Modulation formats for 100G and beyond

The perpetual demand for increasing the bandwidth of optical carrier networks leads to the advent of new transmission hierarchies beyond the current installed basis which are mainly consist of 2.5, 10 and 40 Gb/s wavelength channels. In research and development there is a big pressure to investigate new transport technologies and to develop and design the next generation of optical systems carrying data on one channel of 100 Gb/s for the todays need and 400 Gb/s or even more for future networks. Standardization efforts for client side interfaces supporting a 100-Gb/s Ethernet was kicked-off in 2006 by the IEEE higher speed study group and was finished in 2010 with the IEEE802.ba standard for 10 km and 40 km reach, using 4 lanes with 25 Gb/s, aiming to find an optimum solution for the upgrade of carrier networks with 100 Gb/s channels to achieve lower costs for the terminal equipment and network operation. In addition, a new direction was given in order to focus work on a reduction of the energy consumption of our network to reduce significantly the carbon footprint of ICT, which exhibits a dramatic annual increase mainly due to tremendous growth of Internet traffic. Commercial deployments of 100 Gb/s systems in the optical networks of several service providers are in progress since 2010. Optical systems with bitrates beyond 100 Gb/s are currently investigated in research and the kick-off for the standardisation activities for 400 Gb/s and even 1 Tbit/s are expected soon. Significant research has been undertaken recently to study physical-layer line transport options for 100 Gb/s.