Comparative Performance Evaluation of FSO Links Using NRZ and RZ Line Codes with APD and PIN Receivers in Different Weather Environments

This paper presents a comparative performance analysis of Free Space Optical (FSO) communication links operating at a wavelength of 1550 nm using Non-Return-to-Zero (NRZ) and Return-to-Zero (RZ) line coding techniques in combination with Avalanche Photodiode (APD) and Positive-Intrinsic-Negative (PIN) receivers under different atmospheric conditions. The performance of the FSO system is evaluated in terms of pointing error and received signal attenuation in clear air, haze, and fog environments. The obtained results reveal that the NRZ-APD configuration exhibits a pointing error of 11.62 urad, which is slightly higher than the 11.22 urad observed for the RZ-APD configuration. However, the RZ-APD setup experiences comparatively higher signal attenuation under all considered weather conditions. In the case of PIN receivers, maximum pointing errors of 10.55 urad and 10.42 urad are observed for NRZ-PIN and RZ-PIN schemes, respectively, particularly under foggy atmospheric conditions. The analysis demonstrates that the 1550 nm operating wavelength provides reliable and efficient performance for FSO communication links in varying weather environments. Furthermore, NRZ-APD and RZ-PIN configurations show improved performance in terms of pointing accuracy and system reliability. The findings of this study offer useful insights for the development and optimization of robust high-speed FSO communication systems operating under adverse atmospheric conditions.