  A new cost-efficient concept to realize a real-time monitoring of
quality-of-service metrics and other service data in 5G and beyond access
network using a separate return channel based on a vertical cavity surface
emitting laser in the optical injection locked mode that simultaneously
operates as an optical transmitter and as a resonant cavity enhanced
photodetector, is proposed and discussed. The feasibility and efficiency of the
proposed approach are confirmed by a proof-of-concept experiment when optically
transceiving high-speed digital signal with multi-position quadrature amplitude
modulation of a radio-frequency carrier.
