Future bandwidth-intensive services, which will have a wide impact on our daily lives, from entertainment, to business and health-care, demand high capacity, flexible, resilient and secure underlying networks. Simultaneously, rising energy costs and climate change concerns are increasing the pressure to adopt power-efficient solutions in communication networks. Most of these requirements are best fulfilled with optical networks, which are expected to provide the targeted high capacities together with an increasing number of functionalities, leaving behind the label of “dumb pipe” associated to them in early deployments. This paper presents an overview of the challenges and some of the trends in optical networking, covering developments in multiple layers of the protocol stack, from the physical up to the application layer, and aimed at different network segments, from the access to the core network.