Research Of The Laser Diode Decoupling Control Based On DSP

Laser diode (LD) has been widely used because of its superiority low driving voltage, direct modulation and moving easy. LD has high power density and quantum efficiency. It is very sensitive to driving current and temperature, so even a tiny fluctuation will lead to remarkable change its output light or parameter, and cause serious damage to laser device further more. Therefore, in practical applications, driving current and temperature of LD should be well controlled.To further enhance the output performance of LD and easily operate, this paper made improvments in the LD driving system’s hardware and control algorithm based on initial work. These mainly improvements perform as follow:The system selected SEED-DEC2812as the control core, in the LD temperature control circuit, a PWM push-pull driver circuit was designed according to the thermoelectric cooler (TEC) driving characteristic, it can solve the problems of PWM drive circuit’s flow-through and linear drive’s low efficiency. While a linear program was designed to increased the temperature accuracy of driver circuit. A isolating circuit was designed to reduce the effect between LD driver and temperature control modules, which can significantly enhance the stability of LD system. Analysised the LD components’heat transfer characteristic through the research of TEC, then designed related circuit to improve the temperature control efficiency of LD system. Research the LD system’s characteristics relationship between energy balance, material balance, momentum balance, chemical reaction rule, electronic principles and so on, then established LD’s coupling mathematical model in mechanism. Input different signals, and studying the LD’s relationship between output response and input stimulus signal, then estimated LD’s coupling mathematical model in experiment. Research decoupling control method such as diagonal matrix decoupling, unit matrix decoupling and feed-forward decoupling, then established LD decoupling model for simulat and analysis in software of Simulink, and designed related control program. Compared response curves of the temperature and output optical power under decoupling control algorithm and ordinary PID algorithm, analyzed the advantages and disadvantages of those decoupling control methods.The experiment result indicates that:in room temperature, the output optical power surging of LD’s driving system was successfully kept around0.01W within25seconds, the temperature surging was kept less than±0.1℃within80seconds. Compared with traditional algorithm, it has advantage of higher accuracy, lower overshoot and stronger ability of self-adaptation. It was proved by the experiment that the LD system’s performance can be improved by decoupling control. In the last part of this paper, laid out the existing problems and the future ameliorations.