- 标题
- 摘要
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- 实验方案
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Free Space Optical Communication (System Design, Modeling, Characterization and Dealing with Turbulence) || 6. Quality metrics and reliability analysis of ground-to-ground free space laser communication in different weather conditions together with beam steering system
摘要： Over the past two decades Free Space Optical Communication (FSOC) has become more and more interesting as an adjunct or alternative to Radio Frequency (RF) communication. Optical wave propagation in an FSOC channel is severely affected by turbulent atmospheric parameters and they lead to the degradation of the data transmission quality and reliability. Among the various atmospheric effects, beam wandering is the main cause for major power loss and cannot be solved without incorporation of a Beam Wandering Compensation (BWC) control system. Therefore, a closed form treatment describing beam wandering effect mitigation is required. Simplex FSOC data transmission (data rate is 155 Mbps) transmitter-receiver experimental setups are established for the data link range of 0.5 km at an altitude of 15.25 m at the college campus. A near IR 850 nm optical source is used for data transmission. The more accurate values of atmospheric attenuation (Atten) and turbulence strength (C2n) are obtained using the new models developed according to local weather data. The transmittance of the FSOC channel is calculated using the estimated atmospheric attenuation. The methods of measuring the Q-factor and Bit Error Rate (BER) by postprocessing the received signal are described and used to validate the performance of the FSOC system. The improvements on received signal strength and centroid stability by incorporating the BWC control system are analyzed with various communication key parameters in the very weak to very strong atmospheric turbulence conditions. The average BER at a value of 9.82 ? 10?9 is maintained with the Q-factor value of ≈ 6 in almost all atmospheric turbulence conditions with compensating beam wandering effects, i.e. pointing error losses. Evidence of the suitability and effectiveness of the developed controller in terms of received power (Pr), transmittance (T), eye diagram, Q-factor, Signal to Noise Ratio (SNR), BER, link margin and decoding decision threshold values are comprehensively analyzed through experimental results and reported in this chapter.
关键词： atmospheric turbulence,Beam Wandering Compensation (BWC),Q-factor,Signal to Noise Ratio (SNR),Bit Error Rate (BER),Free Space Optical Communication (FSOC)
更新于2025-09-12 10:27:22
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[IEEE 2019 24th OptoElectronics and Communications Conference (OECC) and 2019 International Conference on Photonics in Switching and Computing (PSC) - Fukuoka, Japan (2019.7.7-2019.7.11)] 2019 24th OptoElectronics and Communications Conference (OECC) and 2019 International Conference on Photonics in Switching and Computing (PSC) - Scintillation Suppression by Gain Saturated SOA with Differential Signal Transmission in Free Space Optical Communication
摘要： This paper proposes scintillation reduction by gain saturated SOA with differential signal transmission in FSO. Experimental results show that scintillation and extinction ratio degradation from gain saturated SOA are compensated effectively by the proposed technique.
关键词： atmospheric turbulence,extinction ratio,free space optical,differential signal,fixed threshold decision,Semiconductor optical amplifier
更新于2025-09-11 14:15:04
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Fiber Optic and Atmospheric Optical Communication || Transmission of Information Data in Optical Channels: Atmospheric and Fiber Optics
摘要： The chapter discusses the transmission of information data in optical channels, focusing on atmospheric and fiber optics. It highlights the challenges posed by atmospheric effects on wave propagation, including attenuation, optical signal amplitude, and phase scintillations caused by atmospheric turbulence. The chapter also explores the impact of these phenomena on the data stream parameters, such as bit error rate (BER) and signal-to-noise ratio (SNR), and proposes methods to mitigate these effects to achieve high performance in optical communication links.
关键词： atmospheric turbulence,bit error rate,optical communication,spectral efficiency,signal-to-noise ratio,scintillation,fading,Ricean K-factor,fiber optics,multipath channel
更新于2025-09-11 14:15:04
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Removing Atmospheric Turbulence Effects in Unified Complex Steerable Pyramid Framework
摘要： Simultaneously removing atmospheric turbulence-induced geometric distortion and blurry degradation is a challenging task. In this paper, we propose an effective method to remove or at least reduce turbulence effects in unified complex steerable pyramid (CSP) framework. The proposed method first decomposes the degraded image sequence by CSP. Then, the local motion and energy information of the image sequence can be represented by multiscale and multidirectional phases and amplitudes. To mitigate turbulence-induced random oscillation, we use temporal average phase as the initial reference phase. Then, the reference phase is iteratively corrected, using the proposed phase correction method which is capable of correcting the large displacement. To reduce blurry degradation, optimal amplitude selection and fusion methods are proposed to reduce blur variation and CSP reconstruction errors. Finally, the corrected phase and fused amplitude can be synthesized to generate a reconstructed image. To further enhance the image quality, a blind deconvolution approach is adopted to deblur the reconstructed image. Through a variety of experiments on the simulated and real data, experimental results show that the proposed method can effectively alleviate the turbulence effects, recover image details and significantly enhance visual quality.
关键词： image restoration,Atmospheric turbulence,complex steerable pyramid
更新于2025-09-10 09:29:36
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Novel approximate and asymptotic expressions of the outage probability and BER in gamma-gamma fading FSO links with generalized pointing errors
摘要： In this paper, a novel closed-form approximate probability density function (PDF) at high signal-to-noise ratio (SNR) for the composite gamma-gamma (GG) atmospheric turbulence with a generalized pointing error model using the Beckmann distribution is derived in terms of an appropriate gamma distribution by a moment generating function (MGF) matching approach. Based on the obtained PDF, novel closed-form approximate and asymptotic expressions for the outage probability and the average bit-error rate (BER) are derived. Then, the average BER performance and the outage performance of the considered FSO system at high SNR are investigated with different turbulence conditions, receiver aperture sizes, nonzero boresight, and different jitter variances. Numerical results and Monte Carlo simulation results verify the accuracy of our derived approximate and asymptotic expressions over a wide SNR range. This work can be further extended as well to diversity links.
