Investigation of single beam near-infrared free space optical communication under different weather anomalies

The Free space optics (FSO) is a wireless optical communication system that connects directly to the atmosphere, where the connection is established between transmitter and receiver within in the line of sight. The FSO poses a high-speed broadband, which is the last mile wireless optical communication, deployed relatively fast. However, there are some weather factors may affect the performance of FSO transmission. In this paper, we analyzed the performance of Non-Return to Zero (NRZ) modulation schemes, which is used in FSO communication under extreme weather conditions over a range of 2Km. The performance has been analyzed under 980nm wavelength, Bit Error Rate (BER), and Q-factor using Opt system. The largest attenuation measured is 340dB/Km, correlate to the visibility of 50m. In addition the visibility exceeding about 50m, The Kruse formula provides a good measurement of optical attenuation over long distances under the clear weather and haze conditions respectively

Atmospheric propagation issues relevant to optical communications

Atmospheric propagation issues relevant to space-to-ground optical communications for near-earth applications are studied. Propagation effects, current optical communication activities, potential applications, and communication techniques are surveyed. It is concluded that a direct-detection space-to-ground link using redundant receiver sites and temporal encoding is likely to be employed to transmit earth-sensing satellite data to the ground some time in the future. Low-level, long-term studies of link availability, fading statistics, and turbulence climatology are recommended to support this type of application

Short-Wave Infrared Lidar on Atmospheric Aerosols and Insects

This thesis focusses on the implementation of two elastic lidar (light detection and ranging) techniques for the monitoring of atmospheric aerosols and insects at short-wave infrared wavelengths. Data acquisition software was developed for a time-of-flight system, housed in the Lund University Mobile Biosphere Observatory (LUMBO), with consideration to the intended entomological application. Once up and running, the background signal and noise present in the system was characterised to facilitate future data filtering and background subtraction. The acquisition of a signal from a nearby building was achieved, but revealed that the signal-to-noise ratio of the system was too poor to be able to reliably distinguish any insect events. Attempts to improve the signal-to-noise ratio were made through the construction of a transimpedance amplifier for the receiving avalanche photodiode, but were unsuccessful. Proof-of-concept dual-band measurements on atmospheric aerosols and insects were performed with a Scheimpflug lidar system. The measurements demonstrated the high spatiotemporal resolution of the system, making possible the localisation and identification of, for example, vehicle emissions. Moreover, it was shown that the ratio between the backscattered signal in the two bands can be used to distinguish between different particle plumes, indicating the potential of the technique to identify aerosols. Furthermore, the dual-band measurements on insects demonstrated the ability of the apparatus to resolve the wing beat frequencies of the organisms in question, along with several associated higher harmonics in the Fourier transform of the time series data.Att skjuta lasrar ut i luften och på insekter: varför? En laser är en väldigt stark, enfärgad ljusstråle. De allra häftigaste lasrarna hittar man så klart bara i Star Wars, men faktum är att man kan hitta lasrar precis överallt. När polisen mäter hur fort bilar kör så sker det med en laser. När backvarnaren på bilen börjar pipa har det skett en lasermätning som avgör avståndet till ett hinder. Ovanstående mätningar sker med en teknik som heter “lidar”. Detta examensarbete går ut på att tillämpa två olika typer av lidar, time-of-flight (TOF) lidar och Scheimpflug-lidar, i mätningar utav olika aerosoler och insekter i atmosfären. “Lidar” står för “light detection and ranging” och är en teknik som går ut på att man skickar ut laserljus, antingen i form av an puls eller en kontinuerlig stråle, och analyserar ljuset som reflekteras utav hinder i laserstrålens bana. Genom att analysera ljuset som reflekteras tillbaka kan man avgöra vissa av hindrets egenskaper, till exempel hur långt borta det är eller vilka pigment det innehåller. När man skickar ut laserpulser så kallas det ”time-of-flight” (TOF) lidar – beroende på när pulsen kommer tillbaka kan man avgöra hur långt bort föremålet som reflekterar ljuset är. Med Scheimpflug-tekniken används en kontinuerlig laserstråle, och här avgör man hur långt borta ett föremål är med hjälp av den optiska Scheimpflugprincipen som även används inom fotografi. När ett föremål träffas av lasrar med olika färg (frekvens) så reflekterar det oftast färgerna olika mycket. Ett exempel är att melanin, som finns i de flesta insekter i olika halter, sprider ljus med 1550 nm våglängd mycket mer än ljus med 980 nm. Förhållandet mellan hur mycket olika färger sprids kan därför användas för att karaktärisera vad man tittar på. Lidar på aerosoler och insekter Lidar kan användas för att titta på koncentrationer av olika aerosoler i atmosfären, och även på insekter! Fördelen med tekniken är att mätningar kan göras på väldigt långt håll. Om man tillämpar lidar i atmosfärsmätningar innebär det, till exempel, att koncentrationen av olika gaser över ett stadsområde kan kartläggas för att se var flest utsläpp sker, eller helt enkelt avgöra hur förekomsten av en viss gas varierar med höjd i atmosfären. När man tillämpar lidar i entomologiskt syfte så kan man observera insekter på flera kilometers avstånd. Man kanske till och med kan identifiera dem! Olika insekter slår med vingarna olika snabbt. Just insektsvingarna brukar reflektera laserljuset starkare än insektskroppen; om insekten då befinner sig i laserstrålen tillräckligt länge så kan man se vingslagen som en variation i styrkan på signalen som man får tillbaka. Informationen om vingslagsfrekvensen kan hjälpa till att identifiera insekten, någonting som är användbart om man vill övervaka en viss insektsart t.ex. om man vill veta hur förekomsten av malariamyggor varierar med tid inom ett visst område. Vi har jobbat med ett TOF-system som kan detektera insekter och deras vingslagsfrekvenser på flera kilometers håll. Vi har även visat att ett Scheimpflug-system som använder sig utav två olika våglängder potentiellt kan användas för att identifiera både aerosoler och insekter

