Free-space optical communication with m-ary pulse position modulation under strong turbulence with different type of receivers

With the exponential increase in demand for high speed precision communication system, free-space optics (FSO) has been proven to be a viable solution to this problem. This relatively new technology has gained popularity because of its wider bandwidth, comparatively greater security and relatively economical configuration. However, in FSO links, due to the atmospheric turbulence which is one of the characterizing elements in the system between the transmitter and the receiver, the magnitude of received signal intensity and also the phase of the received light signal wavers. To diminish fading in FSO systems combination of single or multiple transmitter and receiver are used. Moreover, the efficiency of the FSO systems are enhanced by utilizing the most pertinent modulation technique and channel model, making a suitable compromise between system implementation complexity and overall performance. Taking everything into account, we focus our attention in this paper on m-ary pulse position modulation (PPM) with gamma-gamma atmospheric turbulence model, under strong turbulent condition. Furthermore, APD and PIN photodiodes are used as receiver and a comparison of performance is also been made between them. The overall performance of the system are computed in the form of bit error rate (BER) and the simulation results confirm the analytical findings.