Design of Temperature Controller for Laser Diode Based on DSP and Fuzzy-PID Control

Abstract

Semiconductor laser diode(LD) is widely used in optical fiber communication, integrated optics, laser printing, gas sensing, laser beam flying, optical disc memory and many other areas. LD is very sensitive to the influence of heating effect during its working, research results indicate that LD wavelength drifts by 0.2~0.5 nanometer when the LD temperature changes by 1°C, moreover, temperature increment result in the promotion of LD threshold current and shortening its working life. So, a steady and reliable LD temperature controller is necessary. The temperature control of small or middle power LD is investigated in this thesis, and a kind of high stability LD temperature control system has been developed, which takes TMS320F28335 as the controller, negative temperature coefficient thermal resistor (NTC) as the temperature sensing device, thermoelectric cooler(TEC) as the temperature control conduct device. This system is centered on DSP, combined with temperature monitor and control peripheral circuit, replace conventional PID algorithm with Fuzzy-PID algorithm to control the output power of thermoelectric cooler(TEC) to regulate laser temperature coarsely or finely. Coarse regulation can rise or reduce the temperature of TEC quickly, fine regulation can ultimately bring system into dynamic balance. It has many advantages such as convenient in use, high stability, strong anti-jamming capability, and so on. From test, we obtain the temperature variation curve while LD power on/off in five minutes. We set 20.0°C as characteristic temperature point to verify the stability and response time, the experimentally obtained results indicate that the stability of temperature control system is better than 0.1°C, and the setting time is about 2 minutes.