طراحي، شبيه سازي و بررسي تجربي اثرات عوامل محيطي بر لينك مخابرات نوري فضاي آزاد

چكيده انگليسي :

Design Simulation and Experimental Investigation of environmental effects on a FSO Link Zahra Nazari Chaleshtory z nazari@ec iut ac ir January 10 2016 Department of Electrical and Computer Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi Supervisor Dr Asghar Gholami gholami@cc iut ac ir Abstract In the recent years free space optical FSO communication has been more attracted owing to the advantages of FSOcommunication with respect to other communication links The benefits of FSO communications include high bandwidth high security no electromagnetic interference quick and easy installation and low price The problems of FSO commu nication comprise the difficulty of alignment of the transmitter and the receiver so that should be in line of sight signalattenuation due to absorption and scattering phenomena various sources of noise and air turbulence In this thesis after introducing the free space optical communication systems the comparison between these systemswith other communication systems is introduced Afterwards the applications the equipment features and limiting factorsof FSO communication system are presented In order to investigate performance of FSO systems under different air channelconditions and optical equipment a complete FSO link is simulated and all effective factors on system have been considered Some of these factors are the misalignment of transmitters and receivers broadening of laser beam raining and snowing fog air turbulence wavelength dependency and link distance After then the performance of the FSO system under differentturbulence condition for different received powers is investigated Furthermore the effects of the communication linkdistance and the wavelength dependency under constant turbulence condition are investigated and the results are presented In order to investigate air turbulence a FSO communication link was installed in the university campus Experimentalresults show that turbulence after sunrise is increased and at noon reaches the maximum of its amount After that it decreasesgradually so that the minimum amount occurs at night Although in most papers temperature is known as an effective factoron turbulence by investigating the turbulence changes versus temperature we found that it is also dependent on the time ofthe day Therefore elevation angle was introduced as an affective factor on the system In order to compensate the effects of turbulence on FSO communication systems it could be important to know thefrequency range of fluctuations due to turbulence In this thesis the maximum non negligible frequency of fluctuations thatare due to turbulence was calculated by using the signal spectrum After Analyzing effective frequency band of scintillation temperature and sun declination angle and the sun elevation angle were introduced as effective factors Key Words Free Space Optical Communication Air Turbulence Refractive Index Structure Param eter

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طراحي، شبيه سازي و بررسي تجربي اثرات عوامل محيطي بر لينك مخابرات نوري فضاي آزاد

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