Unmanned aerial vehicle for internet of everything: Opportunities and challenges

Doppler wind LiDAR (Light Detection And Ranging) makes use of the principle of optical Doppler shift between the reference and backscattered radiations to measure radial velocities at distances up to several kilometers above the ground. Such instruments promise some advantages, including its large scan volume, movability and provision of 3-dimensional wind measurements, as well as its relatively higher temporal and spatial resolution comparing with other measurement devices. In recent decades, Doppler LiDARs developed by scientific institutes and commercial companies have been well adopted in several real-life applications. Doppler LiDARs are installed in about a dozen airports to study aircraft-induced vortices and detect wind shears. In the wind energy industry, the Doppler LiDAR technique provides a promising alternative to in-situ techniques in wind energy assessment, turbine wake analysis and turbine control. Doppler LiDARs have also been applied in meteorological studies, such as observing boundary layers and tracking tropical cyclones. These applications demonstrate the capability of Doppler LiDARs for measuring backscatter coefficients and wind profiles. In addition, Doppler LiDAR measurements show considerable potential for validating and improving numerical models. It is expected that future development of the Doppler LiDAR technique and data processing algorithms will provide accurate measurements with high spatial and temporal resolutions under different environmental conditions.

A review of progress and applications of pulsed doppler wind LiDARs

High-sensitive Mach-Zehnder interferometric temperature fiber-optic sensor based on core-offset splicing technique

This paper provides the design, fabrication, and experimental demonstration of a novel, compact, and simple-to-construct optical fiber-tip sensor for the simultaneous measurement of the refractive index (RI), temperature, and level of liquid samples by means of surface plasmon resonance (SPR) phenomenon. The proposed fiber-tip SPR sensor consists of a multimode fiber spliced to a sensing element, it comprises a gold-coated single-mode fiber tip, whose end face is coated with a metallic mirror. By covering part of the sensing element with a thermo-responsive material, whose thermo-optic coefficient is high, it is possible to measure temperature; whereas the metal-bare section is used to measure the changes in the RI and level of a liquid sample. As the RI and temperature of the liquid sample increase, the position of the resonance wavelengths ( ${\boldsymbol {\lambda }_{\boldsymbol {bare}}}$ and ${\boldsymbol {\lambda }_{\boldsymbol {Covered}}}$ ) shifts toward larger and shorter wavelengths, respectively. On the other hand, as the level of the sensed sample increases, the deepness of ${\boldsymbol {\lambda }_{\boldsymbol {bare}}}$ increases too, but the position of ${\boldsymbol {\lambda }_{\boldsymbol {bare}}}$ and ${\boldsymbol {\lambda }_{\boldsymbol {Covered}}}$ remains constant for a particular liquid and temperature. We expect that this novel sensor becoming a promising candidate for biomedical, food, and/or industrial applications.

SPR Fiber Tip Sensor for the Simultaneous Measurement of Refractive Index, Temperature, and Level of a Liquid

This paper evaluates the wake vortex characteristics using pulsed coherent Doppler lidar (PCDL) under near-ground effect (NGE). A wake vortex visualization demonstrator (V2D) is developed in order to visualize wake vortex in real-time. The combination of radial velocity distribution and FFT spectrum characterization are used to identify the core position of wake vortex. The velocity envelope and Burnham-Hallock model correction are used to retrieve the circulation of wake vortex under NGE. The circulation error, which is caused by PCDL scanning mode, is simulated and corrected. To investigate the dissipation rate’s effect on wake vortex in real atmosphere, the cross wind and atmospheric turbulence are concurrently retrieved from the same measurement of wake vortex by using structure function. The statistics of wake vortex parameters are analyzed, based on the measurement campaign at Beijing Capital International Airport (BCIA) in 2017.

Aircraft wake vortex and turbulence measurement under near-ground effect using coherent Doppler lidar.

