Development Of Fiber Laser Beat Frequency Digital Demodulation System Based On FPG

Among demodulation techniques of various fiber lasers,the beat frequency demodulation technique is a simple,low-cost and easy-to-integrate demodulation scheme.Therefore,this demodulation technology currently is a really good development prospect.Based on the overview of the development history of fiber laser beat frequency and the progress of phase-locked loop technology,this paper proposes a fiber laser beat frequency digital demodulation system based on FPGA for distributed feedback Bragg grating fiber laser,which can realize beat frequency Signal acquisition,processing,transmission and display on the host computer.Carry out the overall frame design of the system depending on the design goals,and select the key chips.Use Verilog language to design digital circuits inside FPGA,which are A/D interface circuit,digital phase-locked loop circuit,Ethernet transmission circuit and the maximum file connecting the above-mentioned module functions.The overall test platform of the system was built to verify the effectiveness of the frequency division module,acquisition module,digital phase-locked loop and Gigabit Ethernet transmission function of the beat frequency demodulation system.After measuring the approximate range of the beat signal generated by the distributed feedback Bragg grating fiber laser due to different wavelengths,it can be determined that the noise of the beat signal is small and the waveform is pure.Utilize the NF WF1968 signal generator to perform the equivalent test and perform the solution on the PC.The modulation display and analysis processing can reach the MHz level of the original signal,and the demodulation error is lower than 0.5pm.The comparison with the measured beat frequency signal source verifies the feasibility and effectiveness of the system.In summary,the fiber laser beat frequency digital demodulation system with FPGA as the core conducts research on the acquisition,processing and transmission of the fiber laser beat frequency signals.It lays the foundation for further miniaturization and modularization of the optical fiber beat frequency digital demodulation system.