Demonstration Of Chaotic Ultra Wideband Radio-over-fiber Communication Link

Recently ultra wideband (UWB) technology has been focused on consumer electronics and communications. Ideal targets for UWB systems are low power, low cost, high data rates, precise positioning capability and extremely low interference. However, its various disadvantages and problems should be concerned and solved. Such as UWB communication systems are limited in range. In order to make UWB interference to other radio systems insignificant, the transmission power of UWB signals has to be bounded under the emission mask set by the FCC. The low output power leads to smaller coverage area. In general, with regular antennas, the range of UWB signals is usually from ten to twenty meters. In order to resolve this problem, researchers proposed UWB radio-over-fiber technology, which is the key technology to realize the "seamless coverage".In this dissertation, we demonstrate a novel scheme of chaotic ultrawideband radio-over-fiber communication link, the main works including: Firstly, we analyze and compare the existing optical UWB generation technologies, point out that regardless of the baseband or mm-wave UWB signals generation, the high frequency electronic device is necessary, which means high cost and complexity. In addition, the methods based on Gaussian pulse shaping theory are different to control the spectrum profile of generated pulse, which confines their applications in the complicated environment and obstructs the evolution and combination of the emerging technologies.Secondly, we propose and demonstrate an approach to the generation of UWB pulse utilizing chaotic dynamics of semiconductor laser. The output UWB chaotic optical pulses generated by semiconductor laser with optical feedback can be controlled when the feedback strength and driving current of the semiconductor laser were tuned. The experimental results are well consistent with the simulated results based on the laser’s rate equations. Moreover, our experimental obtain the UWB pulses with ideal spectrum profile which could satisfy the Federal Communications Commission regulations.Finally, we propose and experimentally demonstrate a chaotic UWB over fiber link based on optical feedback laser diode, in which UWB signals were generated and transmitted at three different bit rates of360,720Mbit/s, and1.44Gbit/s. Without utilizing any dispersion compensation module, the signals at bit rate of1.44Gbit/s were detected using a digital signal processing receiver after10-km fiber and0.6-m wireless channel transmission. The power spectra do not have any discrete spectrum line because of the random output of the chaotic pulses, which means that the harmful effects of discrete spectrum lines could be avoided with this method.