Noise Characteristics Si-APD Background Light Effect Laser Radar

Avalanche photodiodes (APD) is a kind of photoelectric detectors with high quantum efficiency, high sensitivity and good frequency response. APD is widely used in laser radar, weak light detection and fibre communication. Background light is usually the main noise to the APD detector of laser radar with large angle of field working in daylight. So it is meaningful to study the background noise characteristics of APD to improve the SNR of laser radar.Recent research on the structure of APD and theories of APD noise is investigated in this paper. A noise detection system based on the model of laser radar receiver which is developed by Institute of Information and Physics Engineering in NJUST is designed for C30950E which is a kind of Si-APD. Digital oscilloscope TDS5054B produced by Tektronix is used to sample the noise signal. The sampling data is analyzed by the Matlab and Origin software based on digital signal processing method and statistics theories.The research studied the background noise characteristics of APD in laser radar system.Based on the statistics of the noise data, the paper gives the relationship between the RMS of the APD voltage noise, the light power and the bias voltage of APD in constant temperature and discussed the affection of saturation. In the given background environment, the distribution of possibility of noise amplitude is Gaussian when APD works on Linear Mode. The research gets the characteristics of noise power spectral density and system bandwidth after estimation.This research is useful for the design of laser radar receiver and helpful to keep laser radar working with its best state and better SNR. The results of the study are expected to apply on laser radar.