by the WDM controller. Switching Systems: Architecture and Performances Input DWDM comb Output DWDM comb Drop ports FIGURE 7.48 Block scheme of a possible implementation of a Add ports tunable OADM using a WSS. TABLE 7.2 Comparison among the Main Features of OADMs for Different Applications Application DWDM Metro Core Rings Core DWDM Branching Access CWDM Rings Deployment Integrated into the DWDM Integrated into the DWDM Integrated into the system system CWDM system Tunable Fixed Fixed Implemented protection OCh-DPRing Dedicate 1+1 OCh-DPRing Platform 19' rack card 19' rack card ETSI N3 cabinet One for OADM One for each EDFA Embedded controller Technology WSS using MEMs Silica on silicon mux/demux Thin film filters Number of ports Wavelength range Extended C band Extended C band CWDM wavelengths Channel spacing 50 GHz 50 GHz Integrated amplification Two EDFAs Pass through loss 2.8 dB Input power range -24.6 to -0.6dBm -2.6 to 9 dBm -20 to 2 dBm Maximum output power 17 dBm Preamplifier gain 17-22 dB Postamplifier gain Fixed gain of 20.5 dB Power requirements (W) 7.7.6 Add-Drop Multiplexer Conceptually, the ADM is the TDM equivalent of the OADM, where the standard used for TDM multiplexing is SONET/SDH. In practice this is not true. Due to the possibility of realizing big switch fabric rich of functionalities using electron- ics with the scope of switching TDM signals, the ADM is much richer of functionalities with respect to the OADM. The switch functionality of the ADM, in its simpler version, is located at the SONET/ SDH path layer. Thus, the ADM terminates the MSH and the RSH and demultiplexes the tributaries of the aggregated. From a general point of view, the ADM is designed to be applied in self-healing SONET/ SDH rings and, depending on the ring type, can terminate either two counter-propagating fibers or four fibers, a couple for each ring direction. Telecommunication Networks The conceptual scheme of a four fibers SONET ADM is presented in Figure 7.48. On each line side of the ADM (east and west) a couple