Research On Optical Arbitrary Waveform Generation Method Based On Spectrum Shaping Of Optical Frequency Comb

Microwave photonics is an emerging interdisciplinary combination of microwave technology and photonics technology.The generation,transmission,control and processing of signals in the electrical domain can be converted into the optical domain with electrooptical conversion and photoelectric conversion.Nowadays microwave photonics can be found amount of applications in broadband wireless communication systems,electronic warfare systems,smart wireless and the Internet of Things.Photonic generation of microwave arbitrary waveform is an important research branch of microwave photonics with applications in areas such as the rapidly developing highresolution radar,medical imaging and instrumentation systems.And high quality of microwave arbitrary waveforms is necessary to support these applications.The traditional microwave arbitrary waveforms generation method is based on digital signal processing,which has a limited sampling rate and bandwidth and will face with the problem of electronic bottleneck.This problem may be solved by using microwave photonic technology in microwave waveform generation.The generation of arbitrary waveform generation method based on spectrum shaping of optical frequency comb(OFC)is researched in this thesis.The main idea is to build an arbitrary waveform generation prototype system,study the factors which affects the waveform generation,and some optimizing schemes are proposed and simulated.1.An arbitrary waveform generation prototype system is proposed.Based on the research literature,the prototype system of arbitrary waveform generation is constructed by using double parallel Mach-Zehnder modulator(DPMZM),Fiber Bragg Grating(FBG),Fiber Stretcher(FS)and Optical Attenuator(OA).And specific waveforms such as triangular waveform,rectangular waveform and sawtooth waveform are generated by simulation.In the simulation,the influencing factors of arbitrary waveform generation are analyzed in detail,including the factors of the number of optical combs,the spectrum width,the amplitude and phase control errors in spectral shaping and so on.2.Two new OFC generation methods are proposed.Aiming at the multiple combs and narrow bandwidth OFC generation,a method of OFC generation based on a single electrooptic modulator is proposed in this thesis.In addition,two OFC generation methods based on two intensity modulators(IM)and polarization division multiplexing dual Mach-Zehnder modulator(PDM-DMZM)cascade and DPMZM and cyclic frequency shifter cascade are proposed.3.A spectrum shaping scheme is proposed.Firstly,spectral line separation based on FGB,phase control based on FS,and amplitude control based on OA are studied.Then,aiming at reducing the amplitude and phase error of spectrum shaping,a dual array "FBG+FS+OA" spectrum shaping method is proposed,and various waveforms are generated by simulation.4.Two arbitrary waveform generation schemes are proposed.The first scheme is based on cascade "'2IM+PDM-DMZM' and dual array 'FBG+FS+OA'" to generate an arbitrary waveform signal.Waveform signals with different repetition rates are generated in simulation.Then,a Gaussian waveform is generated by simulation using different numbers of OFCs to analyze the relationship between the number of OFCs and the waveform fidelity.The relationship between the number of OFCs and the power ratio and duty cycle is also obtained.The second scheme is arbitrary waveform generation based on cascades "'DPMZM+SSB' and dual array 'FBG+FS+OA'",and Gaussian waveforms of unequal amplitudes are generated by simulation.This thesis presents the application timing of the two schemes by analyzing the simulation results,which provides theoretical basis and practical support for the optical method to generate arbitrary waveforms.