The effect of atmospheric turbulence on the performance of the free space optical communications

Abstract

Abstract-In free space optical (FSO) communication links, atmospheric turbulence has a significant impact on the quality of a laser beam propagating through the atmosphere. Turbulence results in intensity scintillation, which can severely impair the operation of target designation and FSO communications systems. Two important parameters for describing quality of FSO communications systems are the signal-to-noise ratio (SNR) and the bit error rate (BER). In this paper, using a modified model we analyze the effect of atmospheric turbulence on the SNR and BER for an FSO system in both weak and strong turbulence conditions. I.INTRODUCTION FSO systems or optical wireless communication have many advantages when compared with the free space radio frequency based systems such as: high bandwidth, fast deployment, license-free, light weight and reduced size. Unfortunately, free space channel where light propagates is not ideal, thus leading to and suffers from a number of affects including absorption, scattering or displacement depending on the atmospheric condition. However, in clear atmosphere, with a typical attenuation coefficient of 0.43 dB/km, a major challenge facing FSO systems is the effect of turbulence induced irradiance fluctuation on the system performance especially for a link range exceeding 1 km. Atmospheric turbulence is caused by both spatial and temporal random fluctuations of refractive index due to temperature, pressure, and wind variations along the optical propagation path through the channel [1][2][3][4][5][6][7][8]. In this paper we investigate the turbulence effect on performance of an FSO link. We show that BER performance deteriorates with the index of refraction structure parameter (C

Free Space Optical Wireless Communications under Turbulence Channel Effect

“…On the basis of Rytov's analysis [6], the relationship between refractive index structure parameter 2 n C , which characterizes the volume of atmospheric turbulence and relative variance of optical intensity, 2 ,rel I  was set by Rytov as…”

“…In wireless optical communication links, atmospheric turbulence causes fluctuations in both the intensity and the phase of the received light signal, impairing link performance [1,2]. Turbulent fluctuations in the wind velocities in the upper atmosphere mix layers of differing temperatures, densities and water vapor content causes change in refractive index [1,2].…”

“…Turbulent fluctuations in the wind velocities in the upper atmosphere mix layers of differing temperatures, densities and water vapor content causes change in refractive index [1,2]. Thus the index of refraction of each level of the atmosphere fluctuates.…”

Effect of clear atmospheric turbulence on quality of free space optical communications in Yemen

“…These include large bandwidth, fast deployment, being license-free, having low power consumption, enhanced security and insensitivity to interference, being light weight, and having reduced size [1,2]. In free-space optics, the light-wave propagates through the atmosphere channel.…”

Performance of Free Space Optical Communication System with BPSK and QPSK Modulation

“…There are few other circumstances when the performance of the FSO system may get affected which include building sway during earthquake or some temporary blockage between line-of-sight connections required for data transmission. The major issue related to this FSO system is the atmospheric turbulence which depends upon the temperature and pressure of the atmosphere [1] [2]. The power consumption of FSO link is relatively lower and they also provide greater security to the data as the data carrying light rays are confined to very narrow area as the light beam is of small diameter.…”