Performance improvement of optical wireless communication through fog with a decision feedback equalizer

Radiative effects of atmospheric aerosols on the average channel capacity of free-space optical communication systems

Free-space optical (FSO) communication systems employ unguided light beams propagating through the atmosphere to carry a large volume of data. The reliability of such data transfer can be hampered by various atmospheric effects. Based on an analytical model of a differential phase-shift keying FSO system through exponentiated Weibull turbulence, we investigate the effectiveness of beam width optimization and improved beam alignment, along with aperture averaging on the average channel capacity. Our results show significant signal deterioration produced due to the aerosol-induced optical turbulence, which substantially shadows the performance gain achieved through beam width optimization. Strong aerosol-induced atmospheric heating and the consequent enhanced optical scintillations result in reduction of the channel capacity by as much as 50% of its value when these effects are not considered or negligible. FSO systems are more resilient to aerosol-induced optical turbulence when the normalized beam width is less, and the average channel capacity can be significantly improved by improved beam alignment. These variations are weakly dependent under poor transmitter-receiver alignment conditions. Furthermore, the receiver aperture has a strong control on the link performance. While FSO systems with higher magnitude of normalized beam width have improved performance under all aperture diameter conditions; for a given beam configuration, large aperture diameter ensures a significant improvement in the link performance due to reduction in effects of scintillations.

Pointing and tracking errors due to localized distortion induced by a transmission-type antenna in intersatellite laser communications

A truncated ellipse Gaussian model to express localized distortion is developed to a transmission-type optical antenna, based on which the effects of localized deformation on pointing and tracking errors are researched. It is shown that localized distortion has the greatest influence on pointing and tracking errors when distortion deepness h approximately 0.8 lambda, which does not depend on other distortion parameters. To reduce the impact of localized deformation on pointing and tracking errors, the machining precision of the objective lens of the transmission-type antenna should be much better than 0.8 lambda. The requirement of the machining precision for lenses is lower than that for mirrors. The maxima of pointing and tracking errors due to the localized distortion with different radii are given. We hope the results can be used in the design of intersatellite optical communication systems.