Study On The Generation Of Nyquist Pulse Based On Dual Parallel Mach-Zender Modulator And The Generation Of Flat Optical Frequency Comb

With the popularity of mobile phone and personal computer,the capacity of communication system becoming the big challenges.As a result,optical communication networks with Tbit/s transmission rate in single channel become the focus of research.WDM and OTDM technology based on optical Nyquist pulse is the most promising technology to realize super channel and improve spectrum efficiency.It has important practical significance to produce ideal optical Nyquist pulse.Meanwhile,optical frequency comb realized the human precision measurement of optical frequency,and has been widely used in microwave photonic signal processing and optical fiber communication multiplexing system and so on.The method of directly synthesizing optical Nyquist pulse by flat frequency comb becomes a hot research field.The content of this paper is mainly about two parts:flat optical frequency comb and optical Nyquist pulse,and the main work is done as follows:1.A detailed theoretical proof is given to the optical Nyquist pulse generated by frequency domain flat frequency comb.We conduct out the theoretical derivation about optical frequency comb generated by single frequency driving dual-drive Mach-Zehnder modulator,double frequency driving dual-drive Mach-Zehnder modulator and single frequency driving dual-parallel Mach-Zehnder modulator,double frequency driving dual-parallel Mach-Zehnder modulator and having produced flat optical frequency comb in simulation.2.We demonstrated the generation of optical Nyquist pulses using a dual-parallel Mach-Zehnder modulator driving radio frequency signal and its double signal.In our simulation,5 comb lines with a zero spectral flatness are generated in our simulation and the side mode suppression ratio reaches 41 dB,corresponding ideal sinc type Nyquist pulses in time domain.By adjusting the frequency of RF signal,the optical Nyquist pulse sequence with repetition rate of 100 ps,50 ps and 25 ps was generated while the driving voltage was equel to 0.01 V.Besides,optical frequency comb with 9,5,4,3 and 2 lines are produced,the flatness of optical frequency comb with 5,3 and 2 lines are all 0 dB and their side mode suppression ratio are all above 34.5 dB.Compared with previous works,optical frequency comb produced in this paper has higher quality.3.We propose two new methods about producing optical frequency comb with more high flatness after exploring the influence of EAM on the optical frequency comb flatness in a single EAM cascade PM cascade PM and a single EAM cascade MZM cascade PM,they are based on two EAM cascaded PM cascaded PM and two EAM cascaded PM cascaded MZM.Finally,We get flat optical frequency comb with 37 lines in the range of 3dB flatness,which have 31 subcarriers in the range of 0.4 dB flatness based on two EAM cascaded PM cascaded PM and flat optical frequency comb with 37 lines in the range of 1.2 dB flatness based on two EAM cascaded PM cascaded PM.Compared with only one EAM,the flatness of the optical frequency comb produced based on two EAM cascade PM cascade PM is increased by 6.6 dB,and the number of the comb lines in the flat flat frequency comb is increased by 2,and the flatness of the optical frequency comb produced based on two EAM cascade PM cascade MZM is increased by 0.7 dB,and the number of the comb lines is increased by 2.