Noise Analysis of Chirped sinh-Gaussian Beams in Free Space Optical Links

Bandwidth requirements have been raising day by day since the number of users and the size of data increases rapidly. Due to this high demand, it is foreseen that optical wireless communication (OWC) systems will play a crucial role in 6G systems. Accordingly, we studied the scintillation of chirped beams in a turbulent atmosphere for the first time in literature. For this purpose, we selected chirped sinh-Gaussian (CSG) beam at the transmitter of the free space optics (FSO) system. We modeled the atmosphere by utilizing the split-step approach, which is a method to generate atmospheric turbulence in the software environment and compute the received field in wave optics. We computed the most dominant noise in FSO systems and bit error rate (BER). We compare the BER of CSG beam when on-off keying and subcarrier intensity modulated binary phase shift keying (BPSK-SIM) is applied. We observed that chirped factor reduces scintillation noise and BER significantly. According to the results, the point-like scintillation of chirped beams is significantly less than the beam without chirped factor. Considering the scintillation of CSG beam with a large Gaussian source size, chirped factor mitigates approximately half of the scintillation. It brings a significant advantage in BER performance of the beam. This result reflects BER and it reduces it by a significant amount. In light of our results, we expect that chirped beams could be a good alternative to increase FSO performance in 6G systems. Our results will have a potential to use in FSO connection in 6G systems.