240 GBd PDM-16QAM Single-Carrier Coherent Transmission Beyond 130 km SSMF for a Bandwidth Limited System With Low Power Consumption DSP

In this paper, the novel and simple transceiver digital signal processing for a coherent system with Tomlinson-Harashima pre-coding was proposed and digitally implemented at 1 sample/symbol speed for the low power consumption with the high optical power at the transmitter output. The performance of beyond 200 GBd PDM-16QAM signals were evaluated with a system of 74 GHz bandwidth at −3 dB down frequency. The sampling speed of digital-to-analog converter was equal to the symbol rate. The archivable information rates were 1.82 Tb/s and 1.73 Tb/s for the back-to-back and 130 km SSMF transmission, respectively, with 240 GBd PDM-16QAM signals. The net data rates were 1.67 Tb/s and 1.57 Tb/s, respectively, with the assumption of the LDPC code rates of 8/9, 5/6 and an outer BCH code rate of 0.9922. To the best of our knowledge, this work achieved the highest net data rate among the recent reports of coherent experiment beyond 200 GBd with the sampling speed of digital-to-analog converter to be lower than 264 GSa/s. The transmission distance of 130 km was much longer than the other reports. In the receiver DSP, the common issue of timing recovery function for such kind of faster-than-Nyquist signal was solved at 1 sample/symbol processing speed with the adaptive equalizer aided algorithm. The timing recovery performance was confirmed by compensating the sampling error with the monitored jitter of lower than −35 dB.