External Modulator Optical Frequency Comb Generation Technology And The Multi-frequency Local Oscillator Generation

As a new research field,microwave photonics has made effective combination of the advantages of microwave wireless communication and the broadband of optical communication.The Internet and communication industry is developing rapidly,while information transmission is the most basic part of its development.In order to be at the forefront of the development,we need to further study microwave photonics,which is the most promising technology.Microwave photonics is a technology to maximize the advantage of microwave signals and optical signals,and correct each other's shortcomings.The study of the optical frequency comb generation has always been a research hotspot in microwave photonics.Therefore,it is particularly important to find a better scheme to generate optical frequency combs with low flatness,high side-comb suppression ratio,adjustable spacing,adjustable comb number and good stability.This dissertation mainly uses principle analysis,mathematical formula deduction,simulation verification and other methods to study the optical frequency comb based on external modulators.This study will obtain optical frequency comb with good performance and apply it to the multi-frequency local oscillator generation system.Referring to the above purposes,this paper completed the following works:(1)This paper analyzed and simulated the performance of the dual parallel Mach-Zehnder modulator to generate optical frequency combs.First,the system that used dual parallel Mach-Zehnder modulator alone can generate 5-line,7-line,9-line,and 11-line flat combs.Then,the system compensating the upper and lower arm power obtains a 5-line ultra-flat optical comb.Finally,the modulator-cascaded system can generate 25-line and 35-line flat combs.(2)Two new optical frequency comb generation schemes are proposed based on external modulators.Scheme 1 bases on a dual polarization Mach-Zehnder modulator,which generates a 9-line optical frequency comb.The system is achieved by adjusting the RF drive signal amplitudes of the DPol-MZM's upper and lower arm sub-modulators,the DC bias,and the polarization angle a.Proved by simulation and practical experiments,the flatness of the optical frequency comb is within 1d B,and the side-comb suppression ratio is higher than 17 d B.Then,it is the study about performance influence of the amplitude of the RF drive signal and the DC bias.Based on the scheme 1,the scheme 2 based on two cascaded DPol-MZMs,which have a multiple relationship with the frequency of the RF signal.By controlling the multiples of the RF signal and the polarization angles of the two modulators,we can obtain 16,25,36,45 and 81 lines optical frequency combs.The combs has a large number of lines and the adjustable spacing.Finally,the generation of optical frequency comb is applied to the local oscillation signal.A multi-frequency local oscillator generation scheme based on DPol-MZM optical frequency comb generation is proposed.The frequency number is nine and the spectrum interval is 500 MHz.The frequency range spans from 250 MHz to 4.25 GHz.This scheme adopts an optical phase locked loop to deal with phase noise,and uses the PLL loop feedback to balance and compensate the phase noise.