Abstract:
This thesis investigates the performance of terrestrial free-space optical communication (FSO) system based on the On-Off keying (OOK) and Pulse Position Modulation(PPM)inthepresenceofatmosphericturbulenceandpointingerror. The performance analysis is carried out on basis of the bit error rate (BER). Optical signal traversing the atmospheric channel suffers from attenuation due to scattering and absorption by aerosols, fog, atmospheric gases and precipitation. The effect of atmospheric turbulence of an FSO system is presented analytically and experimentally verified both in case of single hop (with OOK modulation) and multiple hop (with PPM modulation). 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. In this thesis, analysis of BER is done under weak atmospheric turbulence i.e. Log-normally distributed and transmission using single hop and multi-hop which is established on amplify-andforward relays. We illustrate combined probability density function for multi-hop FSO system. Changing the modulation order, the BER performance is analyzed. Using multiple hop, the performance is also investigated and power penalty, the total transmission distance are also calculated as the derived curves for a fixed BER in this thesis. Finally, the numerically found results show that the multiple hop transmission along with PPM is a good solution for obtaining desired Bit Error Rate (BER) under the effects of weak turbulence and pointing error than OOK based single hop.
Description:
All praises to almighty Allah, the most gracious and the most merciful, who bestowed upon us the will, for the successful competition of our thesis paper within the scheduled time, without which our paper would not have been possible.
With due sincerity, we would like to express our heartfelt gratitude and indebtedness to the thesis supervisor Professor Dr. Satya Prasad Majumder for his valuable support and guidance in our BSc program. Throughout this entire thesis work he gave us invaluable advices, continuous guidance and constant encouragement. He has helped us to come to terms with the basic concept of free space optical communication and its forthcoming potential. We are very proud that we had the chance to work with him. We are also thankful to the Department EECE, MIST for providing us an excellent research environment and facilities.
