To compensate for fog, systems can keep the link length short and increase laser power during episodes of decreased visibility. Scintillation refers to small spatial variations in the refractive index of the atmosphere. Network planning is simple and links are independent, but the optical link is a single point of failure without redundancy and is not suitable for carrier-grade systems. Rooftop-mounted optical wireless nodes communicate between buildings. Each link is a single point of failure, however, and hub location must be chosen to maximize the number of buildings with line of sight.
Hub cost is generally high.
Given that attenuation effects require short link lengths to ensure carrier-grade service, this is not a very economical architecture. Traffic is collected at specific points for efficient connection to the network. Both mesh and the simpler loop architectures are for carrier-grade networks. The technology can bring OC-12 data rates to the campus and access loop easily and economically. In industrial and urban areas, optical wireless access loop technologies may well be the wave of the future.