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

Abstract

Free space optical (FSO) communication is one of the most recently developed modes of wireless communication. FSO is a technique used to convey data carried by a laser beam through the atmosphere. While FSO offers a broadband service, it requires a line of sight communication between the transmitter and receiver. The atmosphere has effects on the laser beam passing through it. For instance, the quality of data received is affected by the scattering and atmospheric turbulence. The atmospheric turbulence is caused by both temporary and special random fluctuations of the refractive index along the optical propagation path. Clear air turbulence impairs the performance of the FSO due to the fluctuation in the intensity of the laser beam. By referring to the two criteria, namely bit error rate (BER) and signal to noise ratio (SNR), this work includes analysis of the effect of atmospheric turbulence on FSO systems in Yemen by using an appropriate model.

Free Space Optical Communications — Theory and Practices

“…For a 4000 m transmission range, the variance is about 0.56 for 850 nm, 0.42 for 1000 nm, and 0.25 for 1550 nm. These results show that the use of a wavelength of 1550 nm can reduce the variance "atmospheric turbulence" effect on the FSO systems [37]. From the above results, we conclude that the expansion of the spot size of the beam depends on the distance between sender and receiver as indicated on Fig.32, and on the atmospheric turbulence along the transmission range as indicated on Fig.…”

“…With an appropriate design of aperture averaging, the received optical power could be increased and the effect of the scintillation can be dumped. With turbulence, the SNR is expressed as follows [37]:…”

Analysis of Free-Space Optics Development

“…The value of BER also depends on the modulation scheme. For FSO links with the on-off keying modulation, the BER performance is characterized by a signal to noise ratio (SNR) [33]:…”

Characteristics of Cμ2 derived from ultrasonic anemometer in an urban boundary layer

“…The most signifi cant parameter that is used in expressing optical turbulence is refractive index structure function coeffi cient (C μ 2 ) which is a function of position, time and height. When a light beam propagates through such a turbulent medium its interaction with the eddies produces random variations in the amplitude and phase of the signal (Ishimaru, 1997;Altowij, Alkholidi & Habib, 2010). These variations in the refractive index of the Earth's atmosphere are responsible for random fl uctuations in the signal carrying laser beam intensity called scintillations.…”