Study On Applications Of Stimulated Brillouin Scattering In RoF Systems

RoF (radio over fiber) technique uses analogue fiber optic links to transmit and distribute microwave/millimeter wave signals. It integrates the techniques of optical communications and wireless communications, and will act as a more important role in military and wireless communications. RoF has been a hot research field in the world. In this thesis, the stimulated Brillouin scattering in fiber is introduced to solve several critical problems in RoF systems, such as microwave/millimeter-wave all-optical generation, carrier-suppression, microwave frequency up/down conversion, and realization of optical single sideband modulation.Firstly, stimulated Brillouin scattering, one of nonlinear effects in fiber is deeply studied. The distribution of the pumping power and Stokes power in long fiber is obtained and discussed. After comparing Smith's model and Kung's model, the more exact method for calculating the threshold of stimulated Brillouin scattering is investigated. The experiment to measure stimulated Brillouin scattering threshold using Brillouin optical-time-domain reflectometer is done. The results are well agreed with the theoretical predication. Secondly, the model of stimulated Brillouin scattering in fiber grating based Fabry-Perot resonator is studied. The dependence of the transmission power and reflection power of pump wave and Stokes wave on input power is investigated. The distribution of the power of pump wave and Stokes wave in the Fabry-Perot resonator is simulated and discussed. Furthermore, a novel and simple two-frequency Brillouin fiber laser is presented. It is based on a fiber Fabry-Perot cavity with fiber Bragg gratings as reflectors. The laser allows conversion efficiency of close to 100% and suppresses the high-order Stokes waves. The theoretical prediction is presented and the experimental demonstration is realized.The microwave/millimeter-wave all-optical generation and photonic microwave/millimeter-wave singal processings using fiber Bragg grating based two-frequency Brillouin fiber laser and stimulated Brillouin scattering in long fiber ring in RoF system are investigated deeply in this thesis.All-optical technique for micro wave/millimeter-wave generation based on the two-frequency fiber Bragg grating based Brillouin fiber laser is proposed. The mechanism for the microwave and millimeter-wave generation is theoretically analyzed. About 33 GHz millimeter-wave can be achieved through mixing the pump wave with the 3rd Stokes wave. In the experiment, 11 GHz microwave signal is attained. The microwave frequency can be tuned by varying temperatureof the fiber Fabry-Perot cavity of Brillouin fiber laser.The stimulated Brillouin scattering in a long fiber ring is used as a carrier-suppression filter. The modulation depth and RF signal gain increase with the power of input modulated signal. A modulation depth of 100% can be easily attained at a lower input power. The experimental results are well in agreement with the theoretical predictions.The techniques for microwave photonic signal up and down conversion based on the fiber Bragg grating based two-frequency Brillouin fiber laser and long fiber ring using stimulated Brillouin scattering are presented. The principles of these techniques for microwave photonic signal down-conversion are analyzed. The 12GHz microwave photonic signals are experimentally down-converted to 1.13GHz intermediate frequency (IF) signal with the technique. A novel and simple technique for microwave photonic signal up and down conversion based on stimulated Brillouin scattering is presented. The optic-link is simplified using a fiber Bragg grating to extract Stokes wave to mix with microwave photonic signal for down conversion. The down converted IF signal power can be controlled by tuning the reflectivity of fiber Bragg grating. It is also demonstrated that this technique can be used for up converting IF signal to around 11 GHz microwave. The technique for 22 GHz microwave photonic signals down conversion is also presented. It is based on 2nd order Stokes wave resulted from...