Many algorithms are developed to deploy multicast in optical networks. Those algorithms are designed to resolve the main issue of multicasting in optical networks, which is not all optical cross-connect in the network are capable to split an incoming light signal to more than one output interface. Some of those algorithms are based on additional signaling exchanged to generate the appropriate multicast trees, some use rerouting to source, and some generate multiple multicast trees for the same multicast group. The performance of those algorithms depends basically on the number and location of multicast capable cross-connects. A multicast capable cross-connect (MCOXC) is an optical node equipped with light splitter that allows splitting an incoming light signal to any two or more output interfaces. This paper studies how many nodes in optical networks must be equipped with light splitters to assure good performance of multicast algorithms in sparse splitting networks. This depends basically on the topology in terms of number of nodes, the average node degree and the variation of the node degree distribution over the network nodes. The more the variation of the node degree is, the more splitters are required.