Leibrich, Jochen; Rosenkranz, Werner (Lehrstuhl für Nachrichten- und Uebertragungstechnik, Christian-Albrechts-Universitaet zu Kiel, Kaiserstr. 2, 24143 Kiel, Germany)
As the optical fiber channel allows for transmission of four-dimensional signals, in recent years several four-dimensional constellations have been proposed aiming at maximization of power efficiency. On the other hand, a hybrid approach has become popular in order to allow for flexible spectral efficiency. In this contribution, it is shown how to achieve both flexible spectral efficiency and high power efficiency at the same time. Besides the general approach a specific power efficient realization is presented for which 3.33 bits per two-dimensional symbol are transmitted.