Analysis of Free Space Optic Link using Wavelength Diversity over Different Channel Models

Abstract

In recent years, free space optic (FSO) communication has gained significant impor- tance. It has many advantages over radio frequency (RF), such as high data rates, license-free operation, high security, and ease of deployment. The performance of FSO systems can be highly affected by fog and atmospheric turbulence. The turbu- lence effect is one of the biggest problems that face FSO systems, which degrades the overall system's performance. In this thesis, to mitigate the turbulence induced fading the information signal-carrying laser beam irradiance (intensity) is transmitted on more than one wavelength at same time by using wavelength diversity technique. As the refractive index variation will be different for different wavelengths, the fading is not same for different wavelength. The statistical analysis of the random irradiance

uctuations in FSO links is showed through the probability density function (PDF) of different channel model such as Lognormal, Gamma-Gamma, K channel and Ex- ponentiated Weibull channel, from which we can measure the link performance in terms of outage probability and the bit error-rate (BER). The objective of this thesis is to examine the outage probability and BER performance of FSO systems with wavelength diversity over K-channel and Exponentiated Weibull channel. The source information was transmitted onto three carrier wavelengths 1550 nm, 1310 nm, and 850 nm. At receiver side, Optimal Combining (OC), Equal Gain Combining (EGC) and Selection Combining (SC) diversity schemes have been deployed to combine mul- tiple carriers. The achieved results demonstrate that the wavelength diversity improve the performance of the FSO communication link, but at a significant escalation of the system's complication and budget.