We propose a novel optical multicast tree design algorithm for hierarchical optical path networks that exploit waveband
routing. To efficiently groom wavelength multicast trees into waveband trees, we define a generalized inclusive relation
between node groups that identifies neighboring destination groups. The algorithm then establishes a minimum weight
waveband tree that contains the wavelength multicast trees that include the neighboring destinations. Numerical
experiments confirm that the proposed waveband multicast can significantly reduce the number of optical switch ports.