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Free space optical communication is the most growing communication because it is easy to install and has a high speed because the signal is transmitted in the air. So that will introduce the atmospheric affect in the optical wave propagation. Atmospheric turbulence causes fluctuations in both the intensity and the phase of the received signal. So we need to study the effect and the limitation if we introduce a free space optical communication system with dual wavelength (980 nm, 1550 nm). Also studying the effect of turbulence when using two different wavelengths.
Introduction
Free space optical communication is a kind of communication that use light propagation to send data between two points. Free Space Optics are capable of up to 2.5 Gbps of data, voice and video communications through the air, allowing optical connectivity without requiring fiber-optic cable or securing spectrum licenses. So we can use LED’s or Laser for transmission data. Free Space Optics (FSO) technology is relatively simple. It's built on a laser transmitter and a receiver to provide full duplex capability. Each FSO unit uses a high-power optical source, a lens that transmits light through the atmosphere to another lens receiving the information. The receiving lens connects to a high-sensitivity receiver via optical fiber. Because the transmission in occurred in air it is easily upgradable. FSO send a light beam from one point to another using low power lasers in the teraHertz spectrum. This beam is transmitted by laser light focused on photon detector receivers. These receivers collect the photon stream and transmit digital data. If there is a clear line between the two point FSO can operate on a distance of several kilometers as long we have a powerful transmitter.
Features of the laser communications system
Information usually in the form of digital data, data is entered to be