The Investigation of SNR for Free Space Optical Communication Under Turbulence (original) (raw)
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Study of the Atmospheric Turbulence in Free Space Optical Communications
In this paper the effect of atmospheric turbulence on free space optical (FSO) communications is investigated experimentally by designing a turbulence simulation chamber. The distributions of bits '0' and '1' levels are measured with and without turbulence. The bit error rate (BER) is then obtained from the distributions. The temperature gradient within the channel is less than 6 °C resulting in turbulence of log irradiance variance of 0.002. The received average signal is measured and used to characterise the simulated turbulence strength. We then evaluated the BER with turbulence and found that from an error free link in the absence of turbulence, the BER increased significantly to about 10 -4 due to the turbulence effect.
Atmospheric Turbulence Effect on Free Space Optical Communications
This work discusses the effect of atmospheric turbulence on wavelengths transmission in free space. The Rytov variance calculated for plane and spherical waves, were Rytov variance of spherical waves less than from plane waves, on the other hand in spherical waves the values of wavelength 1550 nm less than from the other wavelengths. Scintillation attenuation was calculated depends on Rytov approximation for wavelengths (1550, 850, 633, 532) nm, scintillation attenuation values of the wavelength 1550 nm less than from the other wavelengths. The wavelength 1550nm has a good signal to noise ratio(S/N) from the other wavelengths. The distance between the transmitter and receiver links was (0-1000) m, we take into account the refractive index structure parameter at different turbulence (10 -16 low, 10 -15 medium, 10 -14 high) m -2/3 for all calculations.
Free space optical (FSO) communication technology is a promising candidate for next generation broadband networking, due to its large bandwidth potential, unlicensed spectrum, excellent security and quick and inexpensive setup and used to solve the “last mile” problem to bridge the gap between the end user and the fiber-optic infrastructure already in place [1]-[2]. Its unique properties make it also appealing for a number of other applications, including metropolitan area network extensions, local area network connectivity, fiber backup, back-haul for wireless cellular networks, redundant link and disaster recovery. In FSO communications, optical transceivers communicate directly through the air to form point-to-point line-of-sight (LOS) links. One major impairment over FSO links is the atmospheric turbulence, which occurs as a result of the variations in the refractive index due to inhomogeneities in temperature and pressure fluctuations [3]-[4]. Atmospheric turbulence has been st...
Iet Communications, 2009
Turbulence fading is one of the main impairments affecting the operation of free-space optical (FSO) communication systems. The authors study the performance of FSO communication systems, also known as wireless optical communication systems, over log-normal and gamma -gamma atmospheric turbulenceinduced fading channels. These fading models describe the atmospheric turbulence because of its very good agreement with experimental measurement data. Closed-form expressions for the average (ergodic) capacity and the outage probability are derived for both statistical models. Another contribution of this work is a study of how the performance metrics are affected by the atmospheric conditions and other parameters such as the length of the link and the receiver's aperture diameter. The derived analytical expressions are verified by various numerical examples and can be used as an alternative to time-consuming Monte-Carlo simulations.
Analysis of free space optical link in turbulent atmosphere
Optik - International Journal for Light and Electron Optics, 2014
Free space optical (FSO) communication is an upgraded supplement to the existing wireless technologies. FSO technology provides vast modulation bandwidth, unlicensed spectrum, cost effective deployment, low power consumption and less mass requirement. Today, researchers are preliminary focused to use the free space communication systems for inter satellites links. In this paper, the performance analysis of FSO communication link in weak atmospheric turbulence has been analyzed for different atmospheric transmission windows using OOK modulation. The analysis has been done using bit error rate as the performance metric. The effect of attenuation on the link performance has been investigated by varying distance between transmitter and receiver for a given power and data rate. Further, BER performance analysis has been carried out for varying data rate and transmitted power. Also, the effect of attenuation on received optical power has been studied. The work has been performed in OptSim environment.
Feasibilty Study of Free Space Optical Communication Link Through Atmospheric Turbulent Channel
Conference on Optoelectronic and Microelectronic Materials and Devices, 2004.
Free space optical communication is an effective means of communication at high bit rates over short distances. Rapid deployment, lightweight, high security, are important features of this system. However, attenuation due to adverse weather conditions & scattering due to turbulence are to be mitigated. In this paper the performance of a short distance FSO link in the presence of atmospheric turbulence has been evaluated.
Capacity analysis of free space optical communication system under atmospheric turbulence
Optical and Quantum Electronics, 2020
In this paper, the analytical channel capacity of the free space optical (FSO) system under weak, moderate and strong turbulence is derived. The FSO channel statistics follows the log-normal distribution under weak turbulence and follows the Gamma-Gamma distribution under moderate and strong turbulence. The three generally used adaptive transmission schemes in FSO communication system are as follows (1) optimal simultaneous power and rate adaptation, (2) optimal rate adaptation with constant transmit power, and (3) truncated channel inversion with a fixed rate. The closed-form approximations for the average ergodic channel capacity for these adaptive transmission schemes under different atmospheric turbulence without any pointing error are derived. Simulation results depict the excellent agreement of the proposed analytical models with the Monte Carlo simulation.
Studies of the Effects of Atmospheric Turbulence on Free Space Optical Communications
2005
Even after several decades of study, inconsistencies remain in the application of atmospheric turbulence theories to experimental systems, and the demonstration of acceptable correlations with experimental results. This dissertation shows a flexible empirical approach for improving link performance through image analysis of intensity scintillation patterns coupled with frame aperture averaging on a free space optical (FSO) communication link. Aperture averaging is the effect of the receiver size on the power variance seen at the receiver. A receiver must be large enough to collect sufficient power and reduce scintillation effects at a given range, but must also be of practical size. An imaging system for measuring the effects of atmospheric turbulence and obscuration on FSO links will be presented. Weak and intermediate turbulence results will be shown for an 863 meter link at the University of Maryland. Atmospheric turbulence has a significant impact on the quality of a laser beam propagating through the atmosphere over long distances. Turbulence causes intensity scintillation and beam wander from propagation through turbulent eddies of varying sizes and refractive index. This can severely impair the operation of target designation and FSO communications systems. A new geometrical model to assess the effects of turbulence on laser beam propagation in such applications will be presented. The atmosphere along the laser beam propagation path is modeled as a spatial distribution of spherical bubbles with refractive index discontinuity statistically distributed according to various models. For each statistical representation of the atmosphere, the path of rays is analyzed using geometrical optics. These Monte Carlo techniques can assess beam wander, phase shifts and aperture averaging effects at the receiver. An effective C n 2 can be determined by correlating beam wander behavior with the path length. In addition, efficient computational techniques have been developed for various correlation functions that are important in assessing the effects of turbulence. The Monte Carlo simulations are compared with the predictions of wave theory. This is the first report to present weak and intermediate turbulence results using an efficient imaging technique. It is also the first report to geometrically simulate aperture averaging.