  In this articlewestudy themulticast routing problem in all-opticalWDMnetworks
under the spare light splitting constraint. To implement a multicast session,
several light-trees may have to be used due to the limited fanouts of network
nodes. Although many multicast routing algorithms have been proposed in order
to reduce the total number of wavelength channels used (total cost) for a
multicast session, the maximum number of wavelengths required in one fiber link
(link stress) and the end-to-end delay are two parameters which are not always
taken into consideration. It is known that the shortest path tree (SPT) results
in the optimal end-to-end delay, but it can not be employed directly for
multicast routing in sparse light splitting WDM networks. Hence, we propose a
novel wavelength routing algorithm which tries to avoid the multicast incapable
branching nodes (MIBs, branching nodes without splitting capability) in the
shortest-path-based multicast tree to diminish the link stress. Good parts of
the shortest-path-tree are retained by the algorithm to reduce the end-to-end
delay. The algorithm consists of tree steps: (1) aDijkstraPro algorithmwith
priority assignment and node adoption is introduced to produce a SPT with up to
38% fewer MIB nodes in the NSF topology and 46% fewerMIB nodes in the USA
Longhaul topology, (2) critical articulation and deepest branch heuristics are
used to process the MIB nodes, (3) a distance-based light-tree reconnection
algorithm is proposed to create the multicast light-trees. Extensive
simulations demonstrate the algorithm's efficiency in terms of link stress and
end-to-end delay.
