Integrated Photonics for Radio Access: Where We Are

Integrated photonics is essential in Radio Access Networks (RAN). For example, current pluggable optics and upcoming co-packaged optics (CPO) rely on it to increase capacity and energy efficiency. In addition, Photonic Integrated Circuits (PIC) may perform in future processing functions such as radiofrequency (RF) generation and mixing. This paper provides a comprehensive review of the current and future applications of integrated photonics to radio systems. It starts with the most mature technology (pluggable optics), discussing the challenges to meet the demand for the increase of bandwidth (BW) density expected with the Sixth mobile Generation (6G). Then, it moves to more advanced short reach interconnection technologies, based on CPO and optical Printed Circuit Boards (PCB). These technologies will allow to meet that demand, provided that certain RAN-specific developments, discussed in the paper, are undertaken. The potential of Artificial Intelligence (AI) to further improve the energy efficiency of short reach optical interconnects is also shortly introduced. Finally, Micro-Wave Photonics (MWP) techniques to process the RF signal in the optical domain are presented. The paper elaborates on their potential to improve the performance of radio systems and on the challenges remaining to move these techniques from lab to market. As a conclusion, integrated photonic technologies will expand their role in the evolution of radio systems, but with a variable timescale depending on their degree of compatibility with existing production processes.