Research For All-optical Ultra-wideband Triplet Signal Generation And Modulation

As wireless communication method which needs no carrier and uses nanosecond pulse totransmit information, ultra-wideband (UWB) has low transmission power, low consumption, anti-multi-path effect, penetration ability, high transmission rate and many other advantages. Moreover,the all-optical technology of the UWB transmission in optical fiber (UWB-over-fiber) overcomesthe problem of the short transmission distance in the10meters generated by the low power density.So the research of UWB signal and its all-optical generation attracts widespread interest. Comparedto the first and second derivatives of a Gaussian pulse, low-frequency components in the spectrumof triplet pulse become weaker, which is useful to suppress the interference between UWB andother low-frequency communication services. In the paper, several new schemes about the opticalgeneration and modulation technology of the UWB-triplet signals based on cross-gain modulation(XGM) in semiconductor optical amplifier (SOA) are presented. The main achievements andconclusions are listed as follows:（1）The definition and advantages of the UWB signals are introduced. The internationalresearch development of the generation and modulation is summarized.（2）Theoretical model and the basic equations of the SOAare introduced. Through simulation,dynamic gain characteristics in SOA are analyzed. The overshoot and oscillation phenomenongenerated by gain saturation effect and cross-gain modulation are studied in the two cases of asingle light and dual beam injected into a SOA.（3）A simple method to generate all optical UWB-triplet pulse in the cascaded SOAs isproposed. The scheme has stable performance and is easily operated. The four impacts of sourcepower, pulse width, injection current and source wavelength on triplet signal are studied using thesoftware of Optisystem7.0.（4）An improved UWB pulse generation scheme in a SOA is presented. The scheme usesonly one SOA, which has simpler structure. By simulation through Optisystem7.0software, thethree impacts of source power, pulse width and source wavelength on triplet signal are studied andinvestigated.（5）A new scheme for achieving both phase modulation(BPM) based on a SOA and twoMZM is presented. By simulation through Optisystem7.0software, the four impacts of sourcepower, wavelength, injected current and extinction ratio on modulated signal are investigated. At last, the transmission characteristic of BPM signal in fiber is investigated.