ABSTRACT
Optical and optoelectronic technologies make possible the realization of high-performance optical fiber communication systems and networks with the adoption of wavelength division multiplexing (WDM) configurations and both linear and nonlinear optical amplifications. The last step for increasing the network throughput is represented by the implementation of multilevel modulation formats in coherent optical communication systems, which enable to increase the bit rate/channel, typically in WDM optical communication systems, over 100 Gbit/s/channel toward 400 Gbit/s/channel and beyond. Within this prospect, novel conception multidimensional modulation formats together with non-conventional optical coherent systems can offer significant opportunities and advantages. As general result, from the 4-Quadrature Signaling, all the binary and multilevel, non-coded, constant power modulation formats in two- and three-dimensional spaces can be derived by space rotations and compressions. Therefore, the 4-Quadrature Signaling System can be either directly exploited for information transmission or used to derive modulation formats in three- or two-dimensional spaces.
