To counteract the fog factor, meshed topology proponents shorten laser links from a maximum of 500 meters to the 200-meter range. So with a city that has a lot of fog, we build a smaller diameter cell size. We design it so that whether you re in Phoenix or San Francisco, you still get three nines of availability. It s been reported they re developing products that use unlicensed microwave radio frequencies to transmit laser-based traffic that s being blocked by fog. Another issue for laser transport systems is building movement.
Buildings sway in the wind and, over time, they settle into the ground.
When the sun comes up, they expand. When the sun goes down, they contract. For pinpoint laser transmissions, this minuscule movement can wreak havoc with transport service. A number of vendors have developed auto-tracking systems that detect such movements and automatically adjust the lasers accordingly to maintain proper alignment. Flying objects can also be a problem.