Analog Optical Front-Haul Technologies and Architectures

New traffic-generating technologies such as the Internet of Things and continued growth in mobile traffic are requiring mobile networks to rapidly expand their capacities. However, these increased capacity demands are not coupled to increased revenue, so the efficiencies and new architectures of the access network are required to keep pace. Optical fiber is now the medium of choice for radio access network backhaul due to the range of advantages it offers and the new architectural configurations it enables. These advantages are becoming particularly attractive as radio access networks shift, as predicted, to an increased number of small cells (micro- and picocells) to support 5G coverage. With increased bandwidths and higher-frequency systems, the case for radio-over-fiber systems grows. Although digital techniques currently dominate for fronthaul applications, the increased bandwidth requirements of digital interfaces mean that analog techniques may become favorable as capacity grows. In this chapter, we review the requirements of analog radiofrequency (radiofrequency (RF))–optical transport systems and provide an overview of the different optical configurations that are used or have been proposed for radio-over-fiber networks.