Study Of Optical Arbitrary Waveform Generation Based On FBG And Its Comb Coherent-light Source

In recent years, due to the progress of ultra short optical pulse, optical arbitrary waveform generation(OAWG) techniques has aroused people’s attentions. By adjusting tunable variables of ultra short pulse, we can change the waveform and repetition frequency of pulses. OAWG has potential application prospect in many fields, such as high resolution spectroscopy, T bits per second high-speed optical communication systems, optical radar system, and arbitrary microwave signal generation, etc. At present, people carry out extensive research on high resolution dynamically adjustable pulse shaping device.The main work in this thesis includes the following parts:(1) Experimental study of comb coherent-light source. We obtain frequency tunable and frequency stability comb coherent-light source, using SPM in highly nonlinear fiber, which as the input of O-AWG. Nonlinear coefficient of fiber is an important factor to frequency combs generation. We study measurement of nonlinear efficient by self-phase modulation,illustrating the calculation progress. For highly nonlinear fiber, dispersion is small and can be nelected. However, for single mode fiber with high dispersion, we take dispersion into consideration and deduce the modified formula, and get a more accrate value.(2) Design arbitrary pulse generating system based on single fiber Bragg grating array.The input frequency combs are generated by compressing beat signal. The FBG array incorporates several FBGs, FSs, PCs in alternative arrangement. FBG is used for filtering each spectral line. Amplitude of spectral lines is controlled by polarization controllers and a polarizer, polarizations of spectral lines are different after passing through PCs, and the amplitude varies in different degree in polarizer. Phase of spectral lines is controlled by fiber stretchers. The feasibility of this structure is verified by experiment and simulation. Through dynamical control on amplitude and phase of each spectral line, we obtain pulses similar to sine wave and Gaussian wave.(3) Design arbitrary pulse generating system based on Bragg gratings and 3×3 coupler.Pluse is launched into 3×3 coupler, each port of 3×3 coupler at the other side connects with a FBG, an optical attenuator and a FS. Spectral amplitude control is implemented by optical attenuator. Phase control is realized by FS. We observe the spectrum when taking femtosecond laser and frequency combs as input, respectively. For frequency combs with different width, the waveform in time domain is discussed.