40-km SSMF Transmission of 56/64-Gb/s PAM-4 Signals Using 1.3-μm Directly Modulated Laser and PIN Photodiode

For low-cost reach extension of 400G Ethernet, >50-Gb/s PAM-4 at 1.3-μm over 40-km is demonstrated without optical amplification, enabled by a high-speed and high launch power directly modulated laser, PIN-photodiode, and low-complexity equalization.