Position-Error Compensation Method for FSO using Two-Step Search

To make free space optical (FSO) communications practically used, robust beam alignment techniques are essential. In a general beam alignment process, the transmitter gets the receiver's location from the ground positioning system (GPS) but an additional compensating algorithm should be developed due to the error of GPS. In this paper, we propose a beam alignment algorithm using the property of Gaussian beam by dividing beam searching routes into two steps. We carry out numerical simulations to validate the proposed scheme comparing it to the Max power detection algorithm. From the results, we found that the proposed algorithm improves the detection accuracy by 50% in terms of the prediction distance error. We conclude that the proposed technique shows an advanced performance even under the severe channel fluctuations.