Microwave Photonic Signal Processing Based On A Mode-Locked Laser

Microwave photonics is an emerging technique where photonics and electronic technologies are combined.It not only has the advantages of microwave systems,but also has the advantages of low optical loss,large bandwidth and reconfigurable.With the development of optoelectronics technology,microwave photonics is widely used in communications,radar,instrumentation,and sensing fields.Especially with the emergence of 5G technology,the system has higher requirements for microwave signal processing.In order to meet the requirements of communication and other systems for microwave signal processing,two microwave signal processing methods based on actively mode-locked lasers are proposed and successfully demonstrated:1?A novel method for measuring Doppler Frequency Shift(DFS)based on dispersion-tuned Actively Mode-Locked Fiber Laser(AMLFL)technique is proposed and successfully demonstrated.The measurement principle is based on the fact that the output wavelength of the actively mode-locked fiber laser is linearly related to the Radio Frequency(RF)applied to the modulator in the laser cavity with large dispersion,so that the input frequency and further the DFS can be obtained by measuring the output wavelength of the AMLFL.Influences of system parameters such as the laser cavity length,dispersion,and mode-locked orders on the system performance are theoretically analyzed.Under the guidance of the simulation and for different application condition,two experiments are designed respectively based on long Dispersion-compensated Fiber(DCF)and Linearly Chirped Fiber Bragg Grating(LC-FBG)to provide large dispersion,and DFS measurements are conducted when the carrier frequencies are respectively 12.2 MHz,265 MHz,682 MHz and 1.118 7 GHz.The technique has advantages of simple configuration and flexible design,and may have potential application in measurement of Doppler frequency shift.2?A frequency multiplication and frequency division method based on actively mode-locked laser technique is proposed and successfully demonstrated.By adding a comb filter in the cavity of the actively mode-locked laser,as long as the multiple relationship between the modulation frequency and the frequency interval of the comb filter is satisfied,frequency multiplication or frequency division can be achieved,and the coefficients are tunable.Finally,based on the same structure,the generation of double-frequency,triple-frequency and two-frequency signals is realized.The technique has advantages of simple configuration and flexible design.