Exploring Himawari-8 geostationary observations for the advanced coastal monitoring of the Great Barrier Reef

Larissa developed an algorithm to enable water-quality assessment within the Great Barrier Reef (GBR) using weather satellite observations collected every 10 minutes. This unprecedented temporal resolution records the dynamic nature of water quality fluctuations for the entire GBR, with applications for improved monitoring and management

Establishment Network by Using FSO Link Based on MD Code for Hybrid SCM-SAC-OCDMA Wireless System

Since the wireless systems are working under nature environments and influenced by turbulence, weather in Iraq that leads to extended amount of fading signal, dissipation or attenuation. Basic “hybrid Subcarrier Multiplying Spectral Amplitude Coding (SCM-SAC) of Optical Code Division Multiple Access (OCDMA)" indoor or outdoor optical system depends on generally “Multi-Diagonal (MD)" security code by using optical space known as “Free Space Optic (FSO)" that was proposed in this work. It is found that the mention hybrid wireless systems can be used in operating mesh networks. The main proposed idea of hybrid optical technique was analyzed and simulated by normally taking into simulation account that the directly effecting by rain and haze attenuations. In addition, there are mention and description for atmospheric effects, FSO mesh network, modulation scheme, simulation, and the data security. From simulation results, the hybrid system using MD code produces reduced “bit-error rate (BER)" at heavy storm rain to distance or range of 500 m and at drizzle rain up to 2500 m range. And also investigates the performance of using the proposed system with radio over fiber (RoF) for UWB signals through indoor propagation in building applications of wireless channel

NASA participation in the 1980 PEPE/NEROS project: Data archive

Eight experimental air quality measurement systems were investigated during July and August 1980 as part of the EPA PEPE/NEROS fiel measurement program. Data from those efforts have been entered into an archive that may be accessed by other researchers. The data sets consists of airborne measurements of regional mixed layer heights and aerosol and ozone distributions as well as point measurements of meteorological parameters and ozone obtained during diurnal transitions in the planetary boundary layer. This report gives a discussion of each measurement system, a preliminary assessment of data quality, a description of the archive format for each data set, and a summary of several proposed scientific studies which will utilize these data

