High-precision Optical Axis Deviation Detection Technology In Space Optical Communication

Space optical communication has the advantage of high transmission rate,high security,high antijamming capability,low power dissipation and easily miniaturized,which make it more potential than microwave communication.Due to the narrow divergence angle and high directionality,space optical communication can not cover a large area as microwave communication.So only when the two communication ends accurately tracking each other can make the communication possible.In such background,this article carries out a study on High-precision Optical Axis Deviation Detection and Control Technology in Space Optical Communication.First,we take an investigation on the development process of the optical communication and the structure and parameters of the Acquisition,tracking and pointing(ATP)system.Then we introduce the components and the working process of ATP system,and describe the suitable case of important detectors.Next,we analyse and find out the precision of measuring device and the noise of the detector affect the precision of telescope and lead to the error of communication link.In detail,the lack of measuring precision lead to the low tracking precision of the coarse tracking,because the measuring device feedback the position and speed information of the rotary table.The noise of detector brings the calculation error in the location of light spot,which cause the wrong feedback information,leading to the precision decrease in the precise tracking.We then have an detailed analysis on the photoelectric encoder used in the rotary table,and get the expression and distribution law of the six kinds of subdivision errors,which are named DC error,amplitude error,phase error,harmonic error,noise error and quantization error.In a real telescope system,we conduct a sinusoidal leading experiment and distinguish that the magnitude error is the main error.After compensating for the magnitude error without changing the control system,we can remarkably decrease the tracking error.Besides,we detailedly analyse the technology of light spot position detection using QD as the detector of the precise tracking.Then we describe the position resolution,detection error and position sensitivity and propose that noise is the biggest factor,which affects the precision of QDs detection.In order to solve the problem,we propose using Kalman method to fliter noise.Then we conduct the experiment,including setting up the optical table,designing the filtering circuit and the amplifying circuit.Using Kalman filtering method with modulation of signal beam to process the electric signals output from QD provide a remarkable decrease of the root-mean-square(RMS)of position error.