurate and simultaneous determination of CO, CO2 and temperature. The temperature is evaluated using the CO2 spectrum, which includes many “hot” transitions. The CH4 HITRAN data are deficient at high temperatures, so this method only allows for the evaluation of methane concentrations at room temperature.
Alternative interrogation method for a dual laser sensor based on fiber Bragg gratings to measure temperature using the fundamental beating frequency intensity
基于基拍频强度光纤布拉格光栅测温双波长激光传感器交替询问方法
Optics & Laser Technology, Volume 67, April 2015, Pages 159-163
Abstract: In this work we present an alternative interrogation method for a dual sensor based on a fiber laser used to measure temperature in two remote locations simultaneously. The dual laser consisted of two Fabry–Perot cavities each conformed by two fiber Bragg gratings (FBG). For each cavity, one FBG was used as the reference and the other one as a sensing element. The sensing element interrogation was performed by the quantification of the fundamental beating frequency (FBF) intensity, which was calculated using the fast Fourier transform algorithm. The laser emissions were centered at 1549 and 1556 nm, while the lengths of cavities were of 300 and 400 m, which corresponds to FBFs of 334 and 258 kHz, respectively. The quantification of the temperature was calculated from the difference between the FBF values of both cavities. Such difference describes a geometrical plane in function of the two sensing FBGs temperatures. Consequently, it was possible to achieve temperature measurements in a range of 25–28 °C for the two sensors.
Indium-Tin-Oxide Single-Nanowire Gas Sensor Fabricated Via Laser Writing and Subsequent Etching
应用激光直写和随后刻蚀技术制造铟锡氧化物单纳米金属丝气体传感器
Sensors and Actuators B: Chemical, 6 April 2015
Abstract: We report on the design and nanofabrication of a single nanowire (NW) indium-tin-oxide (ITO) gas sensor and on test results obtained with an oxidizing and a reducing gas. As a novel fabrication approach, direct laser writing and a subsequent etching process on sputtered ITO thin-film layers is applied. For this technique a near-infrared Ti:sapphire laser with sub-15 fs pulses and a repetition rate of 85 MHz is used. NWs for gas sensors are realized in two versions with a thickness of 125 ± 25 nm; one with 350 nm in width and 90 μm in length the other with 700 nm in width and 200 μm in length. The sensors are exposed to nitrogen dioxide (NO2) in synthetic air with concentrations from 1 ppm to 50 ppm showing a significant change in resistance (up to 15.8%), whereas the reaction to 2000 ppm carbon monoxide (CO) turns out to be negligible (0.05%). At ambient temperature, the sensor exhibits integrating dosimeter-like behavior with relaxation times of more than 20 hours. By self-heating, the NW can be reset to its initial condition, thus enabling a new dosimeter run at room-temperature. When the sensors are operated in self-heating mode, a conventional behavior is observed, enabling the detection of NO2 concentrations down to about 1 ppm at a stationary temperature below 200 °C.
A novel NIR laser-based sensor for measuring the surface moisture in polymers
基于NIR 激光器用于测量聚合物表面湿度的新型传感器
Sensors and Actuators A: Physical, Volume 221, 1 January 2015, Pages 53-59
Abstract: In addition to bulk moisture, the measurement of moisture profiles is very important in pharmacy, the food, construction and car industries, the military, etc. In special cases, moisture in the upper layers, close to the surface and at the surface, affects various processes more intensively.
Existing measuring principles, such as those based on nuclear magnetic resonance, are unsuitable for particular applications. For this reason, a novel, non-contact, light-reflection type of moisture sensor was designed and investigated (patent pending). It is based on a water molecule's light-absorbing characteristics in the near-infrared (NIR) spectrum. In order to be able to measure the surface and near-surface moisture on a complex geometry with thin walls, the light from a double laser diode is led through an optical fiber and reflected back to an InGaAs photodiode detector. The high stability of the relatively low-cost laser source was achieved through a constant-power laser-control circuit. The sensor's response was measured by a precision embedded data acquisition system NI CompactRIO and evaluated using a moisture analyzer, which measures the bulk moisture with a loss-on-drying technique.
