Ultra-Wideband Waveform Generation Using Nonlinear Propagation in Optical Fibers

Ultra-wideband (UWB) radio is a transmission technology that is based on short pulses, whose spectral width is on the order of several GHz. UWB signals are free of sine-wave carriers, and their duty cycle and power spectral density are low. These characteristics provide UWB radio with unique advantages: improved immunity to multi-path fading, increased ranging resolution, large tolerance to interfering legacy systems, enhanced ability for penetrating obstacles, and low electronic processing complexity at the receiver. UWB technology is considered attractive for a myriad of applications, including high-speed internet access, sensor networks, high accuracy localization, precision navigation, covert communication links, ground-penetrating radar, and through-the-wall imaging (Yang & Giannakis, 2004). Of the various potential UWB radio applications, much attention has turned to wireless personal area networks, which address short-range, ad-hoc, and high-rate connectivity among portable electronic devices. UWB radio is among the standards that are being considered to replace cables in such networks, due to its multi-path and interference tolerance, low power, and high efficiency. Research efforts in this area have intensified since 2002 when the United States Federal Communication Commission (FCC) allocated the frequency range of 3.6-10.1 GHz for unlicensed, UWB indoor wireless communication (Federal Communications Commission [FCC], 2002). Interest is not limited to indoor wireless communication only: the FCC report relates to imaging systems and vehicular radar systems as well (FCC, 2002). The vehicular radar standard, in particular, specifies a high central frequency of 24 GHz or higher (FCC, 2002). The electronic generation of complex UWB waveforms at such high frequencies is increasingly challenging. The FCC standard imposes several limitations on the transmitted signals. First, the power spectral density must comply with complicated spectral masks (FCC, 2002). In addition, the total signal power is severely restricted, limiting the range of UWB indoor wireless transmission, for example, to only 10-15 m. In many scenarios, UWB radio-based systems would need to extend their wireless transmission range by other distribution means. As the