Such all-optical communication can be comprehended by
using a single wavelength in the multicast tree to establish a connection to each destination, but in
general it may not be possible to find a single wavelength which is available on every physical link in
the tree. Otherwise, all-optical wavelength converters may be used to convert from one wavelength to
another within the network but such converters are prospective to be excessively exclusive for most
applications in the predictable future