A novel differential intensity-measurement high-sensitivity refractive index (RI) sensor based on cascaded dual-wavelength fiber laser and single-mode-no-core-hollow-core-no-core-single-mode (SNHNS) structure is proposed and demonstrated. The sensing unit consists of one uniform fiber Bragg grating (FBG) and an SNHNS structure as all-fiber interferometer filter. The dual-wavelength fiber laser has a ring cavity composed of two FBGs with central wavelengths of 1550.10nm and 1553.61nm. Through monitoring the wavelength shift and the output power difference of the dual-wavelength fiber laser, the simultaneous measurement for RI and temperature is realized. In our experiment, the proposed fiber laser sensor exhibits high RI sensitivities of −193.1dB/RIU and 174.8dB/RIU in the range of 1.334-1.384. The relative variation of output power at the two FBG wavelengths shows a higher RI sensitivity of −367.9dB/RIU with better stability, which is greater than the traditional modal interferometer structure. Meanwhile, the temperature sensitivity of the proposed sensor is 8.53 × 10−3nm/°C, and the changes of laser output power caused by temperature are −0.223dB/°C and 0.215dB/°C.

High-sensitivity refractive index and temperature sensor based on cascaded dual-wavelength fiber laser and SNHNS interferometer.

Airport low-level wind shear lidar observation at Beijing Capital International Airport

Ocean University of China lidar team operated a pulse coherent Doppler lidar (PCDL) for the low level wind shear monitoring at the Beijing Capital International Airport (BCIA) in 2015. The experiment configuration, observation modes is presented. A case study shows that the low level wind shear events at the southern end of 18R/36L runway were mainly caused by the trees and buildings along the glide path under strong northwest wind conditions.

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Airport low-level wind shear lidar observation at beijing capital international airport

We report a dual-wavelength fiber laser sensor based on a uniform fiber Bragg grating (UFBG) and a Polyvinyl alcohol (PVA) film-coated long-period grating (LPG) as sensor probe for simultaneous detection of relative humidity (RH) and temperature. Two UFBGs and the LPG were inscribed in three single mode fibers utilizing phase/amplitude mask technology and mobile scanning technique via the 248 nm UV laser. In our experiment, the RH function based on the differential intensity measurement at dual-wavelength output from 30% to 85% is in a quadratic equation, and the RH sensitivity coefficient of 0.358 dB/% shows good linear relationship and stability from 55% to 85%. Meanwhile, the temperature sensitivity coefficients based on wavelength detection and differential intensity detection are 9.1 pm/°C and 0.21 dB/°C, respectively. The structure of dual-wavelength fiber laser sensor with high signal to noise ratio (SNR), narrow spectral width and good stability enables simultaneous measurement of the RH and temperature with high accuracy and good repeatability.

/pdf/wavelength-and-intensity-demodulated-dual-wavelength-fiber-2ud5xbn0o1.pdf

Wavelength- and Intensity-Demodulated Dual-Wavelength Fiber Laser Sensor for Simultaneous RH and Temperature Detection

Low-level wind shear is usually to be a rapidly changing meteorological phenomenon that cannot be ignored in aviation security service by affecting the air speed of landing and take-off aircrafts. The lidar team in Ocean University of China (OUC) carried out the long term particular researches on the low-level wind shear identification and regional wind shear inducement search at Beijing Capital International Airport (BCIA) from 2015 to 2020 by operating several pulsed coherent Doppler lidar (PCDL) systems. On account of the improved glide path scanning strategy and virtual multiple wind anemometers based on the rang height indicator (RHI) modes, the small-scale meteorological phenomenon along the glide path and/or runway center line direction can be captured. In this paper, the device configuration, scanning strategies, and results of the observation data are proposed. The algorithms to identify the low-level wind shear based on the reconstructed headwind profiles data have been tested and proved based on the lidar data obtained from December 2018 to January 2019. High spatial resolution observation data at vertical direction are utilized to study the regional wind shear inducement at the 36L end of BCIA under strong northwest wind conditions.

https://www.mdpi.com/2073-4433/12/1/50/pdf

Qichao Wang

Papers

High-sensitivity refractive index and temperature sensor based on cascaded dual-wavelength fiber laser and SNHNS interferometer.

Airport low-level wind shear lidar observation at Beijing Capital International Airport

Airport low-level wind shear lidar observation at beijing capital international airport

Wavelength- and Intensity-Demodulated Dual-Wavelength Fiber Laser Sensor for Simultaneous RH and Temperature Detection

Low-Level Wind Shear Identification along the Glide Path at BCIA by the Pulsed Coherent Doppler Lidar