Fpga-based High-speed Electro-optical Strobe System Design

Electro-optic modulation technology is widely used in many areas, for instance, optical communication, optical data storage, Q-switched laser, laser ranging experiment. Acquisition of electrical modulation signal is a significant technology in electro-optic modulation. This article introduces a novel method which is called high speed electro-optic gating system to obtain the high speed electrical modulation signal.The system consist of two modules, respectively, called system sequential controlling module and ultra-fast high-voltage pulse acquisition modulation module. Gating pulse module includes high-speed signal amplifier, FPGA (Filed Programmable Gate Array) delayer and controllable delayed transmission-line. With the property of high density, high integrated, erasable, filed programmable, modulation flexible, the significant control function of system was integrated in FPGA. The overall delay is separated into digital delay and analog delay. Then, FPGA and controllable delayed transmission-line achieve the digital and analog delay respectively. The input of this system is a 4×4 matrix keyboard. Processing, controlling and calculating of data is realized by FPGA. The display mode consists of three digital module. High-voltage modulating module is structured by stacking GaAs FETs.Experiment demonstrates that the system can generate a high-voltage rectangular electrical pulse with repetition frequency 1HZ to 9999HZ, stepping 1HZ, delay range from 0 to 9999ns, stepping 1ns, high voltage range from 0 to thousands Volts, rising edge and falling edge within 10ns, jitter within 1ns. It can be applied in various electro-optic equipments. The utilization of FPGA gets following advantages, abstracting the hardware structure of the system, reducing the system jitter, integrated the function of system and realized the digital delay with a length of integral times of cycle time of the external trigger. It also can input and process the data and commands conveniently and rapidly. The controllable transmission line can realize 0ns to 15.5 ns analog delay controlled by computers. The combination of digital delay and analog delay realize the intending target completely.