25 Gbit/s duobinary and 4-PAM for access networks

Access networks are no exception in the ever continuing increase in data rates. Due to the cost-sensitive nature of these networks it is of interest to be able to reuse the current 10G optics for the upgrade to higher data rates. Therefore, higher order modulation formats can be considered to transmit higher data rates through a reduced bandwidth. At the same time, complexity of the modulation format has to be kept low. In this paper we will present 25 Gbit/s transmission of Duobinary and 4-PAM modulation formats. Comparisons between the two modulation formats will be made.