SDH/SONET, linear OCh protection and linear OMS protection can be imple- mented in point-to-point systems and in mesh networks. The only thing to note is that, while all SDH/SONET protection schemes also protect the optical transmitter, OMS pro- tection is implemented after the transmitter and thus it is not protected. On the other hand, OCh protection is implemented before the transmitter, but requires an individual switch for each wavelength, while a single switch is needed for OMS-p. These characteristics are shown in Figures 3.39 and 3.40 where the OCh layer and the OMS layer 1+1 dedicated protections are depicted decomposing the optical terminals in building blocks representing their main functionalities. Both directions are considered in the figures, and to underline OCh and OMS terminations, an add/drop card (ADC) has Telecommunication Networks Working path Protection path Working path Protection path Bus end Bus end FIGURE 3.39 Scheme of a 1+1 OCh dedicated protection on a point-to-point WDM system with an intermediate branching point: LTE, line terminals; OADM, optical add drop multiplexers; ADC, add drop card; TX and RX, optical transmitter and receiver, respectively; PC, channel protection card. Working path Working path Protection path Protection path RXT TXT Working path Working path Protection path Protection path RXT TXT FIGURE 3.40 Scheme of a 1+1 optical multiplex section protection on a point-to-point WDM system with an intermediate branching point: ADC, add drop card; TXT and RXT, optical transmitter and receiver, respectively, flex a switch. Networks Fundamentals and Present Architectures Working path Working path Protection path Protection path (Protection channel) FIGURE 3.41 Scheme of the combination of a 1+1 optical multiplex section protection and an 1:N transmitters/receivers pro- tection on a point-to-point WDM system with an intermediate branching point: ADC, add drop card; TXT and RXT, optical transmitter and receiver, respectively; TX and RX, electrical transmitter and receiver, resp