Field trial Nyquist-WDM transmission of 8×216.4Gb/s PDM-CSRZ-QPSK exceeding 4b/s/Hz spectral efficiency

We have achieved the first ever field transmission of 8×216.4 Gb/s Nyquist-WDM signals over 1750-km G.652 fiber consisting of 950km field-deployed and 800km lab fibers with 21.6-dB average loss per span and EDFA-only amplification. Each channel is 54.2-Gbaud (216.4-Gbit/s) PDM-CSRZ-QPSK signal on 50-GHz grid with a record spectral efficiency of 4b/s/Hz. The digital post filter and 1-bit MLSE are introduced at the receiver DSP to suppress noise, linear crosstalk and filtering effects.