50 Gb/s PAM4 Modulated 1065 nm Single-Mode VCSELs Using SMF-28 for Mega-Data Centers

Optical interconnections for mega-data centers will require longer link lengths than can be readily provided with today's low-cost vertical-cavity surface-emitting laser (VCSEL)based multi-mode technologies. We demonstrate a solution based on 1065-nm single-mode bottom emitting VCSELs to transmit data at 50 Gb/s using four-level pulse-amplitude modulation over a distance of 2 km using a standard single-mode fiber (SMF-28). We address potential concerns regarding the unwanted higher order LP11 mode that can propagate in the SMF-28 fiber. The single-mode VCSELs have oxide apertures in the 6-7 μm range to reduce series resistance and increase output power.