Research On Ultrashort Optical Pulse Generators

With the rapid development of the optical communication technology and the advent of high-speed optical communications,ultra-short optical pulses have drawn wide attention.The ultrashort laser pulses currently used are mostly generated by lasers,and their application fields are then limited.Therefore,there are many fields that are required to manipulate the shapes of ultrashort optical pulses.Pulse shaping technology is the key to a pulse waveform generator.In this paper,the phase-shifted fiber grating is the focus of the present research,the plastic structure that can synthesize the flat-top pulse and the triangular pulse is designed,and the function of the waveform generator is realized.Firstly,we introduce a variety of commonly used ultrashort optical pulse shaping techniques,analyzes the advantages and disadvantages of each technique from the aspects of shaping effect and equipment complexity,and then propose the idea of using fiber gratings for shaping.Then we analyze the structure,type,preparation technology and application fields of FBG.It provides a good theoretical basis for the plastic structure designed in the following.Secondly,we analyze the characteristics of fiber gratings.Starting with a uniform phase shift grating,its spectral characteristic curve was analyzed,and the change of spectral characteristics was analyzed by changing parameters such as grating length and modulation depth.Then,the phase shift fiber grating is formed by inserting unequal phase shift points into the uniform fiber grating bisector,and the spectral characteristic curves of first-order and second-order phase-shift fiber gratings are analyzed.Thirdly,the integral characteristics of phase-shift fiber grating are proved by theoretical analysis.The phase-shifted FBG first-order integration can be used to shape the Gaussian ultrashort optical pulse into a staircase shape,and then the first-order phase-shifted fiber grating and delay can be used to design a pulse shaping structure.When the Gaussian ultra-short light pulses are input into the system,flat top pulses and triangular pulses can be output by changing the coefficients in the structure.Finally,by analyzing the influence of pulse width,temperature and other factors on the phase-shifted fiber grating,the stability of the designed system is verified.