Amplifierless PAM-4/PAM-8 transmissions in O-band using a directly modulated laser for optical data-center interconnects

Toward the realization of low-cost, long-, and extended-reach 400GbE data-center applications, the performance of pulse amplitude modulated (PAM) signals is studied using a state-of-the-art, high-performance 1.3-μm distributed feedback directly modulated laser, without any optical amplification or complex digital processing. Amplifierless PAM-4 transmissions of up to 64-Gb/s are achieved over 40 km of standard single-mode fiber (SSMF) for standard KP4-FEC, while 84-Gb/s PAM-8 signals are evaluated over 10 km SSMF.