MIMO OPTICAL COMMUNICATIONS AND IMAGING THROUGH TURBULENT CLOUDY ATMOSPHERE
Open Access
- Author:
- Hajjarian Kashany, Zeinab
- Graduate Program:
- Energy and Geo-Environmental Engineering
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- August 25, 2009
- Committee Members:
- Mohsen Kavehrad, Dissertation Advisor/Co-Advisor
Mohsen Kavehrad, Committee Chair/Co-Chair
Iam Choon Khoo, Committee Member
Zhiwen Liu, Committee Member
Dr Jun Shu, Committee Member - Keywords:
- Scattering
Optical
MIMO
Imaging
Communications
Turbulence - Abstract:
- Since the invention of Laser in 1960, Free Space Optics has been revolutionized in every aspect. The ever-increasing demand for high data rate communications, congestion of useful parts of the radio frequency (RF) band, and the costly installation of cable for last mile communications has spurred the use of Free Space Optical (FSO) communication as a novel broadband access technique. Another application of Free Space Optics, i.e. Optical imaging is preferred over RF counter parts due to its higher resolution, faster area search rate, and ease of interpretation by a human observer. All these benefits can be achieved due to smaller wavelength of optical waves. Free Space Optics; however, has its own challenges. In contrast to radio wavelengths, the optical wavelengths are of the same order of particle size in vapor; therefore, such particles interact with laser beams and scatter them. As a result of these multiple scattering, laser beam is broadened and the energy is redistributed in space and time. Furthermore, in an optical imaging system, back-scattered light impinges on the receiver and gives rise to a steady background noise, and hence limits the contrast. Moreover, refractive index variations, across the optical wave propagation path, cause amplitude and phase fluctuations in the received wave-front. While in optical communications system, amplitude and phase fluctuations give rise to fading, optical imaging systems experience severe resolution degradation due to PSF broadening. Multiple-Input Multiple-Output (MIMO) configuration is proved to be effective in fading RF channels. Moreover, multi-spot diffuse configuration, first introduced by Yun and Kavehrad [9], has a great potential to be exploited in optical imaging. In this dissertation, we propose MIMO imaging and communications systems and investigate their performance under various atmospheric conditions. Then using restoration techniques, we try to find a solution for performance degrading atmospheric phenomena.