Research On Key Techniques Of Optical Heterodyne Balance Detection

The balanced detection technology evolved from the optical heterodyne technology,which has the advantages of high sensitivity and strong anti-interference ability.In addition,the balanced detection technology also has the unique advantages of high signalto-noise ratio and high reference light utilization.These advantages make the balanced detection technology quickly attract the attention and research of many researchers since it was proposed,and it has been widely used in optical detection systems.This paper first introduces the previous research results of balance detection technology,and then derives the output photocurrent of direct detection,optical heterodyne detection and balance detection technology,and analyzes their respective advantages.The voltage-mode circuit and the transimpedance amplifier circuit are introduced as two current-voltage conversion circuits,and the bandwidth and gain of the two circuits are derived.The characteristics of shot noise,thermal noise and relative intensity noise in balanced detectors are analyzed,and the expressions of signal-to-noise ratio of balanced detectors are derived.Then,this paper analyzes the problem of large output noise when using a balanced detector in a DVS system.Combined with the characteristics of the noise in the balanced detector,an electrical perspective is proposed to use a differential circuit to process intermediate frequency signals and make targeted adjustments based on signal bandwidth Detector output bandwidth Two methods to optimize noise.A balanced detector for DVS system was produced,and the advantages of balanced detection over single-source detection were verified.Experimental data shows that both schemes can improve the output noise of a balanced detector.Compared to a balanced detector with a single-ended amplifier circuit and a 40 MHz bandwidth,a fully differential amplifier circuit is used to reduce the signal bandwidth to 15 MHz.The overall noise amplitude of the detector has decreased by 14 mv,which is equivalent to the overall noise intensity decreased by 38.8%.These works have certain reference value for optimizing the performance of heterodyne receiving system.