关键词： High SNR,Gamma-gamma distribution,Free-space optical communication,Beckmann distribution,Pointing errors,Atmospheric turbulence
更新于2025-09-10 09:29:36
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High-resolution speckle imaging
摘要： One of the most exciting and challenging pursuits of 21st-century astrophysics is to identify an exoplanet—that is, a planet orbiting an alien sun—on which life may exist. Such a planet is likely to reside in the habitable zone of its sun, meaning that it can harbor liquid water on its surface. Many astrobiologists posit that a life-harboring planet must also be small, rocky, and similar in density to our own. One critical input to any future discovery will be a precise determination of the planet radius, a value that will probably be obtained with the help of high-resolution speckle imaging.
关键词： speckle imaging,exoplanet,adaptive optics,atmospheric turbulence,high-resolution imaging
更新于2025-09-10 09:29:36
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[IEEE 2018 11th International Symposium on Communication Systems, Networks and Digital Signal Processing (CSNDSP) - Budapest (2018.7.18-2018.7.20)] 2018 11th International Symposium on Communication Systems, Networks & Digital Signal Processing (CSNDSP) - M-ary ASK Modulation in FSO System with SIMO over Log-normal Atmospheric Turbulence with Pointing Errors
摘要： In this paper, we analyze the average bit error rate (BER) and outage probability performances of a free-space optical (FSO) system. We used M-ary amplitude shift keying modulation (M-ary ASK) scheme. Lognormal atmospheric turbulence with the effect of pointing errors (PE) and, path loss is employed to model the FSO channel. However, to overcome the degradation in BER performance due to pointing errors, the single-input-multiple-output technique with maximal ratio combining diversity is used. For instance, the average BER for M=2 without using SIMO is 1.944×10?6 at 0 dBm transmitted power, while the average BER for M=2 with using SIMO technique with N=2 become 1.512×10-11 at 0 dBm. The asymptotic expression for average BER and the closed-form expression for outage probability are both driven and tested with and without SIMO.
关键词： pointing errors,Free Space Optical,log-normal atmospheric turbulence,single-input-multiple-output (SIMO),outage probability,M-ary amplitude shift keying modulation (M-ary ASK)
更新于2025-09-10 09:29:36
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Evolution of degree of polarization of partially coherent beams propagation in slant and horizontal atmospheric turbulence
摘要： In this paper, the analytical expressions for the degree of polarization (DoP) of the electromagnetic Gaussian Schell-model (GSM) beam propagating along a slant path in atmospheric turbulence are obtained. The expressions are used to analyze factors such as the waist radius, amplitude ratio, wavelength, and refractive-index structure constant of the polarization properties of the GSM beam, and we come to some new conclusions. The main results that when the components of the waist radius are equal (rx = ry), there is a waist radius within 2 cm \ rx \ 4 cm that can provide the most concentrated DoP distribution, and the axis point DoP will eventually approach the initial value as the transmission distance increases, implying that it exhibits self-recovering characteristics. In addition, compared to a horizontal path, the DoP distribution of the GSM beam propagating along a slant path is more concentrated, and the propagation distance corresponding to the maximum axis point DoP is longer. Therefore, when the GSM beam propagates along a slant path, the detector can receive information at longer distances. The research results provide a theoretical support for the control of the polarization state of local beam in coherent optical communication systems.
关键词： Coherent optical communication systems,Polarization control,Atmospheric turbulence
更新于2025-09-10 09:29:36
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Propagation characteristics of optical vortex pulse in atmospheric turbulence
摘要： To understand the in?uence of atmospheric turbulence on optical vortex pulse, the transmission equation of vortex pulse beam is derived. The multiple phase-screen method is used to calculate the intensity distribution of vortex beam that in?uenced by atmospheric turbulence. Some main parameters, such as pulse width, the topological charge, strength of turbulence and propagation distance, are discussed in detail to show the propagation characteristics of the vortex pulse in atmospheric turbulence. Results show that with the increasing of the strength of turbulence, the vortex pulse beam is distorted more seriously. For the parameters of the vortex pulse itself, with the increasing of pulse width, the ability of resisting distortion is decreasing.
关键词： Beam distortion,Optical vortex pulse,Intensity distribution,Atmospheric turbulence
更新于2025-09-10 09:29:36
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[IEEE 2018 11th International Symposium on Communication Systems, Networks and Digital Signal Processing (CSNDSP) - Budapest (2018.7.18-2018.7.20)] 2018 11th International Symposium on Communication Systems, Networks & Digital Signal Processing (CSNDSP) - FSO Communication for High Speed Trains: Blind Data Detection and Channel Estimation
摘要： We consider an free-space optical (FSO) system for high-speed trains where the sampling clock offset is randomly changing and the receiver does not have any information on the instantaneous channel fading coef?cient. Based on the use of multiple samplers at the receiver, we propose a novel sequence blind detection method, thus without requiring any pilot symbol. Furthermore, using the detected data, we propose a channel estimation scheme for the considered system.
关键词： Free-space optical communications,atmospheric turbulence,time synchronization,data detection
更新于2025-09-10 09:29:36