“…To further increase the capacity, FSAN/ITU-T might opt for increasing the line rate of current XG(S)-PON and NG-PON2 systems to 25 Gbps [9]. The recently started IEEE 100G-EPON Task Force envisions to increase the line rate to 25 Gbps, while at the same time using multiple wavelengths, to achieve a maximum data rate of 25, 50, or 100 Gbps, albeit on a fixed wavelength scheme, i.e., without the use of any tunable optical components [10]. Amongst the promising options to increase the data rate from 10 Gbps to 25 Gbps in a cost-effective manner is the use of more comprehensive modulation formats, as these allow to reuse current 10 Gbps optics.…”