Beyond 100G - high-capacity transport technologies for next generation optical core networks

We discuss physical layer options for next generation optical Ethernet transport systems with interface rates beyond 100 Gb/s. In particular, we focus on the benefits and drawbacks of employing higher order modulation formats such as quadrature amplitude modulation (QAM) or advanced four-dimensional modulation formats such as polarization-switched quadrature phase-shift keying (PS-QPSK). Furthermore, we discuss promising multiplexing methods such as Nyquist wavelength-division multiplexing (WDM). Such multiplexing can be used for the generation of multi-carrier super-channels with bit rates, which by far exceed those of single-carrier signals. In this contribution we report on an experimental investigation of single-carrier 448-Gb/s polarization-division multiplexing (PDM) 16QAM signals in a WDM transmission experiment over 250 km of ultra-large-effective-area fiber (ULAF). Furthermore, we discuss recent experimental results of Nyquist WDM super-channel generation and transmission of an 8×112-Gb/s PS-QPSK Nyquist WDM signal over up to 9000 km ULAF.