Driven by the strong demand for high-definition video, digital health services, the Internet of Things, and virtual reality, broadband, ubiquitous and convergent information access has become the most important engine to drive the development of the modern information society. With increasing numbers of information-based interactions among humans, machines and objects, especially as new services, new terminals and new needs emerge, the networks are required to provide flexible, energy-efficient, safe and broadband access services anywhere at any time, and therefore wideband and ubiquitous information access has become the great demand of the modern information society. However, it is difficult to meet the growing demand with the existing technologies, so new solutions must be explored as a matter of urgency. The intelligent radio-over-fiber (I-ROF) system, which combines the advantages of flexible wireless access and fiber-optic broadband transmission, uses the methods of microwave photonics to realize the generation of multi-band, multi-standard microwave signals in the optical domain, along with broadband processing, large dynamic transmission, fast access and reconfigurable networking, and can thus provide an effective way to achieve broadband and ubiquitous access.
With the support of the National Program for Key Basic Research Project of China (973 Program, Grant No. 2012CB315705) and the National High-Tech R&D Program of China (863 Program, Grant No. 2011AA010306), a research group led by Professor Ji YueFeng, who is with Beijing University of Posts and Telecommunications and who is also the Chief Scientist of the National 973 Program, have focused on I-ROF systems and have studied the fundamental principles, network architecture and enabling technologies of I-ROF systems from the viewpoints of the required modules, system applications and networking. Also, a broadband access and ubiquitous sensing oriented, large dynamic, reconfigurable, and distributed I-ROF system experimental platform has been built to realize broadband wireless access applications. The group's work, entitled "Large dynamic, reconfigurable, distributed intelligent radio-over-fiber (I-ROF) system", was published in SCIENCE CHINA Information Sciences, 2012, vol. 42 (10).
The research group focused on the large demand for broadband access and for ubiquitous sensing for the Internet of Things and other applications, and proposed a large dynamic and reconfigurable distributed I-ROF system, which can meet this great demand. Also, the fundamental principles, network architecture and enabling technologies for these I-ROF systems in terms of modules, system applications and networking have also been studied. From the viewpoint of the modules, broadband and multi-standard microwave/millimeter-wave band vector signal generation, instantaneous photonic microwave frequency measurements, broadband and tunable microwave photonic filters based on photonic crystals, and broadband, high efficiency electromagnetic band gap structured antennas were investigated. For system applications, a large dynamic ROF system, a cognitive, collaborative and power efficient ROF system, and an optical and wireless resources joint management I-ROF system were covered. For networking, the network architecture of the I-ROF and the media access control (MAC) protocol for the distributed ROF network were studied. Based on the results of these studies, a broadband access and ubiquitous sensing oriented, large dynamic, reconfigurable, and distributed I-ROF system experimental platform was built to realize broadband processing of multi-band, multi-standard microwave signals in the optical domain, large-scale dynamic transmission and reconfigurable networking.
This new generation of I-ROF systems is typically representative of microwave photonics, which is broadband and oriented toward ubiquitous information access, and has the advantages of broadband operation over the full frequency band, a reconfigurable architecture and easy scalability. It also allows low operational energy consumption. I-ROF is therefore an appropriate direction for future development and has broad application prospects.