e optoelectronics components can be mounted onto a package using micro-optics methods and they can also be assembled in a hybrid or monolithic chip. In any of these cases, all the considerations already done for the GPON still hold with the further issue that the circuit to convey the electrical signal to the modulator at Gbit/s is much more TABLE 11.4 Possible Optical Interfaces for the Two Classes of XG-PON1: Class 1 Table and Class 2 Table XG-PON1 Class 1 Upstream Max TX power 2 dBm Max loss 29 dB Min RX power -27.5 dBm Direct modulation laser Penalty 0dB APD receiver Downstream Min RX power Max loss 29 dB Max TX power 2 dBm -27.5 dBm APD receivers Penalty 1 dB External DFB modulation XG-PON1 Class 2 Upstream Max TX power 2 dBm Max loss 31 dB Min RX power -29.5 dBm Direct modulation laser Penalty 0dB APD receiver Downstream Min RX power Max loss 29 dB Max TX power 10.5 dBm First alternative -21.5 dBm PIN receiver Penalty 1 dB External DFB modulation + amplifier Downstream Min RX power -28 dBm Max loss 31 dB Max TX power 4 dBm Second alternative APD receivers Penalty 1 dB External DFB modulation Telecommunication Networks complex with respect to that working at 2.5 Gbit/s, thereby further increasing the cost of the OLT optical module package. Besides these elements that are almost all in common with the GPON case, in the case of the XG-PON1, another difficulty arises, that is not present in the GPON. Due to the broadcast nature of the ODN and the continuous change of frame slot alloca- tion among the ONUs because of the DBA, the signal arriving at the ONU is a burst signal and it needs a burst mode receiver. Every ONU receiver must be able to detect the arrival of a burst and to rapidly lock the sampler at the burst, SO as to sample the signal at the right point of the bit interval. While at 2.5 Gbit/s, a burst mode receiver is difficult to implement, at 10 Gbit/s it is a real technology challenge. The first experimental components were presented in the year 2009 (e.g., [33]), but more developments will be need