Analysis of tip-tilt compensation for reflective free-space optical satellite communication

Abstract

Atmospheric turbulences limit the achievable performance of free-space optical (FSO) satellite communication systems. Particularly in retro-reflective FSO satellite communication, tip-tilt disturbances are a dominant source of performance degradation and thus prevent the exploitation of the full potential of this communication system. This publication investigates the total tip-tilt error of a terrestrial optical communication platform for reflective optical communication using a 14-inch telescope with tip-tilt compensation. The compensation system consists of a fast steering mirror (FSM), a quad photo diode (QPD) and a controller. Dynamic error budgeting is used to systematically analyze the system components’ interplay and their contribution to the total error. Based on the results of the system analysis, a feedback controller for the compensation system is designed and tuned for disturbance rejection. The system’s performance is evaluated with a reflective FSO communication link over a distance of 600 m in urban environment. The atmospheric aberration statistic is put into relation with comparable measurements using satellite to earth communication links. Measurement results successfully demonstrate the system’s performance, effectively reducing the tip-tilt error up to a factor of 10.