Channel Robust Free Space Optical Transmission Using Differential On-Off Keying Technique

In this paper, we propose a differential on-off keying (DOOK) technique for free space optical (FSO) communications. Intensity fluctuation caused by atmospheric turbulence is the key factor in intensity modulation and direct detection (IM/DD) systems. Based on quasi-stationary characteristics of atmospheric channel, we used difference of sequential symbols for DOOK detection. The proposed technique is implemented through decision process to compare difference of sequential symbols with the certain threshold. Information of channel model and noise power is used for estimating the optimum fixed threshold in order to obtain optimal bit error rate (BER) performance. The transmission simulation is conducted according to various channel and the result shows the proposed technique is robust for FSO channel.