Protection Strategies and Fault Avoidance in Free Space Optical Mesh Networks

Although fiber technology has been advanced to produce a wide range of fiber types to meet specific needs, new fiber deployment requires long-term planning and installation until full service is established. There are many applications that demand high-data rate connectivity urgently, be it Internet, voice, video or all three. Such applications are due to a natural emergency, a large short term event, or enterprise that needs immediate and private service; free space optical or wireless optical is an optical communication method that meets such needs. Additionally, it is apparent that FSO full-duplex point-to-point links have limited service availability. In addition to natural and man- made link failures, atmospheric conditions may also cause failures because the optical beam is highly attenuated by fog and other airborne particles. As a consequence, only mesh FSO provides enhanced service availability if proper fault detection and protection strategies are incorporated on the node and network level. In this paper, we review the FSO technology, we discuss the mesh FSO topology, and we describe fault detection, fault avoidance and protection strategies of the FSO mesh when one or more of its links fail. We also discuss engineering and traffic management and security issues.