s % Copper local loops Length Italy France FIGURE 3.5 United Kingdom (BT) Germany Statistical distribution of copper pair lengths in dif- ferent countries. United States In practice however this solution is considered unfeasible in many cases due to the fact that it would require a massive deployment of new fiber optic cables in almost every area, comprising city centers. Among all the activities a carrier can undertake to enhance its network, a new cabling of the cities is by order of magnitude more CAPEX intensive and also the most advanced cabling techniques, quite effective for a limited deployment of new cables, does not change this issue [2,3]. For this reason, the fiber access architecture is devised SO as to allow the greatest pos- sible part of the fiber infrastructure to be shared among the maximum number of users. Even if a smart fiber topology is adopted, capable of exploiting at best the available infra- structure, in many situations, connecting each end user with the local exchange directly via the fiber infrastructure requires still too much cabling. In order to have a gradual CAPEX, a gradual fiber deployment strategy is often required. This means deploying optical fiber up to some intermediate point between the local exchange and the end user. In this intermediate point, active equipment converts the opti- cal signal in an electrical one and the end user is reached with a traditional copper pair using a suitable xDSL format (generally VDSL2). Mixed optical-copper architectures are called in different names depending on the distance between the intermediate point and the end user and on the number of users connected to the single intermediate point equipment. In particular, the following nomen- clature is generally used (see Figure 3.6) that is tailored mainly for urban areas, where the deployment of next generation access will come first [6]. Fiber to the home (FTTH) is an architecture where there is no copper and the fiber arrives at the end user. Fiber to the building (FTTB) is an architecture 