**1. Introduction**

The broadband communication environment becomes the essential social infrastructure when we perform a social activity. Above all, the optical fiber network was the main artery which supported a communications infrastructure, and various technology developments have been performed to take in traffic to increase rapidly [Cochennec 2002][ITU-T 2001][ ITU-T 2011]. On the other hand, wireless communication technology is essential element technology to realize ubiquitous communication environment. And new generation service development by new technology is beginning in the fields of mobile communication and broadcast [Lee 2007]. In addition, the research and development of ultra-high speed photonic network [Ben 2006][Zhang 2005][Kitayama 2005] performing the information transmission from the edge of the network to the edge in an optical domain is pushed forward, but an application of the radio technology to raise the flexibility in photonic network is an important problem, and advancement of optical wireless technology having possibility is expected [Kim 1999][Bouchet 1999]. However, it becomes further ultra-high speed/huge-capacity of the optical wireless and wavelength division multiplexing (WDM) limitation factor of the flexibility corresponding to various transmission methods because the current optical wireless system performs from optical to electrical (O/E) conversion of a transmitting and receiving part respectively. Therefore the realization of the optical wireless method that is not dependent on in ultra-high speed/huge-capacity and the interface (a protocol) of the device is enabled more than before if we can connect optical fiber to optical wireless as optical signal without performing O/E conversion, and it is expected that it can be it with the effective means of flexible photonic network construction. It is anticipated that compact optical antennas with an advanced fine optical tracking system will be used for the ultra-fast free space optical communication system in the next generation. Such laser

© 2012 Takahashi, licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2012 Takahashi, licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

communication systems will be used not only for the space communications [Kaliski 1999][Borocom 2005][Koyama 2004] but also the terrestrial long-distance photonic network. In this paper, we discuss demand specifications of optical antennas considering phenomena such as the scintillation which occurs by atmospheric turbulence. And then we explain optics design and the design results to satisfy demand specifications. We also mention the fine tracking mechanism using the fine pointing mirror (FPM) and the feedback of the signal's incident angle detection by the quadrant detector (QD) for the antenna. The influences of fluctuation of laser beam angle-of-arrival (AOA) are reduced effectively. We mention the following research studies of the two optical wireless communication systems such as next generation free-space optical communication (NG-FSO) system and radio on FSO (RoFSO) system.
