Optical subcarrier processing for Nyquist SCM signals via coherent spectrum overlapping in four-wave mixing with...

As one of the promising multiplexing and multicarrier modulation technologies, Nyquist subcarrier multiplexing (Nyquist SCM) has recently attracted research attention to realize ultra-fast and ultra-spectral-efficient optical networks. In this paper, we propose and experimentally demonstrate optical subcarrier processing technologies for Nyquist SCM signals such as frequency conversion, multicast and data aggregation of subcarriers, through the coherent spectrum overlapping between subcarriers in four-wave mixing (FWM) with coherent multi-tone pump. The data aggregation is realized by coherently superposing or combining low-level subcarriers to yield high-level subcarriers in the optical field. Moreover, multiple replicas of the data-aggregated subcarriers and the subcarriers carrying the original data are obtained. In the experiment, two 5 Gbps quadrature phase-shift keying (QPSK) subcarriers are coherently combined to generate a 10 Gbps 16 quadrature amplitude modulation (QAM) subcarrier with frequency conversions through the FWM with coherent multi-tone pump. Less than 1 dB optical signal-to-noise ratio (OSNR) penalty variation is observed for the synthesized 16QAM subcarriers after the data aggregation. In addition, some subcarriers are kept in the original formats, QPSK, with a power penalty of less than 0.4 dB with respect to the original input subcarriers. The proposed subcarrier processing technology enables flexibility for spectral management in future dynamic optical networks.