Hybrid FSO/fiber optic link based reliable & energy efficient WDM optical network architecture

Abstract

Nowadays, free space optics (FSO) is becoming popular and is very competitive to the fiber optic technology for providing broadband services at very high data rates without the requirement of any spectrum licensing. FSO links can be installed within a few hours and at a very low cost. As compared to the optical fiber, FSO links do not have any problem of faults during digging and maintenance of roads. However, during obstructive climatic conditions such rain, the FSO link losses become high and are not suitable for long-distance transmission. While the single-mode fiber (SMF) link is suitable for such conditions as the link losses are almost independent on the climatic conditions. To leverage the benefits of both FSO and SMF, this paper proposes a Hybrid FSO/Fiber Optic based dual-link architecture that is capable of transmitting data at 20GBPS for a distance up to 5 km. The FSO link is useful for clear weather conditions and fiber optic link is useful for adverse environmental conditions especially for rainy days where link losses are high and require high transmitter powers. By imposing the fiber optic link for rainy days, a significant amount of energy consumption is reduced since losses inside the optical fiber are very low. The architecture provides the reliability against the failure of any one of the links by switching the operational link to the ideal link and vice versa. The architecture supports the dedicated point to point, overlay broadcasting to transmit dedicated and common data respectively. The architecture further adds the reliability against the failure of any link between a remote node (RN) arrayed waveguide grating (AWG) to the optical networking unit (ONU), as the services may be continued on the broadcasted wavelength until the recovery of the original link.