Dynamic wavelength capability is well known as a technique with the potential to increase the utilization of network resources and has recently been shown to lead to greater energy efficiency [1]. We examine specifically the energy savings due to dynamic wavelength capabilities that are optimized around particular services and identify key enablers to achieve deep energy savings. The emergence of high bandwidth and/or persistent data flows in packet networks for which the routing energy is strongly determined by the header processing leads to inefficiencies due to a granularity mismatch between the flow size and the packet size. Breaking large flows into many small packets, each with its own unique header, increases the energy consumption. In the extreme example in which the service requires a full, continuous and persistent circuit, the benefits of packet transport are lost while still paying the higher cost in energy. Indeed, circuit or flow based services can be better implemented using end-to-end transparent paths through a network, thereby realizing greater efficiency. Many services, however, have a complex set of needs or performance requirements that must be taken into account to understand the opportunities for using transparent networking capabilities such as dynamic wavelength functionality. In this work, we consider specific service cases related to content distribution networks and examine the potential for energy efficiency gains using dynamic wavelength functionality. While it is instructive to consider equipment efficiencies that reflect commercially available technologies, we further parameterize these technologies in order to understand the relative benefits of efficiency-specific improvements. Content distribution networks are characterized by a library of content stored in one or more locations within the network that enables it to be accessed by individual network users. In this analysis, we only consider implementation cases within the core network and do not include the access network, which we assume is the same in each case and can be removed from the analysis. The energy efficiency is consequently a complex function of the transport efficiency and the storage and server efficiencies. Both content serving and content transport may include computational components associated with functions such as hosting, compression/decompression, addressing, and error correction. Transport is composed of transmission, routing, and switching. Furthermore, in the case of dynamic wavelength services, the energy efficiency is impacted by the time to take down an old network path and provision a new network path [2], including damping of optical power dynamics [3]. Efficient use of dynamic wavelength capabilities is achieved if the content file size is larger than the time bandwidth product of the wavelength setup overhead. This wavelength utilization factor and the relative efficiency of transparent versus opaque transport is a key parameter in assessing the energy efficiency benefit of dynamic wavelengths [4]. In the context of content distribution networks, we quantify the efficiency benefit depending on the popularity and file size distributions within the content library. We find content caching architectures, such as content-centric networks, to have the potential to outperform dynamic wavelength services by caching popular content at the edge of the network. This finding is sensitive to the library size and popularity distributions with smaller content size and steep popularity distributions favoring content-centric networking [5].