Research On All-optical Generation Of UWB Modulation And Transmission Technology For Multi-user Communication

Ultra-wideband (UWB) communication technology has various advantages, suchas immunity to multipath fading, being carrier free, low power spectral density andhigh data rate and so on. Because of the transmitted power of UWB is limited tobelow-41.3dB/MHz, UWB communication systems can only operate in a shortdistance of a few meters to tens of meters. In order to increase the area of coverage,the UWB-over-fiber technology is proposed and it is desirable that the local UWBenvironments would be integrated into wired or wireless wide-range networks withUWB-over-fiber technology. Therefore photonic generation, transmission, modulationand encoding of UWB signals are very attractive since it can be easily incorporatedinto UWB-over-fiber networks and eventually simplify the entire network. The mainachievements and conclusions are listed as follows:(1) The research background and significance of the all-optical generation ofUWB signals are described, and the definition of UWB is sketched out. Theadvantages and applications of UWB are also introduced and the current status ofresearch on UWB is summarized.(2) A new method of all-optical UWB generation which is based on DWDM andPM is demonstrated. In the proposed scheme, the UWB monocycle and doublet pulsecan be generated at the same time without changing the structure of the entire system.By using the software of OptiSystem7.0, the performance characteristics ofall-optical UWB generation signals are studied. By changing the wavelength of lightsource, light source power, and the modulation of Gaussian pulse width to analyze theimpact of UWB pulse waveform generation and its radio spectrum.(3) A scheme of UWB different modulation format which is based on a phasemodulator (PM) cascade with a DWDM multi-channel discriminator is presented. Inthis scheme, we can achieve three modulation ways of UWB, respectively pulseamplitude modulation (PAM), binary phase shift keying (BPSK), pulse shapemodulation (PSM). A scheme based on binary phase-coded UWB codes to conductmulti-user communication is also investigated. At the same time, a hybrid modulationmethod with PAM, BPSK and PSM is proposed by using the same system.(4) At last, the system of UWB-over-fiber which is affected by dispersion is studiedand a new UWB-over-fiber communication is proposed. In this system, the UWBsignals can be generated directly in the optical domain to avoid using an additionalelectrical to optical conversion and it can achieve the remote transmission fordifferent modulation signals. The performance of the ultra-wideband PAM, BPSK andPSM modulated signals in fiber link transmission which are influenced by dispersionare analyzed numerically.