• Document: RX and Polarized CO-OFDM techniques under Atmospheric Disturbances
  • Size: 962.53 KB
  • Uploaded: 2019-02-12 21:18:28
  • Status: Successfully converted


Some snippets from your converted document:

International Journal of Engineering Research and General Science Volume 3, Issue 1, January-February, 2015 ISSN 2091-2730 Simulation and Performance Analysis of Free Space Optical Systems using Multiple TX/RX and Polarized CO-OFDM techniques under Atmospheric Disturbances Reeba Roy1, Jaini Sara Babu2, P.G Scholar1, Asst. Professor2, Dept.of ECE, T.K.M. Institute of Technology, Kerala, India E.mail: reebaroy13@gmail.com, Mob.No 9048373324 Abstract— Free Space Optical (FSO) communication is an optical communication technology in which optical data transmitted wirelessly from one place to another. High security, faster installation, licence free spectrum are its main advantages. The atmospheric conditions like haze, fog, snow etc affects the performance of FSO system. Using some techniques like Spatial Diversity, Coherent Optical Orthogonal Frequency Division Multiplexing (CO-OFDM) with dual polarization, it is possible to reduce the effects of atmospheric disturbances. This paper analyzed the performance of Multiple TX/RX FSO system and CO-OFDM FSO system under clear, haze and fog conditions using Q factor, Bit Error Rate (BER) etc. The simulations are done using a commercial optical system simulator named OptiSystem 12.0 by Optiwave. Keywords— FSO, Spatial Diversity, MIMO, OFDM, CO-OFDM, Dual Polarization, OptiSystem 12.0 INTRODUCTION Free-space optics (FSO) is one of the new optical communication technology which makes it possible to obtain the wireless optical communication with high data rate. This technology reduces the difficulty while laying optical fibers [10]. Wide license free spectrum, easy installation, secure transmission are its key advantages. Lasers and LEDs (Light Emitting Diodes) are used as sources. For long distance and short distance communication lasers and LEDs respectively are widely used. Terrestrial and outer space communications are its practical applications [8]. This technology finds application where a temporary link is needed, be it for a conference or ad-hoc connectivity in the event of a collapse of an existing communication network [12].The energy beams are collimated and sent through clear air or space from the source to the destination, rather than guided through an optical fiber. If the energy source does not produce a sufficiently parallel beam to travel the required distance, collimation can be done with lenses. At the source, the visible or IR energy is modulated with the data to be transmitted. At the destination, the beam is intercepted by a photodetector, the data is extracted from the visible or IR beam (demodulated), and the resulting signal is amplified and sent to the hardware. FSO systems can function over distances of several kilometers. As long as there is a clear line of sight between the source and the destination, communication is theoretically possible. Even if there is no direct line of sight, strategically positioned mirrors can be used to reflect the energy. The beams can pass through glass windows with little or no attenuation. Although FSO systems can be a good solution for some broadband networking needs, there are limitations. Most significant is the fact that rain, dust, snow, fog, or smog can block the transmission path and shut down the network [9]. Diversity is one of the methods to provide high quality services by sending several copies of the same signal. It gives reliability to the transmission. CO-OFDM have provided high data rate and high capacity in the optical communications.These two techniques can be used to mitigate the effects of atmospheric disturbances on FSO systems. SPATIAL DIVERSITY AND CO-OFDM TECHNIQUES Spatial Diversity Spatial diversity is one of the possibilities of including diversity based on the availability of multiple antennas at the transmitter or the receiver shown in Fig.1. It is possible to linearly increase the throughput of the channel with every pair of antennas added to the system. The use of multiple antennas allows to exploit the spatial dimension of the wireless channel and to provide reliability by simultaneously transmitting the same signal through the new degrees of freedom provided by this spatial dimension. The transmitter section and receiver sections of this system contains multiple lenses which provide the diversity. Multiple beams from the transmitters are send to different paths using lenses. Beams after propagation through the channels get attenuated due to the atmospheric disturbances. The attenuation faced by each path will be different and all the multiple copies of the transmitted signals are then received at the receiver section using lenses [7]. 743 www.ijergs.org International Journal of Engineering Research and General Science Volume 3, Issue 1, January-February, 2015 ISSN 2091-2730 Fig.1 Spatial Divers

Recently converted files (publicly available):