Structure Design and Simulation Study of Dual Two-quadrant Coherent Tracking System in Free Space Optical Communication

The free-space optical (FSO) communication has the advantages of high frequency, wide bandwidth and low cost, and has become a hot research topic in recent years. It has great potential in the field of broadband wireless communication, and it is one of the developing directions of the next generation optical communication technology. The free-space optical communication system mainly includes transmitting, receiving and acquisition, tracking, and pointing system, among which the ATP (Acquisition, Tracking, and Pointing) subsystem is one of the key technologies of free space optical communication. Accurate and efficient ATP technology is a necessary condition for Long-distance optical communication. In this paper, a coherent optical receiver terminal has been designed, and dual perpendicular mounted two-quadrant detector structure is developed for tracking in coherent free-space optical communication systems. The dual two-quadrant detector advantages are analyzed according to coherent optical detection theory, and the error compensation algorithm for dual two-quadrant detector is derived. The processing of data can be simplified by this structure. The kind of structure is low in complexity and has the ability to adjust after shock. The system of positioning accuracy and signal-to-noise ratio is improved, and the feasibility as well as superiority of this method are further proved by simulation.