Ultra-High Capacity Optical Transmission Technologies for 100 Tbit/s Optical Transport Networks

This paper describes ultra-high capacity wavelengthdivision multiplexed (WDM) transmission technologies for 100-Tbit/sclass optical transport networks (OTNs). First, we review recent advances in ultra-high capacity transmission technologies focusing on spectrallyefficient multi-level modulation techniques and ultra-wideband optical amplification techniques. Next, we describe an ultra-high capacity WDM transmission experiment, in which high speed polarization-division multiplexed (PDM) 16-ary quadrature amplitude modulation (16-QAM), generated by an optical synthesis technique, in combination with coherent detection based on digital signal processing with pilotless algorithms, realize the high spectral efficiency (SE) of 6.4 b/s/Hz. Furthermore, ultrawideband hybrid optical amplification utilizing distributed Raman amplification (DRA) and Cand extended L-band erbium-doped fiber amplifiers (EDFAs) is shown to realize 10.8-THz total signal bandwidth. By using these techniques, 69.1-Tbit/s transmission is demonstrated over 240-km of pure silica-core fibers (PSCFs). Furthermore, we describe PDM 64-QAM transmission over 160 km of PSCFs with the SE of 9.0 b/s/Hz. key words: coherent optical communication, multi-level modulation, QAM, Raman amplification