Research on Convergence of Radio and Optical Technologies

Broadband telecommunication services have been expanded to all over the world as an indispensable public infrastructure. Global networks for such services would be constructed by various transmission media including optical fibers, radio-wave links, etc. High-speed wireless systems such as LTE (Long-Term-Evolution), wireless local area networks (IEEE 802.11 series) are commonly used for access networks which connect end users to networks, because of exibility of wireless services. However, it is not feasible to rely only on wireless links to transmit all the data traffic, due to limitation of radio spectrum resources. On the other hand, we may increase data transmission capacity by using many optical ber cables. Power consumption of wireless links also would be an important issue. Seamless access communication systems consisting of short distance wireless and high-speed optical fiber links would be useful to mitigate demands on exible access networks, where high-speed wireless services can be provided without using much radio spectrum resources. One of our research targets is on high-speed optical communication systems, using advanced optical modulation technologies. Conventional optical transmission systems use simple modulation techniques, while radio-wave wireless systems rely on advanced modulation formats to increase spectral efficiency. However, state-of-the-art optical modulation techniques can provide precise and high-speed control of lightwave for advanced modulation formats, so that the difference in modulation formats becomes small enough to use optical modulation techniques for radio-wave communications.


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