f 2.5 dB, the switch crossing implies a loss of 10 dB, comprising a margin of 2.5 dB for connections, back plane, and SO on. Adding the AWG and following the same design criterion considered for the PWP OC, we have AOXC = -22.5dB. In this case, however, we can exploit the WC to have a small gain, and, on the other side, we have to take into account its noise factor. A reasonable gain for the overall WC is 6dB, taking into account all the subsystems of Figure 10.22, with a noise factor NFW WC Thus, the gain G1 can be written as G1 = 1/GwcAoxa and we have the following equation expressing the overall OXC noise factor: NF oxc N NF1 + NF WC + NF2 (10.7) SO that with our figures, NFOXC OXC = 0.8 dB. Coupler Wavelength Filter converter FIGURE 10.22 Adopted WC configuration needed to allow no wavelength conversion if needed. Next Generation Networking: Enabling Technologies, Architectures, and Performances 10.3.2.3 LWC Transparent OXC: Example of Performances This case is intermediate between the two we have analyzed up to now. The switch fabric is composed by switches (N + H) X (N + H) and one switch WH X WH, with H the dimension parameter of the OXC. The WH X WH switch supports WH WCs, putting them at the disposal of the incoming connection requests. Since both N and H cannot be SO large, the switch of dimension N + H can be realized in 2D technology, while the switch of dimension WH has generally to be a multistage switch. In our case, we will use 3D MEMs switches of dimension W X W; thus, we will need 2H2 such switches if we want to maintain the cross-bar structure. In all our numerical exam- ples, we will assume H = 2. Using the same approach used for the other OXC, we can calculate the power consump- tion of the switch fabric. Each N + H switch has a power consumption of 175 mW, while the switches supporting the WC have a power consumption of 1.1 W each. At the end, adding as usual 500 mW for the support electronics, the switch fabric power consumption is 21.65W Traversing the OXC, some wavelengths are not convert