Investigation of SAC-OCDMA FSO System Performance Under Fog Attenuation Conditions Using DW-ZCC Code

The present paper investigates a Free Space Optical (FSO) communication system based on Spectral Amplitude Coding—Optical Code Division Multiple Access (SAC-OCDMA). The main advantage of SAC-OCDMA technology is the ability to provide a unique signature code for each user, which differentiates it from other existing users and thus reduces and eliminates Multiple Access Interference (MAI). Several codes with minimal or zero cross-correlation value are exploited in this regard. Furthermore, free space transmission performance is affected by certain factors, notably attenuation caused by unfavorable weather conditions. This work could be considered as an improvement over previous work that has been published in the literature. This is due to the fact that an appropriate study of the performance of a SAC-OCDMA FSO system has been performed using a specific called Double Weight-Zero Cross-Correlation (DW-ZCC). This code represents the main interest of the present study as it is distinguished by a zero cross-correlation value which is better than that of other codes already proposed in previous works related to SAC-OCDMA FSO systems. The present paper investigates the performance of the proposed system using DW-ZCC code under fog attenuation conditions, by evaluating the bit error rate (BER) and the signal-to-noise ratio (SNR) against many parameters such as: transmitted power, data rate and FSO link range. The simulation results, being improved over those already achieved in previous works, prove that the transmitted signal quality is significantly dependent on the attenuation conditions, so that the proposed SAC-OCDMA FSO system provides a maximum range of 2.12 km in clear weather, 1.42 km in light fog, 0.41 km in moderate fog and 0.073 km in heavy fog, at a bit rate of 2.5 Gbits/s and a transmitted power of 14 dBm.