100-Gb/s DMT Transmission for Short-Reach Optical Interconnect With DAC Clock Leakage Compensation

Digital-to-analog converters (DAC) with a high sample rate and large bandwidth are preferred to achieve high data-rate signal generation in an optical discrete multi-tone (DMT) system. Clock leakage is one of the imperfections in high-speed DACs. One or more data subcarriers of the generated DMT signal may be interfered by the additional clock tone, which may cause error floor in bit error rate (BER) performance. In this work, the pre-equalized 16/32QAM-DMT signals with the net data rate up to 121 Gbit/s are generated by an 80 GSa/s DAC with a clock leakage at 20 GHz. Two simple DAC clock leakage compensation (CLC) methods are employed and investigated in the DMT receiver. The results exhibit the two CLC methods have a similar performance. After 2 km of standard single-mode fiber (SSMF) transmission, by using the two CLC methods, the BER performance can be improved by up to about an order of magnitude and below 3.8e-3 for 16QAM-DMT. The receiver sensitivity in terms of the received optical power can be improved by 2-dB in 32QAM case at the BER of 2e-2. Furthermore, the BER performance with two CLC methods has good stability over the measurement period.