The results prove that it is possible to measure the moisture in polymer layers very close to the surface with an approximately 0.1% effective resolution of bulk moisture content below 2 %.
Infrared laser absorption sensors for multiple performance parameters in a detonation combustor
确定爆炸燃烧室多重性能参数的红外激光吸收传感器
Proceedings of the Combustion Institute, Volume 35, Issue 3, 2015, Pages 3739-3747
Abstract: Laser absorption sensors for temperature and H2O near 1.4 and 2.5 μm, CO2 near 2.7 μm, and CO near 4.8 μm were developed, validated, and deployed in an ethylene-fueled pulse-detonation combustor (PDC). Each sensor was fiber-coupled to enable remote light delivery to the PDC and photo-voltaic detectors were mounted directly to the PDC for improved light collection. Measurements were acquired simultaneously along two orthogonal lines-of-sight (LOS) in both the PDC combustion chamber and the throat of a converging–diverging nozzle located at the PDC exit. Measurements in the nozzle throat were combined with a choked-flow assumption to calculate the time-resolved enthalpy flow rate exiting the PDC. All sensors used first-harmonic-normalized wavelength-modulation spectroscopy with second-harmonic detection (WMS-2f/1f) to account for non-absorbing transmission losses and emission. Furthermore, strong mid-infrared absorption transitions were used to enable improved measurement accuracy and precision. These sensors were validated in non-reactive shock-tube experiments at temperatures and pressures up to 2700 K and 50 atm. There, these sensors exhibited a nominal accuracy of 3 to 5% with bandwidths from 2 to 20 kHz. Measurements in the PDC indicated peak temperatures near 3500 K with near-stoichiometric proportions of H2O and incomplete conversion of CO to CO2. The stagnation enthalpy flow rate was highly transient, but repeatable with peak flow rates near 25 MW.
Human–robot interaction based on wearable IMU sensor and laser range finder
基于便携式IMU传感器和激光测距机的人机互动
Robotics and Autonomous Systems, Volume 62, Issue 10, October 2014, Pages 1425-1439
Abstract: Service robots are not only expected to navigate within the environment, as they also will may with people. Human tracking by mobile robots is essential for service robots and human interaction applications. In this work, the goal is to add a more natural robot–human following in front based on the normal human gait model. This approach proposes implementing and evaluating a human–robot interaction strategy, using the integration of a LRF (Laser Range Finder) tracking of human legs with wearable IMU (Inertial Measurement Unit) sensors for capturing the human movement during the gait. The work was carried out in four stages: first, the definition of the model of human–robot interaction and the control proposal were developed. Second, the parameters based on the human gait were estimated. Third, the robot and sensor integration setup are also proposed. Finally, the description of the algorithm for parameters detection is presented. In the experimental study, despite of the continuous oscillation during the walking, the parameters estimation was precise and unbiased, showing also repeatability with human linear velocities changes. The controller was evaluated with an eight-shaped curve, showing the stability of the controller even with sharp changes in the human path during real experiments.
Direct Laser Patterning of a Gas Sensor on Flexible Substrate
软性基板气体传感器的直接激光工艺
Procedia Engineering, Volume 87, 2014, Pages 899-902
Abstract: Flexible gas sensor fabricated by direct laser patterning and its gas sensing properties towards ozone and ammonia are reported. The flexible platform consists in Ti/Pt interdigited electrodes for gas detection and a microheater device. The platform validation has been realized by thermal simulation and its electrical properties have been also studied. The gas sensing properties were investigated using a commercial ink of ZnO nanoparticles at several concentrations and temperatures. The sensor presents excellent responses toward ammonia and ozone at 300 °C and 200 C° respectively, with good reproducibility, and fast response and recovery time in a wide range of concentrations.
