Microwave fiber-optic links for microcellular wireless communication networks.

摘要

The next generation of communication systems promises to provide consumers with a host of new and improved voice, video, and data services. In particular, the rapid development of wireless radio systems has given consumers the luxury of tetherless access to telephone conversation, on-line computing, and cable-television service. This type of wireless access to high quality information and entertainment services is quickly becoming a key component of the information superhighway. New communication systems must have the bandwidth and spatial diversity to supply wireless users at any location within the network with the service of their choice. Optical fiber links, which have proved to be critical to the development of high-speed wired networks, may also provide an excellent connecting infrastructure for providing uniform radio coverage in wireless networks. This thesis is concerned with device technology and system issues associated with the implementation of microwave and millimeter fiber-optic links as the connecting infrastructure in these wireless networks.; The linearity performance of low-cost microwave, and millimeter-wave optical transmitters will be assessed for the wireless application. Using a statistical model of user access in a wireless network, it is shown that by accepting a modest ({dollar}<{dollar}0.5%) percentage of blocked calls, a modest optical link dynamic range of 91dB (1Hz) is required. By using multiple fiber-fed antennae per cell and proper network protocol, the required dynamic range is dramatically reduced to {dollar}<{dollar}80dB for the same blocking probability. Also, it is concluded that the ideal system architecture for providing wireless service is a combination of distributed antennas used for radio coverage, and a centralized base station employed for voice channel capacity.; It is shown that millimeter-wave analog fiber-optic transmission can be accomplished by resonant modulation of a single contact monolithic semiconductor laser at the cavity round trip frequency of 40GHz. Efficient mode coupling is obtained with a single contact device by utilizing the high attenuation of the millimeter-wave modulation signal along the laser stripe. The properties and limitations of this technique are analyzed using a distributed circuit model of the laser.; Ultralow threshold {dollar}rm(Isb{lcub}th{rcub}<100uA){dollar} lasers can be used in ultralow power optical interconnect for digital RF transport, preferably in a bias-free digital optical modulation format. We show that even though optical power requirements for successful transmission may dictate that the pulse drive current be many times that of I{dollar}rmsb{lcub}th{rcub},{dollar} reducing the latter to 10-100{dollar}mu{dollar}A is still essential in minimizing the total driver power to the laser at multi-gigabit data rates.