Simulative analysis of NRZ-OOK point-to-point free space optical link under continental fog in view of retinal safety

Nowadays, the congestion of RF spectrum and increasing demands for high data rate is evident. In such a scenario, Free Space Optics (FSO) is seen as an effective alternative to cater the future bandwidth demands. However, commercial deployment of the technology is hampered owing to the various atmospheric phenomenon that severely limits the link quality of service. Among all the weather conditions, fog causes the maximum attenuation reaching hundreds of decibels per kilometer which results in high data rate drops and frequent link outages. Further, because of detrimental laser hazards in the wavelength band of interest, one cannot increase the laser power beyond a certain limit to improve the system performance. This work analyses NRZ-OOK FSO system under continental foggy conditions keeping in view of laser eye safety limits. Various system parameters such as transmission data rate, beam divergence and avalanche photodiode gain are analyzed. The challenge to operate at lower wavelengths of near infrared band has been discussed. Based on the investigation carried out, the paper is concluded with an optimal parameter selection.