  Intractable is the problem of finding two link-disjoint paths of minimal cost
if the path cost is limited since it can be a special case of the partition
problem. In optical networks, this limit can be introduced by the signal
modulation reach. Even without this limit, the existing literature suggested
the problem intractable because of the spectrum continuity and contiguity
constraints, but we show that the problem can be solved exactly with the
recently-proposed generic Dijkstra algorithm over a polynomially-bounded search
space, thus proving the problem tractable.
