Broadband radio-over-fiber technologies for next-generation wireless systems

The ever-increasing bandwidth demand has motivated the exploration of radio-over-fiber (RoF) for future broadband 5G+ cellular communication networks. The integration of RoF networks makes full use of the huge bandwidth offered by fiber link and the mobility feature presented via wireless link, and therefore it can satisfy the various demands of the access network on the capacity and mobility enhancement as well as the power consumption and cost reduction. Therefore future broadband access networks based on RoF technologies will provide an affordable alternative solution in various application scenarios, including conference centers, airports, hotels, shopping malls, and ultimately homes and small offices. It is expected that, in the future optical-wireless access networks, the millimeter-wave (mm-wave) bands will be utilized to solve the problem of the frequency congestion and to meet the demand for higher signal bandwidth. In this chapter several key enabling technologies for very high throughput RoF networks are reviewed, including simple and cost-effective broadband optical mm-wave signal generation and transmission, multidimensional multiplexing techniques to improve the transmission capacity, radio-frequency-transparent photonic demodulation technique applied for novel RoF network architecture, and low-complexity high-efficiency digital signal processing for RoF systems. We also summarize recent progress on RoF system, including field trials of high-speed and long-distance delivery using these enabling techniques. The results show that the integrated systems are practical solutions to offer very high throughput wireless to end users in optically enabled RoF systems.