Field trial for the mixed bit rate at 100G and beyond

Successful joint experiments with Deutsche Telecom (DT) on long-haul transmission of 100G and beyond are demonstrated over standard single mode fiber (SSMF) and inline EDFA-only amplification. The transmission link consists of 8 nodes and 950-km installed SSMF in DT's optical infrastructure with the addition of lab SSMF for extended optical reach. The first field transmission of 8×216.4-Gb/s Nyquist-WDM signals is reported over 1750- km distance with 21.6-dB average loss per span. Each channel modulated by 54.2-Gbaud PDM-CSRZ-QPSK signal is on 50-GHz grid, achieving a net spectral efficiency (SE) of 4 bit/s/Hz. We also demonstrate mixed data-rate transmission coexisting with 1T, 400G, and 100G channels. The 400G uses four independent subcarriers modulated by 28-Gbaud PDM-QPSK signals, yielding the net SE of 4 bit/s/Hz while 13 optically generated subcarriers from single optical source are employed in 1T channel with 25-Gbaud PDM-QPSK modulation. The 100G signal uses real-time coherent PDM-QPSK transponder with 15% overhead of soft-decision forward-error correction (SD-FEC). The digital post filter and 1-bit maximum likelihood sequence estimation (MLSE) are introduced at the receiver DSP to suppress noise, linear crosstalk and filtering effects. Our results show the future 400G and 1T channels utilizing Nyquist WDM technique can transmit long-haul distance with higher SE using the same QPSK format.