BPSK-SIM- PPM modulation for free space optical communications

In this paper a hybrid PPM-BPSK modulation scheme is proposed. The numerical simulation results for the bit error rate (BER) performance of the PPM-BPSK modulation scheme in the lognormal atmospheric channel for a range of turbulence variance is presented. Results are compared with the BPSK-subcarrier intensity modulation (SIM) and 4-PPM, which shows the performance of the hybrid PPM-BPSK scheme, is superior to the BPSK while having the same bandwidth requirement. However, for all level of turbulence the performance of the proposed hybrid PPM-BPSK is deficient to the PPM scheme. Moreover the paper also presents the experimental results for 4PPM and BPSK (SIM).