60 GHz photonic millimeter wave communication systems
Currently available copper-based Internet access technologies like xDSL and DOCSIS cover data transmission speeds in the range of some 10 Mb/s. With new applications, an increase in bandwidth demand up to the Gb/s-range is expected for the next years. Therefore, an evolution of access networks by gradual replacement of copper-based by fiber-optic infrastructure is presently ongoing. A similar development can be predicted for wireless access technology operating within the classical microwave range. Due to regulatory requirements and a lack of bandwidth alternatives need to be developed in the millimeter-wave band. In this regard, the frequency range around 60 GHz has a special importance due to a worldwide available unlicensed spectrum of several GHz of bandwidth. In this context, the integration of wireless networks in fiber-optic networks by the fiber-optic transport of the radio signal (radio-over-fiber, RoF) is of particular importance. Besides the low-loss optical transport of a 60 GHz radio signal RoF technology furthermore allows to shift complexity from base stations to a central office by a centralized provision of the millimeter-wave carrier. This work deals with the modeling, realization and characterization of 60 GHz RoF systems providing data rates within the multi-Gb/s range. On the theoretical side, a system model has been developed comprising relevant electrical and optical noise sources and the transmission properties of fiber-optic and wireless links as well. This allows for instance to make reliable predictions of the expected system performance in the run-up to RoF system planning and thus to identify optimization potential. Using innovative approaches and technologies, 12.5 Gb/s data transmission has been realized via fiber and wirelessly for the first time over technical relevant distances. Also, if compared to conventional RoF systems the dispersion-limited fiber-optic range has been multiplied. Another RoF system in the frame of this work aimed for an uncompressed HDTV transmission, for instance for video conferencing with high resolution (1080p) and extremely low latency (telemedicine). The wireless transmission of an uncompressed HDTV signal has been successfully demonstrated. Including the previously achieved results and experiences, the system complexity has been significantly reduced.
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