 is standardized in two different dimen- sions: MMS (medium size) and SFF (small size). The mechanical dimensions of the two standards with the positing on the package of the main features are depicted in Figures 5.79 and 5.80. The name comes from the 300 PIN connector that is located on the lower part of the package and assures the contact of the transponder with the host card. The functional scheme of a 300 PIN MSA transponder is sketched in Figure 5.81. From the figure it is evident that the scope of the transponder is to supply also the drivers to the system vendor, mainly for the laser and the modulator. No signal processing is in general present inside the transponder: no FEC, no electronic compensator; the design of a few among these elements is perceived as a differentiator by the DWDM vendors SO that it is not wanted inside a multivendor standard module. However, it is possible that this will change at the moment in which the MSA 300 PIN at 10 Gbit/s will be in competition with the smaller XFP. At that moment it is possible that sub- stantial signal processing will migrate inside the MSA 300 to differentiate it from the XFP. The functional scheme evidences also the digital standard interface that MSA 300 PIN modules use to communicate with the motherboard: the I°C interface [52]. This is a sim- ple standard, comprising a layered description of the transmission system that allows the motherboard both to configure the module and to read alarms coming from it. As far as the MSA 300 PIN at 40 Gbit/s is concerned, no alternative format is present, since transceivers as they are standardized at present are not able to host 40 Gbit/s compo- nents, essentially for a power consumption and for a mechanical dimension reason. 0.539 300 PIN connector 114.31 23.37 46.74 FIGURE 5.79 External dimensions of an MMF MSA 300 PIN transponder. Technology for Telecommunications: Integrated Optics and Microelectronics Fiber pigtail 39.37 nom 0.52 Max (1 Meter) (13.2) 0.525 + 0.010 (13.34 + 0.25) 2.20 Max (56.1) 3.00 Max (76.5) 