Enhancing Urban Connectivity: Free Space Optics as a Resilient Backup Link for Fiber Networks in Urban Environments

This manuscript presents a study on the potential use of Free Space Optics (FSO) communication for high-speed and reliable data transmission in urban areas of Ethiopia, particularly during heavy rain seasons or in cases where fiber connectivity is not feasible or cost-effective. This study has been used OptiSystem and MATLAB to create an FSO model capable of transmitting data at 2.5 Gb/s at ranges of 5, 10, 15, 20, and 40 km, and examines various transmission parameters, including transmission power, bit error rate (BER), Q-Factors, optical signal-to-noise ratio (OSNR), and transmission distances. The study shows that 30 dBm of transmitting power is suitable for improving data transmission during heavy rain and fog seasons in Ambo and Dire Dawa city with a BER below 10−9 for link distances up to 15 km in Ambo and 20 km in Dire Dawa, even in the presence of atmospheric turbulence. The result shows that the Signal-to-Noise Ratio (SNR) can be improved by increasing the Numerical Aperture (NA) sizes for different values of sigma (0.3, 0.5, 0.8) using diversity techniques like Maximum Ratio Combining (MRC), Equal Gain Combining (EGC), and Selection Combining (SC), as demonstrated through simulation results obtained using MATLAB.