Research And Design Of A Laser Driver System With FPGA

With the rapid development of information science and technology, the digitization, broadband and fiber of backbone networks have been realized, while user access network has little changed at the edge of network, which has become the bottleneck of development of the Internet. the development of the semiconductor laser as the key to solve this problem, so the design of the semiconductor laser driver system have gradually draw attention of the people. In this paper, a semiconductor laser driving system is designed with FPGA which make up the deficiency of the analog automatic power control and improved the control precision to achieve the effective control of the output optical power for semiconductor laser.The paper first analyzed the present situation and the trend of the semiconductor laser driving system at home and abroad. depending on the investigation of the working principle and the modulation characteristics of semiconductor lasers, the semiconductor laser driving system is designed. To solve the inadequate of the analog control, I have designed the digital automatic power control to achieve the output optical power of semiconductor laser stability. the whole drive system have been realized by using the minimum system of FPGA and MAX3643which as the main circuit of the system. In the absorption of the foreign automatic power control algorithm and the classical control theory of PID, the APC (digital automatic power control) circuit was designed, which composed by the pseudo binary search algorithm and digital integrator circuit. In order to meet the sudden opening time and jitter of system requirements, a digital PID controller was designed. Using the pseudo binary search as the proportion part reduced the system setup time. Digital integrator as the integral part reduced the jitter of system and improved the control precision. system simulation was completed by the Verilog-A., when the bias current changes from1to70mA and modulation current from10to80mA, the result showed the APC can keep the optical output power stable and the work rate of the system can reach more than1.25GHz through the simulation. so the designed system satisfies the requirements of the system and the simulation results are given.At the end of the paper, the hardware circuit of the whole driver system was designed, through the modular design, made the hardware system simplified and increased the versatility of the system.