Studying the BER performance, power- and bandwidth- efficiency for FSO communication systems under various modulation schemes

In this paper, we are interested in more efficient modulation techniques that achieve a good Bit Error Rate (BER) performance, bandwidth and power efficiencies for Free Space Optics (FSO) Communication Systems. The theoretical expressions of the BER versus the Signal-to-Noise Ratio (SNR), the bandwidth efficiency, and the normalized power requirements for NRZ-OOK, RZ-OOK, PPM, PAM, DPSK, BPSK, and QPSK modulation schemes for FSO communication systems are introduced, and a comparison between these modulation techniques is presented. The comparative study of the PPM and PAM schemes is also discussed and showed that for similar SNR, PPM offered improved BER performance. In addition, the BER performance under BPSK modulation is better compared to OOK, RZ-OOK, PAM, 2-PPM, 4-PPM, DPSK, and QPSK modulation techniques. And for FSO communication systems, although the power efficiency is inferior to PPM, OOK is more commonly used due to its efficient bandwidth usage, but PAM scheme is the bandwidth efficient modulation scheme in this research for more than two bits of information sent, while the PPM scheme is the power efficient modulation scheme for more than two bits of information sent.