Performance analysis in spectral-amplitude-coding-optical-code-division-multiple-access using identity column shift matrix code in free space optical transmission systems

The growing need for high-speed services, coupled with data-intensive technologies like the Internet of Things (IoT), is expected to exacerbate congestion within existing Radio Frequency (RF) communication systems. As a result, Free Space Optics (FSO) has emerged as a promising alternative to RF, offering superior data transmission capabilities. Additionally, ensuring security has become a crucial concern to safeguard sensitive information. Accordingly, in this paper, an FSO system is proposed that uses an Identity Column Shift Matrix (ICSM) code for higher and confidential data transformation. The ICSM code is one of the Spectral-Amplitude-Optical-Code-Division-Multiple Access (SAC-OCDMA) codes which is characterized by easy construction due to zero cross-correlation property. Moreover, the effectiveness of clear, haze, fog and rain conditions are considered while examining the proposed model performance in addition to real meteorological data for two cities (Alexandria, Egypt, and Pune, India). Eye diagrams, received power, and Bit Error Rate (BER) are the evaluation parameters used for the proposed model performance. The simulation results reveal that as weather becomes severe, the FSO span decreases, and the performance becomes worst. As for clear weather, an FSO link of 26 km is obtained which is decreased to 1.1 km under the dense level of fog. Regarding the two cities, the distance covered by the information signal during rainy weather in Pune is 6.7 km, which is smaller than that in Alexandria due to Pune's higher attenuation value. These transmission ranges are obtained with an overall capacity of 3 × 10 Gbps, received power < − 22.8 dBm, and BER below 10^–5.6.