Radio-over-fiber technologies for high data rate wireless applications

The paper discusses two approaches for increasing data throughput needed for the delivery of bandwidth-hungry services to wireless users. Small radio cells are a stop-gap solution for dealing with today´s capacity-limited wireless systems. However, the ultimate path towards wireless communication at gigabit-per-second data rates is millimeter-wave frequencies such as 60 GHz. We discuss the benefits of using radio-over-fiber (RoF) technologies to feed the high-density of remote antenna units present in small-cell wireless systems operating at either low frequencies or mm-wave-frequencies. We investigate the performance of a simple 60 GHz RoF link transmitting 4 Gbps (single carrier), and show that the severe impact of ripples in the link response can be minimized by using simple linear feed-forward equalization, resulting in tremendous system performance improvement. We further demonstrate the use of a RoF system to generate a 7 Gbps QPSK-modulated 60 GHz signal.