Designing a Hybrid Optical Fiber/FSO System For Last Mile Users Under Tropical Weather Conditions

Optical fibers have emerged as a promising frontier for resolving the bandwidth and data rate limitations of last-mile users as the microwave and radio frequency (RF) based links are not capable enough to deliver high data rates to support modern and future technologies. However, fiber-based networks cannot be installed or deployed in remote areas and locations having difficult terrains along with other geographical constraints. Therefore, the integration of optical fibers and free space optical (FSO) links in such locations is an effective approach for establishing high-speed data services for last-mile users. In this study, a wavelength division multiplexing (WDM) based 16-channel optical fiber/FSO hybrid system has been proposed for eliminating the crunch of high data rates in geographically challenging locations. The proposed hybrid system can serve 128 optical network units (ONUs) by integrating a single mode fiber (SMF) of 20 km with an FSO link range lying between 0 to 2 km. Furthermore, the tropical locations experience higher attenuation of FSO beam resulting from rainy weather and hence, the system performance has been evaluated for light, medium, and heavy rain weather scenarios. It has been found that the hybrid optical system can transmit the data reliably for the FSO link distance of 1 km under light rain weather conditions only. Additionally, the maximum attainable FSO link range for ensuring a target bit error rate of 10– ⁸ drops by 48.87 % as the FSO channel conditions switch from light to heavy rain.