Study On Dynamic Optical Arbitrary Waveform Generation And Its Performance Based On Cascaded Modulation Structure

With the rapid development of ultrafast optical pulse technique, optical arbitrary waveform generation(O-AWG) technology has attracted people’s attention. In this type of technology, we can change output pulses’ waveform and frequency of the pulse trains through altering the ultrafast pulse tunable variables. Threfore, O-AWG technology is able to eliminate the electronic bottlenecks at speed, and can be applied in various fields such as pattern generation, format conversion in fiber communication system, dispersion compensation, arbitrary microwave waveform generation, massive parallel readin and readout, control of quantum dynamics as well as chemical reaction control, etc. In recent years, the real O-AWG, namely, dynamic and high resolution O-AWG system is being extensively researched by people in the worldwide laboratories.In this paper, we firstly introduced the research background of O-AWG technology and several basic methods of O-AWG, the principle and function of related optical passive devices are then demonstrated. We proposed a novel cascaded optical modulation structure of O-AWG to realize the dynamic optical pulse shaping. The main novelties are listed as follows: Amplitude of incident OFC can be independently controlled by the interference effect of Mach-zenhder interference(MZI) structure in the optical modulator(O-MOD) of the cascaded structure; dynamic amplitude and phase control of incident optical frequency comb is realized by adjustments of fiber stretcher(FS) in O-MOD. Only one simple uniform FBG is utilized in each O-MOD to filter the spectral component of input pulse, it saves the number of used FBGs; all-optical simple configuration with high compactness and systematic stability as well as low inherent loss is built.The main work in this thesis is as follows:(1) The research background of optical arbitrary waveform shaping technology and several realization methods of this technology are firstly introduced.The emphasis has been laid on introducing the method of manipulation in frequency domain, namely, the line-by-line pulse shaping based on Fourier Transform.(2) Dynamic arbitrary optical pulse generation system based on O-MOD array strucrure of single FBG has been proposed, amplitude control is realized by adjusting phase difference of filtered optical signal in O-MOD by tuning the first FS. Phase control is realized by changing the phase shift of spectral component of OFC by tuning the second FS in each O-MOD. The shping principle of our proposed scheme has been numerically inveatigated,hence the mathmatical model has also been established. Then we demonstrated the function and principle of FBG as optical filter and that of the fiber stretcher realized by piezoelectric transducer(PZT).(3) Arbitrary wavefrom optical pulses have been achieved under ideal and non-ideal assumption, such as double-peak Gaussian pulse, periodic rectangular pulse; Gaussian pulse trains with different complexity degree under ideal assumption have also been obtained. With the help of numerical simulation by utilizing Matlab 2012 b, a comparison has been made between the optical pulse shape generated by proposed system under ideal conditions and the target pulse shape defined by user.(4) Analysis is conducted towards influence of several elements in proposed O-AWG system on the pulse shaping performance, which includes phase variation introduced by fiber stretcher; Diffirent amount of phase drifts error caused by FS correspongding to the central wavelength of OFC; The same phase variation caused by FSs in different order of stages of our proposed scheme.