Pulsed Laser Deposited Nanostructured Vanadium Oxide Thin Films Characterized as Ammonia Sensors
脉冲激光沉积纳米结构氧化钒薄膜氨气传感器特征研究
Sensors and Actuators B: Chemical, 26 February 2015
Abstract: Vanadium oxide thin films were fabricated by pulsed laser deposition. The microstructure and crystal symmetry of the deposited films were studied with X-ray diffraction, scanning electron microscopy (SEM), and Raman spectroscopy, respectively. The films surface morphology was examined by atomic force microscopy. Raman spectroscopy and XRD results showed that the thin film phase-structure was composed of pure orthorhombic V2O5 phase, or they had a mixed phase structure of orthorhombic V2O5 and triclinic V7O16. Surface morphology of the films consisted of nanosized particles, although in pure V2O5 films some bigger agglomerates and flakes were also seen. The conductivity based gas sensing measurements showed a clear response already at ppb-levels of NH3 and strong selectivity to ammonia was found when compared to NO and CO gases. Also, the films showed promising gas sensing behavior in cross-sensitivity measurements between NO and NH3, being able to sense ammonia even in the presence of NO. This is an important property when considering possible sensing applications to control Selective Catalytic Reduction processes, e.g. in diesel engine exhausts, where introduced ammonia, or urea, transforms nitrogen oxide gases in a catalytic converter to nitrogen and water.
Design of a fibre optic sequential multipoint sensor for methane detection using a single tunable diode laser near 1666 nm
基于1666纳米单可调谐二极管激光器的甲烷探测光纤连续多点传感器的设计
Sensors and Actuators B: Chemical, Volume 186, September 2013, Pages 466-477
Abstract: The design of a fibre optic sequential multipoint sensor using a single DFB laser source for measurement of average concentration of methane has been reported. A theoretical model for sequential multipoint sensor is developed. The validation of the sensor is conducted using methane gas cells connected in series via fibre optics to form 2-Cell and 3-Cell networks. The second harmonic detection of wavelength modulation spectroscopy (2f-WMS) is employed. Normalisation of the 2f signals with respect to the laser average intensity and the detector gain is used to correct for transmission variation. The measurements are performed at four laser modulation depths to compare the 2f-WMS signals for the target test conditions. The Q(6) transition of the 2v3 band of methane near 1666 nm has been selected because the transition is relatively free of interference from water vapour and absorption by other major gases in that region. The sequential multipoint sensor has some unique advantages over the single cell and multiplexed multipoint sensors. These include the average concentration measurements, the use of only a single laser source, a detector, and a fibre optic to connect series of gas cells, no need for multiplexing techniques to distribute the laser intensity among multi gas cells, and relatively simpler data analysis.
The measurement of nano dimension standard by laser focus sensor
通过激光焦点传感器实现纳米尺度标准测量
Sensors and Actuators A: Physical, Volume 203, 1 December 2013, Pages 430-433
Abstract: This paper presents a detailed discussion about the measurement deviation of Laser Focus Sensor (LFS) for the measurement of the nano dimension standard sample. A new method is developed to improve the measurement accuracy of the LFS in the nano dimension standard. The experimental results show that the secondary coating technology by sputtering Cu atomic on the nano dimension standard sample can improve the measurement accuracy of the LFS.
High-power ns-pulse fiber laser sources for remote sensors
遥控传感器大功率毫微秒脉冲光纤激光源
Optical Fiber Technology, Volume 20, Issue 6, December 2014, Pages 688-693
Abstract: The development of fiber-based laser sources for space-borne remote sensors must meet many concurrent requirements including high pulse energy/peak power, excellent beam quality, narrow spectral linewidth, simple thermal management, small volume and mass, low power consumption, rugged packaging, and long-term reliability. To address these requirements, many aspects of pulse fiber laser technology must be advanced beyond the state of the art of traditional optical sources used in telecommunications and materials processing. In this article, we discuss component and solutions that enable pulsed fiber laser sources to support remote sensing from space. We also describe several examples of such sources and characterize their performance.
