A method and apparatus for performing event-driven diagnostics and/or prognostics of a network behaviour of a hierarchical optical network comprising the steps of recording at least one set of historical multi-level events representing different hierarchy levels of said optical network; mining of machine learned event patterns within the recorded multi-level events; mapping the determined mined event patterns to a multi-level network topology of said optical network and/or to a channel connectivity of channels through said optical network; and matching observed real-time multi-level target events of said optical network with at least one of the previously determined mined event patterns and performing a unified cause and effect analysis of network states and/or network components of said optical network for a recognized matching event pattern using the network topology and/or channel connectivity associated with the matching event pattern.