The Design And Implementation Of High-speed And Large-current Pulsed LIV Test System

In order to meet the market demand of high reliability and low cost for laser diode, fast and accurate testing of laser diode parameters has become an important part in its production and use process. Laser diode parameters are usually obtained by LIV test systems. Traditional LIV test systems use DC current source to test, but LD will continue to heat in the testing process. In this way, its characteristic authenticity will be affected. To solve this problem, foreigners use pulsed LIV test system and it does not rise the temperature in the testing process. So it has been widely used depending on its reliable test data. Taking into account the high-power semiconductor lasers and fiber lasers test requirement, system requirements can output high current. However, due to the complexity of pulsed LIV test system's design, the country heavily depends on imports. In order to reduce production costs, this paper presents a new solution.Currently,domestic pulsed LIV test system outputs small current and it has low precision and wide pulse width. In terms of these problems, the paper takes pulse signal as wide band analog signal and uses the theory of analog AC constant current source to build a wide band pulse constant current source. And the high-speed pulsed power meter is implemented with the improved I-V conversion circuit.The main contents of this paper are as follows:(1)High-speed and large-current pulsed current source is designed to implement adjustable pulse width and amplitude. How to ensure the pulse edge precipitous and output large current is the key of current source design. In order to realize the two separate controls, the system is broken down into the pulse signal produced module, the magnitude control module and the power-driven module. The system uses a wide band voltage-controlled variable gain amplifier to realize adjustable amplitude with high speed pulsed signal. While in order to compensate the voltage-controlled gain amplifier for its nonlinear, the hardware and software constant current feedback is combined to implement amplitude control of fast precision current. The system uses discrete components to build a MOS push-pull power amplifier of class AB to achieve high current power amplifier. Put a high-gain op amp in its preceding stage to correct Amplitude-frequency response curve.(2)High-sensitivity pulsed current-to-voltage conversion circuit requires higher bandwidth and current gain. The system uses the improved trans impedance amplifier to complete the current-to-voltage conversion. Using T-type resistor network as feedback resistor to improve current gain and signal bandwidth.(3)Synchronization between the pulsed current source and meter can reduce the pressure of data sampling in measurement system.The system takes advantage of pulse rising along the trigger delay synchronization, and then uses RC delay and digital combinational logic to implement complex ADC trigger timing.Based on the theoretical analysis, this paper designs and implements each sub-module circuit then simulates critical circuit. Finally we draw the PCB circuit board. Through the circuit debugging and modifying the system achieve the desired objectives. The pulsed LIV test system has the salient features, such as narrow pulse width(0.5us) and large current(5A).