Network slicing with Quality of Experience/Quality of Service (QoE/QoS) guarantees is seen as one of the key enablers of future 5G networks. Nevertheless, it poses several challenges in both resource provisioning and management that need to be addressed for the efficient end-to-end service delivery. In particular, network slice deployments considering operation across several domains and network segments, require of inter-domain configurations, continuous monitoring, potential actuations, inter-slice isolation, among other, in order to be provisioned and maintained, looking forward to guaranteeing their assured Key Performance Indicators (KPIs). In such scenario, optical networks are of prime importance, enabling the inter-connectivity between multiple far away segments and Points of Presence (PoPs). In light of this, in this paper we present an architecture design enabling network slice provisioning for 5G service chaining in multi-segment/multi-domain optical network scenarios. The presented design is enriched with a policy-based monitoring and actuation framework able to maintain the desired QoS for the provisioned end-to-end (E2E) network slice. We experimentally validated the proposal against real slice deployments and traffic generation, providing a proof of concept for the presented architecture, with special emphasis in the demonstration of the actuation framework as a key element for quality guarantees.