Dynamic routing, also called adaptive routing, is a process for optimizing how data is transmitted. It is comparable to taking the back roads through a city rather than the main road during rush-hour.  When a network’s primary transmission channel is clogged with data traffic, signals are routed to channels with lower data volume. The network uses information about node availability and channel congestion to direct incoming packets in a suitable direction.
In free-space optics, adaptive routing involves channel adaptation and discrete frequency selection in a spectral band. If a channel is covered in interference, say in the case of fog, the transmitter may switch to a different frequency or wavelength to mitigate the interference. However, most optical networks only operate at one frequency. Elastic optical networks (EONs) provide a possible solution to this problem.
Paper: Dynamic routing in Elastic Optical Networks
Paper: Efficient Routing Protocols for an FSO network (paper)