Experimental investigation of VCSEL-based optical heterodyning with PAM 4 and envelop detection for 5G fronthaul systems

Vertical cavity surface-emitting lasers (VCSELs) are power-efficient optical sources for application in passive optical networks. Despite these sources having the potential of generating coherent high-frequency radio frequency signal, their application for high-order amplitude modulation formats is yet to be demonstrated experimentally. In this work, for the first time, we experimentally demonstrate a four-level pulse amplitude modulation...