Performance assessment of noise-suppressed nyquist-WDM for terabit superchannel transmission

This paper focuses on terabit superchannel transmission with enhanced network reach by using an emerging noise-suppressed Nyquist wavelength division multiplexing (NS-N-WDM) technique for polarization multiplexing quadrature phase shift keying subchannels at different symbol rate to subchannel spacing ratios up to 1.28, and for the first time, it was compared experimentally with the transmission capability of no-guard-interval coherent optical orthogonal frequency division multiplexing (NGI-CO-OFDM) on the same testbed. At $2 \times 10^{-3}$ bit error ratio, the maximum reachable distance is 3200 and 2800 km SMF-28 with erbium-doped-fiber-amplifier-only amplification for NGI-CO-OFDM and NS-N-WDM terabit superchannels, respectively, at 100 Gb/s/ch. For 11$\,\times\,$112 and 11$\,\times\,$128 Gb/s/ch NS-N-WDM transmission under assumption of different coding gain with hard-decision and soft-decision forward error correction, their maximum achievable distance was found to be equivalent, which are 2100 and 2170 km, respectively, both were achieved by using digital noise filtering and 1-bit maximum likelihood sequence estimation at the receiver DSP. In addition, the back-to-back characteristics of NS-N-WDM superchannel such as analog-to-digital converter bandwidth requirement and its tolerance to unequal subchannel power were experimentally evaluated and studied.