Experimental demonstration of 20-Gb/s dual-band Nyquist PAM-4 transmission over a short-reach IMDD system using super-Nyquist sampling technique

In this Letter, we experimentally demonstrate a 1550-nm direct modulation laser (DML)-based dual-band Nyquist PAM-4 intensity modulation direct detection (IMDD) system using a real-time field programmable gate array (FPGA)-based receiver. Although the sampling rate of the analog-to-digital converter (ADC) used in the receiver is only 5-GSa/s and there is no mixer at the receiver side, the system can successfully realize 22-km SSMF transmission with 20-Gb/s data rate by using super-Nyquist sampling technique. To our knowledge, this is the first experimental demonstration of non-single-band signal transmission over IMDD system based on super-Nyquist sampling technique. In addition, power weighting technique is also applied in the system. The experimental results show that with the help of power weighting technique, the BER of the system can be reduced from 6.1 × 10−³ to 2.6