Postdoctoral researcher, National Tsing Hua University
High speed 5G mobile communications with fiber-wireless integrated technologies
The coming 5G mobile communications requires its data rate 1,000 times higher than current 4G, employing optical fiber as the transmission media is considered as the most efficient solution. Therefore, fiber and wireless integrated communication technology is very popular and very important to next generation mobile communications. However, instead of just putting fiber and wireless things together, it's always a big challenge to improve the data rate and energy efficiency of a fiber-wireless integrated system. This time, we develop a high efficient fiber-wireless integrated system for 5G mobile communication with "optical polarization division multiplexing" technique. Such multiplexing technique exactly doubles the conventional data rate without using additional mobile spectrum. This should be very attractive to 5G mobile communications. Unfortunately, the optical polarization is always randomly changing during fiber transmission, and some "active polarization state tracking" mechanisms are required in conventional systems. This is one of the big challenges in fiber-wireless integrated systems, because such active mechanisms are usually complicated and energy-hungry. To this issue, we successfully remove those active tracking mechanisms simply with a passive optical filter, and first time demonstrate the feasibility of such system in a 5G mobile system with lab experiments. The signal format is orthogonal frequency division multiplexing (OFDM), the format of 4G-LTE. Our results show that the active tracking mechanism is no longer necessary, and the newly proposed optical filter solution does as good as such mechanism with less system complexity and less energy consumption. The advantage of doubling data rate remains, where we still have doubled data rate in the new system. In summary, we eliminate the constrains of active polarization state tracking mechanism of fiber communications, and successfully employ an optical polarization division multiplexing to a mobile communication system for 5G.
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