This paper considers the problem of routing connections in a
reconfigurable optical
network using wavelength division multiplexing, where each connection between
a pair of nodes in the network is assigned a path through the network and
a wavelength on that path, such that
connections whose paths share a common link in the network are assigned
different wavelengths.

We derive an upper bound on the carried traffic
of connections (or equivalently, a lower
bound on the blocking probability) for any routing
and wavelength assignment (RWA) algorithm in such
a network.
The bound scales with the number of wavelengths and
is achieved asymptotically (when a large number
of wavelengths is available) by a fixed RWA algorithm.
Although computationally intensive, our bound can be used as a metric
against which the performance of different RWA algorithms can be compared
for networks of moderate size.
We illustrate this by comparing the performance of a simple shortest-path
RWA (SP-RWA) algorithm via simulation relative to our bound.

We also derive a similar bound for optical networks using dynamic
wavelength converters, which are equivalent to circuit-switched
telephone networks, and compare the two cases for different
examples.

Finally, we quantify the amount of wavelength reuse achievable in
large networks using the SP-RWA via simulation
as a function of the number of wavelengths, number of edges, and number
of nodes for randomly constructed networks as well as de~Bruijn networks.

We also quantify the difference in wavelength reuse
between two different optical node architectures.
The results show that it is feasible to provide several all-optical
connections to each node in a large network using a limited number
of wavelengths.  For instance, using 32 wavelengths,
it is possible to provide 10 full-duplex
connections to each node in a 128-node random network with average
degree 4, and 5 full-duplex connections per node in a 1000-node random network
with average degree 4.
The results also show that
wavelength converters offer a 10--40\% increase in the amount of
reuse achievable for our sampling of 14 networks ranging from 16 to 1000
nodes when the number of wavelengths available is small (10 or 32).