s to reduce operational cost (OPEX) also drives toward a fiber-optic-based access network. As a matter of fact, optical transmission allows a completely passive access infrastructure to be implemented; much longer spans can be realized, and even the possibility of a delayering of the peripheral part of the network appears (see Chapter 3). Completely replacing the access infrastructure is perhaps the most CAPEX-intensive operation that an incumbent carrier can face. Such carriers have several million termina- tions (e.g., in a country like Italy, the network of Telecom Italia has about 20 million ter- minations) and their copper network reaches almost everywhere, both in cities and in the countryside. In this situation, it is clear that the deployment cost is the main parameter characterizing a given access solution, and a huge effort is directed toward cost reduction. In case civil work is needed to deploy new tubes where fiber cables have to be installed, this is by far the most expensive part of the deployment of the new access infrastruc- ture. However, this situation is not SO common in North America, Europe, and the most advanced Far East countries, especially in the most populated areas where network deployment is likely to start. Over the last 20 years, fiber deployment activity has been constant in the major cit- ies [2]. Moreover, even when fibers are not available, tubes are already in the ground, greatly facilitating fiber deployment. For these reasons, we will not deal with civil work in this chapter; readers interested in this aspect can find a starting point in the bibliog- raphy [3,4]. Beyond the capacity delivered to the end user and the cost, a variety of other merit parameters characterize an optical access network. Due to the huge investment needed for the deployment, next generation access infrastructure has to be future proof. Thus, the access infrastructure has to accommodate changes in the service bundle offered to the end Telecommunication Networks user and the related evolution of the net