Power-over-fiber (PWoF) is an attractive technology for transmitting power utilizing optical fibers. Because optical fibers are nonconductive power lines, and can transmit data signals simultaneously, PWoF enables us to provide usages that are not feasible with conventional electric power supply systems using copper wires. This study presents an overview of PWoF using various types of optical fibers, and introduces a practical application for powering remote antenna units (RAUs) in mobile communications. To power a RAU, the author's group has worked on PWoF using double-clad fibers, which comprise a single-mode core and an inner cladding that surrounds the core. The core structure is more suitable for simultaneous high-speed data signals and high-power feed light transmission than other optical fibers. To demonstrate the feasibility, the experimental demonstrations of the authors' group are introduced in detail. In addition, the latest performance comparison of PWoF reported so far is presented, and future prospects are described. Index Terms-Double-clad fiber (DCF), mobile communications, optical power transmission, photovoltaic power converter (PPC), power-over-fiber (PWoF), radio-over-fiber (RoF), remote antenna unit (RAU).
I. INTRODUCTIONW ITH the rapid development of mobile communication technologies, radio-over-fiber (RoF) has become essential for achieving higher capacity data communications [1]−[3]. It is desirable for remote antenna units (RAUs) to provide wireless communication with mobile terminals over optical fibers in all types of locations, and thus RAUs require operational technologies that can be adapted to various installation environments. In addition, as the carrier frequency of radio-frequency signals increases and cell size decreases, more RAUs with simpler installation techniques will be required.Electric power is always required for communication. In main communication facilities such as network nodes and central offices (COs), it is relatively easy to utilize commercial power supply facilities because they are installed in office areas and densely populated areas where infrastructure facilities are well Manuscript