Recovery of forest canopy parameters by inversion of multispectral LiDAR data

We describe the use of Bayesian inference techniques, notably Markov chain Monte Carlo (MCMC) and reversible jump MCMC (RJMCMC) methods, to recover forest structural and biochemical parameters from multispectral LiDAR (Light Detection and Ranging) data. We use a variable dimension, multi-layered model to represent a forest canopy or tree, and discuss the recovery of structure and depth profiles that relate to photochemical properties. We first demonstrate how simple vegetation indices such as the Normalized Differential Vegetation Index (NDVI), which relates to canopy biomass and light absorption, and Photochemical Reflectance Index (PRI) which is a measure of vegetation light use efficiency, can be measured from multispectral data. We further describe and demonstrate our layered approach on single wavelength real data, and on simulated multispectral data derived from real, rather than simulated, data sets. This evaluation shows successful recovery of a subset of parameters, as the complete recovery problem is ill-posed with the available data. We conclude that the approach has promise, and suggest future developments to address the current difficulties in parameter inversion

Development of laser spectroscopy for scattering media applications

Laser spectroscopy for both large and small spatial scales has been developed and used in various applications ranging from remote monitoring of atmospheric mercury in Spain to investigation of oxygen contents in wood, human sinuses, fruit, and pharmaceutical solids. Historically, the lidar group in Lund has performed many differential absorption lidar (DIAL) measurements with a mobile lidar system that was first described in 1987. During the years the lidar group has focused on fluorescence imaging and mercury measurements in the troposphere. Five lidar projects are described in this thesis: fluorescence imaging measurement outside Avignon, France, a unique lidar project at a mercury mine in Almadén, Spain, a SO2 flux measurement at a paper mill in Nymölla, Sweden, and two fluorescence imaging projects related to remote monitoring of vegetation and building facades characterization. A new method to measure wind speed remotely in combination with DIAL measurements is presented in this thesis. The wind sensor technique is called videography and is based on that images of plumes are grabbed continuously and the speed is estimated by the use of image processing. A technique that makes it possible to measure a gas in solids and turbid media, non-intrusively, is presented in this thesis. The technique is called gas in scattering media absorption spectroscopy (GASMAS) and has been used since 2001. The GASMAS concept means that a traditional spectroscopy instrument, based on tunable diode lasers, is used but the gas cell or optical path is replaced by a material that strongly scatters light. Mostly, wavelength modulation spectroscopy has been utilized. Four projects using the GASMAS technique to measure gases in fruit, wood, pharmaceutical solids, and human tissue are presented. Two applications have shown a great potential so far; to be able to diagnose the health of human sinuses and gas ventilation in sinuses, and to measure gas inside pharmaceutical solids. A performance analysis of the GASMAS technique is included. This thesis also presents a technique to suppress optical noise in fiber lasers and how to construct a compact tunable diode laser spectroscopy system based on plug-in boards for a standard computer

Phase-sensitive plasmonic biosensor using a portable and large field-of-view interferometric microarray imager

Nanophotonics, and more specifically plasmonics, provides a rich toolbox for biomolecular sensing, since the engineered metasurfaces can enhance light–matter interactions to unprecedented levels. So far, biosensing associated with high-quality factor plasmonic resonances has almost exclusively relied on detection of spectral shifts and their associated intensity changes. However, the phase response of the plasmonic resonances have rarely been exploited, mainly because this requires a more sophisticated optical arrangement. Here we present a new phase-sensitive platform for high-throughput and label-free biosensing enhanced by plasmonics. It employs specifically designed Au nanohole arrays and a large field-of-view interferometric lens-free imaging reader operating in a collinear optical path configuration. This unique combination allows the detection of atomically thin (angstrom-level) topographical features over large areas, enabling simultaneous reading of thousands of microarray elements. As the plasmonic chips are fabricated using scalable techniques and the imaging reader is built with low-cost off-the-shelf consumer electronic and optical components, the proposed platform is ideal for point-of-care ultrasensitive biomarker detection from small sample volumes. Our research opens new horizons for on-site disease diagnostics and remote health monitoring.Peer ReviewedPostprint (published version