This paper investigates the survivability of multicast requests in mixed-graph optical networks, where only a fraction of the nodes have optical splitting capabilities (sparse-splitting optical networks). Mixed-graph networks have both bidirectional and unidirectional connections between their nodes, and they result due to resource holding of the already established requests. A new multicast protection heuristic for this category of networks, is presented and evaluated in terms of the blocking ratio of the arriving multicast requests. Its performance results are compared with existing approaches, developed for undirected-graph sparse-splitting optical networks.