own in Figure 11.1. Under a link budget point of view, GPON standard defines different link budget classes, whose parameters are reported in Table 11.1. A new class of performances will probably be standardized called C+ with a link budget higher than 33 dB. Splitter loss depends mainly on the number of output ports on the splitter and adds about the same loss whether traveling in the downstream or upstream direction. Each splitter configuration is assigned a particular maximum split ratio loss, including connec- tors, defined by the ITU G.671 standard and Telcordia GR-1209. When using the 16 or 32 splitting ratio, the standard completely defines all the needed splitter characteristics. Since this is not true for 1 X 64 splitters, network designers must use a single 1 x 2 splitter interfacing two 1 X 32 splitters to make up the 1 X 64 configuration. 11.2.2.1 GPON Transmission Performances Using Class B optics only leaves 5.35 dB of propagation loss. Therefore, even with the best fiber access infrastructure, where the spectral attenuation can be assumed to be 0.31 dB/km, only a 17.25km PON network is achievable without including any of the connectors within the local exchange. A GPON reach of 20km is specified for class B+ and C GPONs. It is very interesting to investigate the physical effects thwarting GPON transmission, since the situation is much more complex than in the WDM-PON case. In the case of A and B classes, the GPON span is essentially limited by the power budget. It is to be noted that in optical access networks, reducing the ONU cost is a key issue. For this reason, in A and B classes, GPON Fabry-Perot laser diodes (FP) are generally used at the ONU, while a PIN photodiode is present at the OLT. FP lasers are multimode lasers, SO that mode partition noise due to the mode statistical fluctuation of the optical source arises [6]. This effect, if not, suitably reduced by a careful design of the lasers, can greatly limit the GPON span. For these reasons, the key charac- teristics of FP lasers to be used 