Modulation formats for 100G and beyond

This paper reviews technological options for the modulation formats for serial optical transmission of 100 Gb/s and beyond. In the first part an overview on various modulation formats for 100 Gbit/s is presented, covering classical binary electronic time division multiplexed 100 Gbit/s NRZ systems, operating a highest speed, and mature product solutions of system vendors running at lower symbol rates which are using quaternary phase shift keying and polarization division multiplexing, coherent technologies and digital signal processing in the receiver. The second part is focusing on the next generation of transmission systems carrying data at channel bitrates higher than 100 Gbit/s, e.g. 400 Gbit/s up to 1 Tbit/s or even beyond, which may apply higher constellation M-QAM modulation of a single carrier or multiple electrical subcarriers and optical superchannels which also form one WDM channel. At both parts, for 100 Gbit/s and higher bitrates, the paper provides a performance comparison together with the main characteristics of the modulation formats and indicates appropriate application areas of transport technologies for future networks. 2011 Elsevier Inc. All rights reserved.