attainable with MSA 300 PIN are better, several optical systems, even when requiring long-haul transmission, adopt XFPs. As a matter of fact, the advantages in terms of space, power consumption, and failure management often over- compensate a certain transmission penalty. The way an XFP is hosted on the motherboard is shown in Figure 5.85. As in the case of the SFP there is a suitable cage that has to be mounted on the motherboard in order to allow the XFP hot plug. Since high-performance XFPs have a high ratio between power consumption and area of contact with the cooling air flux, a heat sink is generally needed to increase the heat exchange area. This is mounted directly on the cage to minimize the thermal resistance (see Section 6.5). Host board Heat sink Cage assembly Connector EMI gasket (not shown) Bezel Module FIGURE 5.85 Hosting of XFP transceivers into a system card. Telecommunication Networks 1.8 V Hot swap 3.3 V Monitor and control RF path interface CW path Power supply FIGURE 5.86 Functional scheme of a DWDM 10 Gbit/s XFP transceiver. The functional diagram of a high-performance XFP is shown in Figure 5.86. From the figure it results that the module is controlled via an I2C interface, the same that is used also to control MSA 300 PIN modules. This clearly declares the fact that an XFP is not conceived as a low-performance module; on the contrary, it is equipped with a suffi- ciently powerful control interface to allow even the most complex features to be config- ured and managed. TABLE 5.12 Characteristics of Practical DWDM XFP Transceivers Optimized for Different Uses XFP 40 km-Fixed XFP 80 km-Fixed XFP 80 km - Tunable Optical DWDM-100G DWDM-100GHz Data rate 10 Gbit/s 10 Gbit/s 10 Gbit/s Channel spacing 100 GHz 100 GHz 50 GHz Wavelength stability +/- 12.5GHz +/- - 12.5GHz +/- 12.5GHz Output power +1 dBm +4 dBm +4 dBm Extinction ratio 8.2 dB 8.2 dB 30 dB 30 dB 30 dB Relative intensity noise -130 dB/Hz -130 dB/Hz -130 dB/Hz Extinction ratio 8.2dB 10 dB Maximum power on -2dBm -4dBm -4 dBm receiver Sens