in our example, where there are 1.4 million crosspoints and 40,000 con- nections, the pure leakage power, that coincides with the power consumption without transiting signal, is about 200 mW, that is, it can be still neglected with respect to the 2kW due to regular current caused by CMOS switching when bits are transmitted. These are not high values, taking into account the footprint of the switch fabric and partially explain why still today almost all commercial OXCs have an electrical switch fabric. A brief description of the main features of a practical OXC built using an electrical switch fabric is reported in Table 7.1. From the table it is evident that in general the OXC is a multi-rack machine, integrating, besides the main OTN switch fabric, a series of other features like the possibility of an embedded carrier class Ethernet switch with the corresponding Ethernet interfaces or a set of line DWDM interfaces at 10 and 40 Gbit/s that are naturally compatible with the DWDM line produced by the same vendor producing the OXC. Other kinds of OXCs could support also digital cross connect (DXC) functionalities like SDH/SONET grooming. 7.7.4.3 OXC with an Optical Switch Fabric Since the OXC switch fabric has to manage high-speed signals and a high switching speed is generally not required, it is natural to consider the possibility to realize the switch fabric using optical switches [33,58]. Optical switches are expected to have a very low power consumption and to be able to manage high-speed channels without any need to decompose them in a larger number of slower data fluxes. For several years this expectation has driven a large amount of research effort in the direction of large optical switches with low losses, effort that has produced several results, mainly in the field of micro electrical mechanical machine (MEMs)-based opti- cal switches, as detailed in Chapter 5. As reported in Table 5.8, MEMs-based switches Switching Systems: Architecture and Performances TABLE 7.1 Summary of the Feature List of an OXC Bas