Experimental performance analysis of a realistic FSO link in weak turbulent channels for 5G backhaul connectivity

Free-space optical (FSO) communication links have emerged as a promising solution for future networks such as 5G, 6G, and beyond by enabling low-cost, power-efficient, and high-speed backhaul connectivity. However, atmospheric turbulence can degrade link performance by reducing the optical signal-to-noise ratio (OSNR), increasing the bit error rate (BER) and limiting the achievable data rate. In this work, we employ a weak-turbulence channel model based on measured temperature and pressure to estimate the refractive index structure parameter (Cn2) and scintillation index (σI2). These parameters are used to quantify turbulence strength and analyze its impact on optical beam propagation. The modeled OSNR and BER are analyzed for varying turbulence strengths. The measured OSNR of approximately 30 dB from the 50 m indoor channel corresponds to an achievable data rate of about 350 Mbps, yielding a BER of 10^-8, which is below the FEC threshold. The calculated OSNR is further validated using values derived from the measured received signal and noise optical powers. Finally, the (Cn2) value obtained from the indoor measurements is used to estimate the outdoor transmission range that provides comparable performance. The analysis predicts an effective outdoor link range of approximately 800 m, demonstrating the potential of this approach for designing FSO backhaul links in beyond-5G/6G microcell networks.