Experimental Investigation of the Performance of OOK-NRZ and RZ Modulation Techniques under Controlled Turbulence Channel in FSO Systems

A number of modulation schemes have been proposed and thoroughly studied for the successful operation of the optical wireless communication (OWC). Each modulation scheme has its advantages and disadvantages for the particular channel conditions. In this paper the comparative studies of on- off keying (OOK) return-to-zero (RZ) and non-return-to-zero (NRZ) modulation techniques have been carried out experimentally under controlled turbulence channel for free space optics (FSO) communication link. Weak turbulence effect is generated within a controlled chamber of 5.5m length. The experiment is performed with a temperature gradient of �¤& at wind velocity of 1m/s. A laser source is modulated using the selective modulation schemes and optical signal is allowed to propagate through the turbulence simulated chamber. The received signal is analyzed to measure the true effect of turbulence on the optical beam carrying information. The eye- diagram and signal distributions are analyzed for comparative studies. This research work is carried out under the EUCOST ACTION IC0802 project.