Free Space Optical communication systems to meet the growing need for high speed and tap proof communication systems. Free space optics causes the spatial and temporal fluctuation of light intensity. FSO is used to reduce the cost as well as in such places where physical optical wire usage is not possible. In this paper we study the quality factor of widely used modulation formats and compare the bit-error-rate performance. Analysis is performed for NRZ and RZ line codes with various different

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... avelengths using APD and PIN photodiodes receivers. Interpretation and explanation of simulation results implemented by the Optisystem through the optical high debit communication system chosen to evaluate the APD and PIN photodiodes performances in function of SNR in order to provide new perspectives for the future transmission axes.