Design And Implementation Of Laser Controller For Frequency Stabilization

With the rapid development of optical communication and electronic information technology,semiconductor laser as the main light source,scientific research and industrial production and other fields have gradually increased the requirements for its working characteristics.Aiming at the problem that the input current and the temperature of the device will affect the output frequency of the semiconductor laser,a set of automatic frequency stabilization laser controller is designed in this paper.In order to accurately control the output frequency,based on the theory of semiconductor laser frequency stabilization,this topic main research work is that,in combination with an embedded chip on current and temperature parameters of the laser active compensation control,adopt the method of fiber Bragg grating feedback frequency corresponding to the reflected light intensity information,and achieve rapid long-term stability of fiber Bragg grating temperature control.This paper focuses on the design of microcontroller software.The innovation point is that the system is designed based on embedded platform.The system is configured with a real-time multi-task operating system(RTOS)with high flexibility,and provides an interface that can set the initial working position and frequency stabilization accuracy,making it easier to customize or expand the operation of the system to meet the practical application.The system consists of two closed-loop processes:laser control and grating temperature control.RTOS is adopted for multi-thread control to realize the cooperation of each thread module.This paper analyzes the principle of laser parameter control.I2C and SPI are used to communicate with the peripheral circuit to adjust the parameters.The light intensity and temperature information acquired by ADC module is converted into digital quantity for calculation.The function of real-time monitoring chip temperature is also added.In order to realize the temperature control function of grating,the comparator module and the counter module are used together with the negative temperature coefficient thermistor sensing temperature.The counter module realizes pulse width modulation(PWM)to control the semiconductor refrigeration chip,and the PID algorithm is used to optimize the control effect to stabilize the grating spectrum.The design realizes automatic determination of the best working point and automatic tracking to adapt to various working environments.Finally,according to the principle that the resonant wavelength of FBG changes with temperature,a new method of temperature sensing based on distributed feedback(DFB)laser is proposed,which uses DFB laser as passive device to realize temperature sensing.The sensing principle is analyzed and a platform is built for experiment.The repeatability,linearity and sensitivity are analyzed and compared with other temperature sensing methods.The results show that this method has the advantages of small size,low cost,eliminating cross sensitivity and so on.