Study On Microwave Photonic Filter And Generator Based On Fiber Bragg Grating

As the key devices in ROF system, microwave photonic filter and generator have potential applications in the future wideband mobile communication system. Under the supports of the National Nature Science Foundation of China and the Ph.D. Programs Foundation of Ministry of Education of China, this thesis is devoted to design and optimize the structure of the microwave photonic filter and generator based on fiber Bragg grating. And the main achievements of this thesis are listed as follows:1. The basic theory of microwave photonic filter is studied including the phase-sensitivity, high quality factor, tenability and reconfigurability. The visual analysis results of the interaction among the multiple characteristic parameters are given for the first time, which provides a theoretical foundation for optimizing the microwave photonic filter.2. The one order infinite response microwave photonic filter (OO-IIRMPF) model is built. Based on it, three kind of different structures of erbium doped fiber loop, erbium doped fiber loop with FBG and erbium doped fiber with a pair of FBGs are proposed respectively. By simulating the amplitude response and optimizing the parameters, the conclusion that infinite quality factor can be realized when the pole of the transfer function is equal to1.3. The alternative flat bandpass and bandstop microwave photonic filter model is built for the first time, which combining the two parts of finite response microwave photonic filter (FIRMPF) based on Mach-Zehnder modulator (MZM) and the OO-IIRMPF. The adjustable amplitude response of bandpass and bandstop are obtained by optimizing the two parts at the same period to realizing the amplitude compensation of crests and troughs respectively.4. Three flat bandpass and bandstop microwave photonic filter with adjustable characteristic are proposed for the first time, including the erbium doped fiber loop, erbium doped fiber loop with FBG and erbium doped fiber with a pair of FBGs. The flat bandpass amplitude responses are got when the coupler factor of FIRMPF equals0.5and the pole of the OO-IIRMPF is1.2,1.2and4respectively. The flat bandstop amplitude responses are realized respectively when the coupler factor of FIRMPF is0.4and the pole of the OO-IIRMPF equals1. By comparing the different structure, the scheme based on the erbium doped fiber loop with FBG has a better flexibility and stability.5. A kind of novel microwave photonic generator based on the single longitudinal mode dual-wavelength fiber lasers using the polarization maintaining fiber Bragg grating as the wavelength-selective filter is demonstrated. The stable single longitudinal mode operation is guaranteed by the feedback fiber loop to increasing the free spectral range and the unpumped erbium doped fiber as the saturable absorber. The stable single longitudinal mode dual-wavelength lasers are got and the22.8GHz microwave signal is obtained by experiment respectively.