Performance evaluation of 640 Gbps IQM-OAM-PDM-OFDM-based free-space optical transmission system under Saudi Arabian atmospheric conditions

Abstract

This paper presents a comprehensive investigation of a high-capacity free-space optical (FSO) transmission system integrating intensity in-phase and quadrature modulation (IQM), orbital angular momentum (OAM) multiplexing, polarization division multiplexing (PDM), and orthogonal frequency division multiplexing (OFDM) techniques. The proposed 640 Gbps IQM-OAM-PDM-OFDM-enabled FSO system was evaluated under realistic atmospheric conditions of Riyadh and Jazan, Saudi Arabia, using year-long hourly meteorological visibility data from 2023. Three empirical attenuation models namely Kim, Kruse, and Al-Naboulsi were employed, yielding mean attenuation coefficients of 0.59–0.64 dB/km under Kim/Kruse and 2.03–2.06 dB/km under Al-Naboulsi, with peak attenuation reaching 169.80 dB/km in Riyadh and 348.70 dB/km in Jazan during severe dust and haze events. The integrated system achieves maximum transmission ranges of 15 km under the Kim and Kruse models and 7.25 km under the Al-Naboulsi model in both cities, a 52 % reduction in reliable range under worst-case versus typical conditions while maintaining pre-FEC BER of approximately 2.46 × 10 ⁻³ (log ₁₀ BER = −2.61), post-FEC BER below 10 ⁻⁹ , and EVM around 14 % at maximum distance. Compared to a standalone OAM-FSO system, the proposed multi-domain architecture delivers a 16-fold capacity increase and an 87.5 % improvement in transmission range, demonstrating its suitability for resilient high-capacity FSO deployment across diverse Saudi Arabian climates.