An Embedded System Of Weak Optical Signal Detection With APD

With the development of weak signal detection technology, the use of APD to detect weak optical signal is getting more and more attention, and the design of peripheral circuit of APD directly affects the performance of the whole detection system. In order to set up the optimal bias voltage, and effectively suppress the noise and better display the advantages of APD high sensitivity, I design a portable and compact embedded system of weak optical signal detection with APD. this paper studies the embedded system based on the embedded technology and semiconductor refrigeration technology.First of all, I study the effect of APD reverse bias voltage and working environment temperature on the parameters of APD. Then I develop a reasonable embedded system of weak optical signal detection with APD. In the actualization of the hardware system, the paper mainly presents the design of the bias circuit, the amplifying circuit, filter circuit and the temperature control unit. In the realization of the software system, the paper mainly presents the transplant of the embedded Linux system, the compilation and transplantation of the driver and the Qt graphical interface program.Secondly, I measure the dark current and multiplication of APD in different reverse bias voltage and working environment temperature by the stable embedded system of weak optical signal detection with APD.And then, according to the data I measured, I use the system to draw the relationship curve among the dark current, reverse bias voltage and working environment temperature and the relationship curve among the multiplication, reverse bias voltage and working environment temperature.Finally, I get an optimum operation condition of APD by analyzing the curve I obtained, and set the APD operating under the optimum operation condition, and then show the data I measured on the LCD.