Optical transport networks (OTN) should be prepared to jointly handle both multicast and unicast traffic. Both opaque and transparent architectures are available to handle these types of traffic. Light-trees have been proposed as a way to transport information in a transparent manner. The light-tree however, may route unwanted information through some links while performing grooming of unicast and multicast traffic. To solve this problem we propose S/G light-tree with the goal of optimising the resources from the point of view of the number of wavelengths and available capacity. S/G light-tree uses detection systems (DS) and splitter and amplifier banks (SABs) to determine when unicast traffic should not be routed jointly with a multicast one by eliminating it optically from the link. This article proposes an online heuristic with grooming policies which allows for the analysis of the effects of the number of SABs on the blocking probability in OTN with dynamic traffic.