Research On The Generation And Application Of Optical Triangular Pulses In Microwave Photonics

With the rapid development of modern optical communication, microwave photonics fusion microwave technology and photonics technology, is widely used in the fields of telecommunications, military defense and broadband remote. And, the research on the special waveform optical pulses has become a hot spot. The research and application of microwave photonics generator based on triangular optical pulse has important significance. In this paper, combined with the project of National Natural Science Foundation of triangular shaped optical pulses occurs optimization method and its application, we carried out related theoretical and simulation study. The main research contents are as follows:(1) Introduce one method of optical triangular generation, which is based on the electro-optic modulation and nonlinear pulse shaping principles. The introduction focuses on theoretical analysis of the optical carrier suppression modulation and fiber dispersion effect. According to the relationship between the harmonic ratio value and modulation coefficient in the expression of output shaping pulses, a conclusion can be draw that the output expression can effectively approximate ideal triangular shaped optical pulses of Fourier series expansions under the condition that the modulation index m=2.305. Thus, we can get an ideal triangle pulse waveform. And, we verify the feasibility of the proposals through the simulation software.(2) Demonstrate a scheme to generate triangular optical pulse which is four times the local frequency based on dual-parallel MZM (DD-MZM) and fiber Bragg grating, and carries out the theoretical analysis. The scheme employs two parallel MZM and a chirped fiber Bragg grating (CFBG), in which the MZM is under carrier suppression modulation mode and the CFBG provides dispersion. By setting the appropriate modulator bias voltage and choosing the parameters of the optical fiber grating, four times the frequency of local frequency triangular pulses of light has been generated. The scheme uses fiber Bragg grating (FBG) instead of the normal dispersion fiber, which has the advantages of small volume, low insertion loss, good wavelength selectivity, easy to integrate the advantages. Considering all kinds factors influencing the generation of the triangle optical pulse, such as the fiber grating length, modulation depth, we generate ideal triangular optical pulses by simulation.(3) Design a method to achieve a wavelength conversion scheme of special optical pulse by introducing the self-phase modulation (SPM) of high nonlinear fiber (HNLF). The wavelength conversion of the Gaussian and the triangular pulse has been realized by the implementation. The article studies the influence of the input power of Gaussian and triangular optical pulse on the frequency-shift of center-wavelength in the case of self-phase modulation and shows the optical spectrum of frequency-shift varying with the input power. The performance comparison of wavelength conversion, the distance of frequency-shift and the conversion efficiency respectively indicates the superiority of triangular shaped optical pulses applied to wavelength conversion.