Performance Analysis of IMC in FSO Systems Over Gamma–Gamma Channel

Free-space optical communication (FSO) offers high security and high bandwidth, which is why it is widely used in digital communication systems. However, atmospheric turbulence or scintillation induces a voluminous degradation to the signal. So, different modulation techniques are introduced to improve the performance of FSO systems. In this paper, a novel inverted Manchester code (IMC) and a 3 bits-per-symbol modulation format are proposed, referred to as IMC/BPSK. The BERs of the IMC/BPSK amplitude branch and phase branch are studied theoretically and numerically over the gamma–gamma channel model separately, and the capacity is also been studied. The simulation comparison with 8-PPM is also made. The results show that the BER performance of IMC/BPSK is better than that of 8-PPM with the same symbol rate. Therefore, the proposed modulation format is feasible, which can effectively improve the tolerance degree of the atmospheric turbulence effect.