  Probabilistic message-passing algorithms are developed for routing
transmissions in multi-wavelength optical communication networks, under node
and edge-disjoint routing constraints and for various objective functions.
Global routing optimization is a hard computational task on its own but is made
much more difficult under the node/edge-disjoint constraints and in the
presence of multiple wavelengths, a problem which dominates routing efficiency
in real optical communication networks that carry most of the world's Internet
traffic. The scalable principled method we have developed is exact on trees but
provides good approximate solutions on locally tree-like graphs. It
accommodates a variety of objective functions that correspond to low latency,
load balancing and consolidation of routes, and can be easily extended to
include heterogeneous signal-to-noise values on edges and a restriction on the
available wavelengths per edge. It can be used for routing and managing
transmissions on existing topologies as well as for designing and modifying
optical communication networks. Additionally, it provides the tool for settling
an open and much debated question on the merit of wavelength-switching nodes
and the added capabilities they provide. The methods have been tested on
generated networks such as random-regular, Erd\H{o}s R\'{e}nyi and power-law
graphs, as well as on the UK and US optical communication networks. They show
excellent performance with respect to existing methodology on small networks
and have been scaled up to network sizes that are beyond the reach of most
existing algorithms.
