Design and Performance Evaluation of Free Space Optical Communication Link in Zaria, Nigeria

Abstract

Free Space Optical Communication (FSOC) is an optical technology with a great chance to complement traditional wireless communication technologies. It offers essential advantages compared to Radio Frequency (RF), such as low power consumption, no frequency restrictions, no electromagnetic interference, security, and a significant increase in bandwidth. Similarly, they have proven a worthy substitute for fiber optics with notable advantages. FSOC systems are usually installed above ground level and are therefore exposed to prevailing weather conditions such as haze, fog, rain, etc. which negatively affect the optical signal transmission. There is a shortage of research on using FSO systems in tropical regions. For this reason, accurate free space optical communication channel modeling helps telecommunication operators to engineer and appropriately manage their networks. Therefore, this research work developed Free Space Optical Communication Channel Model to mitigate the effects of atmospheric attenuations by estimating the specifically induced attenuation caused by both haze and rainfall rates on the FSOC link in the Zaria geographical area using two years of measured visibility data and rainfall rates data of the study location obtained from Nigerian Meteorological (NIMET) agency, Zaria station, located at the Nigeria College of Aviation Technology (NCAT) Zaria and Center for Energy Research and Training (CERT), Ahmadu Bello University (ABU), Zaria. The performance of the FSOC system is analyzed and evaluated through Link Margin (LM) analysis by using the design specifications of a commercial optical transceiver (TereScope 5000). The haze-induced attenuation obtained at 850nm, 950nm, and 1550nm is 5.934dB, 6.402dB, and 3.152dB respectively. Therefore, the result shows that the 1550 nm wavelength has minimum haze-induced attenuation compared to 850nm and 950nm at a propagation link distance of 6km. Furthermore, from the results of the performance evaluation of the LM analysis for the combined effects of Geometrical Attenuation (G_att), Haze-Induced Attenuation (HIA), and Rain- Induced Attenuation (RIA), the result shows that operating a 1550nm wavelength in transmission power greatly improves optical transmission when compared with 850nm and 950nm wavelengths. Generally, the overall outcome of the research concludes that the free space optical communication system has the robustness to handle successful wireless communication during the worst weather conditions in Zaria throughout the year for a link range of up to 6km.